Effects of herbivory on grazed and ungrazed alien and native species in the California annual grasslands was evaluated using greenhouse and field trials. This study was conducted on the Carrizo Plain National Monument that includes the largest California grassland remnant. Due to the discovery of two endangered forbs a portion of the study site was excluded from grazing ten years prior to this study. In the grazing exclosure, 50, 1 x 1 m plots were established to created 10 blocks of five treatments: control, clipped once (late Feb.), clipped twice (late Feb., and early March), clipped three times (late Feb., early March, and early April), mulch removal (late Feb removal of only dead plant material). Plants were clipped to 1 cm above ground level and over three years. Following the first clipping treatment a subplot 0.5 x 0.5 m were used to estimate cover for each species within the plot. Density and cover of both alien and native species were measured over three years. In the greenhouse study, an alien and native grass and forb species were germinated with one plant per pot. Three clipping treatments (no clipping, clipping at 1 month, clipping at 1 and 2 months following planting) were applied to each species. Flowers and fruit were counted 1 month after the last treatment was applied, and total production was also determined. Effect of competition elimination was also evaluated by weeding around individual plants within the exclosure.
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