Plant communities associated with the rare, paleoendemic oak

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Oak ecosystem restoration on Santa Catalina Island, California: Proceedings of an on-island workshop, February 2-4, 2007. Edited by D.A. Knapp. 2010. Catalina Island Conservancy, Avalon, CA.

PLANT COMMUNITIES ASSOCIATED WITH THE RARE, PALEOENDEMIC OAK,

QUERCUS TOMENTELLA ON SANTA CRUZ AND SANTA ROSA ISLANDS, CALIFORNIA

Laura Kindsvater

Save the Redwoods League

114 Sansome St. #1200 San Francisco, CA 94104

[email protected]

ABSTRACT: Descriptive statistics and canonical correspondence analysis were used with vegetation

plot data to discover more about plant communities and environmental factors associated with Quercus

tomentella on Santa Rosa and Santa Cruz Islands. In comparisons with existing data on Santa Rosa Island, plots with Q. tomentella shared the most species in common with closed-cone pine forest, mixed

island woodland, Torrey pine woodland, and mixed chaparral communities. These communities probably

covered a much larger acreage on the islands 200 years ago, before intensive grazing. Of the 162 taxa of

higher plants that were associated with Q. tomentella in this study, 124 are native. Twenty-four native taxa were found in groves near to those sites that have suffered severe soil erosion, and some of these may

be useful for planting in groves in need of restoration, in order to help trap and build plant litter and

topsoil. Ten moderately to highly invasive taxa were found in Q. tomentella groves, and these may be contributing to low regeneration in Q. tomentella because of their tendency to reduce and deplete soil

moisture.

KEY WORDS: California Channel Islands, island oak, woodland, Quercus tomentella, restoration,

chaparral, Canonical Correspondence Analysis

INTRODUCTION

California's Channel Islands are home to a rich diversity of plants. About 1,788 plant species, subspecies,

and varieties grow on the islands (compared to more than 5,800 native species in the state as a whole; Raven 1967, Hickman 1993). As urbanized southern California is one of the world's hotspots for

biodiversity, the lightly populated islands are an important refuge for rare and native plant species.

Restoration managers working on the islands are faced with a difficult challenge: how to restore an

ecosystem without a clear picture of what the pre-European or optimal conditions for a rare and native species might be. Reference sites have become, arguably, non-existent. Non-native grazers and browsers

(including sheep, goats, pigs, cattle, deer, elk, and others) introduced to the islands within the last 150

years have caused soil erosion and greatly changed the distribution and prevalence of native vegetation (Junak et al. 1995, Peart et al. 1994, Van Vuren and Coblentz 1987, Baber 1982, Hobbs 1980, Hochberg

et al. 1980).

Records and maps of what the plant communities were like 150-200 years ago are vague (for example, a

map published in 1886 lists only two plant communities on Santa Rosa: "cactus" and "oak brush"; United

States Coast Survey 1886). In the absence of detailed records or good reference sites, where can

restoration managers turn for information? How do they know where a certain species was in the past? In addition, because ecosystems have changed so dramatically, it may be impossible to restore the land to

past conditions. This is a question of much debate between land managers and ecologists: should we be

trying to restore the past? Or, should we aim to restore to some set of optimal conditions that are different than the past, in which rare species can thrive?

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Island oak (Quercus tomentella) is the rarest of all of California's oak species, and is restricted in its

present-day natural distribution to six islands off the coast of California (Pavlik et al. 1991). It is one of many island species of special concern in need of recovery. Many of its stands in Channel Islands

National Park are not currently recruiting to the seedling and/or sapling stage, a problem not limited to the

islands. Most white oak species in California are suffering from poor regeneration, for reasons that are not

completely understood (Brooks and Merenlender 2001). As the number of non-native grazers and browsers has been greatly reduced on the islands over the past 20 years, and because there are a few

stands where regeneration of island oak has resumed within the last decade or more, island oak may also

offer some insight to scientists working to conserve and restore oak woodlands on mainland California. Gophers and ground squirrels, which significantly limit oak seedling establishment and survival on the

mainland (Tyler et al. 2002), are absent on Santa Cruz and Santa Rosa islands, which may help to reduce

the complexity of the regeneration puzzle.

To inform a plan for recovery of island oak, I have researched its current and potential habitats. The

objectives of this paper are to analyze the habitat of island oak, Quercus tomentella, on Santa Rosa and

Santa Cruz Islands with regard to the species and range of environmental conditions associated with it, and compare its plant assemblages with that of other communities found on these islands. In addition, I

have examined soil conditions (Kindsvater 2006a), and constructed a GIS model based upon associated

environmental parameters identified as a result of fieldwork (Kindsvater 2006c). This knowledge will inform restoration and conservation protocols for the oak and its environs.

This study examines the diversity of species associated with island oak, how consistently these species are found in island oak stands, and which native species are most closely associated with island oak stands

suffering most extensive erosion. Introduced and potentially invasive species associated with island oak

stands were also catalogued. It was hypothesized that Q. tomentella’s distribution might have been

significantly limited by the availability of water, and expected that plant species associated with Q. tomentella would be more similar to those in riparian communities than those in chaparral.

Previous research has shown that Quercus tomentella grows in a variety of plant communities. On Santa Cruz Island, it is found in oak woodland, pine forest, riparian woodland, and chaparral communities

(Junak et al. 1995). On Santa Rosa Island, it forms island oak woodland, and grows in mixed oak

woodland, and closed-cone pine communities (Clark et al. 1990); it has also been observed growing as a

shrub in chaparral on very rocky locations.

METHODS

This study utilizes field data collected during mid-April to mid-May of 2003 and 2004 in 23 large

rectangular plots, ranging from 200 to 225 m2 in size. The plots were located in 11 sites: five on Santa

Rosa Island and six on Santa Cruz Island. Plot locations were chosen to include all geologic substrates, topographic positions, and general vegetation types in which Q. tomentella is known to grow on these two

islands.

Vegetation was sampled using the Braun-Blanquet relevé method (Mueller-Dombois and Ellenberg 1974). Each plant species and its approximate cover within seven cover classes were recorded: a single

occurrence of a plant, < 1% cover, 1 - 5% cover, 6 - 25% cover, 26 - 50% cover, 51 - 75% cover, or >

75% cover. Each tree was included in a maximum of one plot, although some plots were less than 0.5 km apart from each other. Nomenclature for vascular plants follows Junak et al. (1995).

The ideal plot size needed to capture species diversity was determined by beginning with a small plot (1 m

2) and then repeatedly doubling the plot’s area and measuring the incremental increase in number of

species. As long as the increase in number of species met or exceeded 10%, the size of the plot was

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increased. The increase in number of species dropped below 10% at about 200 m2, which is similar to the

optimal plot size for forests in general, given by Mueller-Dombois and Ellenberg (200 - 500 m2 for tree

stratum and 50 - 200 m2 for undergrowth vegetation only; 1974). The objective was to capture as many

species as possible, while limiting the sampling to a homogeneous plant community (Mueller-Dombois

and Ellenberg 1974). Both closed-canopy and partial canopy woodlands were included in the study.

Geologic substrates sampled on Santa Cruz Island included Santa Cruz Island volcanics (Diablo Peak

member), Santa Cruz Island schist, Monterey shale, and the Blanca formation. Geologic substrates

sampled on Santa Rosa Island included the Beechers Bay formation, Rincon formation, and Santa Rosa Island volcanics (basaltic volcaniclastic rocks). Some of these geologic substrates are also found on the

mainland (e.g. Monterey shale).

For each plot, the following environmental data was collected: slope, aspect, elevation, amount of shelter

from the wind (using a scale from 0 to 10, with 10 being maximum shelter), an estimate of the percent of

bare ground and percent exposed rock, topographic position, percent of surface covered by litter, average

depth of litter, and GPS coordinates of the plot’s corners. The number of strata in the vegetation was recorded, as well as which stratum was dominant, and an estimate of the height of the trees.

Soil samples were collected in both 2003 and 2004 and used to calculate each site’s bulk density and soil color (Kindsvater 2006a). Each soil sample collected in 2003 was also tested for its texture (as percent

sand, silt, and clay) and cation exchange capacity. Each sample collected in 2004 was tested for its soil

texture, total nitrogen, total carbon, total phosphorus, exchangeable potassium, and pH by the University of California Agriculture and Natural Resources Analytical Laboratory.

All vegetation and environmental data were entered into the Turboveg database (Hennekens and

Schaminee 2001). Canonical correspondence analysis was used in the ordination program PC-ORD to examine the relationships between each plot’s plant species and its environment.

RESULTS

Species associated with Quercus tomentella and their overlap with other plant communities

All of the vascular plants found to be associated with Q. tomentella on Santa Rosa Island (SRI) and Santa Cruz Island (SCI) in this study are listed in Appendix 1. The following taxa were found in more than half

of this study’s plant community plots: Baccharis pilularis, Bromus diandrus, Galium aparine,

Gnaphalium spp., Hypochaeris glabra, Silene gallica, Sonchus oleraceus, and Stellaria media. Most of these are non-native, weedy species that occur in open grassland or partly shaded woodland. The only

natives among them are Baccharis pilularis and Gnaphalium spp.

Species growing in an intermediate number of plots (i.e., 25-50% constancy) included: Achillea

millefolium, Agrostis pallens, Avena barbata, Claytonia spp., Hazardia detonsa, Heteromeles arbutifolia,

Lotus dendroideus var. dendroideus, Marah sp., Mimulus flemingii, Pentagramma triangularis,

Polypodium californicum, Pterostegia drymarioides, Quercus pacifica, Senecio vulgaris, and Vulpia myuros. Of these taxa, 79 percent are native. Only the following are non-native: Avena barbata, Senecio

vulgaris, and Vulpia myuros.

Other native species were found in five (22%), four (17%), or three (13%) plots. Species found in five

plots include: Chenopodium californicum, Clarkia epilobioides, Lessingia filaginifolia var. filaginifolia,

Melica imperfecta, Mimulus longiflorus, Sanicula arguta, and Trifolium willdenovii. Species found in four plots include: Carex globosa, Dryopteris arguta, Dudleya sp., Eriogonum arborescens, Hieracium

argutum, Lupinus bicolor, Nassella pulchra, Pinus muricata, Selaginella bigelovii, Stachys bullata, and

56


Uropappus lindleyi. Species found in three plots include: Adiantum jordanii, Agoseris grandiflora,

Antirrhinum sp., Arctostaphylos insularis, Arctostaphylos tomentosa, Baccharis plummerae subsp. plummerae, Comarostaphylis diversifolia subsp. planifolia, Eriophyllum confertiflorum var.

confertiflorum, Eucrypta chrysanthemifolia var. chrysanthemifolia, Filago californica, Luzula comosa,

Ranunculus californicus, Rhus integrifolia, and Toxicodendron diversilobum.

Contrary to my hypothesis, plant species associated with Q. tomentella were not more similar to those in

riparian communities than those in chaparral. Only 64% of all species found in riparian woodland and

26% of species in riparian herbaceous vegetation on Santa Rosa Island (Clark et al. 1990) were also found in the Q. tomentella sites, while 74% of all species found in mixed chaparral matched Q. tomentella sites

(Table 1). Three vegetation types had even higher percent similarity on Santa Rosa Island: 79% in mixed

woodland, 87% in closed-cone pine forest, and 76% of all species in Torrey pine forest.

Percent matching species were less for all other habitats: 60% in coastal sage scrub 57% in both grassland

and caliche scrub, 55% in Baccharis scrub, 48% in lupine scrub, 29% in coastal bluff scrub, and 40% and

20% in coastal marsh and coastal dune scrub, respectively (all non-native).

Table 1. Percent of species in Santa Rosa Island plant communities associated with Quercus tomentella.

Vegetation Community % associated

species SRI Closed-Cone Pine Forest 87%

SRI Mixed Woodland 79%

SRI Torrey Pine Forest 76%

SRI Mixed Chaparral 74%

SRI Riparian Woodland 64%

SRI Coastal Sage Scrub 60%

SRI Caliche Scrub 57%

SRI Grassland 57%

SRI Baccharis Scrub 55%

SRI Lupine Scrub 48% SRI Coastal Marsh 40%

SRI Coastal Bluff Scrub 29%

SRI Riparian Herbaceous Vegetation 26%

SRI Coastal Dune Scrub 20%

Canonical correspondence analysis between species and environmental variables

Canonical correspondence analysis of the multivariate relationships between species associated with Q.

tomentella and environmental factors produced no statistically significant results, however, they show some general trends that might become more apparent if more data were collected (Kindsvater 2006b).

The lack of statistical significance could be due to the small number and diversity of plots; the plots

included the diversity of all known types of geology and plant communities in which Q. tomentella is

currently known (mixed woodland, chaparral, closed-cone pine forest, and Q. tomentella woodland).

DISCUSSION: IMPLICATIONS FOR RESTORATION

On Santa Rosa Island, several Q. tomentella groves have suffered severe soil erosion (along Burma Road

in the vicinity of Soledad Peak, and facing the back side of Black Mountain near Pecho Peak), which

57


could be attributed to overgrazing by cattle, elk, and deer introduced to the island. Pig rooting could also

have contributed to this problem. Smith thought that these groves had become denuded of topsoil “probably due to a combination of fog drip and some form of allelopathy” and remarked that he had been

told that cattle had rarely gathered there (1976). Regardless of whether allelopathy or severe grazing has

happened in these groves, soil tests show that the remaining soil is highly acidic, with pH as low as 3.3,

and that soil compaction is higher than in groves in which regeneration is currently occurring (Kindsvater 2006a). In addition, these groves are in extremely windy locations, so leaf litter is swept away by the

wind. There is currently no understory vegetation (Figure 1).

Figure 1. Island oak groves near Soledad Peak on Santa Rosa Island, soil erosion

has been so severe that no topsoil remains.

To begin rebuilding topsoil, it would be helpful to plant native plant species in the understory and in the open areas between island oak trees, which could both produce organic matter and help to trap and retain

it. Park staff constructed coco-fiber swales at the Soledad Peak groves in 2006 in order to begin re-

building topsoil, and surrounded the groves with fencing to keep out elk and deer. Near these swales, where small pockets of moisture from fog drip are common, small herbaceous plants such as Lupinus

bicolor have begun to colonize the site. These volunteers could be supplemented with plantings in the

future.

On the periphery and nearby vicinity of the Soledad Peak groves, there are a few native species present,

and several likely candidate species for planting emerge because they are adapted to the site: Baccharis

pilularis ssp. consanguinea, Nassella pulchra, N. cernua, and N. lepida (Chaney 2004), as well as Bromus carinatus, Calandrinia ciliata, Gnaphalium purpureum, Lasthenia californica, Layia

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platyglossa, Lupinus bicolor, and Sanicula arguta. Other good candidates might be species that are

successfully growing in the nearby (but less eroded) groves (Kindsvater 2006a), as well as species that are well adapted to nutrient poor, extremely acidic soils (McEachern pers. comm. 2004).

The eroded grove near Pecho Peak differs from the Burma Road groves in that it is growing in soils

derived from Santa Rosa Island volcanics (rather than the Monterey shale or Rincon formation, which are sedimentary substrates). On the periphery of the Pecho Peak grove, these native species are present:

Mimulus flemingii, Pentagramma triangularis, Chenopodium californicum, Melica imperfecta, Baccharis

pilularis, Adiantum jordanii, Ranunculus californicus, Toxicodendron diversilobum, Comarostaphylis diversifolia subsp. planifolia, Leymus condensatus, Nassella species, and Sanicula hoffmannii. The grove

would benefit if seeds local to this site were collected, germinated, and planted in order to slow erosion.

Additional work to discover which native species are represented in the nearest neighboring groves (those

on either side of the most severely eroded groves near Soledad Peak) would be of interest, as these were

not sampled in this study. Natives represented in three nearby groves (three of the four that are the

furthest west along Burma Road) include: Melica imperfecta, Agrostis pallens, Bromus carinatus, Lessingia filaginifolia var. filaginifolia, Agoseris grandiflora, Agoseris heterophylla, Pterostegia

drymarioides, Conyza canadensis, Gnaphalium canescens subsp. beneolens, Stachys bullata, Vaccinium

ovatum, Stephanomeria virgata, Solanum douglasii, Trifolium willdenovii, Baccharis pilularis, and Lupinus bicolor. Some of these may be suitable for planting among the eroded groves; additional research

to determine which can survive nutrient poor, highly acidic soils would also be helpful.

Introduced species that were in many of this study’s 23 plots included Avena barbata (nine plots),

Bromus diandrus (definitely in 10 plots, with the possibility of being in eight additional plots),

Hypochaeris glabra (13 plots), Silene gallica (13 plots), Sonchus oleraceus (13 plots), and Stellaria

media (12 plots). Of these species, both Avena barbata and Bromus diandrus received a Moderate ranking from the California Invasive Plant Council, signifying that they “have substantial and apparent –

but generally not severe – ecological impacts on physical processes, plant and animal communities, and

vegetation structure” (California Invasive Plant Council website 2009). Research by Doria Gordon, Kevin Rice, J. M. Welker, and others has shown that Bromus diandrus (as well as other annual grasses and

forbs) can have a significant negative impact on Quercus douglasii (blue oak) seedling growth and

survival by dramatically reducing soil moisture (Gordon and Rice 2000; Momen et al 1994; Gordon and

Rice 1993; Gordon et al 1991; Gordon et al 1989). It is is likely that this is also true for Quercus tomentella’s seedling growth and survival.

Bromus madritensis subsp. rubens was also present in some Q. tomentella plots and has received a High ranking from the California Invasive Plant Council; it is thought to have severe ecological impacts.

According to the Council’s website, the rationale for this is that Bromus madritensis subsp. rubens

increases fuel continuity and flammability, and by contributing to removal of shrub cover, alters microhabitat characteristics and soil nutrient cycling and distribution. This grass may also reduce vigor,

fecundity, and species diversity of native annual plant communities, and may hybridize with both alien

and native Bromus species and become more invasive (California Invasive Plant Council website 2009).

Other introduced species that were present in a small number of Quercus tomentella plots and that

received a Moderate ranking from the California Invasive Plant Council website included Brassica nigra,

Carduus pycnocephalus, Centaurea melitensis, Cirsium sp., Erechtites glomerata, Hirshfeldia incana, Hordeum murinum, and Vulpia myuros. Of these, Brassica nigra, Carduus pycnocephalus, Erechtites

glomerata, Hirshfeldia incana, Hordeum murinum, and Vulpia myuros all have the potential to spread

rapidly (California Invasive Plant Council website 2009). Erechtites glomerata is of particular concern. It was first collected in 1989 on Santa Cruz Island and is noted in Junak et al 1995 as scarce at present but

spreading. It is among the most serious pests in the Channel Islands; it spread rapidly in an established

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grassland on San Miguel Island, displacing native grasses and forbs, and did not require any disturbance

prior to this event. Its rapid rate of spread may be caused by its ability to establish facultative mycorrhizal relationships. Seeds disperse by wind and are thought to have blown from San Miguel to Santa Barbara

Island (California Invasive Plant Council website 2009).

CONCLUSION

In combination with other negative factors such as: soil erosion; herbivory, trampling, and rooting by

non-native grazers and browsers; and possibly climate change and/or drought, competition with non-native annual species for water could be a significant limiting factor in Quercus tomentella’s

regeneration. This seems particularly likely on Santa Rosa Island, where many Q. tomentella groves are

isolated, small stands surrounded by a sea of non-native annual grassland.

The low constancy of natives throughout the plots in this study could mean: (1) that Q. tomentella plant

communities have lost some of the species that were formerly associated with them in recent times, in

some or all of the stands; (2) that modern-day Q. tomentella inhabits a variety of different plant communities, with diverse assemblages; or (3) Q. tomentella plant communities on Santa Rosa Island

may differ significantly from Q. tomentella plant communities on Santa Cruz Island (McEachern pers.

comm. 2004). Based on observations made during fieldwork and my general knowledge of the species, I suggest that all three of these are probably true. The first hypothesis is difficult to impossible to test. The

second is correct, given that Q. tomentella has been found in mixed woodland, chaparral, pine forest,

riparian woodland, and pure Q. tomentella forest and that these plant communities have already been shown by other researchers (Clark et al. 1990; Junak et al. 1995) to have characteristic plant species

consistently associated with them. GIS models depicting Q. tomentella potential habitat for Santa Rosa

and Santa Cruz Island also show a large degree of overlap with chaparral, closed cone pine, Torrey pine,

and mixed oak woodland (Kindsvater 2006c). In the new edition of the Manual of California Vegetation, Q. tomentella will likely be considered a “special element” of other vegetation types, since it is found in

more than one vegetation type, but is not consistently present in any of them (John Sawyer pers. comm.

2008).

In comparing Santa Rosa to Santa Cruz, I suggest that the communities differ somewhat both in terms of

which species are present, and in the relative abundance of the different communities. For example, on

Santa Rosa Island’s Black Mountain, Q. tomentella’s largest populations are thickly forested stands, of 100 percent canopy cover. Yet, on Santa Cruz’s Diablo Peak and Alta 2, Q. tomentella’s largest

populations have less than 100 percent cover, making them more savanna than forest; the individual trees

have large patches of grassland in between. The associated species on Black Mountain are somewhat different than those on Diablo Peak and Alta 2. The idea that plant communities on Santa Rosa are

somewhat different than those on Santa Cruz Island is worthy of more study (a larger amount of data,

from more sampling sites, stratified across plant communities would be needed). It would also be very interesting to see how vegetation types associated with Q. tomentella on these two islands compare to

other islands.

LITERATURE CITED

Baber, D. 1982. Report on a survey of feral pigs on Santa Cruz Island, California: Ecological implications

and management recommendations. Unpublished report submitted to The Nature Conservancy, Santa Barbara, California. 19 pp.

Brooks, C. N. and A. M. Merenlender. 2001. Determining the pattern of oak woodland regeneration for a

cleared watershed in northwest California: a necessary first step for restoration. Restoration Ecology 9:1-12.

California Invasive Plant Council website. Accessed March 15, 2009. http://www.cal-ipc.org.

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Chaney, S. 2004. Protection of endemic island oak and rehabilitation of actively eroding areas on Santa

Rosa Island. Grant proposal to the National Park Service with respect to Channel Islands National Park Resources Management Plan.

Clark, R. A., W. L. Halvorson, A. A. Sawdo, and K. C. Danielsen. 1990. Plant communities of Santa

Rosa Island, Channel Islands National Park. Technical Report No. 42. Cooperative National Park

Resources Studies Unit, University of California at Davis, Institute of Ecology, Davis, CA. Gordon, D. R. and K. J. Rice. 2000. Competitive suppression of Quercus douglasii (Fagaceae) seedling

emergence and growth. American Journal of Botany 87: 986-994.

Gordon, D. R. and K. J. Rice. 1993. Competitive effects of grassland annuals on soil water and blue oak (Quercus douglasii) seedlings. Ecology 74: 68-82.

Gordon, D.R., K.J. Rice, et al. 1991. Soil water effects on blue oak seedling establishment. Pp. 54-58 in:

R.B. Standiford, tech. coord. Proceedings of the symposium on oak woodlands and hardwood rangeland management. USDA Forest Service General Technical Report PSW-126, Berkeley,

CA.

Gordon, D.R., J.M. Welker, et al. 1989. Competition for soil water between annual plants and blue oak

(Quercus douglasii) seedlings. Oecologia 79:533-541. Hennekens, S.M. and J.H.J. Schaminee. 2001. TURBOVEG, a comprehensive data base management

system for vegetation data. Journal of Vegetation Science 12: 589-591.

Hickman, J. C., ed. 1993. The Jepson manual: Higher plants of California. University of California Press, Berkeley, CA.

Hobbs, E. 1980. Effects of grazing on the northern population of Pinus muricata on Santa Cruz Island,

California. Pp. 159-165 in: D.M. Power, ed. The California Islands: Proceedings of a multidisciplinary symposium. Santa Barbara Museum of Natural History, Santa Barbara, CA.

Hochberg, M. 1980. Factors affecting leaf size of chaparral shrubs on the California islands. Pp. 189-206

in: D.M. Power, ed. The California Islands: Proceedings of a multidisciplinary symposium. Santa

Barbara Museum of Natural History, Santa Barbara, CA. Junak, S.A., T. Ayers, et al. 1995. A Flora of Santa Cruz Island. Santa Barbara Botanic Garden, Santa

Barbara, CA and the California Native Plant Society, Sacramento, CA.

Kindsvater, L. C. 2006a. Using soil factors to inform restoration and management: A case study with a rare, endemic oak in Channel Islands National Park. PhD Dissertation, chapter 1, University of

California, Davis, CA.

Kindsvater, L. C. 2006b. Biology, geologic history, and distribution of the rare, paleoendemic island oak,

Quercus tomentella (Fagaceae). PhD Dissertation, chapter 2, University of California, Davis, CA. Kindsvater, L. C. 2006c. GIS applied to conservation and restoration of the rare island oak (Quercus

tomentella) California: Analysis of its potential distribution in recent history. PhD Dissertation,

chapter 3, University of California, Davis, CA. Momen, B., J.W. Menke, et al. 1994. Blue oak regeneration and seedling water relations in four sites

within a California oak savanna. Internaational Journal of Plant Science 155:744-749.

Mueller-Dombois, D. and H. Ellenberg. 1974. Aims and methods of vegetation ecology. John Wiley & Sons, New York, NY.

Pavlik, B.M., P.C. Muick, et al. 1991. Oaks of California. Cachuma Press, Los Olivos, CA and the

California Oak Foundation, Oakland, CA.

Peart, D., D. Patten, et al. 1994. Feral pig disturbance and woody species seedling regeneration and abundance beneath coast live oaks (Quercus agrifolia) on Santa Cruz Island, California. Pp. 313-

322 in: G.J. Maender and W.L. Halvorson, eds. The fourth California Islands symposium: Update

on the status of resources. Santa Barbara Museum of Natural History, Santa Barbara, CA. Raven, P.H. 1967. The floristics of the California Islands. Pp. 57-67 in: R.N. Philbrick, ed. Proceedings of

the symposium on the biology of California Islands. Santa Barbara Botanic Garden, Santa

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Tyler, C.M., B.E. Mahall, et al. 2001. Factors limiting recruitment in valley and coast live oak. Pp. 565-

572 in: Proceedings of the fifth symposium on oak woodlands: Oaks in California’s changing landscape. USDA Forest Service Pacific Southwest Forest and Range Experiment Station, PSW-

GTR-184, Albany CA.

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California. Biological Conservation 41:253-268.

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APPENDIX 1: 162 HIGHER PLANT TAXA ASSOCIATED WITH QUERCUS TOMENTELLA ON SANTA ROSA AND

SANTA CRUZ ISLANDS

Scientific name Common name Endemicity Introduced? Cal-IPC

rating

Cover classes for each plot

Achillea millefolium yarrow + (plot 6), + (plot 7), + (plot 12), + (plot 13), +

(plot 15), + (plot 16), + (plot 17), 1 (plot 18), +

(plot 21)

Adenostoma fasciculatum chamise r (plot 18)

Adiantum jordanii California maidenhair

fern

+ (plot 11), + (plot 13), r (plot 22)

Agoseris grandiflora mountain dandelion + (plot 7), + (plot 17), + (plot 23)

Agrostis pallens bent grass + (plot 6), 1 (plot 7), 1 (plot 11), + (plot 12), 1

(plot 14), 2 (plot 18), 1 (plot 21), + (plot 23)

Agrostis viridis bent grass X + (plot 9), + (plot 14)

Antirrhinum species snapdragon + (plot 12)

Arctostaphylos

confertiflora

Santa Rosa Island

manzanita

1 1 (plot 12)

Arctostaphylos insularis Santa Cruz Island

manzanita

2 1 (plot 2), + (plot 17), 1 (plot 19)

Arctostaphylos tomentosa island manzanita or

subcordate manzanita

1 (plot 1), + (plot 17), 1 (plot 18)

Arctostaphylos viridissima McMinn's manzanita 2 r (plot 15)

Artemisia californica coastal sagebrush r (plot 11)

Avena barbata slender wild oats X Moderate + (plot 1), + (plot 2), 2 (plot 3), 1 (plot 5), + (plot

7), + (plot 9), + (plot 12), + (plot 15), + (plot 17)

Avena fatua wild oats X Moderate + (plot 9), + (plot 13), + (plot 22)

Avena sativa cultivated oats X 2 (plot 4)

Baccharis pilularis coyote brush r (plot 5), + (plot 6), + (plot 7), 1 (plot 9), 1 (plot

11), + (plot 12), 1 (plot 13), r (plot 14), 1 (plot 17),

r (plot 18), + (plot 20), + (plot 21), 3 (plot 22), +

(plot 23)

Baccharis plummerae

subsp. plummerae

Plummer's baccharis + (plot 16), + (plot 17), + (plot 18)

Bloomeria crocea golden star r (plot 11)

Bowlesia incana + (plot 5)

Brassica nigra mustard X Moderate + (plot 1)

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rating


Bromus carinatus California brome + (plot 8), 1 (plot 9), + (plot 13), + (plot 14), +

(plot 17)

Bromus diandrus ripgut brome X Moderate + (plot 1), + (plot 2), 2 (plot 3), 2 (plot 4), 3 (plot

5), 1 (plot 12), + (plot 15), + (plot 16), 2 (plot 17),

1 (plot 23) Bromus hordeaceus soft chess X Limited 2 (plot 3), + (plot 9), + (plot 12), + (plot 22)

Bromus madritensis X + (plot 17)

Bromus madritensis

subsp. rubens

Madrid brome X High + (plot 5), + (plot 12), + (plot 13)

Bromus species brome X Limited to High

1 (plot 1), + (plot 2), 1 (plot 3), 2 (plot 4), + (plot 5), + (plot 7), + (plot 8), 1 (plot 9), + (plot 11), 3

(plot 13), + (plot 14), 1 (plot 21), 2 (plot 22)

Calandrinia ciliate red maids + (plot 9)

Calochortus albus fairy lantern or globe lily + (plot 7), + (plot 12)

Calystegia macrostegia subsp. macrostegia

island morning-glory 3 r (plot 16)

Cardamine californica milk maids + (plot 16), r (plot 17)

Carduus pycnocephalus Italian thistle X Moderate + (plot 13)

Carex globosa round-fruited sedge r (plot 1), + (plot 2), + (plot 12), + (plot 14)

Carex praegracilis clustered field sedge 3 1 (plot 6)

Ceanothus arboreus island ceanothus 3 1 (plot 19), 1 (plot 20)

Centaurea melitensis tocalote X Moderate + (plot 22)

Cerastium glomeratum mouse-ear chickweed X 1 (plot 2), + (plot 3), + (plot 4), + (plot 5)

Cercocarpus betuloides

var. blancheae

mountain mahogany + (plot 21)

Cheilanthes clevelandii Cleveland's lip fern + (plot 18)

Chenopodium

californicum

soap root + (plot 4), + (plot 13), r (plot 14), + (plot 15), +

(plot 22)

Cirsium species thistle X Moderate + (plot 17)

Clarkia epilobioides clarkia, godetia, or

farewell-to-spring

+ (plot 1), + (plot 2), r (plot 3), + (plot 4), 1 (plot

5)

Clarkia purpurea subsp.

quadrivulnera

clarkia, godetia, or

farewell-to-spring

r (plot 12)

Claytonia perfoliata

subsp. mexicana

miner's lettuce + (plot 6), + (plot 7), r (plot 13), + (plot 14), +

(plot 21)

Claytonia perfoliata miner's lettuce + (plot 1), + (plot 5), + (plot 9), + (plot 16), + (plot

17)

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rating


Comarostaphylis

diversifolia subsp.

planifolia

summer holly 2 (plot 17), 1 (plot 20), 1 (plot 22)

Coreopsis gigantea giant coreopsis r (plot 13), 2 (plot 17)

Cotula australis Australian brass buttons X r (plot 3), r (plot 5)

Cryptantha clevelandii + (plot 2)

Datura wrightii jimson weed or thorn

apple

r (plot 13)

Daucus pusillus rattlesnake weed + (plot 4), + (plot 11)

Dichelostemma capitatum blue dicks + (plot 4), + (plot 13)

Dichondra occidentalis western dichondra + (plot 12)

Dryopteris arguta wood fern r (plot 15), + (plot 19), + (plot 20), + (plot 21)

Dudleya candelabrum candleholder dudleya + (plot 21)

Dudleya greenei Greene's dudleya + (plot 17)

Dudleya species + (plot 12), + (plot 14)

Erechtites glomerata Australasian fireweed X Moderate + (plot 13), + (plot 17), r (plot 18)

Eriogonum arborescens Santa Cruz Island

buckwheat

3 + (plot 3), r (plot 5), + (plot 17), + (plot 21)

Eriogonum grande var.

grande

3 + (plot 17), + (plot 18)

Eriophyllum

confertiflorum var.

confertiflorum

golden-yarrow + (plot 13), + (plot 14), 1 (plot 17)

Erodium botrys broad-leaf filaree X Eval No

List

r (plot 9), + (plot 12)

Eucrypta

chrysanthemifolia var.

chrysanthemifolia

r (plot 5), r (plot 13), + (plot 16)

Filago californica California filago + (plot 2), + (plot 12), r (plot 14)

Galium aparine goose grass or cleavers ? + (plot 1), + (plot 2), + (plot 3), + (plot 5), r (plot

7), r (plot 8), + (plot 12), 1 (plot 13), + (plot 14), +

(plot 15), + (plot 16), + (plot 17), + (plot 21)

Galium californicum

subsp. flaccidum

+ (plot 20)

Galium nuttallii subsp.

insulare

Nuttall's island bedstraw 3 r (plot 13), + (plot 18)

Galium porrigens climbing bedstraw + (plot 11)

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rating


Geranium dissectum cutleaf geranium + (plot 9), + (plot 13), r (plot 14)

Gilia angelensis + (plot 4), r (plot 5)

Gnaphalium bicolor bicolored everlasting + (plot 1), + (plot 2), + (plot 13), + (plot 17)

Gnaphalium canescens

subsp. microcephalum

white everlasting + (plot 3)

Gnaphalium luteo-album weedy cudweed X r (plot 23)

Gnaphalium purpureum purple cudweed r (plot 6)

Gnaphalium species cudweed or everlasting ? + (plot 3), + (plot 4), + (plot 5)

Guillenia lasiophylla California mustard r (plot 7)

Hazardia detonsa northern island hazardia 3 + (plot 1), + (plot 2), + (plot 3), + (plot 5), 2 (plot

17), + (plot 21) Helianthemum scoparium common rush-rose r (plot 12)

Heteromeles arbutifolia toyon r (plot 1), 3 (plot 11), + (plot 12), 3 (plot 13), 5 (plot 14), 2 (plot 16), + (plot 18), 2 (plot 19), 1

(plot 20), + (plot 21)

Heuchera maxima island alumroot 3 + (plot 14), r (plot 18)

Hieracium argutum hawkweed r (plot 1), + (plot 2), 2 (plot 18), + (plot 19)

Hirschfeldia incana short-podded mustard X Moderate + (plot 3)

Hordeum murinum foxtail X Moderate + (plot 9), + (plot 13), r (plot 15) ,+ (plot 22)

Hypochaeris glabra smooth cat's ear X Limited + (plot 1), + (plot 2), + (plot 3), + (plot 4), r (plot

5), + (plot 7), + (plot 9), + (plot 12), + (plot 13), r


Juncus balticus wire rush + (plot 14)

Juncus patens common rush + (plot 13)

Lasthenia californica goldfields + (plot 9)

Lathyrus vestitus var.

vestitus

wild pea r (plot 16), 2 (plot 21)

Layia platyglossa tidy tips + (plot 9)

Lepechinia fragrans fragrant pitcher sage + (plot 12)

Lessingia filaginifolia var.

filaginifoia

cudweed aster + (plot 7), + (plot 11), + (plot 12), + (plot 13), +

(23)

Leymus condensatus giant rye + (plot 22)

Leymus triticoides alkali rye + (plot 6), + (plot 20)

Lilium humboldtii subsp.

ocellatum

+ (plot 19), 1 (plot 20)

Lolium temulentum darnel X + (plot 22)

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rating


Lotus dendroideus var.

dendroideus

island deerweed 3 + (plot 1), 1 (plot 3), r (plot 4), + (plot 5), 1 (plot

17)

Lotus species trefoil r (plot 14)

Lupinus bicolor dove lupine + (plot 3), + (plot 5), 1 (plot 9), + (plot 23)

Lupinus concinnus 1 (plot 4)

Lupinus succulentus succulent lupine + (plot 11)

Luzula comosa common wood rush + (plot 7), r (plot 12), + (plot 17)

Madia species tarweed + (plot 2)

Malacothrix saxatilis var.

implicata

cliff malacothrix 3 + (plot 16)

Malva parviflora cheeseweed X r (plot 9)

Marah macrocarpus var.

major

wild cucumber r (plot 15), r (plot 16)

Marah species man-root or wild

cucumber

+ (plot 13), + (plot 17), r (plot 20), + (plot 21)

Medicago polymorpha bur-clover X Limited r (plot 5), 1 (plot 9), r (plot 11)

Melica imperfecta coast range melic + (plot 4), + (plot 13), + (plot 14), + (plot 17), +

(plot 22), + (plot 23)

Melilotus indicus yellow sweet clover X + (plot 11)

Micropus californicus slender cottonweed + (plot 1)

Mimulus species monkey flower 3 + (plot 4), 1 (plot 17), + (plot 20)

Nassella pulchra purple needlegrass + (plot 9), + (plot 12), 1 (plot 13)

Nemophila pedunculata + (plot 5)

Pellaea andromedifolia coffee fern + (plot 16)

Pentagramma triangularis goldback or silverback

fern

+ (plot 1), + (plot 2), + (plot 5), + (plot 13), + (plot

17), r (plot 22)

Pinus muricata bishop pine 1 (plot 17), 1 (plot 19), + (plot 20), 1 (plot 21)

Plantago erecta California plantain + (plot 12)

Poa annua annual bluegrass X + (plot 6), + (plot 9)

Poa secunda one-sided bluegrass + (plot 5)

Polygala californica California milkwort + (plot 19), 1 (plot 20)

Polypodium californicum California polypody + (plot 7), + (plot 13), + (plot 14), + (plot 16), +

(plot 17), + (plot 18)

Polypogon interruptus ditch beard grass X + (plot 7), + (plot 8), + (plot 9), + (plot 22), + (plot

23)

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rating


Prunus ilicifolia subsp.

lyonii

island or Catalina cherry 2 (plot 13), + (plot 14), + (plot 17)

Pterostegia drymarioides fairy mist + (plot 3), + (plot 5), + (plot 11), 1 (plot 12), 1


Quercus agrifolia coast live oak r (plot 2), + (plot 16), 1 (plot 19)

Quercus pacifica island scrub oak + (plot 11), 1 (plot 12), + (plot 17), 1 (plot 18), 2

(plot 19), 1 (plot 20), + (plot 21)

Ranunculus californicus buttercup or crowfoot + (plot 11), + (plot 14), + (plot 22)

Rhus integrifolia lemonade berry + (plot 4), r (plot 7), + (plot 15)

Rhus ovata sugar bush 1 (plot 19), + (plot 20)

Ribes thacherianum Santa Cruz Island

gooseberry

1 (plot 20)

Salvia brandegei Brandegee's sage + (plot 12)

Sanicula arguta snakeroot or sanicle + (plot 7), r (plot 9), + (plot 12), + (plot 14), +

(plot 21)

Sanicula hoffmannii snakeroot or sanicle + (plot 22)

Scutellaria tuberosa skullcap r (plot 3)

Selaginella bigelovii bushy spike-moss + (plot 1), + (plot 2), + (plot 5), + (plot 13)

Senecio vulgaris common groundsel X + (plot 1), 1 (plot 2), + (plot 3), + (plot 4), + (plot

5), r (plot 15), r (plot 21)

Silene gallica windmill pink X + (plot 1), + (plot 2), + (plot 3), 1 (plot 4), + (plot

5), + (plot 6), + (plot 7), + (plot 8), 1 (plot 9), +


Silene laciniata subsp.

major

Indian pink + (plot 18), + (plot 21)

Silybum marianum milk thistle X Limited + (plot 15)

Sisymbrium officinale hedge mustard X + (plot 3), r (plot 15), + (plot 16)

Solanum clokeyi island nightshade 3 1 (plot 16)

Solidago californica California goldenrod + (plot 7)

Sonchus asper prickly sow thistle X Eval No

List

+ (plot 9), r (plot 21), r (plot 22), r (plot 23)

Sonchus oleraceus common sow thistle X r (plot 1), r (plot 3), r (plot 6), + (plot 7), + (plot 9),

+ (plot 11), + (plot 12), + (plot 13), r (plot 14), r

(plot 15), + (plot 16), + (plot 17), + (plot 21) Sonchus species sow thistle r (plot 2), r (plot 5), + (plot 9)

Spergula arvensis var.

arvensis

stickwort or starwort X + (plot 9)

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rating


Stachys bullata hedge nettle or wood mint r (plot 14), 2 (plot 16), 1 (plot 17), + (plot 23)

Stebbinoseris heterocarpa + (plot 7)

Stellaria media common chickweed X 1 (plot 1), + (plot 2), + (plot 5), 1 (plot 6), 1 (plot

7), 1 (plot 8), 2 (plot 9), + (plot 12), 1 (plot 13), 1

(plot 14), + (plot 16), + (plot 21)

Stephanomeria virgata + (plot 23)

Stylocline gnaphalioides everlasting nest straw + (plot 12)

Thysanocarpus curvipes hairy lacepod + (plot 2), + (plot 4)

Thysanocarpus laciniatus narrow-leaved lacepod + (plot 5)

Torilis nodosa knotted hedge-parsley X + (plot 11), + (plot 13), + (plot 22)

Toxicodendron diversilobum

poison oak 1 (plot 11), r (plot 17), + (plot 22)

Trifolium albopurpureum rancheria clover + (plot 3)

Trifolium depauperatum dwarf bladder clover r (plot 2)

Trifolium fucatum bull clover + (plot 23)

Trifolium gracilentum pinpoint clover + (plot 3), + (plot 4)

Trifolium variegatum + (plot 5)

Trifolium willdenovii tomcat clover r (plot 1), r (plot 3), 1 (plot 4), 1 (plot 5), + (plot 7)

Uropappus lindleyi silver puffs + (plot 2), + (plot 3), 1 (plot 4), + (plot 5)

Vaccinium ovatum California huckleberry 5 (plot 20), + (plot 23)

Venegasia carpesioides canyon sunflower 1 (plot 18), + (plot 19)

Vicia sativa vetch + (plot 11)

Vicia species vetch + (plot 1)

Viola pedunculata johnny-jump-up + (plot 4)

Vulpia bromoides brome fescue X Eval No

List

+ (plot 1), + (plot 2), + (plot 12), + (plot 22), +

(plot 23)

Vulpia myuros foxtail fescue X Moderate + (plot 1), 1 (plot 3), 1 (plot 4), 1 (plot 5), + (plot

9), 1 (plot 23) Xanthium spinosum spiny cocklebur X + (plot 9)

Yabea microcarpa + (plot 2), + (plot 5)

Endemicity: 1 = Endemic to Santa Rosa Island; 2 = Endemic to Santa Cruz Island; 3 = Endemic to multiple California islands.

Introduced species: X = introduced; ? = not known whether introduced or native.

Cover classes: r = single individual; + = less than one percent cover; 1 = one to five percent cover; 2 = six to 25 percent cover; 3 = 26 to 50 percent cover; 4 = 51 to 75 percent cover; 5 = 76 to 100 percent cover.

Nomenclature follows Junak et al. 1995.

Documents

Plant communities associated with the rare, paleoendemic oak