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Fire Manages Forests When Used Correctly
MISSISSIPPI STATE -- Forest fires raging out of control in the West give fire a bad name, but in non-drought times, Mississippi foresters use planned fires as management tools.
Glenn Hughes, forestry specialist with Mississippi State University's Extension Service in Hattiesburg, said fire historically has been a natural part of Southern pine forests.
"Some of our original forests occurred because fire was present on a recurring basis," Hughes said. "In many cases we have interrupted that cycle by putting out all fires. This changes the vegetation and can have negative impacts on forestry, wildlife and other resources."
Ground fire is one of the best ways to clear dead limbs, pine straw, brush and other materials from around trees. It is useful as long as there is not enough fuel present to allow the fire to climb into the crowns or get too hot. Pines are especially tolerant of fire, and prescribed burns are used frequently in Mississippi forests to manage timber stands.
"Fire can be a wonderful ally, but a terrible master if you use it at the wrong time," Hughes said.
Without prescribed burning as a management tool, fuel begins to build up. Excess fuel coupled with the drought across Mississippi and much of the country means that any fires started by accident, lightning, arson or some other means can be devastating.
"Because we have prevented fires, the fuel builds up and we have created a potentially dangerous situation," Hughes said. "Instead of fire being at a regular, frequent interval and of low intensity, when a fire is started, it goes from being a relatively small fire to a catastrophic event. Fires in Florida over the last several years were classic examples of this."
While prescribed burns are a great management tool, they must be conducted by those trained to use fire. Hughes said Mississippi law protects the right to burn as long as it is carried out in a reasonable and prudent manner by a certified burner. A one-week class is available to train foresters or landowners in how to use fire safely as a tool.
"One of the major concerns with prescribed burns is the liability from the smoke," Hughes said. "Smoke can drift across roads, and if it contributes to an accident, the person who started the fire can be liable for any injuries or deaths."
Hughes said this reason has caused some people who burned in the past to seek other methods of land management.
"Many can't carry the amount of insurance they need to buy to protect themselves from the liability of smoke over roads," Hughes said.
Burns are also difficult to schedule, a fact that has led some people to seek alternative ways of controlling unwanted vegetation.
Fuel and underbrush have accumulated in many areas where fire was abandoned, and the drought makes conditions ripe for a major fire. Prescribed burns cannot be used in these areas, so material must be removed mechanically or a herbicide sprayed to kill the underbrush. Moisture, temperature and time decompose the fuel, allowing fire to be used again in a few years.
Andy Ezell, MSU forestry professor, said both pines and hardwoods can benefit from controlled burns, but unless the burner is skilled, fire can heavily damage hardwood stands.
"The lethal threshold for trees is an internal temperature of 140 degrees Fahrenheit for one to two seconds," Ezell said. "It takes more heat to raise the internal temperature of trees with thicker bark or bark with higher insulating properties."
Ezell said that the majority of a tree is not living. The cambium, or layer of living tissue between the bark and the wood, must be protected from lethal temperatures.
When planning a prescribed burn, Ezell said to consider the variables of fuel load, fuel moisture content, wind speed and ambient air temperature. Ezell said most prescribed burns are done in the winter when air temperatures are cooler. A fire during 90 degree summer weather must only raise the tree's internal temperature 50 degrees to kill it.