GEOLOGIC AND EDAPHIC CONTROLS ON THE DISTRIBUTION OF ABRONIA ALPINA (RAMSHAW MEADOWS SAND VERBENA) IN THE SIERRA NEVADA MOUNTAINS, INYO NATIONAL FOREST, CA

The California Floristic Province (CFP) is a biodiversity hotspot in the Western United States. Here, intense diversification and endemism have been attributed to complex edaphic and topographic conditions produced by California’s dynamic geologic landscape. The Abronia alpina (Ramshaw Meadows Sand Verbena) is a narrow alpine endemic and CFP inhabitant found in only 2 meadow systems of the Inyo National Forest in the Southern Sierra Nevada Mountains. All known populations are restricted to the sandy gravel margins of decomposed granodiorite that are ubiquitous in the forest’s meadows. However, the few that are occupied by Abronia alpina are uniquely situated next to extensive basalt flows and scoria deposits of the Quaternary Golden Trout Volcanic field. The potential contribution of iron and magnesium nutrient rich minerals to the substrate of Abronia alpina warrants an investigation into the rare plant’s edaphic constraints.

This project uses a combination of field measurements and soil sample analyses to quantify the influence of local geology on the geochemical composition of soils collected from occupied and unoccupied meadows of the Inyo National Forest. While soil analyses are still underway, mafic airfall deposits were identified in the topsoils of the occupied Ramshaw Meadows. These deposits are likely sourced from the adjacent South Fork scoria cone and suggest a non-negligible contribution of volcanic minerals (or ash) to the inceptisols that form Abronia alpina’s preferred substrate. X-Ray diffraction tests on powdered soils should thus reveal larger concentrations of olivine and pyroxene, soil minerals that, in abundance, are associated with highly selective flora. Teasing apart the factors that lead to range restriction of rare species can provide essential land management tools for soil conservation and the maintenance of plant biodiversity. This is particularly true for high elevation systems, like those found in the Inyo, which will be most susceptible to the increased temperatures and decreased precipitation rates produced by climate change.