A FLORISTIC STUDY OF SWANTON PACIFIC RANCH, SANTA CRUZ COUNTY, CALIFORNIA

Abstract

The Swanton Pacific Ranch (SPR) is located north of the town of Davenport, in Santa Cruz County, California, and is owned by California Polytechnic State University, San Luis Obispo. SPR is approximately 1295 ha and contains areas of salt marsh, coastal prairie, coastal bluff scrub, northern coastal scrub, riparian forest, redwood forest, mixed evergreen forest, and chaparral. The property extends over an elevational gradient from 0 m to 420 m. In this study, we conducted a floristic inventory at SPR and documented 636 taxa. Between 2017 and 2019 we vouchered 547 taxa with 974 specimens. We were unable to locate 63 taxa that had been previously reported, 27 represented from historic collections and 36 represented by personal observations, but lacking vouchers. We relocated, but did not collect, 26 taxa known from previous collections. Overall, we documented 93 families at SPR, with Asteraceae, Poaceae, and Fabaceae having the most species, respectively. California rare taxa, listed by the California Native Plant Society, made up 2.5% of the flora (n = 18). Locally rare taxa made up 10% of the flora (n = 65). Non-native taxa made up 26% of the flora (n = 169). We vouchered one new taxon for Santa Cruz County, Senecio aphanactis Greene, which has a California Rare Plant Rank of 2B.2; documented a new occurrence of Hesperocyparis abramsiana (C.B.Wolf) Bartel var. abramsiana, a Federally Threatened conifer; and collected a form of Sanicula crassicaulis Poepp. Ex DC that we have published as a distinct variety. Overall, this relatively small coastal ranch contained approximately 10% of the flora of California. The 2020 CZU Lightning Complex Fire burned ca. 90% of SPR within a year of this study being completed. This opens the possibility for this study to be used as a baseline for future studies examining post-fire shifts in plant diversity at a landscape scale.