Regional Disturbance Effects on Herb Succession Patterns in Coastal Sage Scrub

Abstract

A more prolonged grazing history and higher summer air pollution loads in the basin inland of Los Angeles may be acting in concert to eliminate native perennial grasses there; such grasses comprise a significant part of the post-fire herb flora in coastal sites of coastal sage scrub. In addition, low resprouting vigour of subshrubs inland after fire permits a higher level of herb cover, initially of forbs, and later of non-native annual grasses. The divergent successional patterns of the post-fire herb stratum at the coast versus inland appear to result from subtle interactions between natural and anthropogenic forces in the region. Strict 'fire annuals' species that exhibit high cover in the first postburn year and disappear thereafter were not found in the study sites. Annuals that were present in large numbers in the first year persisted to varying degrees in the 4 years