Prescribed Burn

Many natural ecosystems are maintained by wildfires. In the absence of this sort of disturbance, these ecosystems would gradually transform into another type through the process of succession. For example, most of the original tall-grass prairie of North America occurred in a climatic regime that was capable of supporting shrubs or oak-dominated forests. However, the extensive transformation Use of controlled burning for prairie management in South Dakota. Photograph by Stephen J. Krasemann. National Audubon Society Collection/Photo Researchers, Inc. Reproduced by permission. of the prairie into these ecosystems was prevented by frequent ground fires which were lethal to woody plants but could be survived by most of the herbaceous species of the prairie. Today, tall-grass prairie has been almost entirely converted into agricultural usages, and this is one of North America's most endangered types of natural ecosystem. The few remnants of tall-grass prairie that have been protected are managed using prescribed burns to prevent the incursions of shrubs which would otherwise degrade the integrity of this ecosystem.

Tall-grass prairies are maintained by relatively frequent fires. However, some types of forests may need fires on a much longer rotation to prevent their conversion into another type of forest community. For example, forests in California dominated by redwoods (Sequoia sempervirens) need occasional fires in order to reduce the abundance of more tolerant species of trees and thereby prevent these from eventually dominating the community. Fire is also useful in the redwood ecosystem in preventing an excessive build-up of fuels that could eventually allow a devastating crown fire to occur which would kill the mature redwood trees. In some cases, prescribed burning is used to satisfy the requirement of redwood forests for low-intensity fires.

Prescribed burns can also be used to prevent catastrophic wildfires in some other types of forests. In this usage, relatively light surface fires that do not scorch the tree canopy are used to reduce the biomass of living and dead ground vegetation and shrubs and thereby reduce the amount of fuel in the forest. When this practice is carried out in some types of pine forests, there is an additional benefit through enhancement of natural regeneration of the pine species which require a mineral seedbed with little competition from other species of plants.