The Flora of Red Rock Canyon State Park:

Revisiting Twisselmann’s 1970 Checklist

Floristic inventories based on the collection of voucher specimens serve to establish important baseline data for biodiversity research and permits research to be repeatable. Revisiting floras can help to assess how diversity may change over time. Red Rock Canyon State Park in Kern County, California, occupies a unique transition zone where the Mojave Desert, Sierra Nevada, and Basin and Range geomorphic provinces meet. Consequently, two floristic provinces also intersect here: the California Floristic Province and the Desert Floristic Province. The uniqueness of this area has long been recognized by botanists, and importantly, by Ernest C. Twisselmann, who produced a preliminary checklist for Red Rock Canyon in 1970. Yet, there has never been a published flora for the park. This study aims to update the floristic knowledge of the park based on the collection of voucher specimens and to assess floristic change through comparisons with previously unpublished checklists. Red Rock Canyon State Park hosts several rare and endemic plants, including the Red Rock monkey flower (Erythranthe rhodopetra) and the Red Rock tarweed (Deinandra arida). This study also aims to provide updated information on special status species within the park. As climate change, increased drought, and other impacts pose major threats to California’s biodiversity, an updated floristic inventory for Red Rock Canyon State Park will be critical to assess changes in diversity over time and to inform conservation management decisions for this dynamic and significant flora.