The Role of Fire in Natural Communities: An Example from the Southern Sierra Nevada, California

Abstract

The exclusion of fire from the low-elevation foothills of the southern Sierra Nevada of California over the past century has resulted in large expanses of over-mature, senescent chaparral. The fuel buildup associated with this situation poses a threat, in that any fire which gets started has the potential of becoming a major holocaust.A detailed analysis is made of the vegetational succession following fire in four different-aged stands of Chamise chaparral in the southern Sierra Nevada. Progression from a diverse multi-species herb and shrub community towards a dense, structurally uniform, low-diversity stand dominated by a single woody species, Adenostoma fasciculatum (Chamise), is demonstrated. An increase in shrub cover and height along with the amount of dead material found laddered through the canopy, create optimal conditions for combustion within some 35 years following the last fire. The herbaceous vegetation shows a high diversity and cover in the first few years after burning, but rapidly decreases thereafter. Evidence is presented that frequent fires are required to maintain the chaparral community in a vigorous and healthy state. The need to institute progressive fuel-management programmes which recognize the natural role of fire in the evolution of the chaparral type wherever it is found, is discussed and advocated. Attempts are also made to relate these findings to the preservation of other fire-adapted vegetation types of the world.