Wildfires can cause great damage to woodlands. Even in stands where the trees are not killed outright, fires may weaken and eventually kill trees, cause wounds where insects and diseases can enter, increase soil erosion, and reduce soil fertility, wildlife habitat, and recreational quality of a stand. Fire also can be used constructively to manage forest vegetation.
Forest fires are classified as surface, crown, or ground fires based on the way they spread. Most forest fires in the Lake States are surface fires. They burn only the litter and other small fuels on the forest floor. They may scar the bases of large trees and kill small trees.
Crown fires usually start as surface fires that reach into the canopy with the help of dry winds and fuel ladders. A fuel ladder is combustible vegetation that bridges the space between the ground and a tree crown, allowing a fire to climb to a tree crown. They occur most often in conifer stands and are very damaging and difficult to control. Intense crown fires will produce showers of sparks and glowing embers that easily jump firebreaks and set additional fires well in advance of the leading edge. Although conifer crowns frequently catch fire, true crown fires that spread through the air from one crown to the next are much less common than ground fires in the Lake States.
Ground fires burn and smolder below the surface, sometimes going undetected for days or weeks. They consume soil that is high in organic matter, including dried peat and thick litter. Ground fires produce enough heat to kill most of the trees in their path by cooking their root systems. Such a fire may cross firebreaks through roots and dry organic matter. Ground fires are very difficult to control, but are likely to occur only in dry years. Figure 7-11. Fires that reach tree crowns will kill trees.
Few woodland owners can afford their own fire suppression equipment. Instead, most rely on state and local agencies to control fires. While these organizations respond quickly, there may be some delay before a fire is reported and crews arrive on the scene. For this reason you need to maintain your land so wildfires cause minimal damage before they are suppressed. The following practices will help:
Controlled burns are fires that are set intentionally under specific fuel and weather conditions to:
Soil chemistry and physical processes change temporarily after a burn, but eventually will return to normal. However, a poorly planned or improperly controlled burn may kill crop trees and cause other property damage. Consult a forester about firebreak placement, weather requirements, tools needed, legal liabilities, and other important issues. Controlled burns always pose some risk, but they can remain an option if they fit into your management plan.