[Wikipedia] As Ecologic Indicator: As ecologic indicator Aspidotis densa is a regional ecologic indicator on areas where ultramafic rocks (serpentine) are patchy, such as the Klamath and Siskayou Mountains of northern California and southwest Oregon and the Wenatchee Mountains of Washington.[4] Areas of serpentine soil can typically be seen as areas with sparse plant coverage or open forest bounded by closed forest on the non-ultramafic soils, with Aspidotis densa concentrated in the serpentine areas. (link added by Mary Ann Machi)