LEAF Guide Supplemental Resources - Wildland Fire

Unit 9-12

General Wildland Fire Information

  • Wildland fire includes two types of fire; wildfire and prescribed fire. Wisconsin wildfires can start through human causes like debris burning or arson or natural causes such as lightning. Prescribed fires are used to mimic ecological or natural fires that have been part of ecosystems throughout history. Prescribed fires are ignited and controlled by land managers.
     

  • For fire to ignite and spread, three elements must be present heat, fuel, and oxygen. There must be heat to start and continue the combustion process, fuel to burn, and oxygen to facilitate combustion. The three elements can be seen as sides of the fire triangle. If any one of the sides is removed, the fire will extinguish.
     

  • Fuel characteristics determine how intense a wildland fire burns and how far it spreads. These characteristics include the type of fuel, its chemistry, size, and shape. The quantity of fuel and the way it is arranged also influence fire behavior. 

    Examples of fuel include trees and tree litter, grass, shrubs, and logging slash (piles of brush left behind after an area is logged). Light fuels, like grass, burn very fast and hot. While heavy fuels, like logging slash, burn for long periods of time. Light fuels dry much faster. Their moisture varies throughout the day as temperature, humidity, and wind speed changes. Often the fire danger increases during the day and decreases as night approaches.
     

  • Weather and topography are major influences on fire behavior. Weather is constantly changing because of local, regional, and continental influences making it difficult to predict fire behavior. Weather influences can dry fuels and cause fire to spread. The three most common weather characteristics that determine when fire danger is high are moisture in the air, temperature, and wind.

    In Wisconsin, most dangerous wildfires occur during the months of March, April, and May. This time of year, known as the fire season, is especially dangerous because much of the landscape is absent of living plants, and trees have not yet grown leaves.