Forest fire is the uncontrolled burning of vegetation in areas dominated by trees. Forest fires may be ignited by human activities or by natural causes. Such natural causes include lightning, volcanic activity, or even intense sunlight. The fires sometimes burn for several months. Forest fires are generally more dangerous and destructive than other wildfires, such as grass fires.
Fire is a natural occurrence in most forests, with the possible exception of wet tropical forests. The frequency of natural fires varies from about once every 5 to 10 years in a dry pine forest to once in several hundred years in tropical rainforests. Fire can move rapidly through a forest in extreme weather conditions, such as high temperature, high wind, and low humidity.
Areas prone to forest fires generally have tree species that are adapted to fire. Some trees have thick bark and large buds to insulate them against the heat. Some trees grow their crowns high to avoid flames. Still other trees have seeds that germinate (sprout) after fire. Certain plants regrow rapidly through quick seed formation and sprouting.
Forest fires rapidly introduce several chemical elements to the surrounding environment, especially carbon and nitrogen. These two elements are oxidized (combined with oxygen) when plants burn. The resulting compounds are then released into the atmosphere. Other elements become mixed into the soil. There, they are available to plants as nutrients. Some elements are transferred to groundwater and carried to other locations.
In some areas, prevention measures have reduced the influence of fire on forests. In some dry forests, however, resource managers purposely burn small trees and underbrush in a practice called prescribed burning. This type of burning helps to reduce fuels available for forest fires, limiting the hazard to nearby communities. Prescribed burning also benefits fire-adapted species.
See also Forestry (Fire and forests) ; Peshtigo forest fire .
