Assessment of wildfire frequency and coastal sage scrub vegetation dynamics in the Santa Monica Mountains of Southern California

The distribution of coastal sage scrub (CSS) vegetation in Southern California is strongly influenced by local disturbance regimes. Focusing on CSS stand boundary shifts over time in the Cheseboro and Palo Comado Canyons of the Santa Monica Mountains, this study assesses the influences of wildfire frequency on changes observed in multiple historical aerial photograph sets. Fire perimeter data and field sampling data were also utilized to evaluate vegetation cover change over two distinct time periods: 1929-1976 and 1976-2003. Fire perimeter data and burn frequencies were correlated with CSS coverage change calculations at a coarser scale, and field sampling data was analyzed to determine the influences of fire frequency on CSS stand dynamics at a finer scale. While dramatic CSS coverage loss was observed in portions of the study area with documented high fire frequencies, correlations between CSS/grassland ecotone fluctuations and fire frequency were inconclusive.