Fire frequency impacts non-sprouting chaparral shrubs in the Santa Monica Mountains of southern California. In: Margarita A, Papanastasis VP (eds) Ecology, conservation and management of Mediterranean climate ecosystems

ABSTRACT: Adult non-sprouting chaparral species are killed by fire, relying on the germination of refractory seeds for post-fire reestablishment. An increase in fire frequency (fire return intervals of <12 years) may prevent non-sprouting chaparral seedlings from reaching reproductive age, thus limiting recruitment prior to succeeding fires. A previous study found that a fire return interval of 6 years resulted in the localized extinction of the non-sprouting chaparral species Ceanothus megacarpus from a coastal site. We examined sites throughout the Santa Monica Mountains in southern California to determine if this pattern is generalized. We sampled 4 sites with fire return intervals of 6 years. Each site was matched to a nearby control site of similar slope aspect and elevation with a fire return interval of 12 years. We used a point-quarter sampling method for chaparral shrubs in tandem with a canopy-coverage sampling method for exotic weeds and grasses. Increased fire frequency reduced the frequency of non-sprouting chaparral shrubs, with shorter fire intervals having the greatest impact. Shorter fire intervals also increased gaps in the shrub matrix increasing the abundance of coastal sage scrub and non-native forbs and grasses.