Fire has been an agent of change in nearly every terrestrial vegetation type on Earth, shaping both the species composition and structure. The probability of occurrence and the effects of fire vary widely depending upon the amount of fuel present, topography, climate, sources of ignition, and present species composition of the area. Fires may be severe, causing great mortality of existing plants and significantly changing the species composition of the burned area, or they may have little impact on the composition and consume only the dry dead plant material present. They may burn intensely as fast-moving fires with flame lengths greater than 25 meters, or they may occur as slow-moving fires with flame lengths less than 0.5 meter. These sources of variation influence the effects that fire has on the vegetation and the ecological role of fire.

The California Department of Forestry holds a prescribed burn of shrub-chaparral...