INTRODUCTION

Background. Hollister Ranch is a 14,500 acre private land holding located on the South Coast of Santa Barbara County (Fig. 1). The Ranch's boundaries extend from the ocean to the ridge of the western Santa Ynez Mountains at an elevation of about 1600 feet, and from Gaviota State Park west to Cojo Canyon, about 3 miles east of Point Conception. Although the Ranch has been subdivided into 100-acre parcels (Fig. 2), most of the land remains undeveloped and continues to be managed as a cattle grazing cooperative. As a result, Hollister Ranch comprises one of the largest, relatively pristine natural areas along the coast of southern California (Fig. 3).

Introduced plant and animal species, as well as agriculture and other human activities, have had their impacts on the landscape, as in most of coastal California. In spite of these alterations, Hollister Ranch continues to support a surprising variety of native habitats as well as an unusual and interesting native flora. The expanding urbanization of the Coastal Zone of California has resulted in the increasing rarity of natural resources such as those at Hollister Ranch. Documenting these coastal resources is an important step in the understanding and protection of the biodiversity of the natural areas that remain. 

Purpose and Scope. This botanical study is the result of a cooperative effort between the Hollister Ranch Conservancy and the Museum of Systematics and Ecology (MSE) at the University of California, Santa Barbara (UCSB). The main goal has been to update an earlier floristic study (Fletcher 1983), also conducted through UCSB, and to use current technology to produce quality maps of the geology, soils, and vegetation. A more complete phytogeographic analysis and updated information on sensitive plant species were among the tasks envisioned.

An attempt was made not only to describe the vegetation of the Ranch and the species that characterize that vegetation, but to examine the influence of geology, soils, geographical location, microclimate, and human activities on the flora and vegetation. Understanding these relationships is crucial to making decisions about the management of natural resources that are affected by all these factors. Recommendations on management opportunities are also an important component of this project, because the Hollister Ranch Conservancy is very interested in active management of the natural resources of the Ranch. 

Methods. Flora. We made 24 collection trips over a two year period to document species not found in Fletcher's 1983 flora, to document locations of some of the sensitive and unusual plants, and to confirm doubtful species identifications. Most trips took place between March and July; however some were made in August, September, and October, to obtain late-blooming species. Plant collections were pressed, dried, mounted, and labeled. They are deposited at the UCSB MSE. Initial plant identifications were made by Beth Hendrickson and confirmed by Wayne Ferren; additional confirmation and help in identification for some taxa was provided by Steve Junak of the Santa Barbara Botanic Garden. Tamara Klug provided assistance with plant collecting, field notes, and identification, pressing, and labeling of voucher specimens.
We attempted to locate plants that had not been documented previously but which were likely to occur on the Ranch, based on information in the Flora of Santa Barbara County (Smith 1976) and other sources. We also examined collections from Hollister Ranch in the herbaria at the UCSB MSE and at the Santa Barbara Botanic Garden. Clifton Smith recounted his recollections of the area, gave access to his notes from field trips to the Ranch, and provided much help in confirming plant taxonomic identifications.

Botanical names were updated based on the Jepson Manual (Hickman 1993). In a few cases, older names were retained to preserve local subspecies or varieties that were deleted from the Jepson Manual. The plant catalogue in Appendix I of this flora contains 512 taxa (species, subspecies and varieties), an addition of 115 to the previous flora.

Biogeographical information is primarily based on the distributions given in the Jepson Manual. Habitat information for each species was compiled from a variety of sources, including specimen labels, information in Hickman (1993) and Fletcher (1983), and field observations of the authors. Beth Hendrickson compiled the database of distributions and habitat information for each species (see Appendix 1), which was used as a basis for her biogeographical analysis reported in Part IV.

Vegetation. We examined the various plant communities systematically. They were described and categorized according to the dominant species. Geologic formation, elevation, slope, and aspect of each sample site was recorded. This method revealed the influence of site conditions (habitat) in producing variations in species composition within a broad community class such as coastal scrub. The descriptions of the upland plant communities are by Beth Hendrickson; Wayne Ferren provided the characterizations of the various wetland habitats and plant communities.
Vegetation communities were mapped by Beth Hendrickson using the United States Geological Survey (USGS) topographic maps (7.5 minute quadrangles) for this area. The maps were enlarged 200%, to a 1: 12,000 scale. A zoom-transfer scope was used to transfer outlines of vegetation onto the maps from 1:12,000 scale aerial photographs (Pacific Western Aerial Surveys 1989). The UCSB Map and Imagery Laboratory provided equipment and valuable assistance in this project.

The Hollister Ranch geology map was based on those prepared by Thomas W. Dibblee Jr. (1988), including Lompoc Hills, Point Conception, Santa Rosa Hills, and Sacate. The soils map was based on that prepared by the Soil Conservation Service (Shipman 1981). The maps of Hollister Ranch were digitized by Joe Walsh at the Biogeography Lab, Department of Geography, University of California, Santa Barbara.