STIPA PULCHRA, A SURVIVOR FROM THE PRISTINE PRAIRIE

California’s grasslands demonstrate dramatically both the deliberate and accidental impacts of man. Beginning with the arrival of livestock at mission San Diego in 1769, new land uses affected not just a few dominant species but changed the entire flora of the grasslands. Livestock and alien animals had replaced the pristine grassland before scientific botanical observers arrived. Students of vegetational changes are handicapped by the lack of even a small surviving piece of exclusively native grassland. Introduced species are everywhere present. Historical records are scanty and lack sufficient detail to permit reconstruction of the original vegetation. When the American ecologist Frederick Clements rode the train to California in 1917 he noted bunchgrasses along the fenced rights-of-way. Near Fresno he recorded the dominance of purple needlegrass (Stipa pulchra) where livestock were excluded. It is generally thought that California’s grassland was formerly a bunchgrass type, with Stipa pulchra as the dominant native species, contrasting with today’s annual-dominated vegetation. Yet many scholars doubt that the driest areas were ever densely populated by perennial grasses and suggest that the density of perennial species in the pristine grassland was correlated with rainfall: the grasses of the wetter areas to the north and nearer the coast perhaps were almost exclusively perennial; the drier inland areas had few and scattered perennial grasses. Native annual grasses occupied the spaces Purple needlegrass at Point Molate with Mt. Tamalpais in background. Photograph by Mitchel P. McClaran