Vol. 26, No. 4 October 1998 FREMONTIA A Journal of the California Native Plant Society 'V* 4? ¦ ft / SPECIAL ISSUE: WEEDS FREMONTIA Vol. 26 No. 4 October 1998 Copyright © 1998 California Native Plant Society Phyllis M. Faber, Editor • Laurence J. Hyman, Art Director • Beth Hansen, Designer • Robert Ornduff, Editorial Advisor California Native Plant Society Dedicated to the Preservation of the California Native Flora The California Native Plant Society is an organization of lay- men and professionals united by an interest in the plants of Cali- fornia. It is open to all. Its principal aims are to preserve the native flora and to add to the knowledge of members and the public at large. It seeks to accomplish the former goal in a number of ways: by monitoring rare and endangered plants throughout the state; by acting to save endangered areas through publicity, persuasion, and on occasion, legal action; by providing expert testimony to government bodies; and by supporting financially and otherwise the establishment of native plant preserves. Much of this work is done through CNPS Chapters throughout the state. The Society's educational work includes: publication of a quarterly journal, Fremontia, and a quarterly Bulletin which gives news and announcements of Society events and conservation issues. Chapters hold meetings, field trips, plant and poster sales. Non- members are welcome to attend. The work of the Society is done mostly by volunteers. Money is provided by the dues of members and by funds raised by chapter plant and poster sales. Additional donations, bequests, and memorial gifts from friends of the Society can assist greatly in carrying forward the work of the Society. Dues and donations are tax-deductible. Another CNPS triumph! PLANT LIFE IN THE WORLD'S MEDITERRANEAN CLIMATES by Peter R.. Dalman PLANT LIFE IN THE WORLD'S MEDITERRANEAN CLIMATES There are only five areas in the world with a mediterranean climate and this book, a co-publication with the University of California Press and Oxford University Press, covers all five. The book is highly readable and richly illustrated with maps, drawings, and stunning color and b/w photographs. CNPS Press. 1998. 258 pages with 78 color and 114 b/w photographs, plus 27 maps and 46 illustrations. Available from CNPS, 1722 J Street, Suite 17, Sacramento, CA 95814. $29.50 softcover $42.95 hardcover EDITORIAL One of the greatest threats to California's native plants, both rare and common, is the increasing number of aggres- sive weedy plant species that endanger and eliminate many native species. This special issue details some of California's problems with invasive exotic weeds in vari- ous habitats and in parks and reserves. Carla D'Antonia and Tom Dudley from the University of California, Berkeley, are in large part responsible for this issue on weeds. Carla and Tom defined the issues, solicited articles, worked with the authors, and did first- round editing. Their effort can be measured in years. Publication of this special issue has been made possi- ble through generous grants from the Bureau of Land Management, the California Exotic Plant Council, and the Environmental Protection Agency. CNPS is grateful to each for helping to cover the extra costs of such a large issue. Phyllis M. Faber THE COVER: Pampas grass (Cortederia jubata) is one of the most aggressive weeds along coastal terraces and bluffs. Photograph by Beth Hansen. 5^-r Mt. Bullion Youth Conservation Corps members hand-cut and remove bull thistle (Cirsium vulgare) from a Yosemite Valley meadow, July 1989. Photograph by John Randall. CHARACTERISTICS OF THE EXOTIC FLORA OF CALIFORNIA by John M. Randall, Marcel Rejmanek, and John C. Hunter CALIFORNIA HAS a remarkably rich and diverse flora with about 4,850 native species, according to the Jepson Manual and subsequent publications. The state's exotic flora—species introduced to the state by the direct or indirect actions of humans—is also remark- able in its number and variety of species. At least 1,045 exotic species grow without care in California. In other words, 17.7 percent of the plant species that can be found in the wild in California are exotic. This is all the more remarkable because of the rela- tively short time since these introductions began. The first recorded visit by European explorers to the territory we now call California did not occur until 1524, and people of Old World ancestry did not attempt to settle here until 1769. It seems safe to assume that the vast majority of the exotic plants were introduced after this time, although a few might have been brought in earlier by way of trading networks linked to older Spanish settlements in Mexico. In fact, the writings of academically trained botanists who visited California before the Gold Rush and statehood suggest that few exotic species were established before the mid-1800s. Thus, as best we can determine, over 1,000 species became established in California since the late 1700s and the great majority did so in the past 150 years. VOLUME 26:4, OCTOBER 1998 FREMONTIA 3 We were curious about how the rate of exotic species establishment had changed over time and whether it was still increasing. Therefore, when The Jepson Manual was published in 1993 we compared the number of exotics it reported with the numbers reported in earlier floras and estimates for the late eighteenth and early nineteenth centu- ries by Frenkel. This comparison required that we apply the same criteria for delimiting species, for recognizing species as native, and for recognizing species as established that were used in The Jepson Manual to the earlier floras. We plotted the adjusted numbers of exotic species reported or estimated versus year as shown. In the graph below these data indicate that the number of exotic species increased exponentially until the late 1950s or 1960s, after which it increased more slowly. The number of exotic species increased from sixteen during the period of Spanish colonization (1769 to 1824) to seventy-nine during the period of Mexican occupation (1825 to 1848) to 134 by 1860 following American pio- neer settlement, according to Frenkel's 1970 estimates. By 1880 a total of 102 exotic species were recorded in Geo- logical Survey publications for the state by Brewer (1876) and Watson (1880). Jepson's original Manual, the first comprehensive flora covering the entire state, was pub- lished in 1925 and recognized 292 exotic species. After a. Number of exotic vascular plant species in California during the period 1700 to 1993. Fitting the data with a logistic function results in sub- stantially different prediction depending on whether the number published in the new Jepson Manual and Errata (1025) is included (solid line) or not (dashed line) (from Rejmanek and Randall 1994). b. The number of human residents in California plotted for the period 1850 to 1997 based on U.S. Census Bureau data and estimates. CALIFORNIA 1700 1750 1800 4 FREMONTIA 1850 1900 Year 1950 2000 2050 accounting for taxonomic inconsistencies between the new Jepson Manual and Munz and Keek's A Flora of Califor- nia, we found that Munz and Keck, published in 1959, included 725 exotics and their Flora and Supplement, published in 1968, included a total of 874. Using their own criteria, Munz and Keck had reported 797 exotics in 1959 and the 1968 supplement increased the total to 975. The new Jepson Manual reported 1,023 exotics and the ac- companying errata published in the Jepson Globe later in 1993 added two more, for a total of 1,025. We found reports of another eight exotic species not listed in the new Jepson Manual, bringing the total to 1,033 species. Since that time at least twelve more exotic species have been reported in the literature. A review of records at the California Department of Food and Agriculture supports the suggestion that the rate of exotic species establishment has begun to slow. Like- wise, Welsh and co-workers, who compared numbers of invasive plants reported by year in Utah, indicated that the rate of introductions there increased exponentially until about the middle of this century but had begun to slow since then. On the other hand, Carr's analysis for the state of Victoria in Australia indicated that the rate of introductions there is continuing its exponential increase. A major weak- ness in these analyses, including our own, is the likely under-reporting of exotic species by the first few genera- tions of academically trained botanists who worked in these areas. These people were most interested in the distinctive native species and likely overlooked or failed to report many of the exotics that were familiar in Europe or the eastern U.S. where they had been trained. Even today, detection and reporting of new species may lag behind their establishment by decades in many cases, indicating that the decline in the rate of exotic establishment suggested by our analysis may have actually started decades ago. As an aside, population in California has increased exponentially since about 1850, and the shape of a plot of numbers of residents over time is remarkably similar to that of the plot of exotic species numbers from the mid- 1800s to the mid-1900s. The shape of the curves diverge after the late 1950s, when the rate of increase of new exotics reported apparently slowed while human popula- tion growth continued to accelerate. Exotic Plant Pests There are at least two widely recognized lists of pest plants, or weeds, in California: the California Department of Food and Agriculture Noxious Weed List and the Cali- fornia Exotic Pest Plant Council's Exotic Pest Plants of Greatest Ecological Concern in California. The state's Noxious Weed List contains 140 species regarded as pests of agriculture, including croplands, orchards, vineyards, nurseries, rangelands, and production forests. Of these, 123 species are exotic and seventeen are native. Forty-six VOLUME 26:4, OCTOBER 1998 The California Exotic Pest Plant Council's List of Exotic Pest Plants of Greatest Ecological Concern in California—August 1996 Revision The list is subdivided into the following categories. List A: Most Invasive and Damaging Wildland Pest Plants (aggressive pest plants that displace native plants and natural habitats, this list is broken down into sub-lists: A-l Widespread Pest Plants andA-2 Regional Pest Plants); List B: Wildland Pest Plants of Lesser In vasiveness; Red Alert: Species with Potential To Spread Explosively; Infestations Currently Restricted in Size; Need More Informa- tion and Considered But Not Listed categoric ? are not included in this table. For copies of the full list contact Sally Davis, 31872 Joshua Dr. #25D, Trabuco Canyon, CA 92679; (714) 888-8347; e-ma 1: sallydavis@aol.com. List A-1 Most Invasive Wildland Pest Plants: Widespread Scientific Name Common Name Comments Distribution Ammophila arenaria European beachgrass invades coastal dunes SCo, CCo, NCo Arundo donax giant reed invades riparian areas cSNF, CCo, SCo, SnGb, D, GV Bromus tectorum cheatgrass invades sagebrush, pinyon-juniper, other desert shrub communities; increases fire frequency GB. D Carpobrotus edulis ice plant invades many coastal communities, esp. dunes SCo, CCo. NCo, SnFrB Centaurea solstitialis yellow star-thistle invades grasslands CA-FP (uncommon in SoCal) Cotoneaster pannosus cotoneaster invades many coastal communities CCo, NCo, SnFrB C. lacteus Cortaderia jubata Andean pampas grass, invades coastal habitats NCo, NCoRO, SnFrB, CCo, W, jubatagrass TR, SCo C. selloana pampas grass invades coastal dunes, coastal scrub, SnFrB. SCo, CCo Monterey pine forest, also on serpentine Cynara cardunculus artichoke thistle invades grasslands CA-FP Cytisus scoparius Scotch broom invades coastal scrub, oak NW, CaRF, SNF, GV, SCo, woodlands, Sierra foothills SnFrB C. striatus Portuguese broom often confused w/ C. scoparius SnFrB, SCo, PR Foeniculum vulgare fennel invades grasslands; esp. SoCal, Channel Islands CA-FP Eucalyptus globulus Tasmanian blue gum spreads in riparian areas, NCoRO, GV, SnFrB, SCoRO, grasslands, moist slopes SCo, nChi Genista monspessulana French broom invades coastal scrub, oak NCoRO, NCoRl, SnFrB, (=Cytisus monspessulanus) woodlands, grasslands SCoRO. sChl, WTR, PR Hedera helix English ivy spreads in coastal forests and riparian areas CA-FP Lepidium latifolium perennial pepperweed invades coastal and inland marshes CA (except KR, D) Myriophyllum spicatum Eurasian water milfoil invades lakes, ponds, and streams SnFrB, SnJV, SNH(?) Pennisetum setaceum fountain grass invades grasslands, desert canyons; roadsides Deltaic GV. CCo, SCo, SnFrB Rubus discolor Himalayan blackberry, invades riparian areas, CA-FP (=R. procerus) marshes, oak woodlands Delairia odorata Cape ivy invades coastal and riparian areas SCo, CCo, NCo, SnFrB (=Senecio mikanioides) Taeniatherum caput- medusa-head invades grasslands, particularly alkaline NCoR. CaR, SNF, GV, nSCo medusae and poorly drained areas Tamarix chinensis, T. gallica, T. parviflora, T. ramosissima tamarisk, salt cedar invades desert washes, riparian areas SCo, D, SnFrB, GV, sNCoR, (=T. pentandra) sSNF, Teh, SCoRI, SNE.WTR Ulex europaeus gorse invades north and central coastal scrub NCo, NCoRO, CaRF, n&cSNF VOLUME 26:4, OCTOBER 1998 FREMONTIA 5 List A-2 Most Invasive Wildland Pest Plants: Regional Scientific Name Common Name Comments Distribution .\iriplcx scmibaccata Australian saltbush invades coastal grasslands and scrub, and "high marsh" of coast sail marsh CA (except CaR, c&sSN) Hm.wica lournefortii Moroccan mustard washes, alkaline flats and disturbed areas in western and southern Mojave SW,D Citrihiriu draba white-top, hoary cress invades riparian areas, marshes of central coast problem only in CCo coast also agricultural lands, disturbed areas narrow-leaved ice plant invades coastal dunes, sandy soils near coast, roundleaf ice plant as best documented in San Luis Obispo and Santa Barbara counties CCo Elaeagnus angustifolia Russian olive invades interior riparian areas SnJV, SnFrB, SNE, DMoj Ehrharta calycina veldt grass invades sandy soils, esp. dunes CCo, SCoRO, WTR Egeria densa Brazilian waterweed invades streams, ponds and sloughs n&sSNF, SnJV, SnFrB, SnJt, SNE Eichhornia crassipes water hyacinth established in natural waterways, especially troublesome in Sacramento-San Joaquin Delta GV, SnFrB, SCo, PR Euphorbia esula leafy spurge invades rangelands in far northern CA eKR, NCo, CaR, MP Ficus carica edible fig invades Central Valley, foothill, south nSNF, GV, SnFrB, SCo coast and Channel Island riparian woodlands Lupinus arboreus bush lupine native to southern and central CA; invades north coast dunes problem only in NCo Myoporum laetum myoporum invades coastal riparian areas; problem only in SCo Spartina altemiflora Atlantic cord grass S.F. Bay salt marshes, populations in Humboldt Bay believed extirpated CCo species, including just two natives, are A-rated weeds. The state Department of Agriculture requires that these be targeted for eradication, containment, or other holding action at state and county levels. Fifty-five species, includ- ing two natives, are B-rated, meaning they may be tar- geted for eradication, containment, or control at the discre- tion of county weed control commissioners. Twenty-one exotics and thirteen natives are C-rated, meaning that the state will endorse eradication or holding actions only when they are found in a nursery. Five exotic species have not yet been given a permanent rating. The list also includes fifteen exotic species that are believed to have potential to become established pests but that are either not reported in the 1993 Jepson Manual or are mentioned only as possibly naturalized. CalEPPC's list of Exotic Pest Plants of Greatest Eco- logical Concern in California contains a total of seventy- six species and all are exotics. The list includes only invasive pests of natural areas that support native ecosys- tems and communities, including national, state, and local parks and ecological reserves and wildlife areas on na- tional forests, BLM lands, or other public properties. These species damage natural areas by changing ecosystem pro- cesses such as nutrient cycling, hydrology, or the fre- quency and intensity of wildfires, by outcompeting native plants and thus often depriving native animals of food and shelter, by altering succession, and in some cases by hy- bridizing with related native plants. The CalEPPC list is divided into several categories. List A-1, the most invasive and damaging wildland pests that are widespread, con- tains twenty-seven species. List A-2, the most invasive and damaging species that are regional in extent, contains thirteen species. List B, wildland pests of lesser invasive- ness, contains twenty-five species. The Red Alert list contains eleven species of currently restricted range but that are believed to have the potential to spread explo- sively and become major pests. An additional thirty-six species are listed under the heading Need More Informa- tion because it was not clear to CalEPPC whether they are capable of invading and/or degrading wildlands not sub- jected to significant human disturbance. The list does not adequately account for many of the Mediterranean annual grasses and forbs that dominate vast expanses of Cali- fornia's grasslands and savannas, but CalEPPC plans to 6 FREMONTIA VOfUME 26:4, OCTOBER 1998 remedy this in an update of the list, which should be completed in 1999. Twenty of the species on CalEPPC's list are also on the state's Noxious Weed List, indicating some overlap of agricultural and wildland pests. While more of the exotic species established in Califor- nia may be recognized as pests in the future, it is important to recognize that the majority of established exotics are relatively harmless. It is also important to recognize that only a small minority of the many thousands of exotic species that have been brought to California have become established here. For example, the most recent edition of the Sunset Western Garden Book lists some 2,900 exotic species and several thousand more exotic subspecies, vari- eties, and cultivars currently available for sale in western nurseries. Unfortunately, the small subset of established exotics, which is in turn a small subset of all the plant species brought to California, causes great ecological and economic damage. Origins of California's Exotics We were also curious about the origins of the exotics that have become established here. The majority are from Eurasia and North Africa (roughly sixty-five percent). This includes the well known Mediterranean annuals such as Avena spp., Bromus spp., and Erodium spp. now domi- nant in most of the state's grasslands and savannas. It also List B: Wildland Pest Plants of Lesser Invasiveness Scientific Name Common Name Comments Distribution Ageratina adenophora eupatory invades coastal canyons, Marin to CCo, SnFrB, SCo, SCoRO {=Eupatorium adenophorum) San Diego Co; San Gabriel Mts. Ailanthus altissima tree-of-heaven invades riparian areas, grows rapidly CA-FP Bassia hyssopifolia bassia invades alkaline habitats CA (except NW, SNH) Bellardia trixago bellardia invades grasslands, moving into serpentine where a threat to rare natives biocontrol efforts initiated NCoRO, CCo, SnFrB Cardaria chalapense lens-podded white-top invades wetlands of Central Valley CA Carduus pycnocephalus Italian thistle invades grasslands sNCo. sNCoR, SNF, CW Centaurea calcitrapa purple star-thistle invades grasslands NW, sCaRF, SNF, GV, CW, SW C. melitensis tocalote sometimes confused with C. solstitialis (yellow star-thistle) CA-FP, D Cirsium arvense Canada thistle especially troublesome in riparian areas CA-FP C. vulgare bull thistle invades riparian areas, marshes, meadows CA-FP, GB Conium maculatum poison hemlock mainly in disturbed areas but may CA-FP invade wildlands; has been known to po son wildlife Ehrharta erecta invades wetlands SnFrB, CCo, SCo Erechtites glomerata, Australian fireweed invades coastal woodlands and scrub NCo, NCoRO, CCo, SnFrB, E. minima SCoRO Mentha pulegium pennyroyal invades Santa Rosa Plain (Sonoma) vernal pools NW. GV, CW, SCo Mesembryanthemum crystalline ice plant threat to coastal bluffs, dunes, scrub NCo,CCo,SCo,ChI crystallinum and grasslands; concentrates salt on soil surface Myriophyllum aquaticum parrot's feather streams, lakes, and ponds NCo, CaRF, CW, SCo Phalaris aquatica Harding grass invades coastal sites, csp. w/moist soils NW, cSNF, CCo, SCo Ricinus communis castor bean aggressive in SoCal coastal riparian habitats GV, SCo, CCo Robinia pseudoacacia black locust spreads to riparian areas, canyons CA-FP, GB Schinus terebinthifolius Brazilian pepper invades riparian areas sSCo Senecio jacobaea tansy ragwort invades grasslands; biocontrol agents NCo, wKR, s&wCaR, nSNF, established nScV, SW Spartium junceum Spanish broom invades coastal scrub, oak woodland; NCoRO, ScV, SnFrB, SCoRO, roadcuts SCo Verbascum thapsus woolly mullein invades e CA meadows, sagebrush, pinyon-juniper woodlands CA Vinca major periwinkle invades riparian areas, oak woodlands, coastal NCoRO, SnFrB, sSCoRO, SCo Red Alert: Species with Potential to Spread Explosively; Infestations Currently Restricted in Size Scientific Name Common Name Comments Distribution ,4 lliagi pseudalhagi camel thorn noxious weed of arid areas; most GV, sSNE, D (=A. camelorum) infestations in California have been eradicated Arctotheca calendula capeweed seed-producing types are the problem; most arc vegetative only NCo, SnFrB Crataegus monogyna hawthorn recent invader, colonizing healthy native forest around Crystal Springs reservoir on SF peninsula SnFrB Halogeton glomerulus halogeton noxious weed of rangelands; report locations Food & Ag: eradication program in place GB to CA Helichrysum petiolare licorice plant invades north coastal scrub; one population on Mt. Tamalpais, w. Marin county; not in Jepson Hydrilla verticilktui hydrilla noxious water weed; report locations to CA Food & Ag; eradication program in place: found in Clear Lake (Lake Co.) in 1994 Lythrum salicaria purple loosestrife noxious weed of wetlands sNCo, NCoRO, nSNF, ScV, SnFrB, nwMP /tetania monosperma (=Cenisla m.) bridal broom first noted at Fallbrook Naval Weapons Station, San Diego Co.; could rival other invasive brooms San Diego Co. Sparlina anglica cord grass scattered S.F. Bay & Humboldt Bay salt marshes not in Jepson S. densiflora dense-flowered cord grass scattered S.F. Bay & Humboldt Bay CCo, NCo salt marshes S. patens salt-meadow cord grass one site in S.F. Bay, also Siuslaw estuary, OR and Puget Sound, WA CCo includes fourteen species (over one percent) that are en- demic to the Canary Islands and/or Madeira. Other parts of North America and Central America contributed fifteen percent of the exotic flora, while seven percent are from South America, seven percent from sub-Saharan Africa (most from southern Africa), five percent from Australia and New Zealand, and one percent from other parts of the world (e.g. Madagascar, islands of the South Pacific) or their original range is not known. California's Exotics A wide variety of growth forms and life histories are represented by California's exotics, including annual grasses and forbs, biennial forbs, perennial grasses and forbs, shrubs, vines, trees, and submerged, emergent, and floating aquatic plants. The plant families with the highest numbers of exotics in California are the grasses (Poaceae, 181), composites (Asteraceae, 151), legumes (Fabaceae, ninety), and crucifers (Brassicaceae, sixty-three). It is in- teresting to note that over forty percent of California's grasses are exotics. There are fourteen exotic species in the genus Bromus alone. One hundred percent of members of several small families in California's flora are exotic, including Myrtaceae (eleven species), Tamaricaceae (five species), Molluginaceae (three species), Moraceae (three species) and Commelinaceae (two species). On the other hand, just four exotic ferns are reported in The Jepson Manual, and no exotic fern allies have been reported. No exotic gymnosperms were reported in the new Jepson Manual, but we found reports of two in other publications: Italian stone pine {Pinus pined) on Santa Cruz Island and Pinus halepensis on San Bruno Mountain. The number of exotic sedges (Cyperaceae) is also remarkably low, just fifteen, or seven percent of the species in the state. The 8 FREMONTIA VOLUME 26:4, OCTOBER 19 98 number for lilies (Liliaceae) is still lower: eleven species or 4.7 percent. There is just one exotic orchid, Epipactis helleborine, even though the Orchidaceae is the world's largest family of monocots, and there are no exotics in several small to medium-sized families such as the Rham- naceae, Polemoniaceae, and Fagaceae. Where Do Exotics First Invade? Most exotics introduced to California in earlier times first established at coastal sites in and around ports, mis- sions, or early settlements. The Jepson Manual reported a total of 151 exotic species not reported before in any state- wide flora, and many of these are established in the San Francisco Bay and south coast areas as well. On the other hand, all of the major geographic subdivisions of the state support at least one of these "new" exotic species. Some of the newly reported species are already widespread, but twenty-seven were reported from just one county. Together these counties cover almost the entire length and breadth of the state, including the counties of San Diego, Los Angeles, Riverside, Ventura, Santa Barbara, San Luis Obispo, Inyo, Monterey, Santa Clara, Stanislaus, Alameda, Marin, Sonoma, Placer, Colusa, Butte, Plumas, Humboldt, and Lassen. The great speed and reach of modern transportation systems and the still growing global trade in plants and other commodities enabled these "new" exotics to reach and become established at sites all over the state rather than around just a few ports and coastal settlements. Exotic Vascular Plants in i California by Family for All Families with Ten or More Exotics, Percentage of Exotics in Family, Estimated Species in Family Worldwide, Percentage of Species in Family Not Native to But Reported Established in Califo rnia, and Percentage of Species in Family Native to California* Family # Exotics # Natives % Exotics # Species % of Potential % Native Worldwide Exotic Species in CA toCA Poaceae 177 261 40.4 9,000 2.1 2.9 Asteraceae 151 725 17.2 21,000 0.7 3.5 Fabaceae 90 307 22.7 16,400 0.6 1.9 Brassicaeeae 63 228 21.6 3,000 2.3 - 7.6 Caryophyllaceae 40 71 36.0 2,070 2.0 3.4 Scrophulariaceae 38 253 13.1 4,450 0.9 5.7 Chenopodiaceae 31 64 32.6 1,300 2.6 4.9 Solanaceae 29 30 49.2 2,600 1.1 1.2 Polygonaceae 28 192 12.8 1,150 2.8 16.7 Geraniaceae 23 8 74.2 730 2.6 1.1 Apiaceae 20 130 13.3 3,100 0.7 4.2 Boraginaceae 19 139 12.0 2,500 0.8 5.6 Rosaceae 18 137 11.6 3,100 0.6 4.4 Lamiaceae 15 105 12.5 5,600 0.3 1.9 Cyperaceae 14 195 6.7 3,600 0.4 5.4 Iridaceae 13 20 39.4 1,800 0.7 1.1 Malvaceae 12 50 19.4 1,550 0.8 3.2 Aizoaceae 11 2 84.6 2,400 0.5 0.1 Amaranthaceae 11 9 55.0 800 1.5 1.1 Liliaceae 11 221 4.7 4,500 0.3 4.9 Myrtaceae 11 0 100 3,850 0.3 0.0 Onagraceae 10 137 6.8 650 1.9 21.1 * Numbers include all species reported as exotic in Hickman 1993; Wilken / 993; and the nine additional species noted in liejmdnek and Randall 1994, with the exception of those listed as hybrid. ¦. VOLUME 26:4, OCTOBER 1998 FREMONTIA 9 Exotic Vascular Plant Species in Geo graphic Subdivisions of Jepson Manual, Area of Subdivision, and Mean Number of Exotics Per Square Ten Kilometers* Jepson Manual Area # Exotic Exotic Sub-Region (1000 km2) Species Species / Log(Area) South Coast 10.6 594 147.6 San Francisco Bay Area 7.8 543 139.5 Central Coast 6.2 480 126.6 San Joaquin Valley 42.8 424 91.5 Sacramento Valley 15.8 417 99.3 North Coast 3.1 411 117.7 Outer North Coast Ranges 17.4 405 95.5 Outer South Coast Ranges 14.4 376 90.4 Northern Sierra Nevada Foothills 9.9 345 86.3 Inner North Coast Ranges 9.2 339 85.5 Western Transverse Ranges 8.5 321 81.7 Providence Range 9.8 321 80.4 Central Sierra Nevada Foothills 5.9 316 83.8 San Jacinto Mountains 0.45 315 118.7 Klamath Region 19.7 315 73.4 Southern Channel Islands 0.4 314 120.7 Inner South Coast Ranges 8.9 311 78.7 High North Coast Ranges 6.6 309 80.9 Northern Channel Islands 0.5 302 111.9 San Bernardino Mountains 2.2 296 88.6 San Gabriel Mountains 2.3 296 88.0 Cascade Range Foothills 9.1 291 73.5 Northern High Sierra Nevada 17.5 286 67.4 Southern High Sierra Nevada 9.2 281 70.9 High Cascade Range 11.6 276 67.9 Central High Sierra Nevada 9.4 252 63.4 Tehachapi Mountains 1.7 238 73.7 Southern High Sierra Nevada 7.1 237 61.5 Modoc Plateau 21.1 150 34.7 Warner Mountains 1.7 144 44.6 Sierra Nevada East 11.7 125 30.7 White and Inyo Mountains 3.8 123 34.4 Desert Mountains 5.5 118 31.5 Sonoran Desert 29.2 115 25.8 Mojave Desert 68.5 115 23.8 sf.Mean number of exotic species per 10 km2 represents the number of exotics in subdivisions divided by the log area of the subdivision. Areas of the subdivisions were determined from a map produced by Karen Beardsley, Information Center for the Environment, University of California, Davis. Numbers of species based on a database compiled from The Jepson Manual by Leslie Hartman, Steve Hartman, John Hunter, and Jennifer Riggle. Distribution of Exotics California's exotic flora is far from uniformly distrib- uted across the state. Of California's exotics, less than one- tenth are found throughout the state and less than one-fifth are throughout the California Floristic Province. In con- trast, over one-third of our exotics are known from only one to three of the thirty-five geographic subdivisions of Cali- fornia defined in the 1993 Jepson Manual. The composi- tion of the exotic flora differs between the subdivisions, and the numbers of exotic species decline with increasing el- evation and with increasing distance from the coast. California's exotic flora is richest near the coast. Of the Jepson geographic subdivisions, the South Coast has the most exotic species (594), followed by the San Francisco Bay Area (543) and the Central Coast (480). About forty of these coastal exotics are species of ocean front or salt marsh habitats. However, even excluding those species, the coastal subdivisions are still the richest in exotics. To the interior, the number of exotics drops considerably. The Inner Coast Ranges have fewer than 400 exotics, as do the foothills of the Sierra Nevada. The Sonoran Desert and Mojave Desert subdivisions have the fewest exotics, with just 115 each. California's exotic flora is also richer at lower eleva- tions than at high. Over half of our exotics occur only at elevations below 1,500 feet, and more than four-fifths only below 6,000 feet. As a consequence, regions of primarily higher elevations contain fewer exotics. For example, the Sierra Nevada High regions contain fewer exotic taxa than their adjacent foothills, and the North Coast Range High region has fewer exotics than the adjacent Inner and Outer Coast Ranges. Few exotics are reported above 6,000 feet elevation, and we are aware of only four exotic species that have been reported from above 9,000 feet: Capsella bursa- pastoris; Chenopodium foliosum; Poa pratemis ssp. pra- tensis, and Taraxacum officinale. Why do coastal and lower-elevation areas contain more exotics? Past and present human influences probably both contribute. Coastal areas were settled first and remain the most heavily populated. The majority of exotics probably were first introduced into coastal and lower-elevation re- gions, particularly around seaports. Since lower-elevation areas contain a disproportionate share of the state's settled areas and agricultural lands, they also have large areas of disturbed vegetation and soils, the primary habitat of many exotics. Coastal areas also have milder winters and a summer dry season tempered by cool ocean air and fog, and this more equable climate may allow naturalization of more introduced species from temperate areas of Europe and Asia. To look at the distribution of exotics in the state in another way we also analyzed a series of county and regional floras for coastal California. This revealed two peaks of exotics, a higher one around the San Francisco Bay and a somewhat lower one along the south coast from Santa Barbara County to the border. San Francisco County VOLUME 26:4, OCTOBER 1998 had the highest percentage of exotics of the areas analyzed. This is not surprising in light of the fact that this area was and still is an important port, was settled earlier than most other parts of the state, and is highly urbanized with rela- tively few remaining natural or open spaces. Santa Cruz County had the highest absolute number of exotics. What Does the Future Hold? Nearly eighteen percent of the plant species that grow without cultivation or care in California today are exotic. Several other states have even higher percentages of ex- otic species in their floras, but only New York and Florida have higher absolute numbers. The diversity of California's exotic flora may be at least partially explained by the state's enormous diversity of climates, soils, and eleva- tions, factors that also help to explain the incredible diver- sity of our native flora. Numbers of exotic species in our flora will continue to increase, however. In the four years since our 1994 analysis of exotic species in California was published in Madrono, more than twenty-five new exotic species have been reported for the state in the literature and at least fifteen more have been deposited at herbaria or reported as possibly established. Few if any of these estab- lished exotics will be eliminated from the state. As de- Giant reed (Arundo donax) grows in the Santa Margarita River floodplain at Camp Pendleton, San Diego County. Photograph by John Randall. Numbers of Native and Exotic Vascular Plant Species in Coastal Counties and Regions California and Baja California of County/Region # Native Species # Exotic % Exotics Species Area (km2) Source Mendocino 1,784 418 19.0 9,080 1 Sonoma 1,280 487 27.6 4,088 2 Marin 1,030 408 28.4 1,346 3 San Francisco 661 465 41.3 236 4 San Bruno Mt. 404 255 38.7 12 5 Santa Cruz 1,203 468 28.0 3,588 6 Monterey San Luis Obispo Santa Barbara 1,501 1,308 1,371 343 18.6 354 21.3 439 24.3 8,611 8,585 7,089 7,8 9,10 11 Santa Monica Mts. 644 236 26.8 195 12 Orange 806 351 27.9 2,025 13 San Diego 1,559 473 23.3 11,016 14 Punta Banda (Baja California) 208 50 19.4 30 15 Sources: 1. Smith and Wheeler, 1990; 2. Best*Fg «*"* •*»%.- *, « ^*"':"¦"' * Tamarisk (Tamarix sp.) lines Coyote Creek in the Anza-Borrego Desert in May, 1993. Seedlings have sprouted following a winter flood. Photograph hy Carla D'Antonio. Jti COMMUNITY AND ECOSYSTEM IMPACTS OF INTRODUCED SPECIES by Carla M. D'Antonio and Karen Haubensak INTRODUCED SPECIES are everywhere. We depend on them for food and fiber, and we purposefully import and pamper them in our parks and gardens. Many arrive inadvertently and disappear shortly thereafter. It is safe to say that only a fraction of the species that are purposefully or accidentally brought to California estab- lish and escape from the places where they are introduced. These are the species we refer to as exotic invaders. Of these, a small but increasing fraction not only invade our natural communities but cause ecological and economic damage. Scientists and concerned members of the public are now beginning to consider the seriousness of the im- pacts of this small but significant group of invaders. The first scientist to explore the potential ecological importance of introduced species was Charles Elton, who noted in 1958 with foresight that"... we are seeing one of the great historical convulsions in the world's fauna and flora." Peter Moyle, an ecologist from the University of California at Davis who studies fish introductions in Cali- fornia, makes the generalization that most successful in- troductions are made into habitats that are already highly disturbed; introductions into disturbed habitats usually VOLUME 2 6:4, OCTOBER 1998 FREMONTIA 13 Giant reed (Arundo donax) growing in the Santa Clara River estuary in Ventura County. Photograph by Tom Dudley. displace native species, often through competition. Al- though there are no documented examples of introduced plants known to have caused the extinction of a native species in California, we believe it is important to consider the more subtle but potentially far-reaching impacts of invaders. Exotic species not only displace native species, they also can change substrate stability, disturbance re- gimes, and soil chemistry. These changes are most likely persistent, and may make site restoration more difficult. Our knowledge about the effects of invaders on communi- ties and ecosystems is far from complete. This article provides an overview of what is known about the impacts of invasive, non-native plants on wildland communities in California. Ecologically Damaging Species in California In the 1993 Jepson Manual 1,025 species are listed as introduced to California and naturalized (i.e., have self- replacing populations). According to ecologists Marcel Rejmanek and John Randall of UC Davis, at least another eight are present that are not listed in the Jepson Manual. This list of 1,000 plus species includes many innocuous exotics that are little more than garden nuisances. How- ever, it also includes many that are both invasive (spread rapidly) and damaging to natural ecosystems. The Califor- nia Exotic Pest Plant Council (CalEPPC), a group of academics, agency biologists, concerned citizens, and con- sultants, put together a list of the most invasive and dam- aging wildland plant species in California. Their A list includes twenty-three species that are widespread and highly damaging and thirteen that are regionally confined but damaging, for a total of thirty-six high-priority spe- cies. Their B list species are considered damaging but perhaps less invasive, and includes twenty-four more spe- cies. If you add in the "red alert" species—those that have been shown elsewhere to be damaging and have the poten- tial to spread—you come up with a total of seventy-six species. The lists includes fourteen grasses, thirty-two herbaceous species (six aquatic), three succulents, twelve shrubs, ten trees, and four vines. What is it about this group that causes them to rate highly to these experts? The ecological impacts of these species can be broadly lumped into the following categories: (1) alteration of natural disturbance regimes, (2) alteration of substrate stability and geomorphology, (3) alteration and simplifi- cation of food webs, (4) direct competition with native species, (5) rapid preemption of resources following dis- turbance by persistent perennials, and (6) alteration of soil chemistry or chemical processes. As ecologists we are concerned with species that either directly outcompete native species and then persist in a more or less monospe- cific stand thereafter and those that alter processes that sustain native species. Such species affect local and re- gional biological diversity and ecosystem services such as water and topsoil retention, successful pollination, support of wildlife, and aesthetic and recreational enjoyment. Alteration of Natural Disturbance Regimes Perhaps one of the least reversible and most significant impacts on native species occurs when introduced plant species alter the frequency and intensity of fire. In the intermountain west, the plant species that has affected the largest area is cheatgrass (Bromus tectorum). Plant ecolo- gists observed some thirty to forty years ago that invasion by B. tectorum increased fire frequencies and led to in- creased invasion by cheatgrass, setting in motion a cycle that is difficult to break. More recent work by Steve Whisenant, at Texas A&M University, has quantified dra- 1 4 FREMONTIA VOLUME 26:4, OCTOBER 1998 matic alterations in fire frequency and the almost complete loss of native species in large areas of the Idaho Snake River Plains as a result of lightning-caused summer fires fueled by dead cheatgrass. Could this happen in Califor- nia? Red brome (B. rubens) and other annual grasses increase fire frequencies in the western Mojave Desert in California. Rich Minnich and graduate students at the University of California, Riverside have documented de- structive fires fueled by these grasses in sites where fire was previously rare. A grass that is already altering the diversity and func- tion of riparian corridors throughout California and that promotes fire is giant reed {Arundo donax). Its distribution and habitat preferences are described elsewhere (see Dudley, this issue). In southern California it has fueled Dudlcva caespitosa (above) being invaded by Malaphora crocea on Anacapa Island. Photograph by Carla D'Antonio. • Water hyacinth (Eichornia sp.) (below) in foreground and giant reed (Arundo donax) in background growing in the Sacramento Delta. Photograph by Tom Dudley. i&uW*^' *v* ii ... -55\ jk;Sl. m » e=«#ir. "VC^T MfC VOLUME 26:4, OCTOBER 1998 FREMONTIA 1 5 Giant reed (Arundo donax) removal along Sonoma Creek. Photograph by Tom Dudley. fires around urban areas in Orange County and has trans- formed river courses from natural barriers to fire spread into fire wicks. Investigators in southern California claim that native riparian species in these habitats are not toler- ant of the hot fires fueled by giant reed. Although a multi- agency task force (Team Arundo) has been formed to try to control its spread (see Kan, this issue) in southern California, it is still abundant throughout coastal regions of the state. The grass-fire cycle begins with initial invasion—a process that in arid-land plant communities often does not require an initial disturbance. Because of the inherent flammability of dry grasses and the abundance of ignition sources (human activities and lightning), invasion ulti- mately results in the spread of fire. Grasses recover rapidly via regeneration from the seed bank or from root crowns, and their abundance increases with increasing fire fre- quency while woody species decline. While much of the California coastal mountains and foothills is covered with fire-maintained chaparral where grass invasion is unlikely and regeneration of native woody species is promoted by fire, fires fueled by grasses aerially seeded into chaparral burns have been known to negatively impact woody chap- arral species. For example, in the 1980s chaparral burns in southern California were aerially seeded with the intro- duced grass, Lolium multiflorum. The presence of dense stands of dry Lolium plants resulted in reburning of a site near Ojai and one near San Diego within three years of an initial fire. This fire frequency is much higher than the typical intervals of thirty-five to sixty-five years for chap- arral in this region and appeared to kill many shrub seed- lings. Substrate Stability and Geomorphology There have been few attempts to quantify the impacts of introduced plants on substrate stability and geomor- phology relative to native counterparts that would other- wise occupy the site. However, it is clear that some spe- cies, particularly sand-binding grasses, can alter substrate movement and accumulation. Perhaps the best example in California is European beachgrass (Ammophila arenaria), which occurs in dune systems throughout the state. Beachgrass has an extensive root system and an impres- sive ability to keep its photosynthetic structures above the sand surface. As it binds sand and grows upward, it alters the shape of the dune, creating a high ridged foredune and well-stabilized backdune. Few native plants or insects occur within these new foredune habitats. In 1977 an investigator from U.C. Berkeley's entomology depart- ment compared the numbers of native insects in beachgrass dunes versus nearby dunes dominated by native plant species and found that foredunes dominated by European beachgrass were depauperate in insect species. At U.C.'s Bodega Marine Reserve, we have observed that sand sta- bilization by this beachgrass promotes a low-diversity foredune, but that the back-dune is now so stabilized that beachgrass is declining in vigor and coyote brush {Baccha- ris pilularis) is beginning to invade. It is likely that many other species alter substrate stabil- ity, but impacts are rarely quantified. According to Air Force personnel at Vandenberg Air Force Base, seeds of South African veldt grass (Ehrharta calycina) were aeri- ally sprayed in dune systems for substrate stabilization in central California. It is now recognized as a rapidly spread- ing pest that can outcompete native dune species. Pampas grass, giant reed, and salt cedar probably also affect sub- strate stability and the geomorphology of invaded sites. 1 6 FREMONTIA VOLUME 26:4, OCTOBER 1998 Competition with Native Species Many of the wildland weed species on CalEPPC's list and species that are the targets of control efforts through- out the state are believed to be aggressive competitors against native species. Some species, such as highway ice plant {Carpobrotus edulis), invade intact communities and overgrow native species. Through removal experi- ments Carla D'Antonio was able to document that ice plant competes with native species for water and reduces their growth, reproduction, and survival. In addition, the dense mats that it forms on the soil surface preclude establishment by other species. European annual grasses are now well known to have a negative impact on the establishment and seedling growth of native woody species in California. Gerlach and co- workers from U.C. Davis have documented the impacts of ripgut brome and other introduced grasses on the estab- lishment and growth of blue oak (Quercus douglasii) seedlings. Others, such as Karen Danielson with the U.S. Forest Service, have documented negative impacts of these grasses on the establishment and growth of valley oak (Q. lobata) seedlings. The suspected mechanism of competi- tion in most of these cases is competition for water. Other invading species are also known to be excellent competitors for water. Stan Smith and Dave Busch at the University of Nevada at Las Vegas have demonstrated that salt cedar (Tamarix) can reduce water availability to na- tive riparian species in western watercourses. However, in many of the river courses where Tamarix is now well established, it is suspected that altered hydrological condi- tions due to human intervention (dams, impoundments, etc.) has given Tamarix an advantage over native species by changing the physical and hydrological conditions un- der which native species are expected to persist. Tamarix is less successful where hydrological conditions are not modified. There are only a few vine species on CalEPPC's list, but these are notable for their ability to overgrow native species. For example, German ivy, now called Cape ivy (Delairia odorata, formerly Senecio mikanioides), over- grows trees and shrubs in riparian corridors and drastically reduces light availability. English ivy (Hedera helix) and periwinkle (Vinca major) may spread less readily to new sites, but may shade out native understory species. Preemption of Resources after Disturbance It is well known that many invasive exotic species respond rapidly to disturbance and are abundant in hu- man-disturbed habitats. Their persistence in these habi- tats is problematic if these sites provide an avenue for entry of aggressive exotics into natural habitats. Zink and co-workers studied the spread of exotics along a power line right-of-way through intact natural habitats in south- VOLUME 26:4, OCTOBER 1998 Ice plant (Carpobrotus edulis) invades a chaparral area three years following a fire in Burton Mesa, Vandenburg Air Force Base. Ice plant was present but not abundant prior to the fire. Photograph by Tom Dudley. era California. They found that the right-of-way was an avenue of entry for several exotic species, including black mustard (Brassica nigra) and ripgut brome (Bromus diandrus) into native coastal scrub, oak woodland, and grassland habitats. The establishment of aggressive weeds on disturbed sites can also seriously impede restoration efforts. Natural disturbances are also common in California environments, and exotic species that respond rapidly to natural disturbance must be carefully watched. The activi- ties of many native animals, particularly rodents, are chronic natural disturbances in plant communities from the coast to high montane habitats. Their activities promote the occurrence of highway ice plant in coastal grassland com- munities, introduced annual grasses in serpentine grass- lands, and introduced annual and perennial grasses in northern coastal prairie. Non-native animals, such as the European wild boar and livestock, may also promote plant invasions. Fire is also a natural and chronic disturbance in many California plant communities and has been observed to promote invasive exotic species in a few habitats in Cali- fornia. On Vandenberg Air Force Base we have found that chaparral fires promote highway ice plant by removing competitors and providing sites for ice plant seed germina- tion. Minnich and co-workers in the Mojave Desert have documented that introduced annual grasses respond more rapidly to fire than the poorly adapted native species and thus increase their abundance. Germination of some ex- otic species is stimulated by fire, which can have impor- tant implications for restoration of sites that have been invaded by species with large seedbanks. For example, we have found that more seeds of French broom (Genista monspessulana) germinated in burned than unburned grass- land habitat in Marin County. We also observed that FREMONTIA 1 7 growth and survival of seedlings were enhanced in burned areas. Another natural disturbance that can promote estab- lishment of exotics is flooding. Giant reed appears to be spread by floods, which break up and distribute rhizomes. Rhizomes grow rapidly into adult plants, perhaps to the detriment of native species. Salt cedar can also respond rapidly to flood disturbances. After a twenty-year interval flood in Anza Borrego State Park, we observed that salt cedar was reduced more than any of the native species, but then it increased cover faster than any of the natives. One year after the flood, streamside substrates were carpeted with tamarisk seedlings and regenerating adults. Alteration of Soil Chemistry Many introduced species that are thought to compete with California natives alter soil chemistry. For example, highway ice plant acidifies the soil in some of the sites that it invades, reducing soil pH from around 6 to 4. Such a change should impact the availability of nitrogen and may contribute to ice plant's negative effect on native species. A relative of highway ice plant that also alters soil chemistry is crystalline ice plant, Mesembryanthe- mum crystallinum. Nancy Vivrette has documented that it concentrates salts in its tissues and then deposits them on the soil surface annually as plants senesce. Enormous areas on the Channel Islands are covered with dead crys- talline ice plant and have high soil salinity. Attempts at revegetation by the National Park Service have largely been unsuccessful. At least six of the most invasive and damaging shrub species in California are nitrogen fixers, so called because of the symbiotic relationship they maintain with rhizobial bacteria. These bacteria are provided with carbon from the host plant, and in exchange provide the host plant with nitrogen. The most widespread of these nitrogen fixers are brooms: French broom (Genista monspessulana), Scotch broom (Cytisus scoparius), Portuguese broom (C. striatus), Spanish broom {Spartium junceum), and gorse broom (Ulex europaea). Together, these species have invaded plant communities from coastal southern California to Sierra Nevada foothills and northern redwood forests. In addition to having fast growth rates, high fecundity, and broad physiological tolerances, these nitrogen fixers have the potential to increase the total amount of nitrogen and the way in which nitrogen cycles through these ecosys- tems. Researchers in Oregon and England have shown that broom species can fix nitrogen at levels that are similar to other species that are well recognized as important sources of nitrogen in plant communities (e.g., bush lupine and alder). Nitrogen enrichment by these invaders, however, is unlikely to benefit native plants. Research has shown that increased nitrogen availability can reduce species diver- sity in cases where a dominant competitor is able to take over. This has been documented at Bodega Marine Re- serve, where bush lupine invades diverse native coastal prairie. After insect-induced die-off of adult lupines, nitrogen- rich patches under lupine are invaded by European grasses (mostly ripgut brome and Italian rye grass) and thistles to the detriment of native coastal prairie species. Thus, the nitrogen added to the system by lupine appears to be an important factor in creating a distinctly different commu- nity than was present before lupine invasion. The system is being studied intensively by reserve steward and biolo- gist John Maron, who is concerned that cycles of lupine germination, growth, and dieback are causing a decline in the native diversity of the coastal prairie ecosystem. Declining Biological Diversity It is easy to find evidence that introduced animals and pathogens have caused the extinction of native animals and plants. It is harder to argue that introduced plants by themselves do the same thing. However, in the State of California's Annual Report on the Status of Threatened and Endangered Plants and Animals, exotic plants are listed as contributing to the decline or endangerment of at least thirty-eight plant taxa. In reality, entire communities of native species, not just individual species, are threat- ened by the success of invaders. One need only to compare the abundance of native species in exotics-dominated grass- lands on sandstone-derived soils with the rich native grass- land communities immediately adjacent to them on ser- pentine-derived soils to realize that, at least on a local scale, biological diversity is threatened by introduced plants. In this case the harsh soil conditions on serpentine soils will not support dense stands of aggressive annual grasses such as wild oats (Avena spp.) and ripgut brome (Bromus diandrus). The diverse native flora of California reflects the complex geological and evolutionary history of this state. This history and the aesthetic and other values of our wildlands are currently threatened by a wide range of human activities and by the invasion of aggressive exotic species. While only ten percent of the invasive exotic species in California probably cause ecological damage in the sites they invade, the impacts of this group can be enormous. Invaders that are persistent and alter ecologi- cal processes such that it is difficult to maintain or return to a more native-dominated condition must be carefully watched and regulated. In those regions of the state that are most impacted by introduced species—from the Cen- tral Valley to the coast—we must use creative manage- ment, volunteer efforts, and education to retain our natu- ral heritage. Carla M. D 'Antonio and Karen Haubensak, Department of Inte- grative Biology, University of California, Berkeley, CA 94720 1 8 FREMONTIA VOLUME 26:4, OCTOBER 1998 THE GENETICS AND DEMOGRAPHY OF INVASIVE PLANT SPECIES by Kristina A. Schierenbeck, Kelly G. Gallagher, and Joanna N. Holt SCIENTISTS HAVE BEEN searching for generaliza- tions about the genetic and demographic character- istics of colonizing species since a seminal confer- ence, The Genetics of Colonizing Species, in 1965. One result of this conference, which was organized by Herbert Baker and G. Ledyard Stebbins, was to produce a list of traits common to colonizing species, now known as Baker's list. Non-native invasive species are colonizing species that are able to colonize habitats in which they did not evolve. Attempts to verify predictions about the genetic or demographic characteristics of non-native invasive spe- cies have been only moderately successful. For example, high levels of genetic variation, generalized pollination systems, large geographic distributions in the home range, and high rates of reproduction are often listed as traits common to invaders. However, some of the world's worst invaders are exceptions to these generalizations; cheatgrass (Bromus tectorum) has virtually no genetic variation, kudzu (Pueraria lobata) has a specialized pollination system, and Monterey pine (Pinus radiata), native to just a few populations in California and Baja California, has escaped from forest cultivation in Australia and New Zealand. Genetic Variability Patterns of variability within and among populations of species are generally studied by examining protein or DNA variation and quantitative genetic traits. These tech- niques examine patterns of variability within and among populations of species. Allozyme studies examine variation at locations on chromosomes (loci, singular locus) that provide the ge- netic code for proteins and their different forms (isozymes). Genetic variability can be assessed by measuring the pat- terns of occurrence of different genes (alleles or allozymes) for isozymes within and among populations. DNA tech- niques with potential application in examining variability at the population level are restriction fragment length polymorphisms (RFLPs), randomly amplified polymor- phic DNA (RAPDs), and microsatellite variation, but their use in the population genetics of invasive species has been limited. Here we focus on the use of isozyme data as a measure of genetic variability. Statistical measures of allozyme data include number of polymorphic loci, mean number of alleles per locus, and various levels of heterozygosity. A polymorphic locus is one in which there is more one than allele present and the most common allele is present less than ninety-nine percent of the time. Heterozygosity is the percentage of VOLUME 26:4, OCTOBER 1998 Pampas grass {Cortaderia selloana) extensively invades coastal dunes and coastal scrub along the California coast. Photographs by Kristina Schierenbeck. loci that have more than one allele in an average indi- vidual. In measures of heterozygosity the theoretical as- sumption is that more genetic variability will provide an organism with greater ability to respond to environmental change. However, as will become apparent, this assump- tion is not always valid. James Hamrick and his associates at the University of Georgia analyzed 113 invasive species and found patterns FREMONTIA 1 9 European beachgrass (Ammophila arenaria) was introduced to stabilize native dune plants. of genetic variability that support the following tenden- cies: widespread species have higher levels of variability than geographically limited species, outcrossing species with generalist pollination systems have higher levels of variability than species with specialized pollination sys- tems, and colonizing species have greater levels of vari- ability than species present in later successional stages. If we examine the data for invasive species in light of Baker's list and the trends found by Hamrick, the following ques- tion arises: do high values of variability and diversity correspond with an increased ability to invade? Low levels of genetic variability and diversity within and among populations have been observed in many inva- sive species. Suzanne Warwick at the Biosystematics Re- search Centre in Canada found no polymorphic loci in jimson weed {Datura stramonium), a common exotic in parts of the western United States. Similarly, Robert Allard at the University of California at Davis documented ge- netic uniformity in California populations of slender wild oat (Avena barbata). Low levels of genetic variation also have been found in four species of weedy foxtails (Setaria spp.) according to Rong-Lin Wang, Jonathan Wendel, and Jack Dekker at Iowa State University. Spencer Barrett and B. J. Richardson at the University 20 FREMONTIA :s in urban areas and has become widespread, crowding out and replacing of Toronto found that low genetic variability for wide- spread, aggressive exotics could be the result of a founder effect. This phenomenon results when a large population is produced from a few individuals; the only genetic varia- tion present in the resulting large population will be that which was present in the original, small founding popula- tion. Other possible explanations for very low levels of genetic variability are apomixis (producing seed without fertilization), cleistogamy (entirely self-pollinating due to closed flowers), and self-pollination due to incompatibil- ity with other individuals. A possible adaptive strategy of very low levels of variability is what Baker initially re- ferred to as "the general purpose genotype," in which the genotype of an organism allows it to occupy a wide variety of different habitats. These individuals are thus "general- ists" and have the capacity to survive and reproduce in a wide array of habitats. In contrast, abundant genetic variation has been noted in other studies of invasive species. We found that the South African Hottentot fig {Carpobrotus edulis) in Cali- fornia contains levels of polymorphic loci (forty-seven percent) and total heterozygosity (twenty-five percent) that are higher than expected for species with similar life history characteristics. Similar examples are black locust VOLUME 26:4, OCTOBER 1998 (Robinia pseudoacacia; total heterozygosity = thirty-four percent) and eucalyptus {Eucalyptus obliqua; total het- erozygosity = forty-nine percent). It is hypothesized that genetic polymorphisms could provide some invasive spe- cies with the genetic variability needed to survive and reproduce in a variety of habitats. Furthermore, genetic polymorphisms may be maintained by the heterogeneous nature of disturbed habitats where invasive species are often abundant. Whether genetic diversity in highly variable invasive species occurred before or following a colonization event is, in many cases, speculative. There are few studies that compare genetic variation between species in their home and introduced ranges. Steve Novak and Richard Mack at Washington State University found that cheatgrass had low levels of genetic variation in both its home and introduced ranges. Slightly lower values in the intro- duced range were hypothesized to be due to a genetic bottleneck. Baker suggested comparing the genetics of an intro- duced species with a sympatric (overlapping geographic distribution) native congener as a means of detecting ge- netic attributes that characterize invasive species. How- ever, a comparison of Japanese honeysuckle (Lonicera japonica), an invasive species in the southeastern United States, with the native coral honeysuckle (L. sempervirens) found little difference in genetic variation. Hybridization and introgression between native and non-native species has the potential to increase the detri- mental effects of an invasive non-native species or to swamp the gene pool of the native species. In California the native Suisun thistle (Cirsium hydrophilum var. hydrophilum) is now considered to be extinct due to intro- gressive hybridization with introduced Cirsium species. Mark Albert at UC Berkeley and Kelly Gallagher at Fresno State have provided morphological and allozyme evidence, respectively, for widespread hybridization and unidirec- tional introgression from the putative native sea fig (Carpobrotus chilensis) into the South African invader, Hottentot fig. The ecological and evolutionary implica- tions of hybridization between other native and non-native species still need experimental assessment. The study of quantitative genetics examines variation in polygenic traits or traits that are coded by many loci. There are few studies that provide a quantitative genetic measure of those characters considered most important to invasive ability (e.g. ovule or pollen production, seed set, and growth rate). In the classic work by Clausen, Keck, and Hiesey on yarrow (Achillea millefolium), it was estab- lished that plants grow better in their home environment than in other environments. Years of reciprocal transplant experiments established that there was a genetic basis for the decreased ability of yarrow to survive and reproduce outside the native range. The question remains, when alien species grow better than native members of a community, how does variation in quantitative genetic traits contribute to an increased ability to invade? Reciprocal transplant experiments such as those of Clausen, Keck, and Hiesey are necessary to control for different environmental condi- tions and predict which quantitative genetic traits increase survival and reproduction in different environments. Most environmental control for experiments on quantitative ge- netic variation has been in the greenhouse with plants not considered invasive. It remains to be seen whether we can quantify the genetic variation associated with an increased ability to invade and under what conditions invaders have higher fitness than other members of a community. Demographics of Weeds The demographic study of plant populations includes the examination of population size, density, distribution, growth rate, age structure, and number of breeding indi- viduals. Variation in any of these parameters can influence how the number of individuals in a population can change over time. Breeding system characteristics, such as self- fertilization and service by generalist pollinators, also warrant consideration here because they are inseparably tied to seed set. We have yet to fully comprehend how demographic and reproductive traits may favor success for an invasive species growing under specific environmental conditions and how they can influence the pattern of local and regional spread. In addition, there is little empirical evidence to support how specific demographic factors influence genetic diversity or how interspecific relation- ships within a community can influence the interaction between genetic and demographic factors. Understanding the properties of an invaded commu- Tamarisks (Tamarix ssp.) invade waterways, clogging them, depleting water supplies and crowding out native species. VOLUME 26:4, OCTOBER 1998 FREMONTIA 21 Ice plant (Carpobrotus edulis) creates thick carpets over sand, elimi- nating other species from dunes. nity is a large component of predicting the demographic change and geographic spread of a species invading that particular community. The initial rate of spread of many invaders is dependent upon the pattern (i.e., size, shape) and frequency of habitat disturbance. According to Fakrhi Bazzaz at Harvard University, species that require distur- bance to enter new habitats must have long-distance seed dispersal capabilities, a short life cycle (relative to indig- enous members of a community), and early reproductive maturity. Species that depend upon disturbance for establish- ment and spread in isolated patches have been termed guerrilla species by ecologists Mark Bertness and Aaron Ellison. For example, if disturbances create isolated patches of open habitat, an invader that is adept at spreading as many small, isolated populations will have an advantage over those species that need a large continuous area in order to survive and persist. A large seed set and an effective means of seed dispersal are important character- istics in the spread of guerrilla species. Invaders are more likely to become established after repeated introductions of large numbers of dispersed seeds than from a small number of seeds. An analysis of the spread of cheatgrass in the western U.S. by Richard Mack and his colleagues supported the hypothesis that population expansion and establishment are faster from several small areas of intro- duction than from one large area. In a patchy distribution an invader may benefit by having an increased ability to self-fertilize. Cheatgrass, which is cleistogamous, ensures seed production without the necessity of pollinators, and seed dispersal distance thus can be increased. A single mature plant of tamarisk (Tamarix spp.) can produce 500,000 seeds on a single mature plant, which has enabled this invader of riparian habitats to spread quickly through the southwestern U.S. 22 FREMONTiA Humans can be important agents in this long-distance dispersal of invasive species. Although the evidence is anecdotal, examples in California include many species introduced accidentally into the Central Valley from re- peated agricultural contamination such as slender wild oat, ripgut brome (Bromus diandrus), Johnson grass (Sor- ghum halepense), yellow star-thistle (Centaurea solsti- tialis), Russian thistle (Salsola spp.), and storksbill (Ero- dium botrys). Intentional introductions have brought us a variety of horticultural escapees from other continents, including Hottentot fig, fountain grass (Pennisetum seta- ceum), pyracantha (Pyracantha angustifolia), and coto- neaster {Cotoneaster franchetii). Bertness and Ellison referred to species that spread as an advancing front and not via long-range dispersal as phalanx species. European beachgrass (Ammophila are- naria) is an example of a phalanx species that has ad- vanced in waves from localized populations or rhizome fragments. Through aerial photography, Ann Buell and her colleagues at Humboldt State University have docu- mented that the distribution of European beachgrass in Humboldt County increased 574 percent in total area from 1939 to 1989. When a species is invading an area in which it did not evolve, factors such as an increased rate of seedling estab- lishment and fewer reproductive losses between flower- ing and seed set will increase its success. Few studies, however, compare the ecology and reproduction of a spe- cies in the new versus home range. Researchers in West- ern Australia found that reproductive losses of acacia (Acacia longifolia) were lower and the seedbank was fifty times larger in the invaded compared to the native habitat. Interaction between Genetics and Demography The establishment and spread of an invading species depend on the interaction of many of its characteristics. The intricate connections between genetics and demogra- phy can be most clearly illustrated with the example of an established, easily dispersed invasive species with a large seed set. The movement of seeds between populations increases the possibility of new successful genotypes be- ing added to a population and subsequently an increase in genetic variation. Introducing new genotypes through multiple introductions increases the possibility of a match of adaptive genotypes with the environment. In those species in which a high level of genetic variation is an advantage, genetic variation will be maintained or in- creased through multiple introductions. The persistence of a seedbank is characteristic of most invasive exotics and will assist continued reestablishment and spread. New gene combinations can arise through the union of offspring from persistent seedbanks and new introductions. The introduction of genetic variation could increase the growth, spread, and success of new popula- VOLUME 26:4, OCTOBER 1998 tions, but little research has been conducted in this area. In species where no outbreeding depression is apparent, (e.g., Hottentot fig) the introduction of new genotypes through pollen movement actually may provide adaptive genetic diversity in the invading population. Interestingly, Hottentot fig can also reproduce through apogamy (without fertiliza- tion); such breeding system flexibility clearly can be an advantage for invasive species. A single selfing individual can establish a new population, and genetic variability can be added later through outcrossing. This scenario provides the genotypic and phenotypic plasticity necessary for the invasion of a wide range of habitats. Experiments are currently being conducted by the authors to examine the roles of genetic variation and phenotypic plasticity in the spread of Carpobrotus species in California. Species interactions also can affect the genetics and demography of invasive species populations. An invasive species can alter ecological relationships in such a way that the invader is given an advantage over the native flora. When a new species establishes in a community, adjust- ments must be made among all native species in order to adapt to new selection pressures. Characteristics that may have been advantageous for a genotype of a particular native species prior to the introduction of an alien species may now be neutralized or even detrimental to the persis- tence of that resident. Peter Vitousek and his colleagues at Stanford University are studying this phenomenon in Ha- waii. Metrosideros polymorpha, a native early succes- sional species, historically has established on young vol- canic nitrogen-limited soils. Myricafaya, an invasive non- native that maintains a symbiotic relationship with nitro- gen-fixing bacteria, can also establish on these sites and, in doing so, increase the amount of available nitrogen in the soil. Although Metrosideros is a good competitor in nitrogen-limited soils, it has been replaced by Myrica in many areas because it is unable to compete under the new condition of increased soil nitrogen. Understanding those adaptations that provide the abil- ity to invade and the range of habitats over which a species might invade is key to developing more efficient and site-specific invasive species management. As cumu- latively illustrated by the preceding examples, invasive species are too diverse to be subjected to predictive gener- alities. Our understanding of the complexity of genetic characteristics, demographics, and species interactions of invaders can be increased only through increased experi- mentation. References Albert, M.E. 1995. Morphological variation and habitat asso- ciations within the Carpobrotus species complex in coastal California. M.A. thesis, University of California, Berkeley, CA. Baker, H.G. and G.L. Stebbins. 1965. The genetics of coloniz- ing species. Academic Press, London. Barrett, S.C.H. and B.J. Richardson. 1986. Genetic attributes of invading species, p. 21-33 in R.H. Groves and J.J. Burdon (eds.), Ecology of biological invasions. Cambridge Univer- sity Press, Melbourne, Australia. Bazzaz, F.A. 1986. Life history of colonizing plants: some demographic, genetic, and physiological features, p. 96- 110 in H.A. Mooney and J.A. Drake (eds.), Ecology of biological invasions of North America and Hawaii. Bertness, M.D. and A.M. Allison. 1987. Determinants of pattern in a New England salt marsh community. Ecologi- cal Monographs 57:129-47. Buell, A.C., A.J. Pickart and J.D. Stuart. 1995. Introduction history and invasion patterns of Ammophila arenaria on the North Coast of California. Conservation Biology 9:1587- 93. Burdon, J.J., R.H. Groves, and J.M. Cullen. 1981. The impact of biological control on the distribution and abundance of Chondrilla juncea in southeastern Australia. Journal of Applied Ecology 18:957-66. Clausen, J.D., D. Keck, and W.M. Hiesey. 1940. Experimen- tal studies on the nature of species. I. The effect of varied environments on western North American plants. Carnegie Institution of Washington Publ. 520. Washington, D.C., Carnegie Institution of Washington. Gallagher, K.G. 1995. Allozyme evidence for hybridization and introgression between and introduced and a putative native species of Carpobrotus (Aizoaceae). M.A. thesis, California State University, Fresno. Fresno, CA. Hamrick, J.L. and M.J.W. Godt. 1989. Allozyme diversity in plant species, p. 43-63 in A.H.D. Brown, M.T. Clegg, A.L. Kahler and B.S. Weir (eds.), Plant population genetics, breeding and genetic resources. Sinauer, Sunderland, MA. Mack, R.N. 1985. Invading plants: their potential contribution to population biology, p. 127-42 in J. White (ed.), Studies on plant demography: a festschrift for John L. Harper. Academic Press, London. Newsome, A.E. and I.R. Noble. 1986. Ecological and physi- ological characters of invading species, p. 1-20 in R.H. Groves and J.J. Burdon (eds.), Ecology of biological inva- sions. Cambridge University Press, Cambridge, England. Novak, S.J. and R.N. Mack. 1991. Genetic variation in Bromus tectorum (Poaceae): comparison between native and intro- duced populations. Heredity 71:167-78. Schierenbeck, K.A., J.L. Hamrick and R.N. Mack. 1995. Comparison of allozyme variability in a native and an introduced species of Lonicera. Heredity 75:1-9. Warwick, S.I. 1990. Allozyme and life history variation in five northwardly colonizing North American weed species. Plant Systematics and Evolution 169:41-54. Weiss, P.J. and S.J. Milton. 1984. Chrysanthemoides moni- lifera and Acacia longifolia in Australia and South Africa, p. 159-60 in B. Dell, (ed.), Proceedings of the 4th interna- tional conference on Mediterranean ecosystems. University of Western Australia, Nedlands. Joanna Holt, California State University, Fresno, Department of Biology, Fresno, CA 93705; Kelly Gallagher, New Mexico State University, Department of Biology, Las Cruces, New Mexico 88005; Kristina A. Schierenback, California State University, Chico, Department of Biology, Chico, CA 95926 VOLUME 26:4, OCTOBER 1998 FREMONTIA 23 §*¦: ''^KfrVV aii-.«*i '=***>: 5H $?"iS£Sii! iitS -C » %&*$»*%; v' "IS&il J|Pfc' ^f -ST; •swti v i#fc,fx'«••** The tree-of-heaven {Ailanthus altissima), shown growing on the right, invades riparian areas. It was brought to California by the Chinese working in the gold mine operations and is now commonly found along foothill streams and throughout the state. Photograph by Tom Dudley. EXOTIC PLANT INVASIONS IN CALIFORNIA RIPARIAN AREAS AND WETLANDS by Tom Dudley Although much OF California is considered arid or semi-arid, the state encompasses a tremendous variety of aquatic and riparian habitats, from small springs and vernal pools to large rivers, coastal marsh- lands, and natural and man-made lakes. These wetland ecosystems support a great diversity of native species and are focal habitats in the majority of protected natural areas of the state. Of the 217 state-listed rare, endangered, or threatened plant species, over one-third are associated with aquatic habitats, while fully half (thirty-seven) of threatened or endangered animal species depend upon declining wetlands. California's wetlands and the species that depend upon them are imperiled by development and destructive land use practices, pollution, and damming or diverting of natural waters. Less common in discussions of wetland protection is the role played by invasive exotic organisms in threaten- ing native species and altering the dynamics of aquatic ecosystems. Yet these present some of the most serious impediments to the conservation of aquatic resources. This article discusses plant invaders of riparian ecosys- tems across the state. Riparian communities are a product of hydrology and geomorphology more than of autoeco- logical adaptations to soil and climate conditions; thus they share traits and biota more closely across regions than do upland ecosystems. Streams or ponds of similar size 24 FREMONTIA VOLUME 26:4, OCTOBER 19 9 8 and topography, but in different regions, share many ripar- ian plant species, such as Acer macrophyllum, Alnus rhombifolia, and Phragmites communis. Likewise, many of the invasive species in California wetlands, such as Arundo donax, Tamarix ramosissima, or Rubus procerus, tend to be distributed widely within broad riparian habitat types. Riparian systems are linked by river flows in a way that terrestrial systems are not, such that invasions regu- larly occur as a consequence of downstream dispersal of seeds or plant parts. Many of the exotic plants that have established in riparian and aquatic habitats are discussed elsewhere in this special issue, so this is an overview of the subject. In response to the lack of general information on the status and composition of exotics in wetland ecosystems, we conducted a survey entitled Biological Invasions in Cali- fornia Wetlands, which is summarized here; the original report (Dudley, T. and B. Collins 1995, published by Pacific Institute for Studies in Development, Environ- ment, and Security, Oakland) is available from the author. We surveyed resource managers from forty-eight areas designated for wildlands protection in six bioregions of the state (North Coast, six areas; Central Coast, five areas; South Coast, thirteen areas; Central Valley, four areas; Sierra Nevada, thirteen areas; and Desert, seven areas). The survey included national forests, national parks, sea shores, and recreational areas; federal wildlife refuges; state parks; natural reserves of the University of Califor- nia; and preserves of The Nature Conservancy. We incor- porated information on impacts of non-native plants (and animals, which will not be discussed here) to protected ecosystems and their control and costs. Our intent was to compile a comprehensive view of the species that are considered problems or potential problems by those ac- tively involved in wildland management. Fifty-seven plant genera were reported by managers to be problematic in aquatic and riparian habitats in their reserves; others that were not reported were included, yielding a total of seventy-two problem genera. Some are native to California, but may have spread beyond natural boundaries or achieved nuisance densities. A majority are a concern in two or more reserves, and the numbers of moderate to high threat taxa in each bioregion ranged from nine in the Central Valley to twenty-eight in the Central Coast (South Coast = twenty-six, North Coast = fourteen, Sierra Nevada = ten, Deserts = fourteen). Differences between regions may have been in part due to the different numbers of areas surveyed, as well as to different levels of botanical expertise on the part of man- agers queried. Still, in the San Joaquin-Sacramento val- leys agricultural development or intensively managed wild- life habitat often precludes the presence of native plant communities to invade, while in high-elevation sites (greater than 6,000 feet) only Canadian thistle (Cirsium arvense) was mentioned as a management concern where it invades wet mountain meadows in the Sierra Nevada. Physiological stress at high elevations, as well as in desert regions, presumably restricts the number of invader spe- cies to those adapted to establishment in these harsh envi- ronments. Invasive plants are certainly not equally problematic. Of those listed in the accompanying table, we considered sixteen to be serious problems with documented threats to native species or ecosystems. Over half are also listed by the California Exotic Pest Plant Council as top priorities (Randall, this issue), and examining that list we find that fully one-third of the CalEPPC A-list plants are associated with wetlands of some sort. In general, these are plants that are widespread and form dense, often nearly mono- specific, stands that crowd out native species in riparian areas. Some are trees, such as salt cedar {Tamarix spp.), tree-of-heaven {Ailanthus altissima), or blue gum (Euca- lyptus globulus). Salt cedar has been discussed elsewhere (Kemp, Pitcairn, this issue), but regional descriptions miss the fact that tamarisk is found throughout the state now, not just southern desert areas, with dense populations established in some Sacramento Valley streams (e.g., Cache Creek near Sacramento), the South Coast (e.g., Santa Clara River), and in the Owens Valley (also Oregon, Idaho, and Montana). It continues to expand further north than many assumed it could survive. Ailanthus, which is difficult to control because of its extensive root sprouting, has also become established in a surprising variety of sites, now found beyond the Sierra foothills to include desert areas such as Anza-Borrego State Park and Butterbredt Springs, an important Audubon Society-managed site near Red Rocks State Park. Ailanthus is also known to produce allelopathic chemicals that inhibit germination by other seeds, but not its own. Shrubby and reedy plants such as giant reed (Arundo donax) and perennial peppergrass (Lepidium latifolium), likewise form dense thickets in riparian zones and wetland margins outside their previously assumed boundaries. For example, extensive Arundo thickets are now present along the Russian and Napa rivers and in numerous streams in the Sacramento Valley, as well as in the better known, massive infestations in coastal southern California. Pep- perweed is found in coastal estuaries (especially San Fran- cisco Bay/Delta) as well as in Great Basin seasonal wet- lands. Recruitment by native species is reduced in these monocultural stands, but further research is needed to evaluate mechanisms of native species displacement. It is clear that many of these large-statured weeds provide poor-quality habitat for native wildlife species, and we have documented greater than fifty percent reductions in abundance and diversity of insects on giant reed as com- pared to native cottonwood/willow vegetation. In turn, insects are essential to making riparian woodlands critical habitat for neotropical migrant songbirds. Fire and flood risks are also increased by these thicket- forming species. Salt cedar in Anza-Borrego State Park provided fuel that allowed wildfire to destroy mesquite VOLUME 26:4, OCTOBER 1998 FREMONTIA 25 Problem Exotic Plants Reported in California Wetlands TAXON COMMON NAME THREAT* REGION** Acacia spp. (esp. A. melanoxylori) wattle, acacia 2 SC Ageratina (=Eupatorium) adenophora eupatory 1 sccc Agrostis stolonifera creeping bentgrass 2 sc,cc Ailanthus altissima tree-of-heaven 2 CC,NC,SN,D Ammophila arenaria European beachgrass 1 SC,CC,NC Andropogon virginicus broomsedge bluestem 4 (J) Anthriscus caucalis bur chervil 3 CC,SN Aponogeton distachyon Cape pondweed 4 (J) Arundo donax giant reed 1 SC,CC,NC,CV,D Berula erecta (N) cutleaf water parsnip 2,t CC,SN Cardaria draba hoary cress 2 CC,(E) C. chalapense, C. pubescens lens-pod, white-top 4 CV,(E,J) Carpobrotus edulis ice plant, Hottentot fig 1 SC,CC,NC Catharanthus roseus Madagascar periwinkle 4 D,(J) Ceratophyllum demersum (N) aquatic hornwort 4 D Cirsium arvense Canada thistle 2 SN,D C. vulgare bull thistle 2 CC,SN Conium maculatum poison hemlock 2,t SC,CC,NC,D Cortaderia jubata Pampas grass 2 SC,CC Cotula coronopifolia brass buttons 3 SC,CC,NC Cynara cardunculus artichoke thistle 2 sccccv Cynodon dactylon Bermuda grass 2 SC,D Cytisus scoparius Scotch broom 1 SC,CC,NC,SN Datisca glomerata Durango root 4,t (J) Delairia odorata {-Senecio mikanioides) Cape ivy (German ivy) 1 SC,CC Eichhornia crassipes water hyacinth 1 NC,CV Egeria densa Brazilian waterweed 1 CV Eleagnus angustifolia Russian olive 1 D,(E) Elodea canadensis (N) common waterweed 4 SN Eucalyptus globulus blue gum 2 SC,CC Ficus carica edible fig 4 CV Foeniculum vulgare fennel 2 sccc Gunnera tinctoria gunnera 4 CC,(J) Hedera helix. H. canadensis English ivy, Algerian ivy 2,t sccc Hippurus vulgaris (N) mare's tail 4 sccc Hydrilla verticillata hydrilla 1 SC,NC,CV,D Lactuca serriola prickly or wild lettuce 4,t SC Lepidium latifolium perennial pepperweed 1 CC,NC,CV,D Lythrum salicaria purple loosestrife 1 NC,SN,D L. hyssopifolium, L. spp. loosestrife 4 CC,NC,(J) Melilotus alba white sweet clover 3 C,CC,NC Mentha pulegium pennyroyal 4,t CC,(E) Mesembryanthemum crystallinum crystalline ice plant 1 SC Myoporum laetum myoporum 2 sccc Myriophyllum spicatum Eurasian milfoil 1 CV M. aquaticum parrot's feather 4 (J) 26 FREMONTIA VOLUME 26:4, OCTOBER 1998 TAXON COMMON NAME threat* REGION** Nerium oleander oleander -i.i D.(i-:i Nicotiana glauca live KiKiicn 2.1 sc.ee. d Ottelia alismoides ollelia 4 C'\.(.li Parentucellia viscosa paivnuu-cilia -1 ("CNCil-l) Phalaris aquatica llanlinj> prass 1 Sf.CC Phoenix dactylifera dale palm ;, 1 ).(.¦(.'¦• Phyla (=Lippia) nodiflora lippia ¦i nil Phragmites australis (=communis) (N) I'oiniiKin reed \ SN.CV.I.) Piptatherum miliaceum smilo yra-s -> SC.ik) Pistia stratiotes w ;iIlt lettuce ¦> 1.1) Poa pratensis Kentucky hlik'jii'ass ~i CC.NC.SX.I) Ricinus communis castor beau 2.1 sc.tc Ranunculus muricatus hulleicup 1 1.1) R. aquatilis var. aquatilis water hulk'ivup ;, sc Robinia pseudoacacia lilaek lodisl -» CC.NC.SN Rorippa nasturtium-aquaticum watercress ; sc.ee Rubus procerus (=R. discolor) Himalayan blackberry T SC.CC.NC.SN Salix alba wink' willow ¦1 SN Salsola tragus, S. soda, S. spp. Russian ihisilc. luinhlcwecd -t ee.cv.n Schinus molle Peruvian pcppcrliee "» sc S. terebinthifolius lira/Minn pcppcilicc 4 se.ee Scirpus spp. (incl. S. setaceous, S. mucronatus, S. tuberosa) bulrush, alkali luilrush ¦> NC.SN.I; Spartina alterniflora liiiropean cord sirass i ce S. densiflora, S. patens cord grass i ce Tamarix ramosissima (=T. chinensis, T. gallica, T. parviflora, etc.) salt cedar, tamarisk i se.cc.c v.sN.n T. aphylla allk-l .V-l i) Tropaeolum majus trnrden iiasiiirlium ;, sc Verbascum spp. mullein .1 SN.l) Veronica spp. (incl. V. anagallis -aquatica, V. beccabunga, V. catenatd) speedwell, hmokliine ¦ 1 sen Vinca major periwinkle T se.ee Washingtoniaftlifera (N) Ian palm ¦1 sc.cv.n Xanthium spinosum, X. strumarium (N?) cocklchur .s sc.nc.cv.sn Zantedeschia aethiopica ealla lily 1 1 ee Distributions in many cases are broader than suggested n rjpmiin;:. ;iiul in cases where no w ioii i- ei\en plain.- are included based on information from other sources (J = Jepson Manual, E - "aliloruia lixmic IVst I'lani Council li-u (Ni - \alive in (' ililoruia. pos-ibl\ limn another region of the state. *Threat Levels: 1 = Serious documented threat to sensitive species onvoswenis 2 = Moderate threat to native species or ecosysten -. nol lo special sialiis spp., ul poisonous 3 = Benign, low-risk exotic species, or too common rmcoMrol unay In- problem in ccriain area-1 4 = Potential threats undocumented, some related o problem e\oiie -pciics t = Toxic to livestock or humans **Regions: SC = South Coast, CC = Central Coast, NC - \oiih Cnasi.CV -Cenlral Valley. SN - Siena Nevada. I>. - IVscrlsl VOLUME 26:4, OCTOBER 1998 FREMONTIA 2 7 bosque that would otherwise have resisted ignition. De- structive fires fueled by fifteen-foot-high giant reed have occurred in the Santa Ana River of southern California and the Russian River further north. Such continuous, flammable vegetation is now changing riparian corridors from barriers to the spread of fires into wicks that carry fire up and downstream, into highway bridges or crowns of native, fire-sensitive riparian trees. Also, Arundo biom- ass uprooted by stormflows backs up behind bridges, and is increasingly seen as a major concern by flood control agencies throughout the state. Another group of smaller-statured, sometimes vine- like invaders form dense understory growth in riparian zones of streams and rivers. Himalayan blackberry (Ru- bus procerus) has become ubiquitous throughout Califor- nia, and besides making access to these areas difficult, seems to displace natives. Ivy has more recently become a similar concern, as escaped English ivy (Hedera helix) and Algerian ivy (H. canariensis) cover extensive riparian slopes in many coastal watersheds. Ivy is unusable by most herbivores, resulting in a depauparate wildlife as- semblage, and is considered by some to give good cover for non-native black and Norway rats. Two other shrubby species that are less known but increasing in south and central coast stream environments are Myoporum laetum and Eupatorium (= Ageratina) adenophora, the latter noted to be displacing native Oxalis and Stachys species in red- wood groves. A true vine, Cape ivy (Delairia odorata; previously called German ivy, Senecio mikanioides) spreads from the ground high into trees in many coastal riparian areas, often draping trees as thickly as does the much-hated kudzu (Pueraria lobata) in the southeast U.S. Not only does it shade out native plants, but Cape ivy apparently produces chemicals that can inhibit herbivores from reducing its abundance. Many riparian invaders are also toxic to humans and/or livestock, increasing the level of concern about myoporum in shady habitats, and sun- and moisture-loving pests such as castor bean (Ricinus communis), poison hemlock (Co- nium maculatum), tree tobacco (Nicotiana glauca), and oleander (Nerium oleander), which is increasingly being seen away from widespread planting sites. Castor bean is finally being perceived as a problem, and is the object of eradication efforts, at least in San Luis Obispo Creek. Several invasive plants form dense mats in otherwise open water. Water hyacinth (Eichhornia crassipes) in the Sacramento/San Joaquin Delta is costing hundreds of thou- sands of dollars annually to control (mechanically and with introduced weevils as biological control agents). Occur- ring with floating hyacinth and contributing to huge biom- ass accumulations in the Delta is a rooted exotic, Brazilian waterweed (Egeria densa). With little hope of eradication, managers try to reduce the annual growth of both plants to tolerable levels. It seems that the true aquatic plants are better known than many mesic-zone terrestrials, based on extremely damaging epidemics elsewhere, especially in the eastern states, and this has helped concentrate attention on some species early in an infestation. For example, hydrilla (Hydrilla verticillata) and purple loosestrife (Lythrum salicaria) have been found several times in the Sacramento River system, and loosestrife around Lake Tahoe and Tule Lake, but prompt attention by water man- agers has so far kept these species from establishing in protected wetlands. Such early detection is particularly critical because uncommon species in aquatic systems are often more difficult to detect than upland species since sites are relatively inaccessible and visibility, especially underwater, is poor. Once established, aquatic and riparian species may often be harder to control because the aquatic medium rapidly transports propagules to a wide area. Even in salt marsh, invasive plants are becoming major problems. In particular, smooth cord grass (Spartina alterniflora) is expanding its range in San Francisco Bay, where it competes with the more restricted native cord grass, S. foliosa. It invades tidal mudflats upon which numerous wading birds depend, and changes them into dense grass beds. Based on experiences in Washington State, this plant could probably establish in many other coastal estuaries of California if propagules reach them. Two other cord grass species, S. densiflora and S. patens, are also present in the Bay but at low densities so far. S. densiflora was transplanted from Humboldt Bay, where it is still found and was mistakenly thought to be a subspe- cies of S. foliosa, while the small population of S. alter- niflora appears to have been eradicated from Humboldt Bay. Along with hoary cress (Cardaria draba), Russian thistle (Salsola tragus), and perennial pepperweed, these species can cover most of many salt marsh tidal zones. A novel invader that we are seeing in a number of high salt marsh sites around the Bay is the California palm (Wash- ingtonia filifera). While native to the state, it is hardly an appropriate species (along with an unidentified date-type palm) for coastal wetlands. This last point further highlights the need to identify potential invaders early, while they are novelties instead of once they have become epidemic, and especially to note species establishing over broad areas or a wide variety of habitats, such as: Ailanthus (which we have also observed increasing in the Columbia River Gorge), Hedera (both the Algerian and the English ivies are too often considered innocuous interlopers from adjacent horticultural areas), edible fig (Ficus carica, which The Nature Conservancy has been eradicating from the Cosumnes River Preserve), Eupatorium, Myoporum, Russian olive (Eleagnus angusti- folia, not noted in the survey but known as a pest in many parts of the West and still given away by some federal wildlife managers), or Harding grass (Phalaris aquatica) and Bermuda grass (Cynodon dactylon), which can form dense mats directly in the stream channel. Many of these species originally established through human activity, and anthropogenic disturbance of soils and natural vegetation has often been considered as a 28 FREMONTIA VOLUME 26:4, OCTOBER 1998 Weedy European beachgrass and ice plant are commonly found growing together along coastal dunes. Photograph by Carla D'Antonio. factor promoting invasion by exotic plants, but a some- what different relationship may be important in riparian ecosystems. Most aquatic and riparian species are adapted to the volatile nature of river flows in California, and survive natural floods and droughts by various strategies of resistance to or resilience in recovering from stresses. However, modification of the natural disturbance regimes through water management appears to be providing more desirable habitats for many accidentally and intentionally introduced species. This is particularly the case for exotic animals, in that we have created reduced and more consis- tent flow regimes that favor species such as bullfrogs, centrarchids (bass, bluegill, etc.), catfish, Asian clams, and many others that are naturally associated with warmer, siltier, and slower waters. Many exotic plant species do thrive on the open sub- strates created by natural floods, as researchers have shown in many regions, but these often are pioneers that tend to drop out during riparian community succession (and most are not included in the table). As with animals, the disrup- tion of natural disturbance regimes may also favor many of the more serious invasive plants, such as tamarisk, pepperweed, and loosestrife, that seemingly explode un- der reduced flooding regimes. In unregulated streams in both Anza-Borrego State Park and Arizona we have docu- mented greater mortality to tamarisk than to native ripar- ian trees as a consequence of scouring floods, and it appears that relatively frequent flooding could keep some pest densities to a tolerable level. Some exotic species even seem to interact with each other, synergistically facilitating the success of each other, often through biological modification of disturbance re- gimes, in a sort of invasion complex. For example, we've seen that Bermuda grass (Cynodon dactylon) carpeting the bottom of an unregulated desert stream allowed numerous species of exotic and native aquatic macrophytes growing within its tough mat to survive flooding, thereby short- circuiting succession and allowing plants to quickly rees- tablish dominance in an otherwise sandy habitat; in turn, this favored non-native fish (e.g., fathead minnow) over declining native fishes. Although further research is needed on the relationship between disturbance and invader success in many habitats, it is important to keep in mind that to protect native species, we should direct management toward maintain- ing natural disturbance regimes (especially flood and drought) that fostered the evolution of these species in the first place. This has been attempted in some locations, such as in the Grand Canyon, where sediment and tama- risk have built up as a consequence of diminished flows, through controlled flood releases of water to simulate natural scouring. Despite mixed results, more manage- ment strategies of this nature, including restoration of tidal flows and salinity changes in estuarine wetlands, as with restored fire cycles in some terrestrial habitats, should be considered rather than trying to protect native species by forced natural ecosystem stasis. Tom Dudley, Department of Integrative Biology, UC Berkeley, CA 94720-3140 VOLUME 26:4, OCTOBER 199! FREMONTIA 29 ¦>™.y . *fW' ¦(* ". '¦// ": W It . 1. - 1. i ~M'[ r>. w- * ¦ ¦ ¦ '"¦• *r» !¦ 'k. V i '-IP - . i' ' ::'.¥.: $' £* /" By the late 1800s, red brome (Bromus madritensis subsp. rubens), first collected by Parish in San Bernardino County, had spread throughout the entire Great Basin. Photographs by Matt Brooks. EXOTIC SPECIES OF CALIFORNIA DESERTS by Paul R. Kemp and Matthew L. Brooks The number OF exotic species that have become established in the Mojave and Sonoran (Colorado) deserts is rather small in comparison to other re- gions of California. Only about twenty-five species of exotic plants are widespread (or spreading) into natural habitats of the warm deserts of southeastern California. Nevertheless, several of these species appear to be in- creasing in abundance as well as range, and may bring about changes in the structure and functioning of the desert plant communities. Principal Exotic Species: Eurasian Annuals The number of exotic species reported in local or re- gional floras of the Mojave and Sonoran desert areas of California (or adjacent southwestern Nevada or western Arizona) varies from about five to twelve percent of the total flora. These percentages typically include some ex- otic species collected from non-desert habitats within the desert region, such as mountains, riparian, or other natural wetlands, agricultural areas subject to past or present irri- gation and fertilization, or disturbed areas subject to run- off (e.g., roadsides). Thus, only a restricted group of re- corded exotic species can be considered as having become established and spread into natural desert habitats. Our assessment as to which species make up this group is based upon species distributions in local floras as well as our own observations in the Mojave and Sonoran deserts. Within this group of exotic species there are some differ- ences in regional distributions and, perhaps more impor- tant, there are differences in microhabitat distributions, which may reflect how successful some species have been, or will be, at colonizing particular desert habitats. For 30 FREMONTIA VOLUME 26:4, OCTOBER 1998 example, some exotic species are found in wide variety of desert habitats (e.g., under shrub canopies, in open areas, in washes), whereas others may be more restricted to certain habitats. A few species are still confined largely to highly disturbed areas within the desert, but their abun- dance or establishment in other arid habitats suggests that they should be considered potential invaders of some natural desert habitats in California. Most of the exotic species that have become estab- lished in California's desert habitats are of Eurasian (espe- cially Mediterranean) origin. Three families predominate: Poaceae, Chenopodiaceae, and Brassicaceae. All except Australian saltbush {Atriplex semibaccata) are annuals, and for the most part all are found throughout southern California, often in dry, disturbed habitats. Thus, for the most part, the exotic species of the California deserts appear to represent a subset of California's Eurasian exot- ics that were pre-adapted to the driest habitats associated with their Mediterranean climate origins. Lack of Perennial Exotics Riparian and various other desert areas with supple- mental water (from high water tables or runoff from roads) have been invaded by a number of exotic woody and herbaceous perennial species. In some areas, species such as tamarisk (Tamarix spp.), giant reed (Arundo donax), or Bermuda grass (Cynodon dactylon) have become the domi- nant species, resulting in major impacts upon the commu- nity. However, aside from these areas, perennial exotic species have not been successful in natural habitats of California's warm deserts. This contrasts with some desert areas elsewhere. In the eastern Sonoran Desert of Arizona, several exotic perennial grass species have become abun- dant following their introduction. In the northern Chihuahuan desert of Texas and New Mexico native shrubs such as mesquite and creosote bush have invaded some areas that were previously dominated by native grasses. The lack of exotic perennials in California's deserts may be related to several factors. The exotic perennial grasses that have invaded the Sonoran Desert of Arizona are warm-season grasses that utilize summer rainfall, which greatly diminishes across the Sonoran Desert from eastern Arizona into California. The lack of exotic shrub species in the California deserts may be partly related to the difficulty of shrub establishment in the desert. Most desert shrubs establish only episodically when a sequence of years with favorable moisture allows seedlings to generate sufficient root systems to survive normal drought. This requires a continuous supply of seeds to a region in order to support continuous attempts at establishment. Invasion of the arid grasslands in the Chihuahuan desert by woody perennials has been accomplished through periodically moving fronts adjacent to seed-source shrublands. So far in California, apparently no exotic shrub species has the Close-up of red brome. combination of drought tolerance and abundance of seed sources sufficient to promote establishment in the desert. An additional factor that may favor exotic annuals over perennials in California deserts is that the principal source of exotics for these winter-rainfall deserts has been the Mediterranean region, which has few woody species.as potentially invasive as its annuals. Historic Establishment of Exotics Most exotic species apparently first entered the Cali- fornia deserts during the middle to latter part of the nine- teenth century, following the Gold Rush of 1849. Some examples include: red brome {Bromus madritensis ssp. rubens), which Parish collected from San Bernardino County in 1889, and labeled it as a recent introduction); cheatgrass (B. tectorum), which spread relatively rapidly throughout the Great Basin in the late 1800s; and Russian thistle (Salsola tragus), which was first found in Califor- VOLUME 26:4, OCTOBER 1998 FREMONTIA 31 nia near Lancaster about 1895. Three others, red-stem filaree {Erodium cicutarium), pigweed (Chenopodium mu- rale), and barley (Hordeum murinum), probably entered the deserts well before this period, as they were estab- lished in cismontane California prior to 1800. Following their introduction, most exotics did not be- come abundant and widespread in California deserts until after about 1930. For example, Parish noted that in a 1912- 1913 survey there were no exotic species found estab- lished in the Imperial Valley. However, shortly thereafter several exotic species became relatively abundant, includ- ing cheatgrass, red brome, chickweed (Mollugo cerviana), and Russian thistle. Red brome was collected at several locations in the Mojave Desert and Great Basin from 1907 to 1917, but not until 1930s and 1940s was it labeled as common or abundant from collections throughout the west- ern Mojave and Sonoran deserts, and it was not common in the eastern Mojave Desert (Nevada) until after 1950. According to Oscar Clarke, U.C. Riverside botanist, Schismus species seemed to appear overnight throughout the warm deserts sometime during the 1940s. Burgess and co-workers outlined five factors that they consider important in fostering establishment and/or spread of exotics into the Sonoran Desert: favorable climate (simi- lar to the exotics' native habitat); prior occurrence in regions with intensive pastoralism; livestock grazing of the habitat; favorable reproductive biology; and minimal integration into food webs. To this list we would add habitat disturbance. Habitat disturbances, including graz- ing, have played several key roles historically in promot- ing establishment and spread of exotics into California deserts. Most exotics first appeared in the desert following the boom in cattle and sheep grazing that accompanied the California Gold Rush of 1849. Overstocking of desert ranges probably occurred within two decades following the start of the Gold Rush and resulted in enormous reduc- tion of native grass cover and damage to the cryptogamic desert crusts, both of which had prevented seed germina- tion and seedling establishment of at least some exotic species. An additional disturbance that was important his- torically to the establishment of exotics in the California deserts was road and railroad construction. This not only provided a huge network of interconnected disturbed sites, but also the means along which seeds of such species as puncture vine (Tribulus terrestris) and Russian thistle entered from outside regions. Roadsides also offer refuge (via runoff) for exotics that might otherwise be eliminated during the normal strings of drought years encountered in the desert. The importance of disturbance to many exotic species in the desert is demonstrated by some subtle differences in their distributions relative to native annual species. Desert areas that have been denuded of vegetation are colonized initially by mostly exotic species, such as red brome, red- stem filaree, and Russian thistle. Many exotic species, such as ripgut brome (Bromus diandrus), Russian thistle, and puncture vine, seem to be largely excluded from pris- tine desert habitats, perhaps by competition with the native annuals or shrubs, or perhaps by the inability of their seeds to germinate on crusted desert soils. However, it seems that some other exotic species are able to enter pristine desert habitats as readily as, or more than, any native annual. This group of exotics includes those whose native distribution was originally desert (e.g, schismus), as well as those with a long history as an exotic in semi-arid regions of North America (e.g, red-stem filaree, red brome). Current Status of Exotics in the Desert Biologists studying public lands in California deserts indicate that exotic species appear to be increasing in many areas. In the northeastern Mojave Desert (Nevada test site), Hunter has documented marked increases in red brome and cheatgrass over the period from 1975 to 1988. In the Arizona Sonoran Desert, Burgess and co-workers have found that exotic species have continued to invade pristine habitats and have increased in abundance during the last couple of decades. Brooks has found that exotic species (primarily red brome, schismus, and filaree) now account for the majority of total annual plant biomass in many regions of the California Mojave Desert. Explanations for causes of recent pulses of exotic ex- pansion in the desert may require looking beyond those historical factors that fostered initial establishments. In the examples cited above, exotic species have greatly in- creased in relatively undisturbed habitats. Thus, distur- bance no longer appears to be such an important prerequi- site. Hunter suggests that the recent increases in red brome may be related to some specific biological attributes, or possibly to weather (a sequence of years of abundant rainfall). The biological explanations that Hunter offers, fibrous rooting and surface shading by the exotics, would apparently become effective in favoring exotics over na- tive species only after exotic species achieved a certain threshold density. Fluctuations in weather could conceiv- ably alter growth and survival of any plant species, but it is unclear how these fluctuations might favor exotic species over native species. The suggestions offered by Hunter for increases in exotics are essentially specific examples from two general categories of factors—extrinsic and intrinsic. Among ex- trinsic factors that may warrant study for effects on exotic distributions include factors associated with human-in- duced atmospheric changes: rising atmospheric carbon dioxide (C02) and rising levels of atmospheric pollutants. Researchers have found that some weedy exotics respond very strongly to increasing CO,. They suggest that in- creasing CO, may lead to increased invasiveness and perhaps expanded ranges of exotics. For example, Smith and co-workers found that red brome had greater growth at elevated CO, than two native Great Basin perennial 32 FREMONTIA VOLUME 26:4, OCTOBER 19 98 Most Commonly Encountered Exotic Plant Species in California Deserts Initial Introduction Current Distribution Species Family Date Location Origin Desert Range Habitat Abundance Bromus arenarius Poaceae 1905 San Bern. Co Australia Mojave/Sonoran disturbed + B. diandrus Poaceae 1862 San Francisco Europe W Moj./W Son. disturbed + B. madritensis rubens Poaceae 1880s Plumas Co Europe all CA deserts natural +++ B. tectorum Poaceae >1889 Eurasia G. Basin/Mojave natural +++ B. trinii Poaceae Chile all CA deserts natural ++ Hordeum murinum Poaceae <1775 Spanish missions Europe all CA deserts disturbed/natural + Schismus barbatus, S. arabicus Poaceae 1930s Fresno Co Eurasia Mojave/Sonoran natural +++ Sonchus oleraceus, S. asper? Asteraceae <1825 Europe all CA deserts + Brassica tournefortii Brassicaceae 1930s Colo. River V N Africa Sonoran/Mojave disturbed/natural ++ Descurania sophia Brassicaceae Eurasia G. Basin/Mojave disturbed/natural ++ Sisymbrium altissimum Brassicaceae 1910s Europe G. Basin/Mojave disturbed/natural + S. irio Brassicaceae 1910s Europe all CA deserts disturbed/natural + Atriplex semibaccata Chenopodiaceae Australia all saline areas saline/alkaline locally abundant Bassia hyssopifolia Chenopodiaceae 1920s San Joaquin V Eurasia G. Basin/Mojave saline/alkaline locally abundant Chenopodium murale Chenopodiaceae <1775 Europe all CA deserts disturbed + Halogeton glomeratus Chenopodiaceaf G. Basin/Mojave saline/alkaline locally abundant Salsola paulsenii Chenopodiaceae Eurasia G. Basin/Mojave disturbed/natural ++ S. tragus Chenopodiaceae 1895 Lancaster Eurasia all CA deserts disturbed ++ Erodium cicutarium Geraniaceae <1775 Eurasia all CA deserts natural +++ Malva parviflora Malvaceae <1825 Europe all CA deserts disturbed ++ Mollugo cerviana, M. verticillatal Molluginaeeae 1929 San Bern. Co Eurasia/ C&SArn Mojave/Sonoran natural ++ Portulaca oleracea Portulacaceae 1850s Colo. River V Europe all CA deserts disturbed + Tribulus terrestris Zygophyllaceae 1902 Los Angeles Eurasia all CA deserts disturbed + Compiled from Frenkel, Parish, Robbins, and Munz. grasses. Improved water-use efficiency brought about by increased CO, might also partially explain the gradual increase of cheatgrass into drier, lower-elevation sites in the Mojave Desert. A number of atmospheric pollutants could impact desert plants either through stimulation or inhibition of growth. Most notable among the potential stimulants is nitrogen (N). High rates of N deposition have been suggested as a means of facilitating increases of exotics in native com- munities. Little is known about rates and distribution of N deposition in California desert areas, but some areas "down- wind" of large metropolitan areas can be expected to be receiving large inputs of N. Recent studies by Brooks in desert communities have shown that exotic annual species can be much more responsive (increased biomass/plant) to low-level N amendments than are native annual species. The second group of factors (intrinsic) that could influ- ence the distribution of exotic species are those brought about by the increased presence of exotic species them- selves. Invading exotics are known to compete with native Sisymbrium irio is one of the exotics that are increasing in California deserts, perhaps in response to human caused atmospheric changes. VOLUME 26:4, OCTOBER 1998 FREMONTIA 33 species in plant communities of mesic or semi-arid habi- tats. In arid plant communities, competitive interactions are less well documented. However, Brooks found that removal of red brome and Schismus seedlings increased density, biomass, and diversity of native annual plants at several study sites in the Mojave Desert, and Hunter sug- gests that the dense cover of red brome almost certainly affects native annuals in the eastern Mojave. Some exotic annuals (e.g, red brome, Schismus) appear to be more regularly abundant from year to year than the native spe- cies, with numerous small plants setting seed in all but the most extreme years. Exotic species may have less strict seed dormancy and/or density dependent germination re- sponses. These situations could lead to fundamental changes in the high between-year variation in production and soil seedbanks that has governed much of the interac- tions among annual species as well as other trophic levels dependent upon annual plants and their seeds. A significant intrinsic factor that may develop in desert communities with abundant exotic species is fire. Produc- tion of large amounts of biomass by exotic species may increase the ability of the community to carry a fire. Frequent fires may remove non-resistant native perennials and foster perpetuation of annual exotics. This situation has been a key factor in the spread of cheatgrass through- out the Great Basin. A similar situation may be developing in some portions of the Mojave and Sonoran deserts where red brome is prevalent. Fires are more frequent where biomass of red brome is high, and fires have become more frequent since the invasion of red brome into this desert region. What's Ahead At present we have an incomplete understanding of the factors that are important in controlling the establishment and spread of exotics in desert habitats. We have even less understanding about the potential impacts of these exotic species upon native plants and communities. More basic research is needed to document changes in distributions of exotics in the desert, both spatially and temporally; to correlate distributions of exotics with various extrinsic and intrinsic factors; to determine how various extrinsic and intrinsic factors influence growth and distribution of exotics in relation to native species; and to determine how abundance of various exotic species affects plant commu- nity structure and function. In the meantime there is good reason to be concerned that exotic species will continue to increase in numbers and biomass in desert plant communi- ties. Increases in exotics could be expected to have signifi- cant impacts upon the native ephemeral species (their most direct competitors), and with the addition of wide- spread fire, could alter the general nature of desert ecosys- tems, much as they have in the Great Basin shrub-steppe or Central Valley grasslands. References Beatley, J.C. 1966. Ecological status of introduced brome grasses (Bromus spp.) in desert vegetation of southern Ne- vada. Ecology 47:548-54. Billings, W.D. 1990. Bromus tectorum, a biotic cause of ecosystem impoverishment in the Great Basin. In G.M. Woodwell (ed.), The Earth in Transition: Patterns and Pro- cesses of Biotic Impoverishment. Cambridge Univ. Press, Cambridge, England, pp. 301-22. Brooks, M. in preparation. Ecology of a biological invasion: alien annual plants in the Mojave Desert. Dissertation. University of California, Riverside. Brown, D.E. and R.A. Minnich. 1986. Fire and changes in creosote bush scrub of the western Sonoran Desert, Califor- nia. Amer. Midi. Nat. 116:411-22. Burcham, L.T. 1957. California Rangeland. An historico- ecological study of the range resource of California. Dept. of Natural Res., Sacramento, CA. Burgess, T.L. J.E. Bowers, and R.M. Truner. 1991. Exotic plants at the desert laboratory, Tucson, Arizona. Madrono 38:96-114. diCastri, F. 1989. History of biological invasions with special emphasis on the Old World. In J.A. Drake, H.A. Mooney, F. diCastri, R.H. Groves, F.J. Kruger, M. Rejmanek, and M. Williamson (eds.), Biological invasions: a global perspec- tive, SCOPE 37, John Wiley and Sons, New York, NY. pp. 1-30. Frenkel, R.F. 1970. Ruderal vegetation along some California roadsides. Univ. Calif. Press, Berkeley, CA. Hunter, R. 1991. Bromus invasions on the Nevada Test Site: present status of B. rubens and B. tectorum with notes on their relationship to disturbance and altitude. Great Basin Nat. 51:176-82. Karpiscak, M.M. 1979. Secondary succession of abandoned field vegetation in southern Arizona. Arizona-Nevada Acad- emy of Sciences, Supplement No. 23. Mack, R.N. 1986. Alien plant invasion into the intermoun- tain west: a case history. In Mooney, H.A. and J.A. Drake (eds.), Ecology of Biological Invasions of North America and Hawaii, Springer-Verlag, New York, NY. pp. 191-213. Morecroft, M.D., E.K. Sellers and J.A. Lee. 1994. An ex- perimental investigation into the effects of atmospheric ni- trogen deposition on two semi-natural grasslands. J. Ecol. 82:475-83. Parish, S.B. 1920. The immigrant plants of Southern Califor- nia. S. Calif. Acad. Sci. Bull. 19(4):3-30. Robbins, W.W. 1940. Plants growing without cultivation in California. University of California, Agricultural Experi- ment Station Bulletin 637, Berkeley, CA. 128 p. Smith, S.P., B.R. Strain, T.D. Sharkey. 1987. Effects of C02 enrichment on Great Basin grasses. Func. Ecol. 1:139-43. Webb, R.H. and H.G. Wilshire. 1980. Recovery of soils and vegetation in a Mojave Desert ghost town, Nevada, U.S.A. J. Arid Environ. 3:291-303. Williams, R.B. and K.L. Bell. 1981. Nitrogen allocation in Mojave Desert winter annuals. Oecologia 48: 145-50. Paul R. Kemp, Department of Biology, University of San Diego, San Diego, CA 92110; Matthew L. Brooks, Department of Biol- ogy, University of California, Riverside CA 92521 34 FREMONTIA VOLUME 26:4, OCTOBER 1998 EXOTICS OF SOUTHERN CALIFORNIA'S VERNAL POOLS AND OTHER SPECIALIZED HABITATS by Ellen T. Bauder VERNAL POOLS ARE temporary wetlands that com- bine clay soil with a highly variable seasonal inundation pattern. Human activities that have created disturbed soil or drainage have vastly altered this special habitat by the introduction of exotic plant species. Southern California has an especially rich assemblage of plant species that are specialized for habitats of limited extent. These habitats have unique growth conditions that occur infrequently or unpredictably, are limited or patchy in distribution, or may be uncommon both over time and in the landscape. Some of the most interesting examples of these specialized habitats are associated with unusual soils such as those derived from gabbroic rocks or those with high clay content. Serpentine and gabbro-derived soils develop from meta- morphic and granitic rocks and are found worldwide, including in California. Serpentine soils are known for their low calcium-magnesium ratios and unusual mineral content, all of which contribute to reduced growth. Toler- ant populations and even new species have been docu- mented for serpentine soils, as described by Kruckeberg and others. Gabbro-derived soils in the Peninsular Ranges support narrowly distributed shrubs such as Parry's tetracoccus {Tetracoccus dioicus), Vail Lake ceanothus {Ceanothus ophiochilus), and Gander's ragwort (Senecio gander i). Patches of clayey soil also support numerous species of very limited distribution. Large shrubs are usually absent, and a unique combination of grasses and forbs—espe- cially succulents and geophytes (plants with bulbs or corms)—flourish. Little is known about the requirements and tolerances of plants restricted to soils high in clay, but it is usually assumed that clays provide a soil water regime different from surrounding soils and that this somehow favors grasses and forbs. An interesting feature of the edaphic or soil specialists is the poor competitive ability of tolerant individuals when grown off their specialized soil. Why this is so is not known for certain, although experi- mental work by both Kruckeberg and McNeilly suggests that it may involve reduced growth for tolerant species, making them a poor match for more robust non-tolerant species or populations. Some of the more notable clay soil endemics found in southern California and northern Baja California, Mexico, are San Diego thornmint (Acantho- mintha ilicifolia), thread-leaved brodiaea {Brodiaea fili- folia), variegated dudleya {Dudleya variegata), chocolate lily {Fritillaria biflora), and Otay tarplant {Hemizonia conjugens). VOLUME 26:4, OCTOBER 1998 Dense circle of exotic plants germinated from an ant nest adjacent to a vernal pool. Photographs by the author. Ebert and Balko described vernal pools as habitats patchy in both time and space. They pond water seasonally and are distributed in a landscape having different soils and vegetation from those of the pools. Another dimen- sion is the year-to-year variation in rainfall, a distinguish- ing feature of Mediterranean climates. Pool basins may fill completely with water in a particular year and remain filled for an extended period of time, but fail to pond at all during drier years. The unpredictable inundation pattern, FREMONTIA 35 both within and between years, has resulted in the exclu- sion from pool habitats of upland and marsh plants alike, leaving a unique flora supplemented with temporary wet- land species of worldwide distribution. Toleration of lim- ited periods of inundation is an attribute shared by all vernal pool species, and my work has shown that some species find pools a refuge from competition with upland dominants that can be dense at pool edges. My analysis of soil texture along transects crossing vernal pools also indicates that soils of pool basins have a much higher clay content than do the adjacent uplands, which are dominated by sand and gravel. Pool endemics include Cuyamaca Lake downingia {Downingia concolor var. brevior), San Diego button celery (Eryngium aristulatum var. parishii), California orcutt grass (Orcuttia californica), San Diego mesa mint (Pogogyne abramsii), and Otay mesa mint (P. nudiuscula). As with the soil endemics, some of these extend into northern Baja California, Mexico. Exotics in Southern California's Specialized Habitats The exotic species associated with two of southern California's most specialized plant habitats—clayey soils and vernal pools—can be divided into two groups: prima- rily upland plants and those tolerant of an inundation period greater than one week. The upland plants are, in general, the same "bad actors" we find in other disturbed California wildlands, especially more xeric ones. These are mostly members of the grass (Poaceae) and sunflower (Asteraceae) plant families, with a good measure of mus- tard (Brassicaceae) and geranium (Geraniaceae) thrown Exotic grasses germinated from seeds dropped along a harvester ant trail crossing a vernal pool basin. in. Species of note are the brome grasses such as foxtail chess (Bromus madritensis ssp. rubens), soft chess (B. hordeaceus), and ripgut grass (B. diandrus). Slender wild oat (Avena barbata) and wild oat (A. fatua) are also com- mon, along with Vulpia myuros. Ubiquitous composites include smooth cat's ear (Hypochaeris glabra) and vari- ous thistles, tocalote (Centaurea melitensis), for example. Black mustard, Brassica nigra, and various species of filaree (Erodium cicutarium, E. moschatum, and E. botrys) can be dominant in some landscapes. These species, either alone or in combination, can account for over ninety percent of the plant cover at the upland edges of vernal pools or in herbaceous vegetation underlain by clay soils. The introduction and spread of most of these weedy species are well documented. They came with the advent of Spanish settlement. According to Burcham, overgraz- ing during the nineteenth century facilitated their spread and contributed to the diminution of the native flora. Tillage and overseeding of cleared brushlands with forage species such as oats (Avena spp.), barley (Hordeum spp.), or rye (Lolium spp.) were other important factors. For vernal pools, the dominant exotics vary from year to year, depending on the amount of seasonal rainfall. In wet years, upland plants are excluded from pool basins because of their intolerance of inundation. The boundary between upland and pool plant communities is clear and readily observed. Dry years present a totally different picture. Upland annuals, particularly the more readily dis- persed, can dominate pool basins. Some exotics found in vernal pool basins have habitat preferences similar to the native species. They are espe- cially abundant in years that are wetter than average. These include the grasses Pacific bent grass (Agrostis avenacea), nit grass (Gastridium ventricosum), perennial ryegrass (Lolium perenne), and annual beard grass (Poly- pogon monspeliensis) and a composite, brass buttons (Cotula coronopifolia). Unlike the upland plants, which are generally xeric grassland species originating from Eu- rope or western Asia, the origins of these species are diverse and, as we would expect, associated with wetlands of some sort. Where pool hydrologic regimes have been altered to include inundation periods approaching year- round, a grab bag of exotic wetland plants invades. Dispersal and establishment of freshwater aquatic plants are natural processes that have been augmented by man's activities, particularly modification of existing habitats and creation of artificial habitats in channels and im- poundments. Ashton and Mitchell summarize modern- day range expansions of aquatic plants and conclude that these generally involve species capable of rapid vegetative multiplication from very small portions of the plant body. Cattails (Typha spp.), which are rhizomatous, have been found in vernal pools receiving runoff from broken pipes and roads. Frequently plants are introduced by humans for specific purposes such as use in aquaria (Cape pondweed, Aponogeton) or landscaping (umbrella plant, Cyperus 36 FREMONTIA VOLUME 26:4, OCTOBER 1998 A dense stand of filaree grows out from a harvester ant nest. involucratus). Both of these plants have invaded vernal pools where disturbance causes water to stand too long. Another successful biological attribute facilitating dis- persal from one aquatic environment to another is posses- sion of spores or seeds that resist desiccation and can be disseminated in or on animals, particularly waterfowl. This dispersal mechanism, although widely invoked, has little direct documentation to support it. Indirect docu- mentation may come from the fossil record of the diminu- tive mosquito fern (Azolla filiculoides), which lost range during glacial periods but reinvaded during interglacials. It is found in southern California in stock ponds and on the shores of reservoirs, but rarely in vernal pools or other natural wetland habitats. The case of grass poly (Lythrum hyssopifolia), a com- mon species found in vernal pools, is particularly interest- ing, for it raises some important issues regarding what is and what is not an exotic. Various California floras in this century noted that grass poly was widespread, sidestep- ping the issue of nativity. Herbarium records suggest that it was introduced on the East Coast early in the nineteenth century and to California near the end of the century. The recently published Jepson Manual describes it as a native of Europe. Its origins are murky, and European references are inconclusive regarding its status as native or exotic. Was it so widely introduced so long ago that its origins are now unknown? Has it always been a wide-ranging spe- cies, like mosquito fern, with the ability to grow in most temporary wetland habitats? Is its presence in California's pools more closely associated with human activities in the last century? Answers to these questions are not inconse- quential. Is it simply one of those sub-cosmopolitan spe- cies that occupy ephemerally wet habitats of many types and thus should be considered a normal component of vernal pool vegetation? If it is a recently introduced ex- otic, should it be managed so as to favor the native flora? Where found, it can occupy a significant fraction of a vernal pool basin, occasionally in dense stands with few other pool plants present. Impacts of Exotics The most obvious impacts of exotics on southern Cali- fornia vernal pools and other specialized habitats must be the changes they have brought to the appearance of the landscape. Because the major events occurred so long ago, we can only know this from descriptions in the historical record or the mental exercise of subtracting species from the present landscape. The texture, coloring, seasonal pro- gression of bloom, and variety of species must all have been substantially impacted where exotics have become a dominant or important component of the vegetation. To understand these changes we need to ask ourselves a series of questions. Have exotics mainly filled in blank space that was not, for some reason, occupied by natives? Have they actually excluded natives? Or have they simply reduced their abundance or shifted their distribution? How have exotics changed the relationships of native plants with other important members of the ecosystem such as VOLUME 26:4, OCTOBER 1998 FREMONTIA 37 pollinators, herbivores, or granivores? Have natural distur- bance regimes such as fire and grazing been disrupted? Are current human activities favoring exotics over natives? Experimentation and careful observation have pro- vided answers to some of these questions, but most await our attention. In controlled-competition experiments in- volving the vernal pool endemic, San Diego mesa mint, pitted against several exotic herbs under different mois- ture conditions, I found that mesa mint suffers from com- petition through increased mortality and reduced seed production. Long inundation, by killing plants, has an effect similar to planting at lower densities, whether the mint is growing alone or with exotics. I have also found that removal of exotic grass thatch (annual beard grass) favors mesa mint. The possible upland origins that McMillan has postulated for the genus Pogogyne may explain its particular sensitivity to upland exotics. The thatch and shading effects are especially evident where unnatural runoff or damming by roads allows freshwater marsh plants to invade pool habitat. The relationship between density of weeds and growth of the clay soil endemic, San Diego thornmint, was first noticed in studies conducted by a consulting firm in con- nection with a mitigation effort intended to compensate for loss of thornmint habitat. I am at present exploring the possible negative impacts of exotics on thornmint using field experiments where I manipulate density of weeds in naturally occurring stands of the native. Herbivores such as quail, rabbits, and fossorial rodents are common in the Mima-mound/vernal pool landscape of coastal southern California. Exotics may have expanded the food supply for these animals. Hunt and Cox examined the stomach contents of pocket gophers (Thomomys bottae sanctidiegi) on the Miramar Mounds Natural National Landmark in San Diego, and they found that oats, brome grasses, and filaree were a large part of their diet. Har- vester ants (Pogonomyrmex californicus) are active in the vicinity of southern California vernal pools and produce a yard-wide collar of seed and chaff around their nests. With the beginning of the seasonal rains these "collars" produce dense stands of exotics such as cat's ear, Vulpia myuros, and filaree. Occasionally, collars are produced in pools, too, where they have an important effect on the micro- topography and distribution of pool plants. Ants moving along trails leave a mini-swath of exotic seeds in their wake, evidenced by the stripe of non-native upland plants crossing the pool in the next rainy season, if there is an insufficient period of ponding to kill them. Stands of exotics may also change the effect of fire on both the habitat of clay endemics and vernal pool basins. The grassland patches supporting clay endemics are usu- ally embedded in a matrix of fire-prone shrublands. It is unknown whether or how dense stands of exotics within the grasslands affect most of the endemic flora when fires sweep across them. In relatively undisturbed pools scant dry biomass remains after the wet season, leaving little 38 FREMONTIA fuel to carry a fire. A low-intensity fire in a vernal pool area on Naval Air Station Miramar had a modest favorable impact on pool vegetation, according to a study by Cox and Austin, and cover of upland exotics was significantly reduced in burned pools. Human Activities and Exotics The elimination of grazers, both natural and intro- duced, and exclusion of fire may allow exotic plants, especially the palatable grasses, to gain dominance. Stud- ies in California are underway to explore these questions. Another human activity that favors exotics in pools and on clay soils is frequent disturbance by vehicles that reduces or eliminates sensitive native plants and removes surface soils. In vernal pools, an additional disturbance involves alterations to hydrology that tip the balance towards non- natives able to grow under these unnatural conditions. References Ashton, P.J. and D.S. Mitchell. 1989. Aquatic plants: patterns and modes of invasion, attributes of invading species and assessment of control programmes. In J.A. Drake et al., (eds.), Biological invasions: a global perspective, pp. 111- 54. SCOPE 37. John Wiley and Sons, Ltd, Chichester. Bauder, E.T. 1987. Species assortment along a small-scale gradient in San Diego vernal pools. Doctoral dissertation, University of California, Davis and San Diego State Uni- versity. 275 pp. Burcham, L.T. 1957. California range land. California De- partment of Natural Resources, Division of Forestry, Sacra- mento, CA. Cox, G.W. and J. Austin. 1990. Impacts of a prescribed burn on vernal pool vegetation at Miramar Naval Air Station, San Diego, California. Bulletin of the Southern California Academy of Sciences 89(2):67-85. Ebert, T. A. and M.L. Balko. 1987. Temporary pools as islands in space and in time: the biota of vernal pools in San Diego, Southern California, USA. Arch. Hydrobiologica 110(1): 101-23. Hickman, J. 1993. The Jepson Manual: Higher Plants of California. University of California Press, Berkeley, CA. Hunt, J. 1992. Feeding ecology of valley pocket gophers {Thomomys bottae sanctidiegi) on a California coastal grass- land. American Midland Naturalist 127: 41 -51. Kruckeberg. A.R. 1954. The ecology of serpentine soils: III. Plant species in relation to serpentine soils. Ecology 35(2): 267-74. McNeilly, T. 1967. Evolution in closely adjacent plant popu- lations III. Agrostis tenuis on a small copper mine. Heredity 23: 99-108. Shinners, L.H. 1953. Synopsis of the United States species of Lythrum (Lythraceae). Field and Laboratory 21:80-89. Ellen Bauder, Biology Department, 5500 Campanile Drive, San Diego, CA 92182-4614 VOLUME 26:4, OCTOBER 1998 GRASSLAND AND FOOTHILL WOODLAND ECOSYSTEMS OF THE CENTRAL VALLEY by John Gerlach, Andrew Dyer, and Kevin Rice Central Valley grassland and foothill wood- land ecosystems have been dramatically altered by exotic plant invasions and by serial changes in ecosystem management practices. In some areas as much as ninety-five percent of the herbaceous biomass is pro- duced by a handful of Mediterranean annual species. The distribution and extent of woody species also have been dramatically altered. Unfortunately, no historical records exist that adequately describe either the pre-invasion con- dition of the ecosystems or the invasion process and re- sulting ecosystem changes. However, we do know that many of the changes were driven by reasonably well documented changes in ecosystem management practices. Recent experiments have shown that the resulting ecosys- tem changes are significant, and that many species of native plants are poorly adapted to the modified environ- ments. These environments are being further degraded by an invasion of longer-lived annual dicots. This new inva- sion is modifying significant ecosystem properties and threatens adult native plants as well as seedlings. The Ecosystems Grassland and foothill woodland ecosystems are dis- tributed as two concentric bands that almost encircle the Central Valley. The modern grassland is found immedi- ately above the valley floor on ancient alluvial terraces, at the base of the foothills, and between stands of wood- land. The foothill woodland is generally distributed above the valley floor and is characterized by the presence of either blue oak (Quereus douglasii) or foothill pine (Pinus sabiniana). Together, these ecosystems cover several million acres, and each occurs in patches that vary from less than two and a half acres to more than several thousand acres. The patches are separated by rivers, ranches, farms, and orchards, dissected by roadways of various sizes, and speckled with vernal pools, rock out- crops, towns, and cities. The climate is similar to that of the eastern Mediterra- nean region, with hot, arid summers and cool, humid winters, but there are significant differences between the two regions. California's winter daily minimum tempera- tures are colder, and growth rates of both exotic and native plant species slow markedly during the winter months. While growth rates of all species do not slow equally, the dominant exotic annual grasses tend to respond similarly to low temperatures. The exotic annual grasses are also more frost-sensitive than native species, as was evident when many hillsides in the Sierra Nevada foothills tempo- rarily turned brown in January 1997. This common re- sponse ensures a period of intense competition each spring as daily temperatures begin to rise. California's wet season also differs from that of the eastern Mediterranean region. The season is longer, its beginning and end are less defined, and both within and between season rainfall patterns are more episodic. The intervals between storms can be extremely variable, and month-long droughts during the wet season are not un- common. Extended fall and winter droughts may kill the drought-sensitive seedlings of exotic annual grasses and shift species dominance for that year to annual dicots, such as red-stemmed filaree (Erodium cicutarium), that have drought-tolerant seedlings. Two hundred years of Spanish, Mexican, and Ameri- can settlement have radically altered the vegetation, ex- tent, and location of both ecosystems. Robert Frenkel has described this pattern of vegetation change driven by changes in human occupation as cultural discontinuities. He has used the terms pristine, aboriginal, and modern vegetation to characterize the changes in California's veg- etation. Frenkel's characterizations provide valuable in- sights into the processes driving changes in vegetation because they explicitly include the role of humans in creating and modifying vegetation. Additionally, a wealth of records concerning settlement patterns and ecosystem management practices becomes available for consider- ation once the role of humans is explicitly recognized. Almost nothing is known about the pristine vegetation of these ecosystems. The aboriginal herbaceous vegeta- tion, a varying mixture of perennials and annuals, was rapidly replaced by Mediterranean annual species, and there are no detailed descriptions of its species composi- tion or community structure. However, we do know that both the grassland and foothill woodland were densely settled at the time of European contact and that the ecosys- tems were intensively managed for the production of food crops, plant materials used for baskets and tools, and fish and game. Some information about ecosystem manage- ment practices and the identities of harvested plant species has been preserved, but we have no information about the identities and abundances of plant species that were not harvested. The modern vegetation that began to develop during the Spanish period expanded during the Mexican period and then exploded across the landscape during the Ameri- VOLUME 26:4, OCTOBER 1998 FREMONTIA 39 Yellow star-thistle (Centaurea solstitialis) dominates the herbaceous vegetation in many stands of blue oak woodlands. Photographs by John Gerlach. can period. The conversion process was driven by the alteration and elimination of aboriginal ecosystem man- agement practices and by the serial introductions of Span- ish, Mexican, and American ecosystem management prac- tices. It is important to remember that the alterations and introductions were not instantaneously and uniformly dis- tributed across the region. Also, ecosystem management practices within each cultural period were dynamic and changed as each culture changed. Finally, while the as- signment of ecosystem management practices to discrete cultural periods is an effective way to describe the domi- nant trends, there was also significant overlap in ecosys- tem management practices across cultural periods. The cultures and ecosystem management practices of 40 FREMONTIA the Native Americans in the San Joaquin Valley and in the southern Sacramento Valley were disrupted in the early 1800s when Spanish soldiers entered the Central Valley from the west to capture neophytes for the missions. Neo- phytes learned to ride horses at the missions and would often escape and return to the eastern San Joaquin Valley with herds of tame mission horses. The accounts of the Spanish soldiers who pursued fleeing neophytes indicate that there were large herds of feral horses on the western ^ plains of the San Joaquin Valley. While many of the tame mission horses were eaten, some were saved for transpor- 1 tation, and a horse-based culture similar to that of the Indians of the Great Plains began to develop in the eastern San Joaquin Valley. The Mexican period is characterized by the almost complete collapse of aboriginal ecosystem management practices and by the widespread introduction of Mexican ecosystem management practices. Sherburne Cook deter- mined that pandemics in 1833 and 1837 decimated the native peoples and caused the extinction of many tribelets. The loss of almost all of the Native Americans in the densely settled southwestern Sacramento and northwest- ern and central San Joaquin valleys during these pandemics abruptly ended centuries of aboriginal management prac- tices. Mexican ecosystem management practices spread into the depopulated areas through a series of land grants that established large cattle and sheep ranches in the Sac- ramento Valley and in the western San Joaquin Valley. The sudden loss of aboriginal management practices and the subsequent widespread introduction of vast herds of Mexican ungulates significantly altered the species com- position and structure of the grasslands and foothill wood- lands in the Sacramento and San Joaquin valleys. Changes in ecosystem management practices during the Spanish and Mexican periods certainly caused signifi- cant changes in the vegetation of the ecosystems. How- ever, it was the widespread introduction of industrialized farming practices by the Americans that eliminated much of the native herbaceous vegetation of both ecosystems. During the explosive expansion of grain farming that began in the 1840s and peaked in the 1870s, much of the Sacramento Valley and large areas of the San Joaquin Valley were plowed. Most of the valley floor, valley terrace, and lower foothill soils in both regions were plowed and, in contrast to current farming practices, plowing began during early winter after the soils were softened by fall rains and the seeds of native species had germinated. « The widespread planting and harvesting of crops produced an enormous diaspora of exotic species. The exotics were introduced as seed contaminants in various types of crop seed and were also spread through crop harvest and trans- portation practices. Woody species also declined greatly during the American period as industrialized mining and cattle operations began in the foothills and as the popula- tions of many towns and cities boomed. As Ted Swiecki and Elizabeth Bernhardt recently explained (Fremontia VOLUME 26:4, OCTOBER 1998 22( 1): 17-24), beginning in 1849 hundreds of thousands of acres of foothill woodland were permanently converted to annual grassland through fuel wood cutting, grazing, and range improvement programs. A few descriptions of the early condition of the modern vegetation exist, but most are anecdotal comments by travelers and explorers. One significant exception was recorded by John Muir, who ambled over the Pacheco Pass in April 1868 and descended into the San Joaquin Valley by walking across Rancho San Luis de Gonzaga, which is now under the San Luis Reservoir. Muir, an avid botanist, published some of his observations in a two-part article entitled The Bee-Pastures of California: "Descend- ing the eastern slopes of the coast range through beds of gilias and lupines, and around many a breezy hillock and brush-crowned headland, I at length waded out into the midst of the glorious field of gold. All the ground was covered, not with grass and green leaves, but with radiant corollas, about ankle-deep next to the foothills, knee-deep or more five or six miles out." A few days later in the plains west of the confluence of the San Joaquin and Merced rivers, Muir conducted the first vegetation survey of the Central Valley grassland. He recorded the families, number of species, and potential reproductive output of plants in a "one square yard" sample of the grassland. His findings were first published in an essay entitled Rambles of a Botanist Among the Plants and Climates of California and later republished in the book, Rambles of a Botanist. Muir's comments in The Bee-Pastures of California suggest that he believed what he saw was the pristine vegetation of the Central Valley. What Muir didn't know was that the area he was describing had been the home of the Miumne, Tona Lanos, and Honoumne people for un- Mature plants of the native bunchgrass Nassella puchra growing in an exotic annual grass dominated grassland. told generations. Also, Muir probably didn't know that the populations of wildflowers he described had been grazed by large herds of horses, cattle, and sheep for almost fifty years. Muir failed to mention that by 1854 settlers had begun plowing and planting grain fields in the plains within two miles of the site of his vegetation survey. Muir's errors and omissions were not unique, and the almost complete lack of information about the species composition and structure of the aboriginal vegetation of these systems troubles us today. We suspect that the large variations in climate, soil characteristics, species distribu- tions, and human management practices evident in the Central Valley resulted in equally large variations in the aboriginal vegetation. However, the means to recreate the aboriginal vegetation on a large scale have been lost to us. What we need most now is an understanding of the biol- ogy and ecology of important species in the grassland and foothill woodland ecosystems and how those factors may be altered by different management practices. Effects of Exotic Annual Grasses on Blue Oak Many stands of blue oaks contain only mature trees. These stands will be lost eventually because there are no seedlings to replace the mature trees. Significantly, this widespread failure to recruit new trees began at approxi- mately the same time as the invasion of exotic annual grasses. One explanation for this pattern is that the exotic annual grasses may have affected the regeneration of the foothill woodland by reducing the growth and increasing the mortality of oak seedlings. As part of her dissertation research, Doria Gordon examined the competitive effects of different species of exotic annuals on the growth and mortality of blue oak seedlings. She found that annual grasses could be strong competitors for soil moisture. This effect was especially pronounced in late spring when oak seedlings ordinarily grow most rapidly. By reducing soil moisture during this important period of growth, the annuals reduced both shoot and root growth in the young seedlings. The reduced growth resulted in increased mortality of oak seedlings during the dry summer months. Dissertation research by Tyson Holmes suggests that mature stands of purple needlegrass {Nassella pulchra) can also compete with blue oak seedlings. His studies indicate that adult purple needlegrass plants can have a greater effect on oak seedlings than do stands of annual grasses. If blue oaks and purple needlegrass coexisted in the aboriginal vegetation, there may have been a mecha- nism that reduced the competitive effects of purple needlegrass on oak seedlings. One hypothesis is that natu- ral or human-caused disturbances created relatively open patches of vegetation. Oak seedlings growing in the open patches had to compete only with the less competitive purple needlegrass seedlings and native spring-flowering FREMONTIA 41 annuals. This low-competition environment allowed de- veloping oak seedlings to grow more rapidly into saplings. However, in the modern foothill woodlands disturbed areas are rapidly colonized by exotic annual grasses, and oak seedlings no longer enjoy the benefit of reduced com- petition during establishment. Exotic Annual Grasses and Purple Needlegrass Purple needlegrass was probably a common native grass species in the aboriginal vegetation of the Central Valley. James Bartolome and his co-workers have deter- mined that purple needlegrass was certainly more abun- dant than it is today in the southwestern Sacramento Val- ley. Because of its potential importance in many aborigi- nal grasslands, many attempts have been made to reveg- etate exotic annual grasslands with purple needlegrass. However, establishing purple needlegrass-dominated grass- lands in the Central Valley requires an intensive and pro- longed management effort, and it is still too early to determine the long-term success of many recent revegeta- tion and restoration projects. What environmental changes prevent purple needlegrass from establishing in its native range? The rapid conversion of the aboriginal grassland to a grassland dominated by exotic annuals suggests an obvi- ous starting point for questions about changes in the envi- ronment. A number of recent experiments have shown that purple needlegrass seedlings growing with annual grasses die in much greater numbers, grow much more slowly, and take much longer to reproduce than they do when growing without competition from annual grasses. Early studies by Harold Heady, James Young, and Raymond Evans sug- gest that annual grasses are strong competitors for light and soil moisture resources. Dissertation research by An- drew Dyer focused on identifying the mechanisms that enable annual grasses to outcompete purple needlegrass for those vital resources. Dyer's results show that annual grasses rapidly increase in height and leaf area during early spring and commonly reduce light levels at the soil surface to less than ten percent of full sunlight. Purple needlegrass seedlings could not grow in those dark envi- ronments, and many died soon after germination. Others lingered but ultimately succumbed during the summer drought. Ironically, annual grasses do not usually affect residual soil moisture levels at depths greater than thirty inches, but weakened purple needlegrass seedlings are not capable of using this untapped resource. Exotic annual grasses clearly have altered the environ- ment experienced by purple needlegrass seedlings. During their first year after emergence purple needlegrass seed- lings have minimal energy reserves and in some respects are the functional equivalent of an annual grass. However, unlike true annuals which avoid the effects of the summer rainless period as seeds, purple needlegrass seedlings must survive in a vegetative state. Their strategy is to develop drought-resistant tissues and their growth patterns empha- size root growth over shoot growth and rapid reproduc- tion. In contrast, Mediterranean annual grass species must be strong competitors for light so they can obtain enough energy to reproduce before their almost synchronous se- nescence during late spring. During the warm days of spring the annual grasses allocate most of their resources to the production of abundant leaf tissue. Consequently, little light can penetrate their dense canopies. Purple needlegrass seedlings have no effective response to these low-light conditions. They aren't evolutionarily pro- grammed to reproduce early and avoid the drought as seeds, and they can't produce drought-resistant tissues and deep roots to reach soil moisture reserves in the low-light environments produced by the annual grasses. Changing Ecosystem Properties and Yellow Star-thistle Yellow star-thistle (Centaurea solstitialis) is currently one of the most important exotic plants in the grassland and foothill woodland ecosystems because it has dramati- cally expanded its range and because of its potential im- pact on many native species. The details of its range expansion and biology also provide concrete examples of how invasive species can alter the function of grassland and foothill woodland ecosystems. Dissertation research by John Gerlach has shown that yellow star-thistle was introduced during the American period as part of the farming-generated diaspora of exotic species. It probably first arrived as a seed contaminant in Chilean-grown alfalfa seed some time after 1849. By 1900 it was considered a major pest in alfalfa and grain fields and was spreading rapidly along roadways. During the first half of the 1900s the intensification of farming on the valley floor eliminated yellow star-thistle from many fields and temporarily limited its range. However, its distribu- tion began to change during the 1930s and 1940s as its range expanded from the valley floor to the borders of the large American cattle ranches that were established in the foothills after 1867. Since the 1960s yellow star-thistle's range has grown at an explosive rate as it has invaded both grassland and foothill woodland ecosystems. This period coincides with a period of extensive road building, suburban develop- ment, and ranching. All of these activities are capable of transporting yellow star-thistle seed large distances and establishing new populations. Widely scattered satellite populations produce enormous quantities of seed, which either fall to the ground or are spread into adjacent grass- lands and woodlands through human activities such as hiking, hunting, agriculture, and cattle ranching. These two processes, the establishment of new satellite popula- tions through long-distance seed dispersal and the subse- 42 FREMONT1A VOLUME 26:4, OCTOBER 1998 quent invasion of surrounding vegetation, sustain the ex- plosive rate of range expansion. The persistence of satellite populations and their ability to invade undisturbed annual grasslands are determined by ecosystem properties and by the biology of yellow star- thistle. For example, unlike first-year purple needlegrass plants, yellow star-thistle can survive in the low-light environments that exist within the canopies of annual grasses. However, it is important to distinguish among the light environments experienced by seedling, rosette, and reproductive plants. The seeds of yellow star-thistle, like most other exotic annuals, germinate immediately after the first significant fall rain. The light environment experi- enced by the seedlings can vary enormously, depending upon the depth and density of plant litter, the presence of overstory plants, the distribution and size of surface rocks, and the slope and aspect of the site. Once a plant reaches the rosette stage the light environment becomes increas- ingly affected by the canopies of other plants. Yellow star- thistle rosettes are able to persist within the canopies of annual grasses by being developmentally flexible. When immature plants grow in full sun they form low rosettes and hold their leaves horizontal to the surface of the soil. When they grow within the canopies of annual grasses they abandon their compact rosette form and increase their height to about ten inches by greatly increasing the dis- tance between leaf internodes and by holding their leaves vertically. This upright growth form allows them to obtain much more light until reproductive plants bolt through the senescing canopies of annual grasses in late spring. The ability of yellow star-thistle rosettes to acquire adequate solar energy within the canopies of annual grasses also gives them access to soil moisture reserves that are not used by exotic annual grasses. A multiple-year field study by Gerlach has shown that the effects of exotic annual grasses on summer soil moisture reserves are ex- tremely variable. In some years the dominant annual grasses complete their life cycles before they have significantly reduced soil moisture levels, and the soil at depths greater than about twenty inches remains moist throughout the summer. In other years, such as 1997 when there was no significant rainfall after mid-February, the annual grasses can significantly reduce soil moisture levels to depths of at least four feet. However, during most years annual grasses only reduce soil moisture reserves to moderately dry lev- els and to a depth of about thirty inches. In contrast to the dominant annual grasses, yellow star-thistle uses soil mois- ture reserves much more intensively and to a much greater depth every year. In deep valley floor soils it can signifi- cantly reduce soil moisture reserves to depths greater than six feet, and in three-foot-deep foothill soils it was found to be extracting soil moisture from fissures in the bedrock. In essence, the ecosystem properties of climate, soil, and dominant vegetation type interact to cause a significant ecosystem resource to remain available for the taking. Yellow star-thistle is able to gain access to this soil mois- ture resource because of its developmentally flexible ro- settes and because it is a relatively long-lived annual plant. The biological characteristics that enable yellow star- thistle to invade these ecosystems threaten native species and ecosystem processes. Native species such as blue oak and purple needlegrass depend on summer soil moisture reserves for growth and survival. Because yellow star- thistle uses deep stores of soil moisture earlier than either blue oak or purple needlegrass, every year becomes a drought year from the perspective of native species grow- ing within populations of yellow star-thistle. Large populations of yellow star-thistle are also altering the water cycle of the grassland and foothill woodland ecosystems by transferring large amounts of stored soil moisture to the atmosphere through plant transpiration. Most clay-loam soils in these ecosystems can store the equivalent of about twelve inches of rainfall for each three feet of soil depth. In most years the dominant annual grasses typically reduce soil moisture reserves in the top three feet of soil by the equivalent of four inches of stored rainfall. Yellow star-thistle, which is capable of reducing soil moisture levels to the same degree as mature oak trees, is able to reduce soil moisture levels by the equivalent of eight inches of stored rainfall for each three feet of soil depth. This means that large yellow star-thistle populations are transpiring the equivalent of at least an additional four inches of rainfall for each three feet of soil depth during average rainfall years. This transpirational difference doubles to eight inches of rainfall during wet years. Addi- tionally, this ecosystem-level effect is widespread because the latest estimate from the California Department of Food and Agriculture indicates that yellow star-thistle's range in California encompasses approximately 20 million acres. Clearly, it is impossible to recreate the aboriginal veg- etation of the grassland and oak woodland ecosystems. However, an understanding of how the processes that caused conversion varied over time and from site to site can enhance the effectiveness of vegetation management decisions and narrow the focus of biological and ecologi- cal research. It is also important to broaden the range of native species used in vegetation projects and in scientific studies to capture more details about how these ecosys- tems may have functioned and to provide a better under- standing of how different species respond to changes in ecosystem management practices. Studies of exotic spe- cies can also contribute to our understanding of ecosystem function by providing information about ecosystem prop- erties that may not be apparent from studies of native species. Finally, we need to continually remind ourselves that these ecosystems are uniquely Californian and not transplanted Midwestern grasslands or Mediterranean woodlands. John Gerlach, Andrew Dyer, and Kevin Rice, Department of Agronomy and Range Science, University of California, Davis, CA 95616 VOLUME 26:4, OCTOBER 1998 FREMONTIA 43 stf^f 1?^ ^ ^tfe^isi*^ ip^'~, '(\li* yj|ljf|i«" S^ Zj,yW-. !Hj Volunteers help remove the exotic yellow bush lupine (Lupinus arboreus) from the Lanphere Dunes Preserve in Humboldt County. Photograph by Andrea Pickart. THE NATURE CONSERVANCY'S APPROACH TO WEED CONTROL by Tamara Kan The Nature Conservancy is a non-profit land conservation organization dedicated to the preser- vation of biological diversity. One of the biggest threats to biodiversity is invasive non-native plant species, which have contributed to the decline of nearly half of all threatened and endangered species in the U.S. Recogniz- ing this threat, The Nature Conservancy created the Wild- land Weed Management and Research Program to provide guidance to Conservancy land managers on controlling invasive weeds in natural areas. One outcome of this program has been the develop- ment of guidelines for setting priorities for weed species to be controlled. Prioritizing control efforts is critical, given the myriad weed species and the limited resources avail- able to most land managers. The highest-priority weeds on Conservancy preserves include newly arrived exotics that are known to be invasive and can be eradicated from the preserve with relatively little effort, weeds that impact ecosystem processes and either significantly displace na- tive vegetation or modify the structure of the vegetation, 44 FREMONTIA VOLUME 26:4, OCTOBER 1998 and weeds that can be controlled with available technol- ogy and resources. Of lower priority for control are weeds for which we have no reasonable control strategy, those that have less potential for impacting native species diver- sity or vegetation structure, and those that infest only disturbed areas. The Nature Conservancy has also developed Element Stewardship Abstracts (ESAs) to provide Conservancy staff and other land managers with current information on managing the most noxious weed species. The abstracts, which summarize data from the literature and from re- searchers and land managers actively working with the species, are available on the Worldwide Web (http://tnc weeds. vedaris.edu). Restoring Ecosystem Processes An important goal for Conservancy land managers is to maintain or, if necessary, restore the physical and biologi- cal processes that sustain the native biodiversity on a preserve (e.g. fire, flooding, or natural succession). When these ecosystem processes are functioning normally, they often support the persistence of the native communities and species. In general, the most troublesome invasive weeds are those that significantly alter one or more natural processes or have ecosystem-wide impacts. The eventual result is the alteration of the structure of the plant commu- nity and a reduction in native biodiversity. Understanding and working with the natural processes that regulate species composition have helped The Nature Conservancy devise efficient methods for weed control and ecosystem restoration. In some cases, actively con- trolling a process-altering weed is necessary in order to restore a natural community. Conversely, it is often pos- sible to reintroduce or actively manage a natural process (e.g. flooding) in order to control a weed or suite of weeds. Occasionally, it is possible simply to allow an already existing ecological process to control the weeds. The fol- lowing case studies demonstrate the importance of focus- ing on ecosystem processes to help guide the management of weeds on Nature Conservancy preserves. Controlling Tamarisk Restores a River Tamarisk or salt cedar (Tamarix spp.) is a small tree native to Eurasia. The species is highly aggressive and currently dominates vast areas of desert oases and riparian floodplains throughout the southwestern United States. Tamarisk, with its extremely high evapotranspiration rate, consumes vast amounts of water. Dense thickets of this weed alter the hydrologic regime of a site by lowering the water table, increasing river sedimentation, and producing higher peak flows. As a result, the native flora is often eliminated. When the Conservancy became involved in the man- agement of the Coachella Valley Preserve in Riverside County in 1986, tamarisk infested a mile and a quarter of desert riparian habitat, outcompeting the native palms, willows, cottonwoods, and mesquite. The diversity of native fauna had declined in association with the changed plant community. In this case, although tamarisk had not irreversibly impacted the natural processes, the water table was lowered in the infested areas and the normally peren- nial stream had dried up. Eradication efforts conducted over a five-year period involved cutting down small trees by hand and treating freshly cut stumps with systemic herbicide. Although la- bor-intensive, this method left the remaining native spe- cies alive as seed sources for natural regeneration. The cut tamarisk branches were collected into debris piles, which eventually decomposed. One area of about seven and a half acres, which had virtually one hundred percent cover of tamarisk, was scraped with a bulldozer. Within five years tamarisk was successfully eradicated from the preserve. Once the tamarisk was eliminated, surface water and the natural year-round stream flow re- turned. On all the sites, including the bulldozed area, the native flora recolonized naturally, and native wildlife has returned. Because tamarisk is still common in areas sur- rounding the preserve, a yearly maintenance program is required to remove new seedlings that germinate from seeds blown onto the preserve. Because the river was not dammed or otherwise al- tered upstream, simply removing the tamarisk allowed the hydrologic processes and the native vegetation and wildlife to recover without intensive replanting efforts. Based on the success of this control effort, the Conser- vancy is currently conducting a more ambitious project to eradicate a much larger infestation of tamarisk from ripar- ian and oasis habitats at Dos Palmas Preserve in Riverside County. Restoring the Dunes A similar restoration of natural processes resulted fol- lowing the removal of the invasive European beachgrass (Ammophila arenaria) and yellow bush lupine {Lupinus arboreus) from the coastal Lanphere Dunes Preserve in Humboldt County. Yellow bush lupine is a native of southern and central California, and its natural range does not extend north of Sonoma County. Both species were originally introduced to the region for dune stabilization, but they have displaced the native dune vegetation and altered the normally shifting sands by overstabilizing the dunes. Research by The Nature Conservancy on the invasive ecology of these species led to the understanding that yellow bush lupine can have other complex and long- lasting effects on the dune system. Dense infestations of VOLUME 26:4, OCTOBER 1998 FREMONTIA 45 the weedy shrub provide a shaded, moist microclimate that fosters invasion by other non-native species and in- creases soil organic matter. At the Bodega Marine Lab it has been well documented that the nitrogen-fixing lupine also directly enriches the normally nitrogen-poor dunes. Thus, in addition to overstabilizing the dunes, yellow bush lupine alters the nutrient dynamics and species composi- tion of the dunes. Volunteers have been pulling out yellow bush lupine from the preserve annually since 1977. California Conser- vation Corps crews have been digging out European beachgrass since 1992. Both species have been nearly eradicated from the preserve. At most of the control sites the dunes have returned to their less stabilized state, the native species have recolonized, and no revegetation ef- forts have been required. However, as expected, the ecosystem-wide impacts of the most heavily infested sites persisted despite the re- moval of yellow bush lupine. These sites continue to be overstabilized and populated by other exotic species. It may be necessary to remove the other introduced weeds and the surface litter on these sites to reduce nitrogen levels and allow the native species to recolonize the area. Thus, sometimes it is not sufficient to eradicate a weed; it may also be necessary to repair the more lasting effects on the ecosystem. Giant Reed Control Because weed seeds and propagules do not recognize preserve boundaries, weed control efforts should extend to encompass a wider region. Knowledge of the reproductive biology of a problem weed can be helpful in determining an appropriate scale and strategy for eradication or control. Coastal riparian systems, especially in southern and central California, are highly threatened by the invasion of the exotic giant reed {Arundo donax). Originally intro- duced to California in the early 1800s for erosion control, this Asian grass has spread aggressively along rivers, forming dense stands twenty-five feet tall. Expansion is mainly through vegetative propagation; rhizomes and stems, torn up by flood waters, wash downstream where they take root and establish new populations. Native wildflowers bloom after three years of prescribed burning at Sugarloaf Ridge State Park. Photograph by Joseph M. DiTomaso. 46 FREMONTIA VOLUME 26:4, OCTOBER 1998 Giant reed is highly flammable and resprouts quickly after burning, causing the riparian community to become fire-prone. Unlike native vegetation that shades the river and moderates water temperature, giant reed grows up- right, causing increased sunlight exposure and higher wa- ter temperatures. The altered physical environment harms the native fish and other aquatic life. Nearly impenetrable stands of giant reed provide poor habitat for other native wildlife as well. Since giant reed is so widespread and destructive, more than twenty public and private organizations in southern California have come together to form the Santa Ana River Arundo Management Task Force, also known as Team Arundo. Although the Conservancy does not own property in the areas of the giant reed invasion in southern California, we have joined the team as a scientific re- source, developing ecological models and mapping the giant reed infestations within the watershed. In addition, as a private non-profit organization not restricted by juris- dictional boundaries, the Conservancy has been available to help provide coordination among the many regional agencies of Team Arundo. The Conservancy has also been working with a variety of public agencies and private parties on the Santa Margarita River to develop a coopera- tive approach to giant reed control in that watershed as well. The success of Team Arundo has spawned a number of similar efforts throughout the state, from San Diego to Sonoma County. As giant reed spreads mainly downstream, the plan is to initiate control activities at the top of the watershed and work downstream, eventually eradicating it from the en- tire Santa Ana watershed. Experience has shown that, depending upon local site conditions, a combination of treatments is often needed, but the most effective ap- proach is broadcast treatment of the foliage with a dilute solution of glyphosate. Once giant reed is removed, future flooding will allow the native riparian willows and cotton- woods to naturally recolonize the riverbanks. Employing an ecosystem-wide approach rather than several piecemeal eradication efforts may enable long- term control of giant reed. Our cooperation with other organizations on the effective control of Arundo, a weed with ecosystem-wide impacts, reflects the Conservancy's growing focus on collaborative approaches to difficult conservation challenges. Fire and Grazing With the establishment of exotic annual grasses in California over the past 200 years, native perennial grass- lands have largely been converted to non-native annual grasslands. A few remnant native grasslands remain, but even these are threatened by fast-growing annual grasses. Medusahead (Taeniatherum caput-medusae), a grass of Mediterranean origin, has spread rapidly in grazed and ungrazed pastures throughout the West. The seed awns of medusahead twist and spread wildly when dry, resembling the snake-covered head of the mythical Medusa. Dense infestations of medusahead produce a thick thatch layer that suppresses growth of native grassland species. Jepson Prairie and Vina Plains preserves in the north- ern Central Valley have been invaded by medusahead and other alien annual grasses. These preserves contain di- verse floras and some of the best remaining examples of vernal pool habitat. Medusahead is common in the grass- lands surrounding the pools and in some cases is en- croaching into the relatively pristine vernal pools. Several experimental prescribed burns were conducted at Jepson Prairie Preserve to determine the effectiveness of fire in controlling the weeds and encouraging native spe- cies. Results showed that the most effective time to burn for control of medusahead is late spring, after seeds of most of the native species have dispersed but before the late-matur- ing medusahead grasses have released their seeds. Late- spring prescribed burns are being implemented at several Conservancy preserves that have stands of native grasses. In addition to fire, cattle grazing is also being studied as a means of controlling medusahead. When Vina Plains was first acquired by the Conservancy in the early 1980s, cattle were removed because of concerns about impacts on the vernal pools. A decade later, medusahead had become a dominant species on the preserve but was less prevalent on the neighboring grazed pastures. In the absence of some disturbance such as grazing, weeds may overwhelm the native vegetation in these sites. Though not a natural process, livestock grazing can be used to create a distur- bance regime that reduces the cover of medusahead. Cattle grazing has been reintroduced to pastures on Vina Plains Preserve to observe the effects on medusahead as well as on the native flora. Passive Weed Control The number of exotic species that have become natu- ralized in California's grasslands is overwhelming, and the task of controlling them all is daunting. On Nature Conservancy preserves our goal is not to return to an unattainable pristine state, but to shift the ecological bal- ance in favor of native species. Manipulating the ecosys- tem processes of fire and grazing can be an efficient and effective means for accomplishing this goal. In contrast to the active management programs de- scribed above, some situations call for a more passive approach. In such cases prior research and familiarity with the natural community can provide valuable insight into how ecosystem processes regulate species composition. In 1985 a levee along the Cosumnes River accidentally broke during a major flood, moving sand onto a farm field. One corner of the field that was deeply covered with sand was allowed to go fallow. Within ten years a healthy riparian VOLUME 26:4, OCTOBER 1998 FREMONTIA 47 forest established itself on the sandbar. Shading by the overstory canopy gradually eliminated the farm field weeds. Allowing natural flooding and successional processes to proceed unimpeded by human actions favored the estab- lishment of native riparian forest species. Based on this experience, Cosumnes River Preserve staff are experimenting with reintroducing flooding to marginal farmland on the preserve along the lower Cosumnes River floodplain. In 1995 a levee was breached in three places to allow winter floodwaters to deposit sandbars across the fallow fields, encouraging natural regeneration of riparian tree species and starting the suc- cession process. The first species to colonize the site were several pernicious weeds, including perennial pepperweed (Lepidium latifolium), yellow star-thistle (Centaurea solstitialis), beggar's tick (Bidens spp.), and watergrass (Echinochloa sp.). However, experience with the 1985 levee break has shown that if left alone, the weeds are overtopped by native riparian tree species. Rich Reiner, a Nature Conser- vancy ecologist, says: "The fields are covered with peren- nial pepperweed growing up to your shoulders. But I don't worry about it, because if you look carefully you can see small oak and cottonwood seedlings hidden among them." Within three to four years the fast-growing cotton- wood seedlings shade out the perennial pepperweed and other sun-loving weeds, providing a beneficial microcli- mate in which native oak seedlings can mature. By the seventh or eighth year the oaks overtop the weeds and begin to shade them out. Soon, native understory species such as Leymus triticoides and Carex praegracills begin to colonize the area. Once the mixed riparian forest is established, the shade- tolerant weed Himalayan blackberry (Rubus discolor) can become pervasive. Although the benign nature of Hima- layan blackberry is certainly debatable, this weedy vine seems to fill a niche similar to that of the native California blackberry (R. ursinus), and it does not appear to severely affect the vegetation structure and dynamics of the forest at this site. Reintroducing natural flooding and allowing succession processes to unfold in this riparian system transforms a weedy field into a mixed riparian forest, albeit with one common exotic weed species. An Ounce of Prevention The highest-priority weeds for immediate control are often not the well established, already dominant weeds, but new arrivals that have a minor presence on a preserve and are known to be highly invasive in similar habitats. Ideally, control should be focused on these weeds before they become a severe problem. An analogy can be made to the medical paradigm of prevention versus crisis man- agement. On the Santa Rosa Plateau Ecological Preserve in Riv- 48 FREMONTIA erside County, three isolated artichoke thistles (Cynara cardunculus) were discovered and removed in 1984, and a second small infestation was located and removed more recently. In 1988, on the same preserve, a single tamarisk tree was cut and the stump was treated with herbicide. Both of these highly invasive species were easily eradi- cated from the preserve, preventing them from becoming large-scale infestations. At the Lanphere Dunes Preserve in Humboldt County, two populations of the non-native bull thistle (Cirsium vulgare) were recently observed invading the dune hol- lows. One population containing only five plants was easily eradicated. A second localized population, discov- ered in 1989, has decreased steadily as a result of control efforts. Similarly, at the Cosumnes River Preserve in Sac- ramento County, volunteers are removing the newly in- vading fig (Ficus carica) from the mature riparian forest. This early intervention approach to weed management may not at first appear necessary; after all, it is easy to discount a few stray individual weeds as inconsequential compared to the obvious harmful effects of a full-blown infestation. However, the exponential speed at which some weeds can multiply and spread provides a compelling rationale for preventive measures. It is vital to carry out periodic monitoring for early detection, especially along roadways and in disturbed areas where weeds tend to invade. These simple actions by preserve staff and volun- teers are not usually documented or recognized. Discover- ing and pulling a few weeds is not flashy; one seldom receives credit for preventing what might have been. How- ever, it is possible that the most effective and efficient management is conducted by these unsung heroes. Effective and Pragmatic Weed Control Like other land managers, Nature Conservancy staff have limited resources available for controlling weeds. Developing an effective and pragmatic weed control pro- gram requires weighing many factors, including degree of threat posed by the weeds, ecological value of the infested natural communities, available control methods, staffing, volunteers, and funds. Studying the dynamic natural processes that regulate and are, in turn, regulated by other components of an ecosystem is critical to developing efficient techniques for restoration and weed control. By focusing control efforts on process-altering weeds, we can have the strongest ben- eficial impact, often allowing the system to recover on its own once the offending weeds have been eradicated. When- ever feasible, using ecosystem processes such as fire, flooding, and grazing to control invasive weeds is our most promising tool for tipping the ecological balance in favor of native species. Tamara Kan, 16060 Skyline Blvd., Woodside, CA 94062 VOLUME 26:4, OCTOBER 1998 EXOTIC PLANT MANAGEMENT IN NATIONAL PARKS OF CALIFORNIA by Sue Fritzke and Peggy Moore National parks ARE among the nation's premier places to observe natural ecosystems. However, even these relatively pristine areas are not im- mune to outside threats. Exotic plant invasions have been recognized as a problem for quite some time throughout the national park system, and these invasions threaten many of the natural systems the National Park Service (NPS) is mandated to protect. California's twenty-one national parks have been impacted by the invasion of exotic plants to varying degrees. Some parks have the luxury of winter snow, extreme drought, or other condi- tions that limit the spread of most invasive species. Others have the climate, topography, natural disturbance regimes, or anthropogenic perturbations that result in conditions favorable to the introduction and spread of a wide variety of exotic species. Incursions of exotics into national parks present man- agers with a complex set of challenges. Lack of funding, historic disturbance patterns, vulnerable plant communi- ties, and mandates for natural resource protection all com- plicate the job of identifying problem species and appro- priate control strategies. The NPS Natural Resources Man- agement Guidelines provide overall direction: "The NPS will seek to perpetuate native plant life as part of natural ecosystems___To the maximum extent possible, plantings in all [management] zones will consist of species that are native to the park___" More specifically, "management of populations of exotic plant and animal species, up to and including eradication, will be undertaken wherever such species threaten park resources or public health . . . with high priority . . . given to . . . exotic species that have a substantial impact on park resources and that can reason- A large, previously undetected patch of giant plumeless thistle (Carduus acanthoides) (a California Exotic Pest Plant Council A-rated pest) was discovered in the Vision Fire area of Point Reyes National Seashore. This is a high-priority invasive species the park has been trying to eradicate for more than two decades. Photograph by Sue Fritzke. VOLUME 2 6:4, OCTOBER 1998 FREMONTIA 49 ably be expected to be successfully controlled." The chal- lenge for park managers is to determine which species pose a "substantial" threat to park resources and which species can be successfully controlled. The National Park Service has developed a variety of control and containment strategies as a component of its integrated pest management (IPM) program, which em- phasizes using the most appropriate control methods for each species. These can include mechanical, chemical, biological, and cultural techniques. Reaching beyond park boundaries, the NPS is a co-signer of the National Strategy for Invasive Plant Management, a coalition of local, state, tribal, federal, and private entities dedicated to addressing exotic plant management issues on public and private lands. The NPS is also a co-signer of the memorandum of understanding for fulfilling Section 15 of the Federal Nox- ious Weed Act of 1974, the purpose of which is to coordi- nate the management of undesirable plants on federal and state lands throughout California. This article presents the issues and strategies of exotic plant management used at seven national parks in Califor- nia. Lassen Volcanic, Yosemite, and Sequoia and Kings Canyon national parks have similar environmental condi- tions but different exotics problems due to park histories and current activities. Redwood National Park and Point Reyes National Seashore have varying historic levels of disturbance and are adjacent to population centers that contribute exotic plant propagules to park lands. Channel Islands National Park, a seemingly isolated environment, also has problems associated with recent and historic land use practices. Sequoia and Kings Canyon National Parks The biological communities of these two parks range from foothill chaparral and oak woodlands to alpine communities along the west slope of the southern Sierra Nevada. Exotic plant establishment has appeared to be limited to conversion of the oak woodland understory to Mediterranean annuals, a situation widely viewed as irre- versible. However, between 1985 and 1996, over 600 biological survey plots in these parks yielded scores of taxa previously unknown in the parks, the majority of which were exotic. This information heightened concern about the possibility of new invasions by introduced weedy species, especially in disturbed sites at lower elevations. In 1996 the Sequoia and Kings Canyon Field Station of the United States Geological Survey (USGS), Biological Resources Division (BRD) began a directed search to document introduced plants. The project continued through 1997, and a third field season is planned for 1998 in conjunction with Yosemite. The surveys are conducted by skilled botanists in locations believed to have been in- vaded by introduced plants. These are primarily pack stations, riparian zones, road and trail corridors, historic sites, and other areas, particularly below 4,500 feet, that have experienced anthropogenic disturbance. In the last two field seasons more than seventy introduced plant species not previously encountered in the parks were docu- mented, mapped, and vouchered. Using the distribution information and data gleaned from published literature, each species will receive a rank- ing based on threat and controllability using the system developed by Hiebert and Stubbendieck. This system takes into account reproductive potential, germination require- ments, dispersal ability, known behavior in similar sys- tems, availability and feasibility of control methods, and current distribution and abundance of plants and propagules. Sequoia and Kings Canyon are holding back on formal control efforts until the BRD study is finished in order to focus on the most invasive, controllable, and detrimental species. In the meantime, the park staff will focus on weeding in revegetation projects and some volunteer ef- forts with populations currently causing concern. These include Himalayan blackberry (Rubus discolor) and giant reed (Arundo donax). In a portent of future problems, yellow star-thistle (Centaurea solstitialis) is poised along much of Sequoia's west boundary. David M. Graber (NPS Senior Scientist) Brent Johnson (USGS Botanist) Sylvia Haultain (NPS Plant Ecologist) Yosemite National Park The threat of exotic plants was recognized as far back as the 1920s in Yosemite Valley when a number of nox- ious species, such as bull thistle (Cirsium vulgare), be- came established to the detriment of scenic values and cultivation practiced at the time. Other species were not identified as a problem at that time—annual grasses intro- duced for forage and to replace native species lost during grazing, plowing, and cultivation, and ornamental plants such as hops (Humulus lupulus), periwinkle (Vinca ma- jor), and Himalayan blackberry {Rubus discolor). Today, as Yosemite staff learn more about the ecology of the park's'plant communities, they recognize prob- lems associated with more than 150 exotic species now known to occur within the park. Low-elevation areas with state and federally listed plant species are being invaded by aggressive exotics such as yellow star-thistle to the potential detriment of those rare plant populations. Large wildfires have provided the opportunity for exotics to become established in portions of designated wilder- ness. Yosemite Valley's meadows, sequoia groves, and other highly visited areas are subjected to routine distur- bance and continue to be impacted by numerous noxious species. Over the past ten years park staff have developed and continue to strengthen a three-pronged management ap- 50 FREMONTIA VOLUME 26:4, OCTOBER 1998 proach to document new species and occurrences, assess- ing threats of known populations and species, and imple- menting control actions. Only those species with known effective control methods are being managed at this time. Thus, introduced perennial grass species that have re- tained the basic function of lower montane meadows (which were historically dominated by perennial bunchgrasses) are not being actively controlled, but rather are slowly being replaced by native species as the park continues management actions including appropriately timed pre- scribed burns. Special projects and funding occasionally enable park staff to concentrate on particular areas of the park. For example, funding was received in 1997 and 1998 to do exotic plant monitoring and control work within bound- aries of the 1996 Ackerson fire, a total of over 50,000 acres within the park. Numerous exotics, including bull thistle and yellow star-thistle, have become newly estab- lished within severely burned portions of this fire area, and dedicated, trained labor crews are working in some very rugged lands to remove these pests. A key component of the work accomplished each year in Yosemite comes from volunteer labor. Yosemite now has a web site to solicit exotics-specific volunteer labor from around the country (http://members.aol.com/ GStigall/yosevol.htm). Unfortunately, funding for con- trol of exotics has been extremely limited, and were it not for numerous "weed warriors" willing to dedicate their vacations and weekends to this vital work, the problem would have reached disastrous proportions in some sec- tions of the park. Focus has been on heavily visited areas (e.g., Yosemite Valley, sequoia groves, disturbed areas, and road corridors) generally below 4,500 feet elevation. Targets are typically easily recognized species: bull thistle, common mullein (Verbascum thapsus), numerous mus- tards (Brassicaceae), and yellow star-thistle. Control meth- ods have emphasized manual pulling (mullein) and cut- ting near the ground surface (bull thistle, star-thistle) since these are effective treatments and take little train- ing. Last year more than 2,000 volunteer hours were spent doing eradication work, and the numbers continue to rise. The park has developed working relationships with a number of partners, including the Yosemite Institute and Yosemite Concession Services. In 1998 the USGS Yose- mite Field Station obtained matching funds through a grant from The Yosemite Fund, a private, non-profit, fund-raising organization, to document the distribution, abundance, diversity, and ecology of exotics within the park through literature reviews, surveys, mapping, and spatial analysis. This is an expansion of the work in progress at Sequoia and Kings Canyon. Results will provide man- agers with additional tools for prioritizing control efforts with a focus on species and populations that are new, outlying, highly invasive, or most controllable. Sue Fritzke (Vegetation Ecologist) Resource management specialists with the National Park Service esti- mate the abundance of bull thistle (Cirsium vulgare) in Yosemite Valley meadows prior to eradication efforts. Photograph courtesy of NPS files. Lassen Volcanic National Park Like Sequoia and Kings Canyon, Lassen is in the early stages of defining the extent of its exotics problems and developing strategies for addressing them. Although less than five percent of the park has been surveyed, the num- ber of known introduced plant species in Lassen has nearly doubled in the last thirty-five years. Over fifty species in fifteen families are now known to occur in disturbed areas such as developed campgrounds, roadsides, abandoned borrow pits, and possibly in areas where trespass grazing has repeatedly occurred over the years. Some of the appar- ently more aggressive species include woolly mullein and bull thistle. One of the park's primary concerns is potential changes in plant community structure and function that threaten to displace native species and change fire regimes through increased dominance by fast-burning fuels (grasses, flammable shrubs). In August 1997 the Huffer wildfire burned nearly 2,300 acres in the park. The fire, and its suppression, created conditions favorable to the rapid establishment and spread of exotic plants. Like Yosemite, the park received fire- related funding for two years, beginning in 1998, to moni- tor sub-units within the fire area (such as fire camps, helicopter landing zones, and firelines), map exotic plant populations with global positioning system receivers, and conduct control work. An inventory and monitoring scoping session was com- pleted in the park last year that identified the need for a VOLUME 26:4, OCTOBER 1998 FREMONTIA 51 three-year study to address the park's exotic plant prob- lems. The park now hopes to receive funding to expand on the fire-related work and develop park-wide inventory, prioritization, and control strategies similar to those being developed in the Sierra Nevada parks. Jonathan Arnold (Resource Management Specialist) Point Reyes National Seashore Over on the coast, a strategy for prioritizing exotics removal at Point Reyes National Seashore has been com- pleted. At this time, the park has a zero-tolerance policy (complete removal and consistent follow-up) for gorse (Ulex europaea), yellow star-thistle (Centaurea solstitialis), giant plumeless thistle (Carduus acanthoides), woolly dis- taff thistle {Carthamus lanatus), pampas grass (Cortaderia jubata), oblong spurge (Euphorbia oblongata), perennial sweet pea (Lathyrus latifolius), and water hyacinth (Eichhomia crassipes). In addition, pioneer populations of other weeds in otherwise uninfested areas are identified and eradicated as quickly as possible each year and revis- ited in subsequent years to prevent invasion into pristine areas. The program relies largely on manual removal. How- ever, prescribed fire is increasingly used to manage large infestations of Scotch broom (Cytisus scoparius) and French broom (Genista monspessulana). This work con- sists of treatments based on research by Bossard indicating that managed fire at appropriate intervals is effective in eliminating established shrubs and depleting the seed bank. Point Reyes is another park that received scarce exotics funding following a wildfire, in this case the 12,000-acre Vision Fire in 1995. Approximately a million plants per year were removed manually, and the higher level of staffing improved detection of previously undiscovered populations. For example, a large, previously undetected patch of giant plumeless thistle (a California Exotic Pest Plant Council A-rated pest) was discovered in the burn area. Staffing for work outside of the Vision Fire area is limited. Point Reyes relies on a combination of labor from the Marin Conservation Corps, California Conservation Corps, Americorps, and volunteers using weed wrenches for broom, hand picks for thistles, and pulaskis and chain saws for pampas grass. These efforts have good success in controlling weeds, provided that park staff designate funds for follow-up monitoring and control. With Vision Fire funding in its last year, park managers are now seeking funding for one of their next large programs. Cape ivy (Delairia odorata, formerly Senecio mikanioides) con- tainment and removal, a half million dollar joint project with Golden Gate National Recreation Area, is top priority for this year. Kim Cooper (Acting Resource Management Specialist) Redwood National Park Farther up the coast, Redwood National Park includes Cape ivy and Scotch broom among its priority exotic species designated for control. Established in 1968, Red- wood's enabling legislation focused on the restoration and maintenance of the coast redwood and adjacent areas. As a result, funding was made available for personnel who could concentrate on exotics within the park. Spe- cial, targeted funding for this purpose is unusual but expanding in the NPS as the threat of exotics is more fully recognized. Redwood completed an exotic plant management plan in 1995, identifying priorities, strategies, and methods to be applied to various species. One focus has been tansy ragwort (Senecio jacobaea), which appears to be expand- ing its range throughout the park. Populations that were reduced by a biocontrol beetle release have expanded as the beetle populations decline due to lack of food. Empha- sis has been placed on eliminating small outlying stands of tansy ragwort by hand and continuing biocontrol on exten- sive populations. Primary labor sources for these efforts, aside from park staff, are Civilian Conservation Corps, Youth Conservation Corps, volunteers through Student Conservation Association, school and university students from California and Oregon, and the park's Volunteer in Parks program. Pampas grass poses the greatest problem in those areas that were clearcut prior to the park's 1978 expansion. This species aggressively colonizes open, sunny slopes, out- competes native species within open sites, and poses an aesthetic intrusion. The park recognizes that the elimina- tion of skid and logging haul roads and the regeneration of second growth forest will help to reduce this species. However, it is likely to persist in sites of natural and anthropogenic disturbance. After a few years of experi- mentation, the park has focused on those areas used by visitors (such as the Tall Trees Grove access road and Freshwater Spit). The current control method consists of cutting back the plants and applying herbicide upon re- growth. Since this species produces millions of tiny seeds per plume, mature plants growing in communities upwind of park lands continue to pose a threat and dictate constant management. Other high-priority species are European beachgrass (Ammophila arenaria), which threatens coastal strand com- munities and their accompanying rare wildlife species, English and Cape ivy (Hedera helix and Delairia odorata), which invade old growth forests, Spanish heath (Erica lusitanica), which has been expanding its range northward each year and impacts coastal spruce forests and grass- lands, Himalayan blackberry (Rubus discolor), considered an ecological threat to the native grasslands of the Bald Hills, and yellow star-thistle, which has now been discov- ered in the Bald Hills area. Data on distributions of these high priority species are entered into the park's GIS data- 52 FREMONTIA VOLUME 26:4, OCTOBER 1998 base to aid in management of established plants, seed banks, and resprouts. Diona Roja and Jim Popenoe (Soil Scientists) Channel Islands National Park Applying the same model being used in the Sierra Nevada parks and Lassen, Channel Islands National Park is developing and implementing an exotic plant control strategy for this five-island park off the southern California coast. Starting with a three-year grant from the Natural Resources Protection Program (NRPP), park staff began in October 1996 to gather information on approximately 120 exotic plant species found in the park. The results will be compiled by species into a report format inspired by The Nature Conservancy's Element Stewardship Abstracts. Park staff see the project as an iterative improvement of their knowledge regarding the biology and ecology of a large number of exotic plants fairly common to California, the development of a rational scheme for prioritizing limited control dollars and time, and an opportunity to test known techniques, pioneer new ones, and evaluate their results. The information gained will be freely offered to other land managers who have similar exotic plant problems. The park has used 1998 NRPP funds to hire new staff for two years to undertake exotic plant control on all five islands. The new staff will use volunteers on weed control projects as much as practicable given the difficulties of island logistics. Anyone who can commit substantial ef- fort to the park for a year or more is invited to call (805) 658-5623 to receive a volunteer program application form. Sarah Chaney (Botanist) Our Parks Need Help Nearly every national park in California is impacted to some extent by exotic plants. Impacts include competition with rare species, alteration of plant community structure and function, altered fire behavior, or changes in native plant diversity. Lack of control efforts would have disas- trous consequences for natural communities and protected species in nearly every case. Efforts to respond to these threats have been hampered by insufficient funding and a paucity of information on weed distribution and abundance, life history characteris- tics and invasiveness, natural community impacts, and management strategies. Several research projects are now underway to fill some of these information gaps and pro- vide managers with powerful information tools necessary to gain and/or maintain the upper hand in exotics control and natural habitat protection. Institutionalizing this infor- mation will help provide continuity of vigilance and con- trol efforts despite personnel changes, and the accumula- tion of information on species distributions, behavior, and controllability will allow park managers to respond appro- priately to new threats as they arise. Without institutional- ized funding, however, park staffs will continue to be hampered in their ability to address the problems. Most parks rely heavily on volunteer labor in their exotics control efforts. These programs provide not only an enthusiastic labor pool but opportunities to educate youth and the public about the parks' natural plant com- munities and ecology. It is nonetheless important for the parks also to maintain an internal labor force to ensure the timely detection of newly established exotics, to work in difficult terrain, and to have staff trained in a broad spec- trum of control methods (fire, herbicides, chainsaws, etc.). Few parks have buffer zones where the park has some negotiated influence on management practices and exotics control and prevention. As a result, parks must work not only within their boundaries but cooperatively with neigh- bors to address control and prevention issues that tran- scend political boundaries. This includes working with local, state, and county agencies on erosion control meth- ods, road maintenance, and other management practices. Land managers throughout California are faced with a broad array of non-native species making steady inroads into native communities. The accelerating pace of human commerce, whether for work or recreation, will continue to provide vectors of insidious efficiency. Coordination with others working on exotics will be increasingly impor- tant for communicating new techniques, identifying new invaders, identifying new issues, relating success stories and failures, and re-inspiring all those on the front line. References Bossard, C.C. 1993. Seed germination in the exotic shrub, Cytisus scoparius (Scotch broom) in California. Madrono 40: 41-61. Report of the working group for weed control methods and applications development. CalEPPC News 1(3):8. Oswald, V.H., M.T. Showers, and D. Showers. 1995. A Flora of Lassen Volcanic National Park, California. Second ed. California Native Plant Society, Sacramento, CA. 216 pp. Hiebert, R. and Stubbendieck. 1993. Handbook for ranking exotic plants for management and control. U.S.D.I., Na- tional Park Service, Natural Resources Report NPS/ NRMWRO/NRR-93-08. 29 pp. Moore, P.E., S.A. Haultain, and D.M. Graber. 1997. Distribu- tion, abundance, and ecology of introduced vascular plant species in Sequoia, Kings Canyon, and Yosemite National Parks: baseline data for management. A peer reviewed study plan funded by Biological Resources Division, U.S. Geological Survey. U.S. Department of the Interior. 1991. NPS-77. Natural Re- sources Management Guidelines. Sue Fritzke, National Park Service, Yosemite, CA 95318; Peggy Moore, U.S. Geological Survey, Yosemite Field Station, Box 700, El Portal, CA 95318 VOLUME 26:4, OCTOBER 1998 FREMONTIA 53 EXOTIC WEEDS IN THE NORTH COAST STATE PARKS by Renee Pasquinelli NORTH Coast units of the California Department of Parks and Recreation (DPR) contain wonder- ful examples of California's diverse native flora. Plant communities range from magnificent redwood for- ests to pygmy cypress bogs, from moist coastal prairies to coastal sand dunes. In most of these communities one can still find remnants of pristine vegetation, but in many of them invasive exotic weeds compete with the native flora. Exotic weeds are generally most prevalent where distur- bance by past and current human activities have altered the natural ecosystem. The severe impact of exotic weeds on California's ecosystems has been well documented. DPR's statewide resource management policies and directives recognize the problem and provide clear mandates for the removal of aggressively invading weeds from parklands. DPR pro- grams for the removal of exotics are developed and priori- tized based on several factors, including: the classification of the park unit (e.g. removal of exotics may be a higher priority in natural preserves than in state recreation areas), level of threat to sensitive species or natural ecosystems, and availability of funding. Unfortunately, on the North Coast, as in many areas of the state, availability of funding has become one of the major obstacles to the successful control of exotic weeds. The state park system of the North Coast is divided into two large districts. Northcoast Redwoods District contains twenty-four park units within Del Norte, Humboldt, and northern Mendocino counties. The Russian River/Mendo- European beachgrass (Ammophila arenarid) invades a northern dune system and eliminates native species. Photographs by the author. cino District contains twenty-five park units from Westport in Mendocino County south to Bodega Bay in Sonoma County. Projects to control exotic species in these, as in most districts, have been funded primarily by the Natural Heritage Stewardship Program, which was supported by 1984 and 1988 bond acts. The Department's Resource Management Program, which currently has a statewide annual budget of less than $300,000, has also contributed to exotic weed projects. The failure to pass recent bonds has meant that resource management programs for the control of exotic weeds have had to compete for funds with other park management programs. Because district budgets and staff levels overall are inadequate to fully maintain the parks, resource management and protection programs have seriously suffered. An Anonymous Gift Funds Weed Removal In 1994 the state park system gratefully received a substantial anonymous donation for the purpose of man- aging and protecting natural resources. Over $200,000 from this program (called the Resource Preservation Grants Program) has been used for projects to remove exotic weeds and restore native vegetation in the Russian River/ Mendocino District. At MacKerricher State Park north of Fort Bragg, funds from the Resource Preservation Grants Program helped to remove exotic weeds that threaten two federal- and state- listed native plants. The endangered Howell's spineflower (Chorizanthe howellii) is found only in isolated popula- tions within the coastal dunes from Lake Cleone at Mac- Kerricher State Park north to the Ten Mile River. Menzies' wallflower {Erysimum menziesii ssp. menziesii), also a coastal dune species of limited distribution, is found only in small populations near Fort Bragg and in the Monterey Bay area. Recreational use and invasion by freeway ice plant {Carpobrotus edulis) and European beachgrass {Am- mophila arenarid) impact the habitats of both species. The weed removal project included hand pulling of both ice plant and colonies of European beachgrass, replanting with natives grown from local seed, and fencing to protect one of the newly restored areas. The hand removal process followed techniques that were perfected under the direc- tion of Andrea Pickart at the Lanphere Dunes Preserve north of Areata. Crews from the California Conservation Corps, the Americorps, and local volunteers did a tremen- dous job in completing the work. Additional funds from the grants program were used to remove three exotic tree species from coastal habitats in 54 FREMONTIA VOLUME 26:4, OCTOBER 1998 selected areas from MacKerricher State Park south to Salt Point State Park. Eucalyptus, Monterey pine, and Monterey cypress were introduced to coastal terraces of Sonoma and Mendocino counties for windbreaks, firewood, and land- scaping. All three species readily reproduce by seed, in- vade native habitats, and displace native species. The project focused on cutting the exotic trees and pulling seedlings in park areas where natural ecosystems were most threatened. Other criteria for prioritizing removal areas included historical significance of the planted groves, nesting habitat concerns for native birds, and logistical and political considerations for removal operations. Fol- low-up efforts are now needed to avoid reestablishment of seedlings and sprouts. Ongoing Projects with Financial Needs At Jughandle State Reserve, between Mendocino and Fort Bragg, several DPR programs since 1979 have been dedicated to the removal of gorse (Ulex europaeus). Al- though the bulk of funding came from the Natural Heritage Stewardship Program, monies from the controlled burn program and inmate rehabilitation program have contrib- uted to the efforts. Gorse, which resembles broom, is an extremely invasive shrub that is quite successful at both sexual and vegetative reproduction. The seeds are long- lived (twenty-five years or more under ideal conditions), and resprouting occurs from cut or burned stumps and root fragments. Gorse primarily invades coastal prairie habitats, but is also found in openings in local coastal pine forests. The gorse removal program has taken the integrated pest management approach, utilizing burning, removal by hand and equipment, biological control, and herbicide application. Generally, mature gorse plants were removed by burning or mechanical means, then seedlings or sprouts were treated with herbicide or removed by hand before new seed was produced. In areas of dense infestation, disking is also used to kill smaller plants and to encourage gorse seed germination and the growth of new seedlings, which are then treated. The goal of this program is to eventually deplete the gorse seed bank. Success is depen- dent upon the availability of park funding to prevent flow- ering in treated areas and prevent gorse invasion into new areas. Revegetation with native species has not been suc- cessful in preventing the reestablishment of gorse, as even a low density of gorse will reduce the cover of natives. As of 1996, these efforts had nearly eliminated mature gorse from most of the Jughandle headland areas, west of High- way 1, although some dense patches still remained east of the highway in forest openings. Currently, however, flowering gorse has returned to many of the previously treated areas due to a lack of support and funding to continue the program. In fall 1995 local members of the public expressed opposition to the use of herbicides to control gorse at Jughandle State Reserve. An agreement was reached to ban herbicide use for one year in parks of the Mendocino sector and to hire a part-time volunteer coordinator to organize and oversee a hand-removal program. Although a few devoted volunteers and the coordinator are to be commended for their efforts, not enough people partici- pated, and the volunteer program was less effective than the planned herbicide application would have been. Sev- eral factors contributed to this lack of success. Gorse has an extensive root system, so removing plants by hand can be a difficult, time-consuming task, especially where den- sities are high or where extra care must be taken to avoid digging out protected natives. The future of the gorse removal program now depends upon DPR funding and public support. Past experience and current information indicates that the most cost-effec- tive approach is to continue removal of mature plants with equipment and inmate labor, disk seedlings in accessible areas of high density, and treat seedlings or resprouts with herbicide where hand removal is not feasible. Broadcast burning to control gorse is not a desirable alternative because gorse readily resprouts after burning and burned areas are quickly invaded by Holcus lanatus, an exotic perennial grass that also outcompetes native vegetation. At this time, there is no district funding available to treat gorse and there is still strong local public opposition to herbicide use. Effective weed control alternatives and consistent follow-up efforts are seriously needed at Jughandle State Reserve, as gorse continues to spread and impact native habitats and several sensitive species. Pampas Grass DPR has had several pampas grass {Cortaderia jubata) removal projects in Sonoma County at Salt Point State Park, Kruse Rhododendron State Reserve, Fort Ross State Historic Park, and Bodega Head at Sonoma Coast State Beach. Funding for the projects came from the Natural Heritage Stewardship Program and DPR's Resource Man- agement Program. Most of the pampas grass at Salt Point, Kruse Rhododendron, and Fort Ross (other than road cut infestations adjacent to Highway 1) occurs in forested areas that are recovering from past logging. By the end of a 1995 spray program, all but one large infestation at Salt Point State Park had been treated with herbicide. Because of the large size of pampas grass plants at Kolmer Gulch, in Fort Ross State Historic Park, a follow-up application is needed to kill many of the mature plants. As the forest canopy matures and understory vegetation becomes shaded, pampas grass may be less successful in competing with the native understory species. At Bodega Head in Bodega Bay, Sonoma County, herbicide spray was used to kill pampas grass during the late 1980s. As in most areas where it occurs, pampas grass at Bodega Head was primarily associated with disturbed VOLUME 26:4, OCTOBER 1998 FREMONTIA 55 soils, especially road cuts. Although the initial spray effort killed most of the mature plants, the follow-up program was incomplete, resulting in an abundance of seedlings throughout previously treated areas. Fortunately, devoted members of the Milo Baker Chapter of CNPS have orga- nized work parties to hand remove pampas grass around Bodega Bay. The hand-removal efforts are proving to be successful—pampas grass does not resprout as readily as gorse and is more easily removed when plants are small. At Sinkyone Wilderness State Park in the Northcoast Redwoods District, pampas grass has heavily invaded old logging areas throughout many areas of the park. Local opposition in the late 1980s has prevented DPR from continuing a herbicide spray program. Because much of the area is not easily accessible, the pampas grass popula- tions are so large, and public support for pampas grass control is lacking, hand removal is simply not a feasible alternative. The district currently has no specific plans to control pampas grass at Sinkyone. However, many mature plants have been removed with heavy equipment as part of a watershed restoration program to control erosion by recontouring and removing old logging roads. It is antici- pated that, as the forest canopy matures, populations of pampas grass may eventually become shaded out. Various other exotic weed removal programs have been implemented in many of the North Coast area parks. At Bodega Head large areas of ice plant were treated with herbicide and planted with native grasses. At Sonoma Coast State Beach and Salt Point State Park, eucalyptus trees were cut and either treated with herbicide or sprouts were removed by hand. At Austin Creek State Recreation Area members of the Milo Baker Chapter of CNPS have devoted many weekends to "broom bashing." In Mendocino County members of the Dorothy King Young Chapter of CNPS have volunteered many hours to hand remove Aus- tralian fireweed, German ivy, and pampas grass from af- A private residence is engulfed by gorse {Ulex europaea) near Jug- handle State Preserve in Mendocino. Photograph by Tina Fabula. 56 FREMONTIA fected state park units. A local group associated with Mote Creek in southern Mendocino County has organized work parties to remove Cape ivy from Schooner Gulch. At Stagecoach Hill Azalea Preserve, south of Orick in Hum- boldt County, California Conservation Corps crews have hand removed broom plants. Resource managers in the Northcoast Redwoods District are starting to work with the local CNPS chapter to develop strategies for exotic species removal. Plans also include controlled burn projects at Sinkyone Wilderness State Park to control broom. Efforts to control weedy exotics within the North Coast area state parks have had mixed results. In some areas the programs have been highly successful with eradication of exotics and reestablishment of native species. In other areas, where there are no, or discontinuous, follow-up efforts, weeds quickly return in full force. Mostly, where control programs have continued, we are beginning to see a reduction in weedy exotics. Because control efforts in most areas often lack strategic planning and documentation, it is difficult to quantify results. During a recent meeting of state park resource ecologists, it was recognized that better planning and documentation are crucial if exotics control programs are to receive future support from the DPR and from state legislators. It was also recognized that monitor- ing and planning cannot be improved unless more state park ecologist positions are funded. Other Weedy Exotics in Need of Control This article describes mainly existing weedy exotics control programs within the North Coast parks. There are many populations of exotics within these parks that have never been mapped or treated. Exotic species control is not even considered by DPR to be feasible for a majority of the park units, given current budget allotments. European beachgrass is a major problem on miles of North Coast beaches. This highly invasive grass threatens both sensitive plant species and nesting habitat for the western snowy plover. At Bodega Dunes within Sonoma Coast State Beach hundreds of acres are completely cov- ered with European beachgrass—most of it planted about fifty years ago by the Soil Conservation Service for dune stabilization. Within the natural preserve of MacKerricher State Park, European beachgrass now grows from the mouth of the Ten Mile River southward along an approxi- mately four-mile stretch of beach and dunes. Although colonies of European beachgrass were removed from small beach areas in the southern half of MacKerricher State Park, DPR has no funding to undertake an eradication program in the northern half of the park, which contains the natural dunes preserve. Proposals for European beachgrass removal in the preserve at MacKerricher and on the Navarro River Beach were recently denied grant funding, partly because exotics removal is perceived as a park maintenance function. At Big Lagoon, Stone La- VOLUME 26:4, OCTOBER 1998 goon, and Little River state beaches in the Northcoast Redwoods District, European beachgrass is recognized as a problem, but the district lacks adequate funding to even consider initiating a control program. Nearly all of the coastal prairies throughout the North Coast parks are dominated by exotic annual and perennial grasses. Programs to control exotics have not been at- tempted by the Russian River/Mendocino or Northcoast Redwoods districts. Little is known about the ecology of these prairies, and management practices appropriate for inland and Central Valley prairies are not always appli- cable to North Coast prairies. On the moist North Coast, controlled burn programs, which have produced favorable results on drier climate grasslands, seem to promote the exotic Holcus lanatus over the native grasses. Before man- agement programs are implemented, further studies are needed to determine which practices best control the exotic grasses and still promote native coastal prairie species. Specific control programs for ice plant, pampas grass, Cape ivy, eucalyptus, Monterey pine, Monterey cypress, and broom have been mentioned earlier, but there are many parks where these species prevail, and no program for control has been implemented. Other invasive weedy exotics, commonly found throughout the North Coast parks include English ivy, tansy ragwort, bull thistle, Italian thistle, wild radish, periwinkle, Himalayan blackberry, yellow star-thistle (in inland areas), poison hemlock, fen- nel, creeping buttercup, and many others that locally im- pact native vegetation. There are no control programs for these species, other than removal that may occur as a result of routine park maintenance. Park maintenance, however, is focused more on keeping campgrounds and trails clear for visitor access than on exotic weed control. Education and Public Support Public education about the threat of invasive weedy exotics is crucial to the continuation of control programs in state parks and other natural areas. In Mendocino the Dorothy King Young Chapter of CNPS and the Mendocino sector of the Russian River/Mendocino District parks held two public informational workshops about exotic species control. Both featured speakers from various agencies and organizations and the scientific community. The work- shops were designed to inform participants about control techniques for the most serious local invasive exotics and to generate public support for control programs. Response to the workshops was favorable, and it is hoped that those who attended will continue to inform others and support control programs. Education about weedy exotics is also necessary within the DPR. The DPR's natural resource management staffs are comprised mostly of only one associate ecologist per district, sometimes with one or two assistants on a sea- sonal basis. Therefore, most of the removal of weedy exotics, other than for grant-funded control projects, is left to park operations staff or volunteers. So that operations staff may be better informed about exotics, Assistant Ecolo- gist Tina Fabula, of the Russian River/Mendocino Dis- trict, wrote and distributed a booklet that describes nine- teen local weedy exotics and various control techniques. The local chapter of CNPS has expressed interest in fund- ing additional printings for public distribution. The invasion of weedy exotics is a serious threat to significant natural areas and sensitive native species through- out state park units of the North Coast, as well as other areas of the state. DPR has recognized this threat in the past and has spent hundreds of thousands of dollars on exotics con- trol programs. However, state park budgets for the protec- tion and management of natural areas have been greatly reduced. Natural resource managers within the DPR agree that exotic species control programs need better planning, monitoring, and documentation to justify funding. There is a great need to set priorities and have more comprehensive statewide policies that address funding for all parks. Probably most important for the justification and pro- motion of exotic species control programs are public edu- cation and support. Even though parks have been set aside for the protection and perpetuation of California's natural communities, the number of park visitors increases each year, resulting in greater impacts to native vegetation. If we are to protect the native flora in parks, both regionally and statewide, there needs to be a better balance between natural resource protection and recreational use. There also needs to be a secure funding source for parks so that we can be less dependent upon visitor use fees and outside grants than we are today. Finally, there needs to be more research on feasible ways to eradicate weedy exotics, without the use of existing herbicides, especially in areas such as the North Coast, where there is much public opposition to herbicide use. The educational and support programs of CNPS and the California Exotic Pest Plant Council (CalEPPC) pro- vide a valuable service in promoting protection of the native flora. Communication and cooperative efforts be- tween DPR managers, CNPS, and CalEPPC will be key to successful weedy exotics control programs in the North Coast area parks and throughout the state. References Fabula, Tina. Invasive non-native plants of the Mendocino/ Sonoma State Park Units—the identification, description, and removal. Unpublished California Department of Parks and Recreation booklet. 1994. Hillyard, Deborah. Weed Management in California's state park system. Fremontia 13(2):18-19 (July '85). Renee Pasquinelli, California Department of Parks and Recre- ation, Russian River/Mendocino District, P.O. Box 440, Men- docino, CA 95460 VOLUME 26:4, OCTOBER 1998 FREMONTIA 57 THE CALWEED DATABASE: CALIFORNIA NOXIOUS WEED CONTROL PROJECT INVENTORY by Steve E. Schoenig IN 1995 THROUGH 1997 a memorandum of under- standing was signed by sixteen state and federal agencies to create the California Interagency Nox- ious Weed Coordinating Committee (CINWCC) and CALWEED, an inventory of noxious weeds. The CINWCC also includes many stakeholder groups such as the Califor- nia Native Plant Society, Cattlemen's Association, Cali- fornia Exotic Plant Pest Council, The Nature Conser- vancy, and the Nurserymen's Association. The intent of the CINWCC is to increase cooperation and communica- tion among weed control specialists and land managers in all groups and agencies within California. This partner- ship will result in more timely and effective weed control and eradication projects. The CINWCC holds quarterly meetings, and has formed six subcommittees: Weed Pro- ject Database; Education; Research and Monitoring; Fund- ing and Grants; Regulatory Streamlining; and Regional Working Groups. The CINWCC Weed Project Database Subcommittee has designed the content of the California Noxious Weed Control Project Inventory (CALWEED). The Subcom- mittee is led by California Department of Food and Agri- culture staff, and the California office of the Bureau of Land Management has provided additional funding for the CALWEED database. The project inventory is an Internet- Morrocan mustard (Brassica tournefortii) invades disturbed areas in the Mojave Desert. Photograph by Matt Brooks. based searchable database. Information about a noxious weed control project is entered into the database by having a person affiliated with the project fill out and submit a three-page data form. Information provided includes: project title, purpose, abstract; target weed; project con- tact; cooperators, funders, landowners; location, size, habi- tat, monitoring data, status; and control methods (me- chanical, manual, fire, biocontrol, chemical). After the information is entered into the database, projects can be viewed with an Internet browser. One can search the project database for projects selected on criteria such as county, weed species, control method, organiza- tion, etc. The database will also contain an on-line ency- clopedia of noxious weed biologies and control methods, which is being developed by Joe DiTomaso and his staff at the University of California at Davis. The website will contain links to other weed control related Internet sites. The Internet address of the database is: http://endeavor. des.ucdavis.edu/weeds/. The database focuses on projects that target specific weeds for eradication or long-term control. These can be weeds that threaten natural areas, rangelands, open space, and agriculture. There is less interest in non-specific veg- etation management and weeds specific to urban land- scapes and intensive production agriculture. The technical coding of the database and its housing is contracted to the Information Center for the Environment (ICE). ICE (http://ice.ucdavis.edu) is developing a num- ber of resource management project databases under the umbrella of the Natural Resource Project Inventory (NRPI). The NRPI umbrella structure allows the weed control project information to be available through either a weed- specific interface or under a more general search interface that will access project descriptions for all resource man- agement projects being reported in California. An even wider umbrella under which weed projects will be acces- sible is called the Government Information Locator Ser- vice (GILS). The GILS system will allow centralized information searches for worldwide information. As of May 1998 the CALWEED database is up and running. Currently there are 700 project entries in the data- base. The eventual number may be as high as 1,000. Those wishing to participate can download data forms and in- structions from the website or contact the author directly. Steve E. Schoenig, Integrated Pest Control Branch, California Department of Food & Agriculture, 1220 N Street, Room A357, Sacramento, CA 95814; sschoenig@cdfg.ca.gov VOLUME 26:4, OCTOBER 1998 BIOLOGICAL CONTROL OF WILDLAND WEEDS by Michael J. Pitcairn Practitioners OF biological control suggest that by reuniting an exotic weed with its natural en- emies (insects and diseases), weed populations may be reduced to much lower densities; or, at the very least, the competitive advantage that some exotic plants have over native flora may be reduced. The ability of exotic plants to invade native ecosystems is affected by several factors, including climate, soil type, reproductive biology, amount of disturbance to native ecosystems, and lack of specific natural enemies and diseases. This last factor, the lack of natural enemies, may be particularly significant, for it allows exotic plants to reproduce with greater success in their new habitat than they would nor- mally experience in their area of origin. More seeds are produced, fewer seeds are destroyed, and more seedlings survive to flowering in their new habitat. This increase in reproductive output can result in a competitive advantage over native plants that experience reproductive losses from native natural enemies or other ecological factors. In addi- tion, while some exotic species form dense monospecific stands in their new habitat, many of these species exist as minor components of the community they inhabit in their area of origin. Consider tansy ragwort and Klamath weed, two invasive weeds originally from northern Europe. Though common in their native habitats, they usually do not form thick, monospecific stands, and they exist at much lower densities than were observed in California before the introduction of their biological control insects. It was these observations—the lack of specific natural enemies on introduced species and the low abundance of these same plants in their area of origin, but weedy else- where—that led to the development of biological control of weeds. History and Current Projects The earliest efforts of weed biological control occurred in the mid-1800s with the movement of the cochineal insect, Dactylopius ceylonicus, throughout India and into Sri Lanka (then Ceylon) where it successfully controlled the cactus, Opuntia vulgaris. In the northen hemisphere, biological control of weeds was first practiced in Hawaii in 1902 against Lantana camara, an introduced ornamen- tal shrub that invaded rangelands, hindered reforestation, and formed dense thickets in coconut plantations. Since then, biological control has become a widespread strategy to control invasive exotic weeds and is commonly prac- ticed in Australia, New Zealand, South Africa, Canada, and the United States. Historically, most targets of biological control have been agricultural weeds because of their direct economic impact and strong political support for solutions to agri- cultural pest problems. Some wildland weeds are also agricultural weeds, and their control efforts have ben- efited from biological control research in agricultural systems. A list of wildland weeds for which biological control agents have been released in wildlands and nature preserves in the western United States is presented in the accompanying table. While most of these plants are also agricultural weeds, purple loosestrife (Lythrum salicaria) and melaleuca (Melaleuca quinquenervia) are primarily wildland pests and are now targets of biological control programs. The amount of control achieved by the introduction of biological control agents can be dramatic, as was illus- trated by the control of Klamath weed (Hypericum per- foratum), an invasive weed that became widespread in northern California rangelands. Klamath weed is poison- ous to cattle, sheep, and horses, and heavily infested pas- tures and rangeland are rendered almost worthless. Con- trol resulted from the importation of Chrysolina quadri- gemina, a leaf and stem feeding beetle, in 1945. Within a decade following release, C. quadrigemina reduced Kla- math weed from an extremely common rangeland weed to an occasional inhabitant of roadsides. Currently, Klamath weed exists at less than one percent of its abundance prior to 1945. Klamath weed had also invaded the Yosemite Valley and was considered a serious threat to the native floral community. C. quadrigemina was released in 1950 in Yosemite National Park, where it quickly controlled its host and has maintained control since. There are two projects currently underway that will benefit California's wildlands: biological control of salt cedar and yellow star-thistle. Salt cedar (Tamarix ramo- sissima), in the plant family Tamaricaceae, is one of sev- eral Tamarix species introduced into the United States for use as a windbreak and to prevent soil erosion. It has become widely naturalized, and during the 1930 to 1950s its populations exploded and occupied large areas of bot- tomlands, riparian corridors, and drainages in the south- western United States. It is now considered the worst weed of southwestern riparian areas. In 1986, Dr. Jack DeLoach, a scientist with the United States Department of Agricul- ture, Agricultural Research Service (USDA ARS), Bio- logical Control of Weeds Laboratory at Temple, Texas, initiated a biological control program against this species. The goal of the program is to search for and obtain insects that are capable of feeding on and damaging T. ramosissima, and that do not feed on, or at least do not significantly VOLUME 26:4, OCTOBER 1998 FREMONTIA 59 damage, native plants and Tamarix aphylla, a less invasive introduced species used for windbreaks and shade. Fifty to over 250 insect species are known to feed on Tamarix in Asia and Europe. The highest diversity was observed in the former Soviet Union (more than 250 species), Israel (220 species) and Pakistan (190 species). As a result of these surveys, fifteen insect species were identified as candidates for introduction into the United States. Host specificity testing for two insects, the mealy- bug {Trabutina mannipara) from Israel and the leaf beetle {Diorhabda elongata) from China, has been completed and petition for approval for release has been submitted. Of the remaining thirteen species, four are currently being tested for host specificity in quarantine in Temple, Texas, one has been approved for shipment into quarantine, and the other eight species are being tested overseas, accord- ing to DeLoach and co-workers. DeLoach reported that Trabutina mannipara is a small mealybug whose nymphs and adults feed on the twigs and branches of Tamarix. Large densities of T. mannipara can build up on T. ramosissima, and branches with very high densities of mealybug may eventually die. In quar- antine the waxy young nymphs covered the young twigs of T. ramosissima and eventually killed several of the test plants. Some feeding on T. aphylla was observed but populations were not sustained while populations in- creased four to twenty times on T. ramosissima. Given these observations, this biological control agent is ex- pected to have little or no impact on T. aphylla in the field. The mealybug attacked only members of the genus Tamarix, and feeding on North American native plants was not observed. DeLoach also reports that Diorhabda elongata is a leaf feeding beetle obtained in China, where it attacks only Tamarix species. In China D. elongata is common and causes appreciable damage. In quarantine tests larvae fed almost entirely on Tamarix species. Larvae fed on T. aphylla as well as T. ramosissima. However, adults tended to avoid ovipositing on T. aphylla. If released, it is pre- dicted that the beetle will damage T. aphylla only slightly, if at all. A small amount of feeding was observed on Frankenia species, native to the southwestern United States and northern Mexico, and this was examined fur- ther. A total of 106 young larvae were transferred by hand to Frankenia planted in pots. Only two larvae developed to adults and both were deformed and unable to repro- duce. It was concluded that Frankenia will not serve as a host for D. elongata. In March 1994 petitions for field release of these two insects were submitted to USDA's Animal Plant Health Inspection Service (USDA, APHIS) for approval for re- lease. The technical advisory group of APHIS, a scientific panel that evaluates introduction requests, recommended that both insects be released and an environmental assess- ment was prepared as required by the National Environ- mental Protection Act. However, concerns over the con- trol of Tamarix species have been raised following place- ment of the southwestern subspecies of the willow fly- catcher (Empidonax traillii extimus) on the federal endan- gered species list on March 26, 1995. This bird now uses Tamarix to nest in some of its range where willows and cottonwoods, its natural nest trees, have been displaced by Tamarix. Concerns have been raised that native wil- lows and cottonwoods will not grow in place of Tamarix in some areas because of the increased salt content in the soil and thus that the flycatcher would be negatively impacted. Approval of the environmental assessment de- pends on resolving these concerns regarding the willow flycatcher. It should be noted that this is an issue not just regarding the use of biological control, but of whether Tamarix should be controlled at all in some areas. Thus resolution of these issues affects all efforts directed at controlling Tamarix. Yellow Star-thistle Yellow star-thistle {Centaurea solstitialis), in the aster family or Asteraceae, is an introduced annual weed of Eurasian origin that has become one of California's worst weeds. It infests rangelands, pastures, roadsides, and irri- gation canals. In 1985 it was estimated that this weed infested just under eight million acres statewide. Foreign exploration and host testing by the USDA ARS, Biologi- cal Control of Weeds Quarantine, Albany, California, have resulted in the approval and release of five insects for control of yellow star-thistle in the western United States. None of these insects attacked any of the native plants (including two native Centaurea species) during host speci- ficity testing, and none has been recovered from any native species since their release in California. All five insects feed inside the seed head and reduce seed produc- tion, which is this weed's sole means of reproduction. The bud weevil (Bangasternus orientalis) was first released in 1985 and is now widespread throughout Cali- fornia. It has one generation per year and is active on yellow star-thistle plants from late May through mid-July. The eggs are deposited on the leaves or stem below closed flower buds. The larvae burrow into the stem and up into the flower head and feed on the developing seeds and disk tissue. Adults exit the heads in August and overwinter in plant debris near trees and along fence rows. The gall fly (Urophora sirunaseva) was first intro- duced in 1984 and is also widespread throughout Califor- nia. This fly has two generations per year. The first gen- eration is active mid-April through early June; the second is active mid-June through July. Eggs are inserted between the bracts of the closed flower heads and among the young developing flowers. The larva positions itself at the base of a flower tube within the infloresence and initiates the growth of a woody gall around itself. The gall prevents the development of seeds by the infested flower and some of 60 FREMONTIA VOLUME 26:4, OCTOBER 1998 the neighboring flowers within the inflorescence. Several galls may be found in a flower head. The gall fly overwin- ters as a mature larva in the seed head. The hairy weevil (Eustenopus villosus) was first intro- duced in 1990 and has been released in forty-seven coun- ties in California. However, unlike the previous two in- sects, this insect does not readily disperse from its release site, so it has not become as widespread as the bud weevil and the gall fly. The hairy weevil has one generation per year and is active in late June through August. It impacts yellow star-thistle plants by feeding on and killing young, closed flower heads and by depositing eggs in large swol- len heads, where its larvae feed on the developing seeds. The adult emerges from the seed head in August through September and overwinters in debris at the base of trees and along fence rows. Of the five insects released in California to date, the hairy weevil appears to have had the greatest impact on yellow star-thistle despite its limited distribution. The flower weevil {Larinus curtus) was first intro- duced in 1992. It has been released in five counties, but establishment has been confirmed at only one site in Sutter County. Follow-up surveys at this site have revealed that some weevils are infested with a gut parasite. The flower weevil has one generation per year. Eggs are laid in the open flowers and the larvae feed on the developing seeds. Adult weevils emerge from the seed heads and overwinter away from the plant. The peacock fly {Chaetorellia australis) has been re- leased in eleven counties since 1989 and has established in four counties. This is in contrast with releases in Oregon and Washington, where the fly did become established and is becoming widespread. This may be due in part to the unusually early spring emergence by the fly, before any yellow star-thistle is up. In Oregon and Washington, another invasive exotic Centaurea, bachelor button (Cen- taurea cyanus) is common and blooms much earlier than yellow star-thistle. This host is used by the first generation of peacock flies, which later move onto the yellow star- thistle. The peacock fly has two generations per year. Eggs are laid between the bracts of large closed flower buds. The larvae burrow into the head and feed on the develop- ing seeds. Peacock flies overwinter as mature larvae in the seed heads. Field studies are currently underway to measure the impact of these insects on yellow star-thistle seed produc- tion and recruitment in California. Insect populations are still increasing locally at release sites, so it is too early to know how successful they will be. Two plant diseases are also being examined for their potential for introduction as biological control agents. Puccinia jacea is a rust fungal disease that attacks the leaves and stem of yellow star- thistle plants. Host specificity studies are underway at the USDA, ARS, Foreign Disease Laboratory in Frederick, Maryland, and the fungus may be available for introduc- tion in three to five years. An undescribed species of Aschocyta is a naturally occurring fungus that exists in the soil and attacks the roots of yellow star-thistle seedlings as well as several other plant species. It was first recovered by California Department of Food and Agriculture scien- tists from roots of yellow star-thistle seedlings obtained in Solano County in 1993. In laboratory tests, up to ninety percent of inoculated seedlings were killed with this fun- gus. Host specificity studies are now underway. Benefits and Limitations of Biological Control Biological control of weeds in wildlands is somewhat different in native ecosystems than in agricultural sys- tems. The goal of weed control in agricultural systems is to improve the yield or production of a commodity such as livestock on rangeland. Success in these systems is mea- sured by increased production and economic gain. In con- trast, the goal of weed control in wildlands is to restore or maintain populations of valued native species and native- dominated communities and ecosystems. Thus, success is measured as the absence of decline in species diversity or Adult female peacock fly (Chaetorellia australis); adult flower weevi (Larinus curtus); adult female gall fly (Urophora sirunavseva). Photographs by G.R. Johnson, USDA, Foreign Disease Laboratory, Frederick, Maryland. J"/, VOLUME 26:4, OCTOBER 199! FREMONTIA 61 loss of protected species, vegetation types, or communi- ties, a result not easily expressed in economic terms. Biological control of weeds in wildlands can be an effective control option for many of the same reasons that it is pursued for agricultural systems: once the bioagents establish, they usually maintain control of the pest indefi- nitely; they can spread to other infestations and bring them under control; and in most cases they do not impact other species noticeably. Biological control may also be the only option capable of bringing certain widespread pests such as leafy spurge (Euphorbia esula) and purple loos- estrife under control over large areas. In a management plan for melaleuca, a widespread exotic tree invading the everglades, LaRoche concluded that "the ultimate control of melaleuca in Florida will probably depend on the suc- cess of biological control agents introduced from Austra- lia." In addition, many find biological control to be prefer- able to the use of pesticides because of the danger these compounds may pose to other organisms, including hu- mans, or from movement of pesticides off-site, especially into ground and surface waters. Weed control in wildland areas by traditional methods, such as hand pulling and herbicide treatments, can be problematic due to the lack of uniformity in the distribu- tion of the target weed, the uneven terrain, and the lack of accessibility to infested areas by work parties and equip- ment. Many natural areas have not been subject to road or trail construction. The construction of roads or trails for access by work parties or equipment can open up corridors of disturbance that may serve as conduits for invasion for other weeds. In some situations, even hand pulling and the tramping of the work parties can disturb the soil to the extent that these efforts may be more destructive than beneficial to the native species. In theory, biological control agents are specific to the target plant and leave native species alone. Biological control agents can actively search and discover individual target plants that are difficult to find among thousands of non-target plants in a community. They can also attack plants that are located in areas that are physically inacces- sible, such as cliffs, steep hillsides, roadless areas, and sensitive environments that might otherwise suffer from disruption by activities of work parties. There are also some disadvantages to consider. First, biological control can be achieved only by introducing another exotic organism into the system. Intoduction of a foreign element may seem contrary to the goals of pre- serving or restoring a native ecosystem. Both the direct and indirect potential activities of the biological control agent must be considered before release. The question is: will the biological control agent attack native plants when its intended host plant is reduced in abundance? This is of particular concern because biological control agents are intended to be permanent additions to the ecosystem and spread from their release sites. Safeguards are provided by the host specificity testing that is performed prior to their release. Host specificity testing provides information on the range of economic and native plants that may be attacked and the reproductive potential of the biological control agent. When a natural enemy is considered for introduction, its host specificity is first evaluated by examining host records in its native habitat. If it has been recovered from only one or a few closely related host plants such as those belonging to the same genus, the natural enemy may be highly host-specific. Host specificity is then examined by exposing the natural enemy to representative native and commercial plants that are related to the target weed. The selection of plants for testing is based on an ever-widening circle of relatedness, beginning with close relatives and moving to distant relatives and then to unrelated hosts. Most of the initial host testing of agricultural plants occurs in its native habitat in outdoor gardens or in field cages. Testing of California native plants usually occurs in quar- antine facilities in the United States to avoid growing our natives in new regions where they may escape and become weeds themselves. Host specificity testing of potential weed biological control agents began in the 1920s and initially included agricultural plants growing in the region infested by the target weed. Later, in the 1940s, some native plants closely related to the target weed were included, but it wasn't until the 1970s that the protocols described above were devel- oped. Nevertheless, some biological control agents re- leased before the 1970s have been observed attacking some native plants. For example, Chrysolina quadrigemina was introduced in 1945 to control Klamath weed. Since then it has been observed to attack only Hypericum spe- cies: H. perforatum, its targeted host, H. calycinum, an exotic ornamental commonly planted along highways, and H. concinnum (gold-wire), a native species sympatric with H. perforatum in northern California. The results from the pre-release host specificity tests suggested that several species of Hypericum could serve as hosts. Ap- proval for release was made based on the immense benefit over the small but anticipated risk. For H. concinnum, attack by C. quadrigemina has been limited, and it is still common in its native habitat. Another example is Rhinocyllus conicus, a seed head weevil released in California beginning in 1971 against milk thistle (Silybum marianum), Italian thistle (Carduus pycnocephalus), and musk thistle (Carduus nutans) that has been observed feeding on several native Cirsium spe- cies. While it is unfortunate that this has happened, this was again not unanticipated as the host specificity tests indicated that several exotic Cirsium species could serve as hosts. Approval ofR. conicus was done when all thistles, even native thistles, were considered pests, so there was little concern over observations of their feeding and repro- duction on Cirsium. The impact of R. conicus on native thistles is unknown, but is under evaluation in California by John Herr and Joseph Balciunas, USDA, ARS, Bio- 62 FREMONTIA VOLUME 26:4, OCTOBER 1998 Wildland Weeds Subject to Biological Control in the Western United States Pest Species Scientific Name Common Name Biological Control Agent Locations of Releases by State Acroptilon repens Russian knapweed Subanguina piciridis Oregon Centaurea cyanus bachelor button Chaetorellia australis California Centaurea diffusa diffuse knapweed Bangasternus fausti Larinus minutus Metzneria paucipunctella Sphenoptera jugoslavica Urophora affinis California, Oregon California Oregon California, Oregon California, Oregon Centaurea maculosa spotted knapweed Agapeta zoegana Cyphocleonus achates Larinus minutus Metzneria paucipunctella Terellia virens Urophora affinis Urophora quadrifasciata California, Oregon California California Oregon California California, Oregon Oregon Centaurea solstitialis yellow star-thistle Bangasternus orientalis Chaetorellia australis Eustenopus villosus Larinus curtus Urophora sirunaseva California California California California California Chondrilla juncea rush skeletonweed Cystophora scmidti Eriophyes chondrillae Puccinia chondrillina Oregon Oregon Oregon Cirsium arvense Canada thistle Ceutorhynchus litura Rhinocyllus conicus Urophora cardui Oregon Oregon Oregon Cirsium vulgare bull thistle Rhinocyllus conicus Urophora stylata Oregon California, Oregon Cytisus scoparius Scotch broom Apion fuscirostre Oregon Euphorbia esula leafy spurge Aphthonaflava Aphthona nigriscutis Montana Montana, North Dakota Hypericum perforatum Klamath weed Agrilus hyperici Aplocera plagiata Chrysolina quadrigemina Oregon Oregon California Linaria genistifolia ssp. dalmatica Dalmatian toadflax Calophasia lunula Montana Lythrum salicaria purple loosestrife Galerucella calmariensis Galerucella pusilla Hylobius transversovitattus Nanophyes marmoratus California, Oregon California, Oregon Oregon Oregon Salvia aethiopis Mediterranean sage Phrydiuchus too Oregon Senecio jacobaea tansy ragwort Longitarsus jacobaeae Tyria jacobaeae California, Oregon California, Oregon Ulex europaea gorse Apion ulicis Tetranychus lintearius Oregon California, Oregon Updated from Randall and Pitcairn, 1994 VOLUME 26:4, OCTOBER 1998 FREMONTIA 63 logical Control of Weeds Quarantine, Albany, California, and in Nebraska by Svata Louda, University of Nebraska, Lincoln. All native Cirsium species are heavily attacked by native lepidoptera and tephritid insects, so quantifying impact by R. conicus is difficult. However, current re- search by Louda suggests that it can be significant. It should be noted that, given our current high standard of host specificity, it is unlikely that R. conicus would be approved for release today. Since the 1970s increased interest in protecting native species and preserving biodiversity has resulted in more complete representation of native and economic plant taxa in host specificity tests. The results to date have been encouraging in that unanticipated host shifts have not been observed. Still, the potential for host shifts must be ac- knowledged as all organisms are subject to change through mutation and evolution. Fortunately, this is a compara- tively rare event. Exotic organisms have just as strong an affinity for their host plants as do native species. The probability of a genetic change that will cause an intro- duced bioagent to adopt a new host is no greater than the chance that such a change will occur among thousands of now innocuous native species. The decision to release an exotic biological control agent must result from a balance of risks and benefits of the different control options against the risk of doing nothing. Usually the damage caused by an uncontrolled aggressive weed far outweighs the poten- tial risks of an introduced biological control agent. Gardner and co-workers report that, in Hawaii, biological control is reserved only for those exotic species so well established that they are uncontrollable by hand removal or other mechanical approaches. Another disadvantage is that biological control is not possible for all exotic weeds. For some species, effective natural enemies simply may not exist. This may be due to their poor survivorship or lack of reproduction in their new area of habitation. In some cases, plant populations may not be controlled by their natural enemies in their native habitats. Also, some natural enemies may not be specific enough to justify their introduction. Host specific- ity is a primary requirement for the success of biological control of weeds because highly host-specific natural en- emies have a greater potential for controlling their hosts than less specific agents, and, as noted above, high speci- ficity provides a greater margin of safety. However, the requirement for high specificity can effectively remove several potential bioagents from consideration. Conflicts of interest with the agricultural community may limit the choice of some weed targets. Most of our valued economic crops are exotic, and a related plant species may become a wildland pest. For example, several alien grasses, such as cheatgrass (Bromus tectorum), ag- gressively invade wildlands and substantially reduce the occurrence of native grassland species. Because of the high value of our cereal crops, bioagents that may nega- tively affect cereals will not be approved for introduction against cheatgrass. As a result, biological control has not been pursued against exotic grasses and has focused on species not closely related to economic crops. Lastly, the development of biological control is expen- sive. Foreign exploration and host specificity testing are resource-demanding activities that can take two to four years per bioagent. A complete biological control project can take several scientists ten to twenty years from start to finish and could amount to several hundred thousand dol- lars per project. Yet, however expensive it is upfront, the savings far outweigh the initial expense, as the activity of the bioagents is ongoing and provides a permanent solu- tion to the problem. For example, in 1964 DeBach esti- mated that successful control of Klamath weed amounted to a savings of $21 million dollars to California agriculture between 1953 and 1959. These savings are still being accrued each year and now total $157 million since 1953. References Andres, L.A. 1985. Interaction of Chrysolina quadrigemina and Hypericum spp. in California. In: Proceedings of the 6th International Symposium on Biological Control of Weeds, Delfosse, E.S., (ed.), Agriculture Canada, pp. 235-39. DeBach, P. 1964. The scope of biological control. In: P. De- Bach, (ed.), Biological control of insect pests and weeds, Reinhold Publishing Corp., New York, NY. pp. 3-20. DeLoach, C.P., D. Gerling, L. Fornasari, R. Sobhian, S. Myartseva, I.D. Mityaev, Q.G. Lu, I.L. Tracy, R. Wang, I.F. Wang, A. Kirk, R.W. Pemberton, V. Chikatunov, R.V. lashenko, I.E. lohnson, H. Zheng, S.L. liang, M.T. Liu, A.P. Liu, and J. Cisneroz. 1996. Biological control program against saltcedar (Tamarix spp.) in the United States of America: progress and problems. In: Proceedings of the 9th International Symposium on Biological Control of Weeds, V.C. Moran andl.H. Hoffman (eds.), Stellenbosch, Univer- sity of Cape Town, South Africa, pp. 253-60. Gardner, D.E., C.W. Smith, and G.P. Markin. 1995. Biologi- cal control of alien plants in natural areas of Hawaii. In: Proceedings of the 8th International Symposium on Bio- logical Control of Weeds, Delfosse, E.S. and R.R. Scott, (eds.), DSIR/CSIRO, Melbourne, pp. 35-40. LaRoche, F.B., ed. 1994. Melaleuca management plan for Florida: recommendations from the Melaleuca Task Force, 2nd. ed. Exotic Pest Plant Council, West Palm Beach, FL. Louda, S.M., D. Kendall, I. Connor, and D. Simberloff. 1997. Ecological effects of an insect introduced for the biological control of weeds. Science 277:1088-90. Maddox, D.M. and A. Mayfield. 1985. Yellow star-thistle infestations are on the increase. California Agriculture 39(11,12):10-12. Randall, I.M. and M.J. Pitcairn. 1994. Biologically based technologies for pest control in natural areas and wildlands, unpublished contractor report prepared for the Office of Technology assessment, U.S. Congress, Washington, D.C. Michael J. Pitcairn, CDF A Biological Control Program, 3288 Meadowview Road, Sacramento, CA 95832 64 FREMONTIA VOLUME 26:4, OCTOBER 19 9 8 THE ROLE OF HERBICIDES IN by Jake NO data EXIST for private land, but the Bureau of Land Management estimates that the United States is losing 6,000 acres of public land every day to invasive non-native plants (4,600 acres a day in the West alone), rendering land economically useless and biologi- cally impoverished. In the frequently polarized debate over the use of herbicides in battling aggressive weeds, the subject of biodiversity is too often lost. Herbicides, per se, have become the focus of the debate. This is backwards—biological diversity should be front and cen- ter. This is the pivot on which CNPS policy must turn. Does proper use of herbicides work for or against bio- diversity? Herbicide critics usually isolate the subject. They neglect the differences among herbicides and fail to address the serious weed problem confronting the Cali- fornia flora. I am a proponent of judicious use of herbi- cides, and favor their employment as a vital part of a weed management strategy. Our discomfort with chemicals began with revelations in Rachel Carson's Silent Spring in the 1960s. The use of chemicals as a quick fix for complex problems created a backlash, resulting in a regulatory climate that protects the public against many of the dangerous substances used indiscriminately in the past. Herbicides became entangled in the reaction to chemicals, but evidence is skimpy re- garding negative effects of today's available non-restricted products when used according to label directions. Some people want to prohibit all herbicide use, but they don't address benefits or the level of risk. Those striving to preserve natural communities feel threatened by attempts to deprive them of an essential tool. In an article entitled Killer Weeds in the March-April 1997 Audubon, author Ted Williams excoriates those he calls chemophobes. The article epitomizes the frustration and anger felt by those stymied in their David-and-Goliath battle against overwhelming infestations. He cites a tragic case in Idaho's Craig Mountain Wildlife Management Area, where a program of hand spot-spraying of yellow star-thistle was stopped by a court injunction that resulted from a suit brought by the Northwest Coalition for Alter- natives to Pesticides. The partnership between the Bureau of Land Management and U.S. Forest Service was suc- cessfully controlling the infestation. The injunction al- lowed the thistle to leap out of control, infesting tens of thousands of acres of priceless habitat that had previously supported a great diversity of wildlife such as bighorn sheep, grouse, elk, moose, deer, and wintering bald eagles— habitat that is for all practical purposes gone, possibly forever. In a similar situation, a frustrated Don Schmitz of Florida's Department of Environmental Protection fumes PRESERVING BIODIVERSITY S'gg at those "who are unwilling to accept a short-term envi- ronmental insult to avoid a long-term ecological catastro- phe." Weed warriors are keenly aware that once native biological communities have been displaced by weeds, they find it difficult or impossible to restore them. Losing them sometimes means losing them forever, a needless and deeply painful loss. Our present technologies for countering invasive non- native weeds are rudimentary and few: control by biologi- cal agents, manual eradication, mechanized removal, fire, and herbicides. All have limitations; all are essential. Classical biological control offers the greatest, and perhaps only, hope for some plants and the single best means of reducing need for herbicides. A successful ex- ample of classical biocontrol is provided by Klamath weed (Hypericum perforatum), which was devastating range- lands in northern California and Oregon in the 1940s but which has been reduced to insignificant levels by the introduction of a predatory beetle that feeds exclusively on Klamath weed. On the downside, biocontrol is not feasible for some plants, such as those closely related to agricul- tural crops or those that are attacked only by generalist predators that feed on a wide range of host plants. Devel- oping a biological control agent is initially expensive and time-consuming, and there is no guarantee of success. Up to now it has been inadequately funded but there are now hopeful signs that this may change. Manual eradication can achieve inspiring results in The foreground scene at Horseshoe Cove, Bodega Marine Reserve, was until recently a monoculture of ice plant before being sprayed with a glyphosate formula. The cream cups (Platystemon califomicus), California poppy (Eschscholzia californica), brownie thistle (Cirsium quercetoruni), and California brome (Bromus carinatus) seen here regenerated from the indigenous seed bank. Photograph by Peter Connors. VOLUME 26:4, OCTOBER 1998 FREMONTIA 65 Peter Connors makes the ultimate sacrifice to scientifically determine localized areas—examples are the stewardship programs of the Golden Gate National Recreation Area in the San Francisco Bay Area and the Wildlands Restoration Team in the Santa Cruz Mountains. With increasing popularity of site-stewardship programs, use of this technique can be greatly enlarged. The value of this multi-dimensional ap- proach to weed control cannot be overstated. Still, the fact of millions of acres of overrun wildland in California reveals the limitations of site stewardship as a solution to either the California or the global problem. With the paucity of available techniques, is it any wonder that careful use of herbicides has found accep- tance by thoughtful people? This article addresses herbi- cide use only for the control of wildland weeds that are threatening biological diversity and does not address non- ecological uses such as increasing timber production. There are many examples of indigenous plant communities be- ing saved at the last minute and restored to native stock by an integrated management program in which herbicides played a necessary role. Even highly motivated volunteers have not attempted to save the state- and federally-listed endangered fountain thistle (Cirsium fontinale subsp. fontinale)—endemic to a small area on the San Francisco peninsula—because of its labor-intensive demands. At our request, the California Department of Transportation and the San Francisco Water Department initiated a pro- gram of cutting and painting the invading pampas grass with glyphosate to prevent the thistle being overwhelmed in its serpentine seep habitat; this appears to be a success story in the making. Rich grassland/wildflower areas in and around San Francisco—tiny but precious—are there today because herbicides provided crucial support to vol- unteers teetering on the brink of demoralization in the face of advancing fronts of fennel (Foeniculum vulgare), pam- pas grass (Cortaderiajubata), and French broom {Genista monspessulana) perceived as invincible. An e-mail appeal to activists for other successful ex- amples where employment of herbicides played a crucial role resulted in an overnight torrent: salt cedar (Tamarix spp.) eradication projects in Afton Canyon near San Ber- nardino, The Nature Conservancy's Dos Palmas Reserve, and Lake Mead National Recreation Area; Cape ivy (Delairia odorata), artichoke thistle (Cynara cardunculus), 66 FREMONT1A fast ice plant grows. Photographs by Peter Connors and his survivors. eucalypts (Eucalyptus spp.), and many other weedy spe- cies in Los Penasquitos Reserve in San Diego; castor bean (Ricinus communis), pampas grass, and myoporum (Myo- porum laetum) in Newport Beach, in Big Sycamore Can- yon (Pt. Mugu State Park), Leo Carrillo State Park, Lib- erty Canyon and Malibu Lagoon (Malibu Creek State Park); Team Arundo's Santa Ana River restoration; pam- pas grass on Milagra Ridge in the Golden Gate National Recreation Area near San Francisco; and ice plant (Carpobrotus edulis) at Asilomar State Park, the Marina dunes, and the Marine Lab at Bodega Head in Marin County. Plainly, many of those who value biodiversity seriously enough to donate a large part of their lives to an effort to preserve it consider herbicides indispensable. Aside from cost-effectiveness and time savings, employment of herbi- cides has the considerable advantage of avoiding soil disturbance, which activates the weed-seed bank and fa- vors weeds over natives. In the cited instance of Bodega Head, a project ongoing since 1985, dune natives were being buried under thick carpets of ice plant. Managers sprayed the ice plant, which decayed slowly over a long period. Native plants returned on their own. A similar case is in process in the Marina dunes, managed by the Califor- nia State Parks and Recreation Department. This is an efficient and ecologically sound method that should be employed more often. A Rational Dialogue Difficulty in attaining rational dialogue is partly em- bedded in language. The word "toxic" can be defined in many ways. In addition to a wide variety of meanings, it also carries heavy emotional freight. It has meaning only in relation to something else: oxygen is lethal to some organisms but essential to others. Salt, chlorine, and aspi- rin can be toxic to humans at high dosages but are safely ingested in proper amounts. Modern herbicides have been improved in recent years and are cleverly designed to work in various highly specific ways to interfere with the functioning of a specific target; they may or may not be detrimental to organisms not targeted. It would be con- VOLUME 26:4, OCTOBER 1998 structive to look at what is going on without attaching emotional labels to what may be a harmless process. The first issue of an herbicide policy is safety—to humans, soil microorganisms, wildlife, ecosystems. There are many chemicals on the market for controlling vegeta- tion. As a practical matter when we talk of controlling wildland weeds in California, we are referring primarily to two chemical compounds: glyphosate and triclopyr, usu- ally marketed under the trade names of Roundup Pro/ Rodeo and Garlon/Pathfinder II, respectively. The En- vironmental Protection Agency (EPA) classifies herbi- cides and all pesticides according to four groups, with those considered dangerous enough to be restricted placed in classes I and II, and graduating downward to classes III and IV, which are non-restricted, bear only a cautionary label, and which may be purchased retail. Glyphosate and triclopyr are in class III. All herbicides, including surfactants (which aid herbi- cide adherence and penetration) and inert ingredients, are required to undergo rigorous testing to become registered in the United States. These tests typically include animal toxicity (carcinogenicity, teratogenicity, acute toxicity), effects on non-target organisms, and mode of degradation in the environment. These are extensive tests that take years to complete. It takes chemical companies seven to ten years and forty to eighty million dollars to satisfy EPA requirements and bring a new active ingredient to the market. California requires further tests that take an addi- tional year or more to complete. EPA and the California Department of Pesticide Regulation examine all test results carried out by the manufacturer and have full audit author- ity over the results. There is not enough money in the EPA and CDPR budgets to do independent testing, but their ability to look into company records and to conduct on- site inspections keeps companies fairly honest. The research regarding safety of non-restricted herbicides is accepted by the World Health Organization. Many people distrust assurances on herbicides by agen- cies or corporations. However, faulty data generated for the EPA on chemical safety are easily detected if they are inaccurate, misleading, or incomplete, and there are critics ready to pounce on this highly visible issue. The EPA, the manufacturer, and the testing scientists have too much at VOLUME 26:4, OCTOBER 1998 stake to risk falsifying data or methodology. Non-profit organizations attempting to eliminate or reduce chemical use have zeroed in on herbicides and have succeeded in creating anxiety among some people. However, credible studies documenting negative effects have not been forth- coming. Studies reported in, for example, the Journal of Pesticide Reform, are not subjected to peer review by disinterested scientists. Popularized articles are widely read and believed by readers. This pseudoscientific report- ing accounts for most of the controversy surrounding the subject, and it places another obstacle to the formidable job of preserving biodiversity. Classes III and IV herbicides have been in use for a long time by millions of people, including home gardeners, who may purchase them at their local nursery or hardware store. As a professional gardener in San Francisco's parks and botanic garden, I used glyphosate-formulated herbicides intensively over a period of twenty years. Specific areas were repeatedly and effectively treated without diminution in soil productivity or indication of negative effects, includ- ing to the applicator. Herbicide use vastly increased my productivity. It would have been impossible to maintain these areas in an acceptable manner without spraying. Mod- ern wage rates prohibit manual eradication of weeds on the scale required in our public parks and open spaces, to say nothing of natural resource management, where resource preservation is the primary concern. There is a long history of safe and economical maintenance using herbicides. In the face of this experience, wouldn't we have evidence by this time of negative or harmful effects? It is up to critics to identify and substantiate need for further studies. Species extinction and loss of biodiversity are becom- ing weekly stories in the media. Indifference to the rend- ing of nature's fabric while we deny ourselves a useful and apparently safe weapon is beyond understanding. It is misleading to say that herbicides should be used only as a last resort. On the scale of the larger landscape, we have already passed the last resort stage. Critics would enhance their credibility if they devoted more thought to ways to preserve the miraculous diversity of life we have inher- ited. To date we have been poor stewards of this gift. Jake Sigg, 338 Ortega Street, San Francisco, CA 94122 FREMONTIA 67 PUBLIC EDUCATION AND EXTENSION SERVICE OUTREACH by Joseph M. DiTomaso Invasive exotic weeds in non-crop areas have seri- ous economic consequences and compromise the aes- thetic value, recreational use, and native plant and animal diversity in natural settings. Researchers at the University of California Cooperative Extension Service work closely with other state, federal, and private agencies to develop research projects, organize action committees, and provide information and educational materials. For example, research collaborations directed at developing control options for yellow star-thistle (Centaurea solsti- tialis), Scotch thistle (Onopordum acanthium), perennial pepperweed (Lepidium latifolium), and pampas grass (Cor- taderiajubata) are currently underway with the California Department of Parks and Recreation, California Depart- ment of Food and Agriculture, Cosumnes River Preserve, California Department of Transportation (CalTrans), and industries, including Monsanto, American Cyanamid, and Dow Agro Siences. In addition, a Weed Research and Information Center (WeedRIC) has recently been estab- lished at the University of California to facilitate coopera- tive, interdisciplinary weed management research and in- formation and technology transfer. As a Cooperative Extension non-crop weed specialist at the University of California, my research focuses on developing a better understanding of the biology and ecol- ogy of weeds invasive to rangelands, forests, aquatic ar- A three year prescribed burn site at Sugarloaf Ridge State Park in Sonoma County. Photographs by the author. %mm eas, rights-of-way, utilities, and natural habitats of Cali- fornia, and to use this information to develop economical, effective, and environmentally safe control strategies. The focus of my current research reflects the primary concerns of land managers in these non-crop ecosystems. My re- search program consists of both masters and doctoral students and research staff. Financial support comes from a number of sources, including state and federal agencies, weed science organizations, and private and public do- nors. Concurrent with this goal, my mission is to dissemi- nate information on the biology, ecology, and control of weeds in non-crop environments. This is accomplished through oral presentations, workshops, field tours, and demonstrations, as well as written reports, extension pam- phlets, bulletins, fact sheets, newspaper articles, book chap- ters, and scientific journal articles. Here I provide some examples of my research on invasive weed management and how the information is used to enhance public educa- tion and awareness. Rights-of-Way The California Department of Transportation (CalTrans) manages about 230,000 acres of rights-of-way in Califor- nia, including 15,000 miles of highways. Management of these areas has multiple objectives, including fire pre- vention, impeding the spread of noxious weeds such as yellow star-thistle, Russian thistle (Salsola tragus), and puncture-vine (Tribulus terrestris), ensuring adequate drainage and line-of-sight for drivers, protecting wildlife, and maintaining the integrity of pavement and highway structures. Weed expansion in the past decade or two on California highways is clearly evident with the widespread infesta- tions of yellow star-thistle. Because standing, senesced grasses are a fire hazard beginning in early summer and are common along California highways, it is often neces- sary to mow along these highways soon after grasses dry. Mowing is often undertaken when yellow star-thistle is in the bolting or perhaps the spiny stage of development. Mowing at these stages favors the growth of yellow star- thistle by increasing light penetration to low-growing plants. In collaboration with CalTrans, we have begun testing a new technology that combines mowing and reduced rates of herbicide spraying for yellow star-thistle control on California highways. Simultaneous mowing and spraying provides both fire suppression and effective control of yellow star-thistle, as well as reduced human exposure to chemical sprays. 6 8 FREMONTIA VOLUME 26:4, OCTOBER 1998 Rangeland Rangeland represents the largest non-crop area in Cal- ifornia. The introduction of noxious weeds into rangeland has significantly reduced the forage quality of these areas. Although yellow star-thistle represents the most serious of these introduced species, other members of the sunflower family, particularly Scotch thistle, diffuse knapweed (Cen- taurea diffusa), squarrose knapweed (Centaurea squar- rosa), and purple star-thistle (Centaurea calcitrapa) are also increasing weed problems. Other unrelated spe- cies, including perennial pepperweed and medusahead (Taeniatherum caput-medusae) are also widespread and troublesome. The most significant infestations of yellow star-thistle occur in rangeland. In California, the weed presents a prob- lem from the Tehachapi Mountains in Kern County to the Oregon border. My research has focused on the reproduc- tive biology, seedling development, and water utilization of yellow star-thistle. From these findings we have developed strategies for burning, mowing, grass and legume reseed- ing, herbicides, biological control, and combinations of these methods to control yellow star-thistle. Other research- ers at the University of California have experimented with changes in livestock management practices to suppress weeds and enhance forage quantity and quality. These projects have shown excellent results and provide a number of management options for ranchers. For example, we have shown that a mid-summer burning for three consecutive years can reduce star-thistle densities by over ninety per- cent. In addition, mowing star-thistle plants at the early flowering stage when basal branches are above the mower blades has provided excellent control. The newly registered herbicide clopyralid (Transline) at five to ten ounces of product per acre gives better than ninety-seven percent control of yellow star-thistle. The effectiveness of all these methods, however, depends upon implementation at the proper phenological stage of yellow star-thistle. Additional biocontrol efforts by the California Depart- ment of Food and Agriculture (CDFA) and the United States Department of Agriculture (USDA) have utilized five insects (three flies and two weevils), of which four have become successfully established in California. Insect releases have been made in most counties within the state, and continued explorations are underway to discover other insects or pathogens that feed on or infect yellow star- thistle. Because yellow star-thistle represents the most wide- spread non-crop weed problem in the state, a considerable amount of attention has focused on educating the public about this noxious weed. Numerous state and local meet- ings are held each year throughout the state to inform interested individuals of the biology, ecology, impact, and control of yellow star-thistle. In addition, we are currently providing detailed information on its biology and manage- ment in the WeedRIC home page. A M'liil v'"\--| i'l }.I|.'V. -Ill llli .IV :( •¦•'!.:iirr.: i. ¦! ,.'l'i-l.-n I ^ I. iV. . Illlil.'r newly planted trees. Natural Ecosystems Natural habitats represent some of the most sensitive of California's ecosystems. These include forests, oak wood- lands, wetlands, riparian zones, coastal dunes, vernal pools, and many other habitats found on private or public lands, such as state and national parks. Although it is difficult to ascribe a monetary impact of invasive weeds in these ecosystems, they clearly have a negative effect on native plant and animal diversity. Cooperative extension special- ists and farm advisors, as well as scientists from other universities and state and federal agencies, have been involved in research efforts to control several invasive weed species. Perennial pepperweed is widely distributed along road- sides and in moist areas throughout California and the west. In the past decade perennial pepperweed has become a more important weed problem in riparian zones and re- stored wetland areas, both coastal and inland. In many areas the weed has developed monocultural stands that have nearly eliminated the native vegetation. Because few con- trol strategies have proven successful, we are examining the effectiveness of combining mechanical and chemical tech- niques for perennial pepperweed management. Along north- ern California roadsides and in wetland habitats in the Cosumnes River area we are combining early-season mow- ing or disking with a later-season foliar herbicide applica- tion. In this case we hope to enhance the activity of VOLUME 26:4, OCTOBER 1998 EREMONTIA 69 glyphosate, which is registered for wetland and riparian use. In non-aquatic areas we and other researchers have shown the sulfonylurea herbicides to be quite effective. Pampas grass is found in coastal areas of California from San Diego County to the Oregon border. Each plant can produce nearly a million wind-dispersed seeds in a single year. Although seeds are not viable for long, they can disperse long distances and rapidly establish in ex- posed soils. We have demonstrated that germination is dependent on light and occurs only when seeds are at the soil surface. In addition, establishment does not occur in shaded areas. Thus, reseeding disturbed open sites with a desirable cover may prevent establishment of pampas grass in susceptible coastal areas. Yellow star-thistle not only has spread in rangeland areas and along rights-of-way, but has had a dramatic impact on the integrity of many natural ecosystems, par- ticularly oak woodlands and open grasslands. At Sugarloaf Ridge State Park in Sonoma County, we have used three consecutive summer burns to control yellow star-thistle prior to seed development. The fuel was provided by the dried annual grass populations. Our results thus far indi- cate over ninety percent control, along with a dramatic increase in the vegetative cover of the native perennial purple needlegrass (Nassella pulchra), as well as an in- crease in the diversity of native dicot species. More Information Information on weed control in non-crop areas is avail- able from the Cooperative Extension Service both in writ- ten and verbal form. Published information can be ob- tained by contacting the University of California Division of Agriculture and Natural Resources (DANR) IPM Edu- cation and Publications (UC Statewide IPM Projects, UC Davis, 95616), local UC Cooperative Extension offices, or WeedRIC (http://wric.ucdavis.edu). More research-based information is generally published in scientific journals, including Weed Science, Weed Technology, or progress reports and proceedings of the California or Western Weed Science societies. Pest Notes are available for the biology and management of yellow star-thistle, poison oak, and wild blackberry through the author or DANR IPM Educa- tion and Publications. Other publications on various as- pects of weed control can also be obtained by subscribing (at no cost within the United States) to California Agricul- ture (http://danr.ucop.edu/calag/). University of California Cooperative Extension per- sonnel have presented many seminars and field trips fo- cusing on invasive weeds around the state. These have included lectures, symposiums, field days, and workshops on yellow star-thistle, perennial pepperweed, salt cedar (Tamarix spp.), pampas grass, giant reed (Arundo donax), and brooms (Cytisus spp. and Genista spp.). In most cases these are sponsored by UC Cooperative Extension, but are 70 FREMONTIA occasionally in collaboration with other agencies, such as CalEPPC or BLM. For example, in 1996 a workshop on the biology and management of saltcedar was sponsored by UC Cooperative Extension, CalEPPC, BLM, Monsanto, American Cyanamid, The Nature Conservancy, and sev- eral other organizations and agencies. Scientific meetings of the California Weed Science Society, CalEPPC, Forest Vegetation Management Conference are held annually within the state and often include the most recent results of invasive weed research. In addition, UC faculty, Coopera- tive Extension specialists, and a few guest speakers con- duct a three-day Weed School in February each year to provide detailed information on weed biology and identi- fication, herbicide modes of action, and the interactions of herbicides in the environment. Information on weed publications, calendar of weed- related events, current research efforts in weed science, and personnel involved in weed research throughout the state is available on the WeedRIC homepage. Collaborating Organizations Action committees comprised of several state and fed- eral landholding agencies, including USDA, BLM, Bu- reau of Reclamation, Department of Fish and Game, US Fish and Wildlife Service, CDFA, The Nature Conser- vancy, and others, have come together with UC Coopera- tive Extension and other private and public organizations to develop a memorandum of understanding. The primary objective of this committee is to encourage coordination of invasive weed management, promote and implement an integrated management system, exchange information and awareness, and identify opportunities for collaborative projects among these agencies. Several other committees and working groups designed to promote the exchange of information and coordination of weed management practices have been established among various agencies within the California Exotic Pest Plant Council (CalEPPC) and between Cooperative Ex- tension weed specialists and local IPM advisory commit- tees. For example, work groups have been formed through the CalEPPC to share information and coordinate research efforts on yellow star-thistle, perennial pepperweed, Cape ivy (Delairia odorata, formerly Senecio mikanioides), gi- ant reed, saltcedar, various brooms, pampas grass, veldt grass (Ehrharta spp.), and cord grass (Spartina spp.). These groups have increased the awareness of invasive weed problems in both the public and private sectors. Such efforts also have promoted volunteerism for projects fo- cused on invasive weed management, as well as funding opportunities for UC weed specialists, farm advisors, and CDFA and USDA scientists. Joseph M. DiTomaso, Weed Science Program, University of California, Davis CA 95616 VOLUME 26:4, OCTOBER 19 98 ^^'V^;:. h 4» -jv „. *- - 5* . »W[ ''hi&\r^i]Lz%fci?'*~- '^Mi&r^v. j-r* .' !;;...':¦'• "*'-' 4V " J "" ' "S""C *' v " *_ . , '•' "i'' " ¦ V. s- * - (,# fftf '"*#*, j;' , w.ff ':';v ¦- '* ^*""^fc\*; "* #fe !V^%f/*: Tamarisk (Tamarix sp.) crowding an ephemeral in the Anza-Borrego Desert State Park. Photograph by Tom Dudley. THE CALIFORNIA EXOTIC PEST PLANT COUNCIL AND ALLIED STATEWIDE ORGANIZATIONS by Carla Bossard The homogenization of the earth's flora and fauna is a problem of global significance resulting in irreversible losses to the world's biodiversity and dramatic alteration of ecosystem processes. It is impera- tive that the public be made aware of the threat posed by non-indigenous invasive plants. Gaining public support for prevention of the spread of invasive plants and restora- tion of lands impacted by such species is equally critical. Accomplishing these goals is a complex, protracted, and underfunded process. The California Exotic Pest Plant Council (CalEPPC) was founded in 1992 to address the problems associated with invasive plant species. Initially, four people professionally and personally concerned with these problems invited twenty-nine other California citi- zens whose professions and interests had made them aware of the threats presented to wildlands by invasive plants to a meeting to discuss possible courses of action. It was decided at that meeting to organize a symposium on the subject of invasives and to create an organization to focus on countering the threat posed by exotic plants. In October 1992 the symposium was held and the 150 people attend- ing voted CalEPPC into existence. In addition to CalEPPC, other statewide conservation groups such as the California Native Plant Society (CNPS) and the California Native Grass Association (CNGA) ad- dress these issues in their policies and activities to coun- teract exotic invasive plants. All three organizations have policies that urge public agencies, private organizations, and individuals responsible for land management to adopt and implement exotic invasive plant management policies and to coordinate with each other at all levels on policy formulation and implementation. The three organizations also advocate the assessment of exotic species to ascertain their potential for ecosystem threat before they are intro- duced; encourage exchange of information regarding ex- otic invasive plant control and management; encourage public education about the problem; serve in advisory capacities on impact assessment, management, and con- VOLUME 26:4, OCTOBER 1998 FREMONTIA 71 trol of invasive exotics; encourage research on invasive species and the problems they cause; and support adequate funding for monitoring wildlands for invasive plants and for restoration of habitats threatened by invasive exotics. Where CalEPPC, CNGA, and CNPS differ is in overall scope and focus of their activities. CNGA focuses on preservation and restoration of California's native grass- lands. CNPS focuses on all aspects of the native flora and its preservation. CalEPPC focuses on issues and concerns involving exotic invasive wildland plant species with pro- grams aimed at public and private interests. To increase public awareness and education, CalEPPC frequently supplies speakers for meetings and conferences of commercial, private landowner, and conservation groups. These contacts often lead to other activities. For example, a CalEPPC board member gave a presentation to the California Association of Nurserymen (CAN) board meet- ing on environmental problems associated with the few invasive exotics that are used in horticulture or landscap- ing. As a result, we were invited to contribute a series of articles to the association's statewide journal that outlined the problems and suggested how the nursery industry could help in solving them. Members of CAN and CalEPPC are jointly developing a list of plants that can be substi- tuted for those attractive but invasive exotic species. Two CalEPPC board members addressed the sympo- sium of the American Association of Botanical Gardens and Arboreta on restoration of native ecosystems, control of invasive species, and cooperative efforts that could prevent inadvertent introduction into wildland habitats the few imported garden plants that eventually prove to be invasive. The annual CalEPPC symposium held in October each year provides an excellent forum for exchange of infor- mation about the problems caused by invasive exotics. Speakers address such subjects as the ecology of invasive species, their ecosystem impacts, their history, and perti- nent government regulations. Discussions of control meth- ods by experienced "weed warriors" and field trips illus- trating various successful strategies are also part of each symposium. CalEPPC publishes a list of Exotic Pest Plants of Great- est Concern in California that identifies these species, the habitats in which they are found, and their distribution in California. This list is compiled by a team of land manag- ers, agency biologists, academics, and consultants. It has been sent to land managers throughout the state and is available to the public on request from Sally Davis, 31872 Joshua Drive #25D, Trabuco Canyon, CA 92679. This list has proved particularly useful for those interested in moni- toring wildlands. CalEPPC serves as a resource for technical information on removal and control of particular species. Environmen- tal consulting firms, private conservation groups, and pub- lic land management agencies from all parts of California often consult with us via phone and e-mail on projects 72 FREMONTiA involving removal and control of invasives and post- treatment monitoring plans. The CalEPPC database sub- committee regularly updates the computer database on exotic pest plants. Anyone can tap into this information on the internet at http://www.igc.org/ceppc/index.html. The CalEPPPC quarterly newsletter, sent free to members and available to non-members for a small charge from Sally Davis, contains articles on ecology and control methods for both well known invasive plant species and those that have recently become problematic in California. CalEPPC sponsors and facilitates research on targeted invasive plant species. Two projects, a two-year experi- ment with Cape ivy (formerly German ivy) and a four- year experiment with French broom, were completed in June 1996 with the volunteer assistance of CalEPPC mem- bers. The findings are promising, and articles concerning them will appear in Madrono, journal of the California Botanical Society. CalEPPC has recently overseen the disbursement of funding exclusively for research on pam- pas grass to five projects that will examine the ecology of this invasive plant and various methods of control. A book entitled Wildland Weeds of California, now in press, will increase public awareness and understanding of exotic plant species and their impacts and facilitate their control. It will give detailed visual and written information on the biology and control of the seventy exotic invasive plants of greatest ecological concern in California. Three CalEPPC members, Carla Bossard, John Randall, and Marc Hoshovsky, edited the volume. A number of experts have contributed species accounts that address such topics as recognition, habitat and distribution, origin, means of reproduction and spread, impacts on plants and animals, and means of removal and control. In some areas the activities of CalEPPC and our allied organizations overlap. Both CNPS and CalEPPC com- ment on legislation and governmental activities related to invasive exotic plants and actively encourage governmen- tal and private funding of mitigation measures aimed at exotic species. For example, both organizations put con- siderable effort into keeping open the Albany, California, USDA biocontrol facility. Members of all three organiza- tions are active as volunteers in exotics removal and eco- system restoration projects. However, CNPS and CNGA are more intensively involved than CalEPPC in some activities. CNPS is active in monitoring wildlands for exotic invasive species. CNPS staff and members also serve as a resource for information on California's native flora. CNGA has researched and serves as an information resource on methods of restoration of California native grasses. Mitigating environmental problems associated with exotic invasive species will require the awareness, concerted action, and commitment of not only these orga- nizations but also the public. Carla Bossard, St. Mary's College of California, P. O. Box 5407, Moraga, CA 94575 VOLUME 26:4, OCTOBER 1998 DELIBERATE AMATEURS: VOLUNTEERS AND EXOTIC PEST PLANT CONTROL by Pete Holloran PULLING weeds once saved me from graduate school. Five years ago I had quit my desk job at a local university and began searching for a wiser way to make a living. In the struggle against wildland weeds—or, more broadly, in natural areas stewardship—I found a way of life instead. I found teachers too: nature herself and elders who offered an infectious enthusiasm and quiet wisdom. The tuition for this education was paid in sweat; the classrooms were seldom crowded. Having left an aca- demic career, I was more comfortable in a school without walls. But the identity of my teachers hardly mattered once I began to experience the sorrows of a twentieth-century ecological education. Unlike Aldo Leopold, who after such an education found himself living "alone in a world of wounds," I was not condemned to the prophet's solitary walk. Hundreds of others have chosen, as I have, to be- come regular volunteers as stewards of our local natural areas. We plant natives, collect seeds, monitor rare plants, educate others, and, especially, pull weeds. Why have we chosen to become volunteers? Our rea- sons are as diverse as the native plant communities we seek to restore. Ask the question of volunteers on a sunny October morning—time for a cookie break with breathtak- ing views of the Golden Gate—and the answers are simple and genuine, as conspicuous as our breath in the crisp morning air. "Good work and good company," they say, their words brief because their mouths are full. One volun- teer expressed in a few wise words the simple yet pro- found joy of being a park steward. "I wanted some volun- teer work that brings me outdoors and to learn about nature," Virginia Kibre told us. "I've learned more in the past six months than I ever have looking at guide books." After pausing to admire the view, she brought us back to the beauty in the moment. "This is a great day, isn't it?" she said. At times it is hard to remember the joy. Exotic pest plants are transforming vast landscapes, altering ecosys- tem functions and processes, and contributing to the wide- spread decline of biodiversity. The radical mixing of the world's biota promises to favor cosmopolitan species adapted to cohabitation with humans. One wit has sug- gested that we are witnessing the birth of a new geological epoch, the Homogeocene. Others have compared our cur- rent biodiversity crisis to the great extinction events of the geologic past. Our contributions diminish to almost noth- ing when measured against the passing of geologic time. Even Sisyphus, who was forever doomed to push a rock up Evergreen State College students remove exotic plants from the Manila dunes in Humboldt County. Photograph by Linda Miller. a mountain only to see it roll back down again, matched his strength against a single rock, not a landslide. Aldo Leopold had something different in mind when he asked us to think like a mountain. He too was sensitive to the Sisyphean quality of efforts to develop and practice an ethic of land conservation. He chose to call such initiatives a "revolt against the tedium of the merely economic atti- tude toward the land." The labors of two middle-aged Wisconsin farmers bent on restoring tamarack bogs in the 1940s struck him as "utterly quixotic" but nevertheless essential. They were driven by a curiosity about the land and sought pleasure in its wildness. Leopold called them amateurs, favoring the original meaning of the word and implying no judgment about their competence. They were motivated by a personal curiosity in the land rather than a professional interest in particular outcomes. This deliberate humility inoculates those involved in the struggle against weeds with an antidote to despair. It is easy to be overwhelmed by the magnitude of the prob- lem—according to recent estimates, we lose 6,000 acres to weeds every day in the U.S. Attempts to save the planet from the Homogeocene are futile, for it has already ar- rived. Wise Leopold again: "We shall never achieve har- mony with land, any more than we shall achieve absolute justice or liberty for people. In these higher aspirations the VOLUME 26:4, OCTOBER 1998 FREMONT I A 73 Pampas grass removal (lop) on GGNRA land along Wolfback Ridge in Sausalito, Marin County. • French broom (Genista monspessulana) (bottom) on GGNRA lands. Photographs by Bob Wright. important thing is not to achieve, but to strive." Amateurs seek the art of intelligent tinkering, the pursuit of com- munity, and the joy of participating in the wildness that remains. And in their seeking they manage to remove striking numbers of weeds. A friend of mine is a mighty warrior in the struggle against exotic plant pests. He concentrates most of his energy on the regional and state dimensions of wildland weeds. By operating at these higher levels of organization, he is able to maximize his effectiveness in the struggle. His labors could not be better spent. But a taste for the tangible remains. By spending a few hours every week pulling weeds, he is engaged in a revolt against strict measures of efficiency. By operating on several different scales—state, regional, and the very local—my friend is able to retain some measure of hope in this world of wounds. He enters the world of the amateur. Stories of transformation accumulate when one talks with volunteers engaged in this type of work. Occasion- ally, skeptical organizations and devastated landscapes are among those transformed. When first approached, the state park rangers nearly dismissed Ken Moore's dream— to eradicate pampas grass and other weeds from state parks in the Santa Cruz Mountains—as quixotic, particu- larly since he and his fellow volunteers eschewed herbi- cides. Less than a decade later, Moore and his Wildlands Restoration Team, attracting only a dozen volunteers on any given workday, have become an established program sponsored by the state parks because of their demonstrated ability to eliminate the worst weeds from hundreds of acres of wilderness. Some land managers are downright hostile to volun- teers. One biologist, tasked to remove hundreds of acres of European beachgrass (Ammophila arenaria), told a dune restoration conference that volunteer efforts were point- less. Volunteers were "suckers," he said, since their "feel- good" experience accomplished little when measured against the removal efforts of prison work crews. Others, with less derision, argue that paid crews or herbicides are more efficient than volunteers in eradicating weeds from large areas. In a surprising number of cases, though, volunteers can provide more cost-effective weed control than other tech- niques. In one Humboldt County beachgrass removal ef- fort, The Nature Conservancy and its partners found that volunteers provided nearly a third of its total labor needs despite the site's remote location. The presence of rare plants necessitated hand removal of beachgrass, an ardu- ous method that requires 1,900 hours per acre. After initi- ating extensive outreach efforts midway through the five- year project, the number of volunteer hours rose substan- tially and their costs per acre decreased. In one of the few studies that sought to quantify such costs, a researcher in New Zealand found that paid crews were sometimes two to three times more expensive than volunteers per hectare of weed control. A survey of community-based groups attacking wildland weeds in Australia—like New Zealand, a country with vast rural areas and massive weed prob- lems—found that such efforts were "extremely cost-effec- tive." Even with conservative calculations of the value of volunteer labor, returns on an agency's investment could be as high as 22:1. The intangible returns are even greater. A volunteer- based stewardship program can help build a dedicated constituency for exotic pest plant control efforts, the spon- 74 FREMONTIA VOLUME 26:4, OCTOBER 1998 soring agency, and conservation of natural areas in gen- eral. Natural areas offer an incredible opportunity for coalition-building—they are uncommon places where we can build common ground. As I have argued elsewhere, stewardship programs also can address social justice is- sues by providing employment and educational opportuni- ties for members of disenfranchised communities. And all this happens while achieving worthwhile conservation objectives. Such programs are multiplying and diversifying to ad- dress mounting weed problems. I am often told that volun- teers interested in such work are concentrated in the urban areas of northern California, and yet successful programs are developing all over the state. It is true, of course, that what works in one area may not be effective elsewhere. Volunteers from the Friends of Los Penasquitos Canyon Preserve attack exotic plant pests within the 3,500-acre preserve using chain saws and the herbicide glyphosate. The San Diego Parks Department supports their efforts, but its counterpart in San Francisco, citing union and safety rules, requires that volunteers abstain from using power tools or herbicides. Some programs, such as the ongoing yellow bush lupine and beachgrass eradication effort at Lanphere Dunes Preserve in Humboldt County, depend on relatively small numbers of volunteers. Others, such as the Golden Gate National Recreation Area's sev- eral stewardship programs, accumulated more than 150,000 volunteer hours in 1997, more than any other national park. Prospective volunteer managers would do well to ask amateurs for advice. The suggestions will be abundant and conflicting, but a few lessons would begin to emerge. Programs are doomed to fail if managers view volunteers as a cheap source of labor for weed removal. Such atti- tudes can be a source of discouragement and discontent among volunteers, rendering them as ineffective as some land managers imagine them to be. Volunteers will rise to the challenge if managers are willing to strive for nothing less than personal, social, and ecological transformation. That may be asking too much from an afternoon of pulling weeds. But then I wonder: Sisyphus might have enjoyed more job satisfaction if he had had company. Every park and nature preserve in California deserves a volunteer stewardship program. It would be a tragedy if our natural areas, often purchased at great cost, deterio- rated as more and more people—and other organisms— become dependent on their wildness. Volunteers pulling weeds are engaged in the ultimate recreational activity, one that pays huge tangible and intangible dividends for those involved and for the land itself. CNPS chapters can play an important role in catalyzing interest in such pro- grams by building coalitions among diverse park users and sponsoring community work parties. Several ambitious programs were sparked into existence by deliberate and persistent CNPS organizing efforts. It's break time on the bluffs again. Good food and good VOLUME 26:4, OCTOBER 1998 Many use a weed wrench to effectively remove woody exotics like French broom. Photograph by Ken Moore. company are on everyone's mind. Scratch the collegial surface, though, and you will find serious deliberations about how to improve the quality of our efforts. How can we truly restore this site, rid it of the most troublesome weeds? All the accumulated wisdom of a park system and its resource managers—all the king's horses and all the king's men and women—are sometimes at a loss when confronted with such questions. Perhaps we can learn from those deliberate amateurs who are stopped in their tracks by the beauty all around, listen to the heartbeat of the land, and then pull a weed. References AACM International. 1997. Community involvement in off- reserve and on-reserve management of environmental weeds. Biodiversity Group, Environment Australia, Canberra. Holloran, Pete. 1996. The greening of the Golden Gate: Com- munity-based restoration at the Presidio of San Francisco. Restoration & Management Notes 14(2): 112-123. Holloran, Pete. 1997. Restoring native plant communities at San Francisco's Presidio. Fremontia 25(4): 10-16. Leopold, Aldo. 1970. A Sand County Almanac, with essays on conservation from Round River. Ballantine, New York. Masters, B.K. 1995. Why community networks fail: the role of public servants and the community. In: Nature conser- vation 4: the role of networks, D.A. Saunders, J.L. Craig, and E.M. Mattiske, (eds.). Surrey Beatty & Sons, Australia. Miller, L. 1997. Volunteer programs in rural areas. California Exotic Pest Plant Council, Proceedings of the 1997 Sympo- sium, Concord, October 10-12, 1997. Timmins, S.M. 1995. Community groups and weed control for conservation in New Zealand. In: Nature conservation 4: the role of networks, D.A. Saunders, J.L. Craig, and E.M. Mattiske, (ed.). Surrey Beatty & Sons, Australia. Pete Holloran, 1033 Noe Street, San Francisco, CA 94114 FREMONTIA 75 NOTES AND COMMENTS Letters to the Editor Dear Editor, I read with great interest the article by Constance I. Millar entitled "Reconsidering the conservation of Monterey pine" {Fremontia July 1998). The revised evolutionary interpreta- tion presented was highly interesting, however I wish to take strong exception to many of Millar's derived "conservation implications." Millar's basic premise is that, while we should focus on conservation of the five native stands, Monterey pine intro- duced outside of the current narrow native range of the plant (but within the historical range of the plant since the early Pleistocene) can have conservation value for the species. Such an approach is an unfortunate application of single-species conservation, in which only the existence of the Monterey pine species is the goal. Single-species conservation fundamen- tally differs from the conservation strategy promoted by CNPS and CDFG, which rightly focuses on maintaining viable, self- sustaining ecosystems. Millar recognizes this and cites it in her article. The viable, self-sustaining native stands of pine in- clude a wide variety of associated plants and animals, as well as natural ecological processes; these factors are partly or wholly lacking in introduced stands. Thus, the statement that such introduced stands "could be managed as new native populations" (italics mine) is especially troubling. "Neo- native" seems an inappropriate term for a "human-assisted" introduction site. Perhaps most important is the impact of introduced trees on native habitats throughout the state. Millar's brief dismissal of concerns about the impacts of introduced pines is not compelling. As evidenced from introduced stands of Monterey pine throughout coastal areas of California, the tree can and does have profound and permanent impacts on natural areas to which it is introduced. It seems a poor choice to sacrifice remaining wildlands and a wide variety of associated native species for the benefit of a single species. What is the appropriate genetic stock (or is there any?) for introductions of the pine tens or hundreds of miles outside of its current native extent? Much of the "neo-native" introductions may be from New Zealand lumber stock, as is the case with CalTrans plantings in Monterey and elsewhere. Regardless of the seed source, the introductions are truly a genetic experiment at best, occurring without ecological context. Millar postulates that such introductions could "(provide) opportunity for genetic recombination, divergence, and adaptation." True, but these events would occur in an ecological vacuum—in the absence of the associates and processes present in the five native stands. As Millar states in her conclusion, the true focus for con- servation of the Monterey pine must be the five native stands. We cannot let discussions of the conservation value of introduced, experimental "neo-native" populations cloud the arguments for preservation of large, contiguous blocks of the existing native stands. Only in such areas can the diverse suite of associated plants, animals, and natural processes occur, creating the ecological matrix in which the Monterey pine can adapt and evolve. Additionally, large stands on different soil types and geomorphic surfaces must be protected, as these represent unique forest types within the Monterey pine- dominated natural community. Unfortunately, the native stands are becoming increasingly fragmented and reduced in size, and thus our options are becoming more limited. To accept ex- perimental introductions as "neo-native" is to surrender our responsibility to, and appreciation for, the true native stands. Additionally, it requires giant assumptions about our level of understanding of the ecology and biology of species which I feel are untenable. David P. Tibor CNPS Rare Plant Botanist dtibor® cnps. org Dear Editor: I wish that Connie Millar had retitled 'Reconsidering the Conservation of Monterey Pine' in the July 1998 issue of Fremontia and omitted the last section, Implications for Conservation, in which she went from science to speculation in one easy leap. The leap was into deep waters, where she proceeded to drown. Those who attempt public education regarding weeds find that the public does not easily understand how an organism can experience difficulty surviving in its native range but can be a pernicious weed outside this range. Contrary to statements in the article, coastal Monterey pine plantations aggressively ex- pand and displace surrounding native communities and fre- quently become monotonous, dark, and depressing monospe- cific stands, indistinguishable from similar plantations in New Zealand. It is an aggressive invader in grassland, scrub, dune, riparian, and chaparral communities. The bulk of the California plantings of this pine have occurred in recent decades and point to its inability to integrate into a self-sustaining vegetational community. Millar's statement that "Concerns that Monterey pine would displace native species . . . may be allayed by the fact that . . . associated biotic controls (pathogens are likely nearby, as corroborated by experience with planted pines" needs supporting data, as it is counter to experience. The article is not a contribution to conservation but it has the Just out!—The CNPS 1996 Vernal Pool Proceedings ECOLOGY, CONSERVATION, AND MANAGEMENT OF VERNAL POOL ECOSYSTEMS Edited by Carol W. Witham Session Chairs/Co-Editors: Ellen T. Bauder, Denton Belk, Wayne T. Ferrer, Jr., and Robert Ornduff Available from CNPS Press, 1722 J Street, Suite 17, Sacramento, CA 95814 • $20.00 softcover 76 FREMONTIA VOLUME 26:4, OCTOBER 1998 potential to roil the waters. It is freighted with too many problems to be fully addressed in a letter and in the short time available before press deadline. To attempt putting it into practice would administer the coup-de-grace to the ever- shrinking, fragmented, degraded, and beleaguered coastal communities we have left. Jake Sigg, Chair CNPS Invasive Exotics Committee were counted . . ." The drawing above should replace the drawing on page 9 attributed to the 1687 catalog of the University of Leyden. The Editor deeply regrets these errors. BOOKS RECEIVED Errata: California's Sea Fig Susan H. Bicknell and Ellen M. Mackay note the following correc- tions to their article, "Mysterious Nativity of California's Sea Fig" (Fremontia 26: January 1998). The illustrations on page 5 are reversed so that Bl and B2 are different views of the pollen of Ixmna minor and CI and C2 are polar and equatorial views of the pollen of Bellis perennis (Asteraceae). On page 10, second column, second full paragraph, second to the last sentence should read, "Three hundred known terrestrial pollen grains Wild Heart of Los Angeles: The Santa Monica Mountains by Margaret Huffman. 1998.216pages,maps, 62colorand 147 b/w photographs. Remarkably, the natural habitat of the Santa Monica Mountains, adjacent to one of the largest urban areas in America, has remained relatively unspoiled. In this lavishly illustrated guide, the author shows how the plants, animals, climate, geography, and humans all interact in this unusual ecosystem. Each section of the range is detailed with clear maps. Available from Roberts Rinehart, 6309 Monarch Park Place, Niwot, CO 80503. $29.95 softcover. Sierra Crossing: First Roads to California by Thomas Frederick Howard. 1998. 218 pages, 22 b/w photographs and 3 maps. This fascinating book documents the early efforts to breach the Sierra Nevada during the twenty years between the 1949 Gold Rush and the first railroad. Here are tales of the remarkably short time period when the Sierra was transformed by vigorous exploration and courageous overland road ventures. Available from the University of California Press, 2120 Berkeley Way, Berkeley, CA 94720. $28 hardcover. N EW FROM California Gardening with a Wild Heart Restoring California's Native Landscapes at Home Judith Larner Lowry "An insightful, inspirational, and timely account of the need to understand and foster our ecological heritage through the lens of one's own garden." —Bart O'Brien, Director of Horticulture, Rancho Santa Ana Botanic Garden "If native plant gardening is the way you'd like to spend your courtship of place, this book illuminates better than any I've seen the delights and surprises of such a path." —Freeman House, author of Totem Salmon $35.00 cloth, $17.95 paper, color illustrations Land of Chamise and Pines Historical Accounts and Current Status of Northern Baja California's Vegetation Richard A. Minnich and Ernesto Franco Vizcaino This book shows that the vegetation of present- day Baja California is remarkably similar to that observed in the 18th and 19th centuries, and that historical fire and grazing management has done little to alter the region's resilient mediterranean-type shrublands and forests. University of California Publications in Botany, $32.00 paper, illustrated At bookstores or order 1-800-822-6657 UNIVERSITY OF CALIFORNIA PRESS www.ucpress.edu VOLUME 26:4, OCTOBER 1998 FREMONTIA 77 Planning for Diversity: Issues and Examples by Sheila Peck. 1998. 256 pages, figures, photos, and glossary. This interesting book for planning professionals and students pro- vides an accessible introduction of ecological concepts and planning guidelines for achieving some level of biodiversity in landscape planning. Available from Island Press, 1718 Connecticut Avenue N.W., Suite 300, Washington, D.C. 20009. $27.50 softcover. National Audubon Society Field Guide to California by Peter Alden and Fred Heath. 1998. 447 pages, 1,500 color photographs and maps. This is a regional guide to 1,000 of the birds, animals, trees, wildflowers, insects, weather, and nature preserves of California. Available from Alfred A. Knopf, 201 East 50th Street, New York, NY 10022. $19.95 softcover. The Gardener's Guide to the Sausal Creek Watershed: A Home Companion to Growing Native Plants by Martha Lowe, the Friends of Sausal Creek, and the Aquatic Outreach Institute. 1998. 28 pages. This booklet is an outgrowth of a restoration project of Sausal Creek in Dimond Park, Oakland. Twenty- three native species are described along with growing tips and black-and-white drawings. Free. CLASSIFIED ADS Classified ad rate: $1.00 perword, minimum $ 15; payment in advance. Address advertising inquiries and copy to: Sue Hossfeld, 400 Deer Valley Road, #4P, San Rafael, CA 94903. (415) 507-1667. Publications THE MOST EFFECTIVE thing you can do for California's ecology is to grow native plants. Learn how from the personal (and often amusing) experience of long-time growers through Growing Native Research Institute and its elegant, illustrated, bimonthly newsletter, Growing Native. Annual $30 membership brings other benefits, too, including bonus issue, "The Basics of Growing Natives Successfully." Mention Fremontia and receive free wildflower seeds. Write: Growing Native, PO Box 489, Berkeley, CA 94701, or call (510) 232-9865. THE FOUR SEASONS, annual journal of the Regional Parks Botanic Garden, founded by celebrated writer-conservationist James Roof, devoted to California native botany and horticulture. $ 16 for 4 issues. Regional Parks Botanic Garden, Tilden Regional Park, Berkeley, CA 94708(510)841-8732. PLANTS OF THE SAN Francisco Bay Region by Eugene Kozloff and Linda Beidleman. $35.00 ppd. 2000+ plants in 9 Bay-area counties. 457 color pictures, 227 drawings, complete keys. Quantity discount. Sagen Press, Box 51042, Pacific Grove, CA 93950. (408) 375-1922. A TREAT FOR PLANT lovers, Pacific Horticulture is the West's own gardening magazine. Handsomely printed, excellent color pho- tographs. Quarterly, $20 year. P.O. Box 485, Berkeley, CA 94701. Nurseries and Seeds ELKHORN NATIVE PLANT Nursery. Growers of CA natives for restoration and landscapes. Services include restoration and landscape planning, plant material collection, installation, and maintenance. Visit our nursery and demonstration gardens on beautiful Elkhorn Slough. Contractor #744071. (408) 763-1207. GARDENING AS RESTORING native plant communities. Seeds of grasses, wildflowers, trees, shrubs. Pamphlets $3.50 each: Notes on Growing California Wildflowers. Catalog $2.50. Larner Seeds, P.O. Box 407, Bolinas, CA 94924. (415) 868-9407. NEGLECTED BULBS. Specialists in California native bulbs, calochortus, brodiaea, others. Send SASE for free list to Box 2768, Berkeley, CA 94702. WILD-COLLECTED SEEDS of California native plants. Packets of over 50 taxa, common and uncommon. Low % collection method. List: 916-795-0314, Dan Segal, or dsegal@ucdavis.edu or SASE: Daniel Segal, 413 Abbey St., Winters, CA 95694. SANTA LUCIA FIR TREES (Abies bracteata). California native, rarest fir tree in the world. 15 gallon containers. Beautiful trees. $50 each. George A. Grech. (510) 222-7367. SPECIALIZING IN SEEDS for California native plants including wildflowers, everlasting flowers, drought-tolerant mixtures. Catalog $3. Moon Mountain FR, P.O. Box 725, Carpinteria, CA 93014. (805) 684-2565. GO NATIVE NURSERY extended hours: noon to 6:00 p.m., Wed. through Sunday. 333 Cypress Avenue, Moss Beach, CA 94038. (650) 728-2286. E-mail: gonative@coastside.net. MOSTLY NATIVES NURSERY, growers of coastal natives and drought-tolerant plants. Open to the public. Located in Northwest Marin at 27235 Hwy. One, P.O. Box 258, Tomales, CA 94971. (707) 878-2009. NATIVE CALIFORNIA TREES and shrubs. Hardy plants, superior root systems, ideal size for transplanting. Mail order catalog $1.00. Live Oak Nursery, P.O. Box 2463, Oakdale, CA 95361. INTERMOUNTAIN NURSERY. In the foothills of the Central Sierra in eastern Fresno County on Hwy 168. Specializing in local natives, i.e., Carpenteria, grasses, as well as other drought tolerant plants. Retail hours 9-5 weekdays, Sat. & Sun. 10-4. Retail gift shop, wholesale plants. 30443 Auberry Rd., Prather, CA 93651. (209) 855-3113. Fax (209) 855-8839. NORTH COAST NATIVE Nursery, propagator of quality California native species for revegetation, natural landscaping, and wildlife habitat enhancement. Trees, shrubs, grasses, perennials, and wetland plants for woodland, coastal, and riparian habitats. P.O. Box 744. Petaluma, CA 97953. (707) 769-1213, FAX (707) 769-1230. YERBA BUENA NURSERY and Botanical Gardens. Growers of 600+ varieties of California Native Plants, Ferns & Exotic Ferns. Garden Shop, Tea Terrace. Open daily, 9-5. 19500 Skyline Blvd., Woodside, CA 94062. Call for directions. (415) 851-1668. Catalog $2.00. NOTES ON CONTRIBUTORS Ellen Bauder is lecturer and research scientist in the biology department of San Diego University where she teaches plant structure and function and researches vernal pools. Carta Bossard is professor of biology at Saint Mary' s College of California and a co-editor of the forthcoming book, Wild- land Weeds of California. Matthew Brooks is research scientist for the Biological Resources Division of USGS at it Western Ecological Re- search Center. Carta D'Antonio is associate professor of integrative biology, University of California, Berkeley. Joseph DiTomaso is extension weed specialist in the Veg- etation, Crop, and Weeds Department at the University of California, Davis. Thomas Dudley is research associate and lecturer in the environmental sciences program at UC, Berkeley. 78 FREMONTIA VOLUME 26:4, OCTOBER 1998 Andrew Dyer has a post-doctoral appointment in Israel and is currently in the Department of Agronomy and Range Science at the University of California, Davis. Sue Fritzke is vegetation ecologist with the National Park Service in Yosemite National Park. Kelly Gallagher is in a doctoral program at New Mexico State University, Las Cruces. John Gerlach is research assistant in the Ecology Graduate Group and a doctoral candidate in the Department of Agronomy and Range Science at the University of California, Davis. Karen Haubensak is a graduate student in plant ecology at the University of California, Berkeley. Pete Holloran is president of the Yerba Buena (San Fran- cisco) chapter of CNPS and a volunteer of the Yosemite Volunteer Stewardship Program. Joanna Holt is in a master's program at California State University, Fresno. John Hunter is assistant professor, Department of Biological Sciences at New York State University, Brockport. Tamara Kan, formerly conservation science associate with The Nature Conservancy, is currently a consulting plant ecologist in San Mateo County. Paul Kemp is a part-time faculty member at the University of San Diego and senior research associate at Duke University. Peggy Moore is ecologist in the Biological Resources Division of USGS at their Yosemite Field Station. Renee Pasquinelli is associate resource ecologist in the Russian River/Mendocino District of the California Department of Parks and Recreation. Michael Pitcairn is associate environmental research scien- tist in the Biological Control Program of the California De- partment of Food and Agriculture. John Randall is invasive weed specialist for The Nature Conservancy at the University of California, Davis. Marcel Rejmanek is professor in the Evolution and Ecology Section at the University of California, Davis. Kevin Rice is associate professor, Department of Agronomy and Range Science, University of California, Davis. Kristina Schierenbeck is assistant professor of biology at California State University, Chico, and a long-time CNPS contributor. Steve Schoenig is associate environmental research scientist with the Integrated Pest Control Branch of the California Department of Food and Agriculture. Jacob Sigg is chairman of the CNPS Invasive Exotics Committee and recording secretary for CNPS. California Native Plant Society MEMBERSHIP Dues include subscriptions to Fremontia and the Bulletin. Corporate......$1,000 Supporting....................$75 Life/Benefactor..$1,000 Family, Group, International......$45 Patron...........$250 Individual or Library............$35 Plant Lover......$100 Student/Retired/Limited Income . . . $20 ADDRESSES Memberships; Address Changes; Officers; General Society Inquiries: CNPS, 1722 J Street, Suite 17, Sacramento, CA 95814. Tel: (916) 447-CNPS(2677) Fax: (916) 447-2727 Executive Director: Allen Barnes Fremontia (Editor): Phyllis M. Faber, 212 Del Casa Drive, Mill Valley, CA 94941. Tel. and Fax: (415) 388-6002 Fremontia (Advertising): Sue Hossfeld, 400 Deer Valley Road, #4P, San Rafael, CA 94903. (415) 507-1667 Bulletin: Joyce Hawley, 631 Albemarle Street, El Cerrito, CA 94530. Home: (510) 524-5485; Fax: (510) 527-4858 Rare Plant Botanist: David Tibor, 1722 J St., Suite 17, Sacramento, CA 95814. (916) 324-3816 or (916) 447-2677 Earth Share Liaison: Halli Mason, 4728 Rosita Place Tarzana, CA 91356.(818)345-6749 EXECUTIVE COUNCIL President................................Lori Hubbart Vice President, Administration..................Roy West Vice President, Finance...................Steve Hartman Vice President, Conservation................David Chipping Vice President, Legislation.................Joe Willingham Vice President, Plant Programs...................Ann Dennis Vice President, Publications..................Phyllis Faber Vice President, Chapter Relations................Linda Bell Vice President, Development..................Joan Stewart Vice President, Education.........Carol Baird/Lorrae Fuentes Recording Secretary........................Jacob Sigg Legal Advisor...........................Sandy McCoy DIRECTORS-AT-LARGE Bertha McKinley, Scott Wilson, Sue Britting, Ellen Cypher, Jim Bishop, Carolyn Curtis Chapter Presidents are also members of the Board. CHAPTER PRESIDENTS (AND DIRECTORS) Alta Peak (Tulare)...........................Janet Fanning Bristlecone (Inyo-Mono).......................Scott Hetzler Channel Islands...............................Tom Keeney Dorothy King Young (Gualala).................Lori Hubbart East Bay.................................Holly Forbes El Dorado................................Sue Britting Kern County.............................Ellen Cypher Los Angeles/Santa Monica Mountains........George Stevenson Marin County.............................Robert Soost Milo Baker (Sonoma County).................Betty Young Monterey Bay...........................Ron L. Branson Mount Lassen........................Josephine Guardino Napa Valley.................................John Pitt North Coast..............................Gordon Leppig Orange County.........................Tony Bomkamp Redbud (Grass Valley/Auburn).........Carolyn Chainey-Davis Riverside/San Bernardino counties.........Marty Jacobsmeyer Sacramento Valley..........................Mona Robison San Diego............................Cindy Burrascano San Gabriel Mountains......................Rick Fisher San Luis Obispo............................Dirk Walters Sanhedrin (Ukiah).......................Charles Williams Santa Clara Valley.........................Jean Struthers Santa Cruz County...............Tim Hyland, Janell Hillman Sequoia (Fresno)...........................Joanna Clines Shasta...................................Joe Molter Sierra Foothills (Tuolumne, Calaveras, Mariposa). . . Patrick Stone South Coast (Palos Verdes)..................Ellen Brubaker Tahoe...................................Steve Matson Yerba Buena (San Francisco).................Peter Holloran MATERIALS FOR PUBLICATION Members and others are invited to submit material for publication in Fremontia. Two copies of manuscripts, double-spaced, (plus an IBM- compatible disc in Microsoft Word or ASCII file) should be submitted to Fremontia with name, address, phone number, an identification line for Notes on Contributors, and black-and-white photographs, preferably 8x 10 or accompanied by negatives, or original 35mm color slides. Bo- tanical nomenclature should conform to The Jepson Manual (1993), with common name followed by botanical name. VOLUME 26:4, OCTOBER 1998 FREMONTIA 79 TABLE OF CONTENTS Characteristics of the Exotic Flora of California 3 by John M. Randall, Marcel Rejmanek, and John C. Hunter Community and Ecosystem Impacts of Introduced Species 13 By Carla M. D'Antonio and Karen Haubensak The Genetics and Demography of Invasive Plant Species 19 by Kristina A. Schierenbeck, Kelly G. Gallagher, and Joanna N. Holt Exotic Plant Invasions in California Riparian Areas and Wetlands 24 by Tom Dudley Exotic Species of California Deserts 30 by Paul R. Kemp and Matthew L. Brooks Exotics of Southern California's Vernal Pools and Other Specialized Habitats 35 by Ellen T. Bauder Grassland and Foothill Woodland Ecosystems of the Central Valley 39 by John Gerlach, Andrew Dyer, and Kevin Rice The Nature Conservancy's Approach to Weed Control 44 by Tamara Kan Exotic Plant Management in National Parks of California 49 by Sue Fritzke and Peggy Moore Exotic Weeds in the North Coast State Parks 54 by Renee Pasquinelli The Calweed Database: California Noxious Weed Control Project Inventory 58 by Steve E. Schoenig Biological Control of Wildland Weeds 59 by Michael J. Pitcairn The Role of Herbicides in Preserving Biodiversity 65 by Jake Sigg Public Education and Extension Service Outreach 68 by Joseph M. DiTomaso The California Exotic Pest Plant Council and Allied Statewide Organizations 71 by Carla Bossard Deliberate Amateurs: Volunteers and Exotic Pest Plant Control 73 by Pete Holloran Notes and Comments 76 Books Received 77 The California Department of Fish and Game and the California Native Plant Society proudly present: California's Wild Gardens EDITED BY PHYLLIS M. FABER ". . . a stunning look at about 100flower-filled sites. Use it to plan wildflower outings." —Los Angeles Times This sumptuous book, en route to becoming a classic, celebrates . . . nature, in all her bewildering variety and profusion of flowers." —Kevin Starr, California State Librarian 1997. CNPS Press. 248 pages, 9" x 12", 500 color photographs, maps, glossary, index and bibliography. $29.95 softcover $42.95 hardcover Ph: 916-447-2677 Fax: 916-447-2727 Email: cnps@cnps.org /i?nJ5*4X l^a^f ^s$&\ \ A\f>* f*\sj \jk ^ ^y \i£3i3(Vj/ > p -1 n a. W Njl a. O KJ — res 1 *° 3- V} 3 ¦— 2 I/> n tn 3 n 3 r" S3' <_ i-h - o° o t/i Z n ^ = w 73 0 ~ -¦ CD > re < -Q . fD C va -1 fD w ^ 2 l/J a. OS £) -1 3 ¦£» <¦* (/) O o n (H- -< Nonprofit O U.S. Posta PAID Oakland, C Permit # 37: £> era era