Vegetation Change in Chaparral and Desert Communities in San Diego County, California

Abstract

Arid region vegetation types exhibit patterns of change that do not always conform to existing theories of succession. This is certainly true for the chaparral and desert shrub communities of the southwestern United States in part because of the important role of extreme environmental events and natural disturbances. In the chaparral the problem stems from the overriding importance of fire in determining readily observable vegetation change. The tendency has been either to view fire as preventing chaparral from reaching true climax condition (Horton 1950, cited from Hanes 1971) or to hold that the vegetation is climax because fire is a part of the prevailing climate (Clements 1928). The latter view has been given formal status by Hanes (1971), who proposed the term “autosuccession” to describe the special case of succession in the chaparral in which fire neither causes extinction nor initiates invasion, but rather reestablishes species that are already present.