Harrison et al. studied the effects of livestock grazing and fire in a mosaic of serpentine and nonserpentine soils in California, where most grasslands are dominated by exotic annuals and serpentine soil is the major refuge for native grassland species. In plant communities on non-serpentine soils, exotic species increased in response to fire and native forb richness decreased in response to grazing. Plant communities on serpentine soils had a more variable response to disturbance but in general native species increased following grazing or fire. These results suggest that soil type effects the plant community response to fire and/or grazing in California chaparral grasslands and that soil type needs to be considered before management strategies are initiated in these plant communities.
Ecological heterogeneity in the effects of grazing and fire on grassland diversity