This article is part of the Wildland Fire Learning In Depth series. It is designed for students who want to learn more about fire. Find the complete series on the Fire subject site.
Types of Fire Spread
Ground fires—burn organic matter in the soil beneath surface litter and are sustained by glowing combustion.
Surface fires—spread with a flaming front and burn leaf litter, fallen branches, and other fuels located at ground level.
Crown fires—burn through the top layer of foliage on a tree, known as the canopy. Crown fires, the most intense type of fire and often the most difficult to contain, need strong winds, steep slopes, and a heavy fuel load to continue burning.
Size and Intensity
Even though fire is a fairly common occurrence, very few fires become extremely large. In the United States, 2-3 percent of all fires account for more than 95 percent of the total area burned annually. The blackened plots left behind by these types of large fires contribute to the image of fire as a destroyer of the natural environment. In reality, the opposite is true. A carefully planned prescribed burning program can provide many benefits that enhance the health of an ecosystem.
For example, regular prescribed fires can reduce the amount of ground fuels, thereby lowering the potential for large wildfires. If future wildfires should occur, the fires would be less intense and easier to contain. Fuel reduction can help lessen the possibility of high-intensity crown fires. However, in five to eight years enough litter can accumulate in a forest to return ground fuel quantity to the pre-fire level. Therefore, it is important that a regular, planned burning program is followed rather than a single fire event.
High-intensity fires can cause soil destruction, such as loss of nutrients and removal of debris needed to protect seedlings. In areas where such damage occurs, rehabilitation plans are made and actions are taken to reduce further damage and to try to restore the area.
Wildfires are suppressed in developed areas, where people or structures are threatened, or where high fuel levels create a potential for intense fire capable of spreading into areas with these conditions.
Benefits of Fire
Among the other benefits of prescribed burning are:
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Insect pest control
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Removal of exotic or nonnative species that compete with native species for nutrients and other needs
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Addition of nutrients for trees and other vegetation provided by ashes that remain after a fire
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Removal of undergrowth, thereby allowing sunlight to reach the forest floor to encourage growth of native species
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Encouraging the growth of fire-dependent species
After a Fire
A burned tree is not wasted. It can provide nesting sites for birds, homes for small mammals, and a base from which new plants can grow. When the dead tree begins to decay, it releases nutrients into the soil, enhancing growth of surrounding flora.
The benefits or harm derived from fire can vary greatly from one plant community to another. In the United States, all ecosystems have been affected to some degree by fire.
Last updated: February 13, 2017