Postfire Responses by Southern Arroyo Willow Forest and by Southern-Willow Scrub Dominated bySalix lasiolepisin San Diego County, California

Abstract

Abstract We examined patterns of response of southern riparian forest and southern-willow scrub, both dominated by arroyo willows (Salix lasiolepis), sampled in 1999 prior to fire and in 2008 following an intense wildfire in San Diego County, California. Arroyo willows had vigorous basal and epicormic resprouting in the riparian forest and minimal mortality from fire. While no sapling of S. lasiolepis was noted in 1999, we observed four in 2008. The most striking change in understory of southern-willow scrub was the increase in nonnative plants, particularly graminoids. No willow-scrub plot experienced postburn mechanical disturbance. The herbaceous increase in southern-willow scrub was likely a result of timing of precipitation combined with fire and drought that opened the overstory of trees and shrubs. Interspecific competition for moisture between nonnative herbs and seedlings of S. lasiolepis might negatively impact recruitment of this species and impact its function in these ecosystems.