By Dan Rahn
University of Georgia
In the South, especially, regular burning in pine forests is good when it's properly done, said David Dickens, an extension service forester with the University of Georgia Warnell School of Forest Resources.
"It would have been better if all those ads had said, 'Only you can prevent forest wildfires," Dickens said, emphasizing the "wild."
A basic premise of foresters is that in itself, fire is neither good nor bad. "It simply changes the ecology of the forest," he said. "That can be good or bad, depending on what we value in the forest."
Millions of acresEvery winter in the South, he said, prescribed fires burn roughly 4 million acres of pine forests for specific management purposes.
Done under the right conditions, prescribed fires reduce the risk of more damaging wildfires by clearing out the undergrowth and debris. That makes the forest safer for the trees, wildlife and nearby homes and other property.
Dickens said clearing out potentially dense underbrush and debris has other benefits, too. Among other things, it:
- Improves wildlife habitat, especially for deer, turkeys, quail and black bears, by enhancing the growth of more palatable browse and berry plants.
- Opens up access, allowing people to enjoy their woodlands more.
- Reduces the trees' competition for soil moisture and nutrients.
- Serves a number of forestry and agricultural purposes, from reducing the risk of tree diseases to improving forage for grazing.
The right conditionsForesters prescribe dormant-season fires for these purposes only in the right combination of conditions, which normally begin coming together in early November, Dickens said. By mid-March, weather patterns typically become too unpredictable for prescribed fires.
To burn out the undergrowth and debris without harming the trees, foresters look for:
- A forest that's neither too dry nor too wet. If it's too dry, fires get hotter and more damaging. If it's too wet, the smoke becomes more damaging to air quality.
- Temperatures between 30 and 55 degrees Fahrenheit.
- Relative humidity between 30 percent and 55 percent.
- Fairly constant winds between 5 and 12 miles per hour.
- A reliable wind direction that won't take the smoke into sensitive areas, such as into a residential neighborhood or across a highway.
- A "mixing height," or the point at which smoke hits turbulent air, of at least 1,700 feet.
Better smokeThe smoke from such fires is much less damaging to air quality than that from wildfires, Dickens said.
"Most of the smoke is water vapor," he said. "The whiter the smoke, the higher the water content." People with fireplaces can see this easily if they've ever burned a piece of "green" or unseasoned wood with a high moisture content.
Using fires to manage forests is hardly new, Dickens said. When the earliest European settlers arrived in the Southeast, they found native Americans already using fire to clear out the undergrowth and improve hunting, among other things.
Now, most foresters advise burning pine forests every two or three years. "Burning hardwood forests is a lot trickier," Dickens said.
Even pine forests on steep slopes aren't good candidates for burning, he said. Many conditions have to be right before a fire can produce the desired benefits without causing unwanted damage.
(Dan Rahn is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.)