Effects of exotic species and soil depth on a rare serpentine jewelflower

摘要

Nutrient-poor serpentine soils act as refugia for native plant species due to competitive pressure by exotic species that have invaded California's grasslands. However, some exotic species have recently evolved to tolerate deep serpentine soils, thereby jeopardizing these biologically rich refugia. I hypothesized for this study that Streptanthus albidus var. peramoenus (Most Beautiful Jewelflower) is restricted to shallow serpentine soils due to competition from exotic annual plants occurring in neighboring deep serpentine soils. I performed a factorial experiment manipulating the presence of exotic plant species in shallow and deep soils within patchy serpentine grassland habitat. Results show Streptanthus albidus var. peramoenus to be successful in deep serpentine soil areas when exotics were removed. It follows, then, that populations of this plant may be expanded through restoration efforts focused on reducing neighboring exotic plant abundance.