VASCULAR PLANTS OF RICHVALE VERNAL POOLS, BUTTE COUNTY, CALIFORNIA

The Richvale Vernal Pools site in the Sacramento Valley of northern California is a 32.4 hectare grassland with 120 vernal pools of varying sizes occurring on its alluvial soils. The flora contains 45 families, 131 genera and 184 species of vascular plants, all flowering plants except for two. Annuals comprise 74.5% of the species. As is typical of annual grasslands in lowland California, a portion of the flora consists of introduced plants: the flora occurring in vernal pools is 93% natives, while the grassland matrix between pools is 67% natives. The largest family, Poaceae, contributes the most nonnatives (i.e., 22 introduced, 6 native grasses). Asteraceae is also well represented, but mainly by natives (5 introduced, 18 native). Richvale Vernal Pools is important as a diverse remnant of grassland/vernal pool ecosystems in a region almost entirely cultivated in rice.