Monitoring a Half-Century of Change in a Hardwood Rangeland

J. Range Manage. 55: 412-419 July 2002 Monitoring a half-century of change in a hardwood rangeland

KERRY L. HEISE AND ADINA M. MERENLENDER

Authors are Botanist and Staff Research Associate, Integrated Hardwood Range Management Program, Hopland Research and Extension Center, Hop/and, Calif. 95449; and Cooperative Extension Specialist, Environmental Science, Policy, and Management, University of California, Berkeley, Calif. 94720-3110.

Abstract Resumen

Changes in rangeland species composition can effect forage Cambios en la composicion de especies del pastizal pueden quality, ecosystem function, and biological diversity. afectar la calidad de forraje, la funcion del ecosistema y la diver- Unfortunately, documenting species compositional change is dif- sidad biologica. Desafortunadamente, el documentar los cam- ficult due to a lack of accurate historic records. We took advan- bios de la composicion de especies es dificil debido a la falta de tage of herbarium records dating from the early 1950's to recon- registros historicos certeros. Tomamos ventaja de los registros struct the past flora of a 2,168 ha hardwood rangeland in del herbario, que datan de inicio de la decada de 1950, para reconstruir la flora pasada de 2,168 de un con Mendocino County, California , and then compared this to the ha pastizal arboles current flora of the site. An inventory of vascular plants conduct- de madera dura en el condado de Mendocino, California, y la ed from 1996 to 2001 added 44 native and 15 non-native species comparamos con la flora actual del sitio. Un inventario de las bringing the total number of species and infraspecific taxa at the plantas vasculares conducido de 1996 al 2001 agrego 44 especies study site to 671. Of the original 612 species recorded prior to nativas y 25 especies no nativas totalizando 671e1 numero de this study, 34 native and 1 non-native species could not be relo- especies y taxas intraespecificas en el sitio de estudio. De las 612 cated. The percentage of non-native species increased from 19% especies originales registradas antes de este estudio, 34 nativas y in 1952 to 23% in 2001. Based on estimates from the early 1950's, una no nativa no pudieron ser relocalizadas. El porcentaje de mid 1980's, and 1996 to 2001, at least 13 non-native species have especies no nativas se incremento de 19% en 1952 a 23 % en increased in abundance, while some native species have 2001. Basados en las estimaciones de inicios de la decada de los decreased. Livestock grazing, competition with invasive species, 50's, mediados de la decada de los 80's y de 1996 a 2001, al conversions to different vegetation types, and transportation of menos 13 especies no nativas han incrementado en abundancia, propagules into the site by vehicles and livestock, combined with mientras algunas especies nativas han decrecido. El apacen- the difficulty of relocating rare species, are posed as the most tamiento de ganado, la competencia con especie invasoras, la likely causes for the documented changes. conversion a diferentes tipos vegetativos y el transporte de propagulos al sitio por vehiculos y ganado, combinado con la dificultad de relocalizar especies raras son propuestas como las Key Words: Northwest California, herbarium, oak woodlands, causas mas probables de los cambios documentados. livestock, flora, invasive species

Hardwood rangelands in California cover an estimated 4.5 mil- lion ha and are characterized by an overstory canopy of hard- ty, change in ecosystem function, and reduction in rangeland pro- wood trees, primarily in the genus Quercus. The overstory productivity (D'Antonio and Vitousek 1992, Campbell and Smith vides at least 10% cover; the understory is generally dominated 2000). In particular, exotic annual grasses interfere significantly by exotic annual grasses and forbs. Replacement of the native with native perennial grasses during all stages of growth understory flora with a primarily non-native one occurred rapidly (Hamilton et al. 1999), resulting in an increase in exotic annuals and on a very large scale over the past 200 years (Heady 1977, over time. Invading species can also differ functionally from the Mack 1989). The primary causes of this change are human native species that they are replacing, resulting in a great overar- induced such as livestock grazing, fire suppression, and facilitat- ching effect on ecosystems (Vitousek 1986). ed dispersal (Rejmanek et al. 1991) resulting in an increased Monitoring species compositional changes in California hard- dominance by exotics and a subsequent loss of native species wood rangelands is essential for determining the sustainability of (Mooney and Drake 1987). livestock grazing and necessary to address the lack of oak Change in understory species composition of oak woodlands, seedling survival. Because the understory of California's hard- savanna, and grasslands represents a significant component of wood rangelands are dominated by exotic grasses and forbs, global environmental change including loss of biological diversi- many lower in nutritional quality and palatability than native perennial species, the capacity of rangelands has been seriously decreased (Major 1955, Pettit et al. 1995). Annual grasses are Authors wish to thank Chuck Vaughn, Bob Keiffer, and 2 anonymous reviewers for helpful comments on the manuscript. adapted to heavy grazing and low nutrient availability (Jackson Manuscript accepted 5 Oct. 01. 1985), which has consequences for the way livestock grazing is practiced on site as well as the economic vitality of open range

412 JOURNAL OF RANGE MANAGEMENT 55(4) July 2002 grazing operations. As range conditions (Arbutus menziesii Pursh), and California areas", research pastures, and steep, wood- deteriorate, livestock seek out less palat- buckeye (Aesculus californicus (Spach) ed terrain outside of fenced pasture bound- able plant species, increasing the use on Nutt.). Grasslands and the understory of aries. Rangeland improvement practices these species, oak seedlings included. open oak woodland and savanna are domi- during the 1960's and 1970's, aimed at Additionally, the establishment of exotic nated by non-native annual grasses such as increasing agricultural production, result- annual grasses has been proposed as a lim- slender wild oat (Avena barbata Link), big ed in the conversion of approximately 300 iting factor in the regeneration of some quaking grass (Briza maxima L.), hedge- ha of oak woodland and chamise chaparral native oak species (Muick and Bartolome hog dogtail (Cynosurus echinatus L.), and to exotic grassland (Murphy 1976, 1978). 1988, Gordon and Rice 1993). barbed goatgrass (Aegilops triuncialis L.). In addition, university staff and Due to the scarcity of historic baseline Chaparral scrub consisting of chamise researchers intentionally introduced at information, few studies have examined (Adenostoma fasciculatum Hook. & Am.), least 19 exotic plant species. These were long-term change on California range- Arctostaphylos spp., Ceanothus spp., and seeded into pastures following fire or lands. Using cover data from the 1930's, Quercus spp., along with patches of closed other forms of clearing to improve range Holzman and Allen-Diaz (1991) docu- cone pine (Pinus attenuata Lemmon) are forage, and since have expanded their mented 58 years of change in 21 blue oak common above 675 m. Douglas fir ranges well beyond the initial introduction (Quercus douglasii Hook. & Am.) wood- (Pseudotsuga menziesii (Mirbel) Franco), sites. Some of the common species include land plots in California. Our study docu- California nutmeg (Torreya californica smilo grass (Piptatherum miliaceum (L.) ments change over nearly a half-century Torrey), and canyon live oak (Quercus Cosson), harding grass (Phalaris aquatica by reconstructing the past flora of a hard- chrysolepis Liebm.) form dense shaded L.), orchard grass (Dactylis glomerata L.), wood rangeland in northwest California, canopies on steep north and east facing rose clover (Trifolium hirtum All.) and comparing herbarium data to the modern slopes. Numerous seasonal creeks, sag subterranean clover (T, subterraneum L.). flora. This was feasible due to the estab- ponds, vernal pools and springs provide a lishment of an extensive reference collec- diversity of wetland habitats and plant tion of vascular plants for the site in the communities (Heise and Merenlender Methods early 1950's. A flora was later published 1999). (Murphy and Heady 1983) which included Between 1996 and 2001 we conducted data on species abundance across the site Historic Data an extensive inventory of vascular plants This comprehen- from the early 1980's. The Center was established as a range across the entire Center. First, the infor- in combina- sive set of scientific records, experiment station in 1951. The following mation from over 1,275 specimen labels tion with extensive documentation of land- year, a botanical survey was initiated to from the Center's herbarium was updated us with a means to use at the site, provided document all species of vascular plants on to reflect mis-identifications, recent scien- and identify newly established species the property. By 1954 nearly 450 species tific name changes, and reductions due to document changes in the relative abun- were recorded. During the next 30 years of synonymy (Hickman 1993), and then dance some taxa. of sporadic collecting only 137 species were incorporated into a database. From this, added to the flora, bringing the total to species lists with location, habitat, and almost 600. At this time a list of the vas- collection date were produced to facilitate Study Site cular plants for the Center was published the relocation of previously recorded taxa. (Murphy and Heady 1983). Only a few Most of the herbarium specimens (75%) Vegetation more species were added to the flora contained general location descriptions The study area encompasses the entire through the 1980's and mid 1990's, bring- such as pasture name only, while the University of California Hopland ing the total number of vascular species remaining 25% had more specific site Research and Extension Center, located in and infraspecific taxa to 612. Alfred H. locations. Because of the intensity and the interior north coast ranges of south- Murphy, the Center's first superintendent, thoroughness during the first 3 years of the eastern Mendocino County (39° 00' N, and Harold F. Heady, U.C. Berkeley original botanical survey in the early 123° 05' W). It encompasses nearly 2,168 Professor of Range Management, initiated 1950's, we assume that taxa not collected hectares of moderately steep, predomi- the inventory, and alone contributed 1,177 then were probably sparse, inaccessible, or nately southwest-facing slopes in the specimens to the Center's herbarium, absent. An extensive road system over 72 Mayacmas Mountains, with elevations about 92% of the collection. km in length facilitated access throughout ranging from 183 to 914 m. The natural the Center's property; roadless areas were vegetation reflects a mediterranean cli- Livestock and Forage Management surveyed on foot. Voucher specimens for mate of hot dry summers and cool wet Prior to the University's purchase of the previously unrecorded taxa were collected winters, with an average annual rainfall of property the area was used as a sheep and deposited into the Center's herbarium. 960 mm. Oaks and other hardwoods are range. Since then, between 1,500 and Relative terms describing abundance at the common overstory species of the lower 2,000 sheep continue to use approximately collection site ("Sparse", "Occasional", elevation woodlands and include blue oak 213 of the Center. Much of the livestock "Numerous") were assigned to 479 specimens (Quercus douglasii Hook. & Am.), black grazing pressure across this range is light (313 species) that were collected between oak (Q. kelloggii Newb.), valley oak (Q. because of the terrain and dense wooded 1952 and 1954. This site-specific information lobata Nee), Oregon oak (Q. garryana vegetation; the heaviest use occurs on provided a rough estimate of species abun- Hook.), coast live oak (Q. agrifolia Nee), approximately 300 ha and is concentrated dance across the Center in cases where Shreve oak (Q. parvula E. Greene var. in lambing and winter feeding pastures or there were similar abundance estimates for shrevei (C.H. Muller) K. Nixon), seeded grassland near the headquarters multiple collections of the same species. California bay (Umbellularia californica area. Livestock are excluded from approx- In the early 1980's Murphy and Heady (Hook. & Am.) Nutt.), Pacific madrone imately 435 ha in designated "biological (1983) estimated the abundance of 600

JOURNAL OF RANGE MANAGEMENT 55(4) July 413 vascular plant species across the entire Table 1. Floristic summary data for the University of California Hopland Research and Extension Center using similar non-absolute terms, Center, Calif. which we adopted during our field work to provide consistency. Thus, for about half of the flora we were able to obtain compa- Taxa Families Genera Taxa Taxa rable abundance estimates from the early Ferns and Fern Allies 10 16 0 1950's, early 1980's, and 1996 to 2001, Gymnosperms 3 5 4 1 and for the entire flora between the early Dicots 71 258 1980's, and 1996 to 2001. Given the sub- Monocots 11 75 jectivity of these terms, we only present Total 95 354 taxa that have undergone extreme declines or increases, thus representing notable ing pressure, 3 on moderately grazed, 9 on Changes in Species Abundance change. lightly grazed, and 10 in areas with no Many non-native species presumed grazing. A majority of the 35 species lost absent or sparse during the early 1950's occurred in grassland, chaparral, or wet- Results have since undergone dramatic increases land habitats. in abundance (Table 4). For example, New Taxa The 1996 to 2001 inventory added 59 Table 2. New species found at the University of California Hopland Research and Extension species (44 native and 15 non-native) in Center, California during 1996-2001 inventory period. Habitat: C = chaparral, G = grassland, H hardwood forest, X xeric woodland, outcrop/crevice, W wetland, R roadcut. 29 families to the flora, bringing the total = = 0 = = = Grazing: N none, L light, M moderate, H heavy number of species and infra-specific taxa = = = = at the field station to 671 (Table 1). More Species Habitat Grazing than half (34) of the new additions were native dicots, followed by non-native Dryopteridaceae Athyrium alpestre var. americanum 0 N Y dicots (14), native monocots (8), non- native monocots (1), and fern and fern Selaginellaceae Selaginella wallacei 0 N Y allies (2). Asteraceae was the most repre- Apiaceae sented family with 7 native and 4 non- Lomatium dissectum 0 N Y native species, followed by Apiaceae, Lomatium vaginatum H N Y Cyperaceae, and Scrophulariaceae (Table Oenanthe sarmentosa w N Y 2). Of the 44 native species, 22 were Tauschia kelloggii H L Y found in areas where sheep have been Torilis arvensis X,G N,L,M N excluded, such as the "Biological Areas", Asteraceae rock outcrops, or other areas inaccessible Euthamia occidentalis w M Y to livestock, 12 in areas lightly grazed, 6 Gnaphalium luteo-album w H N in moderate, and 4 in sites with heavy Hesperevax acaulis var. ambusticola C L Y Hesperevax spars iflora G L Y grazing pressure. Of the 15 new non- Layia septentrionalis X L Y native species, 3 were found in ungrazed Solidago californica w L Y areas, 3 in lightly grazed, 2 in moderately Soliva sessilis R H N grazed, 6 in heavy grazed areas, and 1 Stephanomeria elata w L Y found throughout all grazing regimes. Tolpis barbata x L N Almost half of all new species found Tracyina rostrata G H Y Tragopogon porrifolius G L N occurred in wetland habitats such as vernal pools, sag ponds, springs, and seasonal Boraginaceae Myosotis discolor w N Y creeks. Brassicaceae Carderia draba w N N Missing Taxa Erysimum capitatum 0 N Y Species loss was chiefly confined to Campanulaceae plants of low abundance and occurred Heterocodon rariflorum w L Y across a wide variety of habitat types and Caprifoliaceae grazing regimes. Of the original 612 Symphoricarpos mollis H L Y species that were documented at the Caryophyllaceae Sagina apetala W M Y Center prior to this study, 34 native and 1 non-native species could not be relocated Scleranthus annuus ssp. annuus G L N (Table 3). Over half of the missing species Crassulaceae Sedum obtusatum ssp. retusum 0 N Y (21) were native dicots, followed by native monocots (13), and non-native dicots (1). Ericaceae Arctostaphylos canescens ssp. sonomensis C L Y Although 19 families were represented, Chimaphila menziesii H N Y Poaceae, Asteraceae, and Cyperaceae Euphorbiaceae accounted for roughly half of the species Euphorbia spathulata X L Y lost. Thirteen of the missing species occurred on sites that receive heavy graz- (Table 2 continued on page 415)

414 JOURNAL OF RANGE MANAGEMENT 55(4) July 2002 (Table 2 Continued). While many introduced species have become established and have increased in Species Habitat Grazing Native abundance at the Center, some native Fabaceae herbaceous perennials, such as rancher's Lotus pinnatus W N Y fireweed (Amsinckii menziesii (Lehm.) Trifolium gracilentum var. gracilentum G M Y Nelson & J.F. Macbr.), owl's clover Vicia hirsuta W N N (Castilleja densiflora (Benth.) Chuang & Gentianaceae Heckard), Rigiopappus leptocladus A. Cicendia quadrangularis w H Y Gray, and modesty (Whipplea modesta Lamiaceae Torrey), which were considered numerous Satureja douglasii H N Y in the early fifties, are now sparse in Lamium purpureum R H N occurrence. Other species that were com- Linaceae mon in occurrence in the fifties and now Linum bienne W H N missing include Brewer's milkvetch Onagraceae (Astragalus breweri A. Grey), varied-leaf Clarkia concinna ssp. concinna H N Y Epilobium brachycarpum W H Y Collomia (Collomia heterophylla Hook.), and tufted hairgrass (Deschampsia cespi- Polemoniaceae tosa (L.) Beauv. var. cespitosa). Because Gilia sinistra ssp. pinnatisecta Y of the subjective nature of the abundance Polygonaceae smaller changes for other Rumex conglomerates N measures, species have undoubtedly occurred but Portulacaceae cannot be presented with confidence. Claytonia exigua Y

Portulacaceae Claytonia exigua 0 N Y Discussion Rubiaceae Sherardia arvensis N N The initial plant survey at the Center in Scrophulariaceae the early 1950's attempted to catalog all Collinsia parviflora X M Y the known vascular plants, establishing Cordylanthus pilosus X N Y valuable baseline floristic information for Parentucellia viscosa W,R H N a 2,168 ha rangeland. Our study represents Veronica anagallis-aquatica W H N the first step in documenting the floristic Solanaceae changes that have occurred since the early Solanum americanum W N Y 1950's. As a result of our inventory we Valerianaceae trends: 1) the Plectritis brachystemon G M Y observed the following occurrence of new native taxa previously Verbenaceae 2) new non-native species Phyla nodiflora H Y undetected, 3) Verbena lasiostachys N Y have been established at the site, some already established non-native species Cyperaceae 4) Carex barbarae W N Y have greatly increased in abundance, Carex comosa W N Y some missing taxa are clearly extirpated Carex globosa H N Y from the site, and 5) the missing taxa Carex subfusca W M Y include some species that may be too rare Scirpus californicus W N Y to relocate over the course of the study. As Orchidaceae expected, we added more non-native Corallorhiza maculata H N Y species to the Center's flora, whereas the Poaceae addition of native species gave us confi- Festuca arundinacea G L N dence in the thoroughness of our survey H L Y Melica hardfordii methods. From records at the Center there Typhaceae is evidence that some rangeland manage- eurycarpum ssp. eurycarpum W N Y Sparganium ment practices led to species loss and the spread of exotic plants. Access to pennyroyal (Mentha pulegium L.), an and abundant Japanese Hedge-Parsley management records that can help explain herbaceous perennial first collected on the (Torilis arvensis (Hudson) Link.) was first possible causes of change is an advantage of Center in 1969, now dominates the margins collected in 1996, which suggests a rapid doing this type of study on a public research of several permanent ponds and seeps in increase in abundance over the past 10 facility. We documented an increase in non- grazed and ungrazed sites alike. Barbed years. Noted as "sparse" and "occasional" native species richness which is character- goatgrass (Aegilops triuncialis L.), another respectively in 1983, big quakinggrass istic of the spread of invasive species in extremely invasive plant, was first collected (Briza maxima L.) and hedgehog dogtail western lowland California (Randall et al. here in 1961 and is now the dominant (Cynosures echinatus L.) now comprise the 1998). Non-natives at the Center are being species on approximately 125 ha of serpen- dominant understory of oak woodlands on added to the flora at a rate of 1.3 species tine grassland. The currently widespread several south and southwest-facing slopes. per year, while several of those already

JOURNAL OF RANGE MANAGEMENT 55(4) July 415 Table 3. Plants that could not be relocated at the University of California Hopland Research and areas, and are conspicuously absent in Extension Center, California following a 19902001 inventory. Habitat: R = roadcut, C = chap- dense chaparral, shaded hardwood forest, arral, G = grassland, H = hardwood forest,W = wetland, X = xeric woodland. Grazing: N = and on steep rocky outcrops. Roughly one none, L light, M moderate, H heavy = third of the Center's 155 non-native species are annual grasses, followed by Species Habitat Grazing annual forbs primarily in Asteraceae and Apiaceae Fabaceae. Today, non-native plant species Perideridia gairdneri G N Y on the Center comprise 23% of the total Asteraceae flora compared to 19% in the early 1950's, Aster radulinus H H Y Cirsium remotifolium G N Y By the time the University of California Lessingia nemaclada GL Y acquired the property in 1951, the non- Microseris laciniata ssp. laciniata G H Y native flora was already well established. Boraginaceae Herbarium records indicate that by 1954 Plagiobothrys stipitatus var. micranthus W H Y over 90 introduced species occurred on the Brassicaceae Center; of these, 22 were considered Tropidocarpum gracile G L, H Y numerous at their collection sites. Thirty Cistaceae years later there were 136 introduced Helianthemum suffrutescens C L Y species, and by 2001 the number had Crassulaceae grown to 155 (Fig. 1). This represents a Sedum radiatum C N Y 71 % increase in non-native species over a Fabaceae period of 45 years. In contrast, the entire Astragalus breweri G H Y state of California saw a 31% increase in Gentianaceae non-native plant species for a similar peri- Centaurium davyi w N Y od between 1959 and 1998 (Randall et al. Loasaceae 1998). Mentzelia laevicaulis R L Y Many of the new native species found Mentzelia micrantha R L Y during our inventory were likely over- Malvaceae looked during earlier surveys because of Abutilon theophrasti W N N their rarity or locations that were difficult Onagraceae to access. For example, spikemoss Camissonia californica W L Y (Selaginella wallacei Hieron.) was com- Clarkia unguiculata R L Y mon on several north-facing boulders Orobanchaceae camouflaged with mosses and ferns, and Orobanche uniflora G H Y an individual wallflower (Erysimum capi- Papaveraceae tatum (Douglas) E. Greene) was located Dendromecon rigida CN Y within a crevice high on a steep cliff face. Polemoniaceae Many others were found on steep wooded Collomia diversifolia H H Y Collomia heterophylla X N Y slopes outside of fenced pastures. Four in Polygonaceae plants considered rare California were Chorizanthe polygonoides C N Y also found (Skinn e r a nd Pav lik 1994) ' The Bristly is Ranunculaceae sedge (Carex comosa Boott) Aquilegia eximia C N Y considered rare across its entire range in in Cyperaceae several western states the U.S., beaked Cyperus erythrorhizos w N, M Y Tracyina (Tracyina rostrata S.F. Blake) is Cyperus squarrosus w M Y known from fewer than a dozen popula- Eleocharis radicans w M Y tions in northwest California, Sonoma Liliaceae manzanita (Arctostaphylos canescens Fritillaria recurva C L Y Eastw. ssp. sonomensis (Eastw.) P. Wells) Lilium rubescens C N Y occurs on chaparral sites in Northwest Poaceae California, and Colusa Layia (Layia Agrostis hallii X H Y septentrionalis Keck) is a serpentine Calamagrostis koelerioides C L Y endemic of California's Interior Coast Calamagrostis purpurascens C H, L Y Ranges. Documenting these locations adds Calamagrostis rubescens H H Deschampsia cespitosa W H Y to an important body of information for Festuca viridula C L Y conservation biologists and resource pro- Leersia oryzoides W H Y tection agencies monitoring rare species Pleuropogon californicus W H Y occurrences. Over half of the missing taxa were originally recorded as "rare" or "sparse" and established have undergone dramatic local sheep or vehicles. This is similar to find- may have been overlooked during our range extensions. Most of the new intro- ings on other hardwood rangelands in inventory. These species were originally duced species were found in areas California (deNevers 1985, Knops et al. collected in upland areas with little or no accessed by livestock or adjacent to roads 1995), where introduced species are pre- grazing. Furthermore, there was nothing where they could have been carried in by sent mainly in grasslands and disturbed about the species composition at the origi-

416 JOURNAL OF RANGE MANAGEMENT 55(4) July 2002 Table 4. Species that have undergone notable increases or decreases in abundance at the University of California Hopland Research and Extension Center, California. Note: "absent" in 1952-55 column means plant collected after 1955 and therefore assumed not present at the Center or so rare in occurrence it was missed during first years of inventory.

Species Exotic 1952-55 1983 1996-01 Amsinckii menziesii (Fiddleneck) numerous occasional sparse Castilleja densiflora (Owl's Clover) numerous occasional sparse Rigiopappus leptocladus numerous numerous sparse Whipplea inodesta (Yerba de Selva) numerous occasional sparse Aegilops triuncialis (Barbed Goatgrass) x absent occasional Baccharis pilularis (Coyote Brush) sparse occasional numerous Briza maxima (Big Quakinggrass) x absent sparse Carduus pycnocephalus (Italian Thistle) x sparse numerous Cerastium arvense (Field Chickweed) x absent occasional Cynosures echinatus (Hedgehog Dogtail) x occasional occasional Dactylis glonierata (Orchardgrass) x sparse occasional Holcus lanatus (Velvetgrass) x sparse sparse Mentha pulegium (Pennyroyal) x absent sparse Parentucellia viscosa x absent absent Petrorhagia dubia x absent rare Soliva sessilis x absent absent Taeniatherum caput-medusae (Medusahead) x occasional numerous Torilis arvensis (Japanese Hedge-parsley) x absent absent numerous nal collection sites that would suggest grass (Holcus lanatus L.) and pennyroyal species replacement. At the same time, rare with non-native grasses and clovers in wetland habitats (Table 4). The poten- plants are more susceptible to stochastic (unpublished pasture histories). Reed grass tial impact from either of these threats may events, so it can't be ruled out entirely that (Calamagrostis koelerioides Vasey) likely play a role in the observed species loss. In some may have gone locally extinct. It is occurred on a chaparral site that has since particular, barbed goatgrass now domi- difficult to differentiate between what been cleared and seeded with non-native nates serpentine grassland sites and has might have been a stochastic extinction grasses and forbs. become a threat to rangelands across and the inability to locate a species because Thirteen of the 35 species that could not California (Kennedy 1928, Peters et al. of its rarity. Fischer and Stocklin (1997) be relocated occurred originally on sites 1996). Previously, serpentine grasslands noted a similar problem comparing old and that have been under heavy grazing pres- did not support extensive annual grass new records of plant occurrence on cal- sure. Heavy grazing can jeopardize the cover due to the low nutrient levels careous grasslands in the Swiss Jura sustainability of grassland ecosystems by (Huenneke et al.1990) and had been Mountains. They mentioned the possibility reducing soil fertility and water-holding regarded as refugia for California's native that species could have been missing in the capacity (Dormaar and Willms 1998), plants (Harrison 1999, Murphy and Ehrlich new records without actually having gone which can then lead to dominance of exot- 1989). Therefore, documenting the spread extinct, if the old and new records were not ic annual species. At the same time, these of this invasive annual grass is of particular taken at the same location. Similarly, many sites have also undergone dramatic concern for native plant conservation. of our specimens had only vague location increases in several exotic species, notably descriptions, such as "upper Orchard big quaking grass, hedgehog dogtail, and Pasture" or "Lake Biological Area", mak- barbed goatgrass in grasslands, and velvet ing it more difficult to locate the original collection site; more detailed location information was available for only 9 of the Non-natives 3 TotaI 43 missing plants. Conversions of vegetation type appear to be responsible for the extirpation of at least 5 species. Pine grass (Calamagrostis rubescens Buckley) and serpentine Collomia (Collomia diversifolia E. Greene), the latter an uncommon California endemic, were last collected in the spring of 1957. In the summer of the same year the woody vegetation of the 26 ha watershed where these plants occurred was removed and burned, and later seeded with a mixture of non-native clovers and grasses (Murphy 1976). Semaphore grass (Pleuropogon californicus (Nees) Vasey) 1950's 1960's 1970's 1980's 1990's and popcorn flower (Plagiobothrys stipitatus (E. Greene) I.M. Johnston var. micran- Decade thus (Piper) I.M. Johnston) were last col- Fig. 1. Number of vascular plant species reported for the University of California Hopland lected in 1952 and 1953 along a seasonal Research and Extension Center, California. Over 2/3 of the total number of species to date watercourse, since then this pasture has were collected between 1952 and 1954 following the establishment of the field station.

JOURNAL OF RANGE MANAGEMENT 55(4) July 417 The relatively recent establishment and new losses, as well as new additions to the Heady, H.F. 1977. Valley grassland. Pp. 491- spread of species such as big quaking flora. To better demonstrate the spread of 514 in M.G. Barbour and J. Major (eds.), grass, hedgehog dogtail, barbed goatgrass, invasive species, a monitoring program Terrestrial vegetation of California. John Wiley Sons, New York. velvet grass, and pennyroyal also has con- and should be established that includes map- Heady, H.F. and M.D. Pitt. 1979. Reactions sequences for ecosystem function. Eviner ping the distribution of non-native species of northern California grass=Woodland to and Chapin (2001) found differences in through time using the Center's existing vegetational type conversions. Hilgardia decomposition rates, net nitrogen cycling Geographic Information System. While 47:51-73. rates, and phosphorus availability between we note shifts in land-use as a likely cause Heise, K.L. and A.M. Merenlender.1999. Flora single species plots planted at the Center. for the observed changes to the flora, of a vernal pool complex in the Mayacmas In particular, barbed goatgrass plots had long-term experiments on the effects of Mountains of southeastern Mendocino County, Madrono 46: 38-45. greatly enhanced net nitrification, and sup- livestock grazing and species introduc- California. Hickman, J. 1993. The jepson manual: Higher ported the highest gopher activity, sug- tions are essential to test the direct contri- plants of California. University of California gesting that this species may provide a bution that grazing and exotics have on Press, Berkeley and Los Angeles, Calif. more stable soil surface preferred by native flora. In addition, a quantitative Holzman B.A. and B.H. Allen-Diaz. 1991. gophers. This example illustrates how study comparing vegetation composition Vegetation change in blue oak woodlands in changes in the composition and relative and abundance in similar plant communi- California. USDA For. Serv. Gen. Tech. Rep. abundance of herbaceous species can ties on comparable soil types between PSW-126. directly influence ecosystem function, grazed and ungrazed sites would be useful. Huenneke, L.F., S.P.Hamburg, R. Koide, H.A. Mooney, and P.M. Vitousek. 1990. resulting in alterations to the habitat that Studies of this sort would complement this Effects of soil resources on plant invasion and can further affect vertebrate densities. one and provide a better understanding of community structure in Californian [USA] Another consequence of the spread of species turnover and the associated causes serpentine grassland. Ecol. 71:478-491. competitive annual grasses for hardwood in north coast hardwood rangelands. Jackson, L.E. 1985. Ecological origins of rangeland conservation may be reduced California's mediterranean grasses. J. oak regeneration, due primarily to compe- Biogeog.12:349-361. tition for water (Gordon and Rice 1993). Literature Cited Kennedy, P.B. 1928. Goatgrass or wild wheat In addition to the consequences (Aegilops triuncialis). J. Amer. Soc. Agron. these 20:1292-1296. exotics have for ecosystem function and Campbell, B.D. and D.M.S. Smith. 2000. A Knops, J.M.H., J.R. Griffin, and A.C. biodiversity conservation, the quality of synthesis of recent global change research on Royalty. 1995. Introduced and native plants the livestock forage has been reduced. For pasture and rangeland production: Reduced of the Hastings Reservation, central coastal example, pennyroyal, barbed goatgrass, uncertainties and their management implica- California: A comparison. Biol. Cons. hedgehog dogtail, and big quaking grass, tions. Agr. Ecosyst. Enviroment 82: 39-55. 71:11.5-123. have all undergone substantial increases in D'Antonio, C.M. and P.M. Vitousek. 1992. Mack, R. N. 1989. Temperate grasslands vul- abundance at the Center, yet are highly Biological invasions by exotic grasses, the nerable to plant invasions: characteristics and consequences. Pp. 155-179 In J.A. Drake, unpalatable to livestock. grass/fire cycle, and global change. Ann. H.A. Mooney, F. di Castri, R.H. Groves, F.J. Early research at the Center focused on Rev. Ecol. Syst. 23:63-87. de Nevers, G. 1985. Pepperwood flora. Kruger, M. Rejmanek, and M. Williamson vegetation type conversions and reseeding Pepperwood Ranch Natural Preserve. Sonoma (eds.), Biological invasions: A global per- with non-native species in order to County, CA. California Academy of Sciences, spective. John Wiley & Sons, Chichester, enhance forage production and water San Francisco, Calif. N.Y. yield, but this was not without costs. The DiTomaso, J.M., K.L. Heise, G.B. Kyser, Major, J. 1955. Weeds on California range- conversion of a wooded 86 ha watershed A.M. Merenlender, and R.J. Keiffer. 2001. lands. Cal. Agr. 9:3-4. resulted in a dramatic increase of 2 weedy Carefully timed burning can control barb Mooney, H.A. and J.A. Drake. 1987. The ecology of biological invasions. Environ. species along with multiple goatgrass. Cal. Agr. 55(6):47-52. soil slips and 29:10-37. increases in sediment discharge (Pitt et al. Dormaar J.F. and W.D. Willms.1998. Effect of forty-four years of grazing on fescue Muick, P. C. and J. W. Bartolome. 1988. 1978, Heady and Pitt 1979). On the other grassland soils. J. Range Manage. Factors associated with oak regeneration in hand, fire has recently been used to dra- 51:122-126. California. Pp 86-91, In: T.R. Plumb and N. matically reduce barbed goatgrass infesta- Eviner, V.T. and F.S. Chapin III. 2001. Plant H. Pillsbury (Tech. Coord.). Proc. Symp. tions in 2 pastures while simultaneously species provide vital ecosystem functions for Multiple-use Management of California's increasing the abundance of meadow bar- sustainable agriculture, rangeland manage- Hardwood Resources. USFS Gen. Tech. Rep. ley (Hordeum brachyantherum Nevski), a ment and restoration. Cal. Agr. 55(6):54-59. PSW-100. native perennial bunchgrass; thereby Fischer, M. and J. Stocklin. 1997. Local Murphy, A.H. 1976. Watershed management extinctions of plants in remnants of exten- increases rangeland productivity. Cal. Agr. improving forage for sheep (DiTomaso et 30:16-21. al. 2001). The trend toward research sively used calcareous grasslands 1950-1985. Cons. Biol. 11:727-737. Murphy, A.H. 1978. Benefits of chaparral directed at oak woodland and grassland Gordon, D. R. and K. J. Rice 1993. Competitive improvement to livestock and wildlife. Proc. ecosystems and the fact that rangeland effects of grassland annuals on soil water and Ann. Calif. Weed Conf. 30:84-91. conversion is no longer done for livestock blue oak (Quercus douglasii) seedlings. Ecol. Murphy, A.H. and H.F. Heady. 1983. Vascular production will undoubtedly slow the 74: 68-82. plants of the Hopland Field Station, Mendocino spread and establishment of invasive Hamilton, J.G., C. Holzapfel, and B.E. County, California. Wasmann J. Biol. species. Mahall. 1999. Coexistence and interference 41:53-96. D.D. 1989. Hardwood rangelands are the most bio- between a native perennial grass and non- Murphy, and P.R. Ehrlich. Conservation biology of California's remnant logically rich habitat type in California native annual grasses in California. Oecologia 121:518-526. native grasslands. Pp 201-212. In: L.F. (Pavlik et al. 1991), making it essential Harrison, S.1999. Local and regional diversity Huenneke and H.F. Mooney (eds.), that we monitor changes to their flora over in a patchy landscape: Native, alien, and Grassland structure and function: California time. Continued surveys at the Center will endemic herbs on serpentine. Ecol. 80:70-80. annual grassland. Kluwer, Dordrecht. help verify local extinction and document

418 JOURNAL OF RANGE MANAGEMENT 55(4) July 2002 Pavlik, B.M., P.C. Muick, S.G. Johnson, and Randall, J.M., M. Rejmanek, and J.C. Vitousek, P.J. 1986. Biological invasions and M. Popper. 1991. Oak of California, Hunter. 1998. Characteristics of the exotic ecosystem properties: Can species make a Cachuma Press and the California Oak flora of California. Fremontia 26:3-12. difference? Pp. 163-178 In: H.A. Mooney Foundation. Los Olivos, Calif.184 pp. Rejmanek, M., C.D. Thomsen, and I.D. and J. Drake (eds.), Biological invasions of Peters, A., D.E. Johnson and M.R. George. Peters. 1991. Invasive vascular plants of North America and Hawaii. Springer-Verlag, 1996. Barb goatgrass: A threat to California California. Pp. 81-101. In: R.H. Groves, and New York, N.Y. rangelands. Rangelands 18(1): 8-10. F. di Castri (eds.). Biogeography of mediter- Pettit, N.E., R.H. Forend, and P.G. Ladd. ranean invasions. Cambridge University 1995. Grazing in remnant woodland vegeta- Press, Cambridge. tion: Changes in species composition and life form groups. J. Veg. Sci. 6:121-130. Skinner M.W. and B.M. Pavlik. 1994. Pitt, M.D., R.H. Burgy, and H.F. Heady. California Native Plant Society's Inventory 1978. Influences of brush conversion and of Rare and Endangered Vascular Plants of weather patterns on runoff from a northern California. Special Publication No.l (fifth California watershed. J. Range Manage. edition). CNPS. 31:23-27.

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