Early settlers must have gazed in awe at the large expanses of towering pine trees—some 2 feet in diameter or more across. They ascended above abundant stands of low-growing vegetation that provided both food and cover for multitudes of deer, quail, turkey and other game.
Modern researchers are trying to recreate those pristine scenes that have been lost to an invasion of thick, low-quality hardwood trees and vines.
Mississippi State University scientists have developed a three-step program that eliminates those undesirable hardwoods, giving more favorable plants the opportunity to flourish. In the process, they not only have improved wildlife habitat, but also have increased timber growth.
MSU scientist Steve Demarais explains that millions of acres of pine stands across the South have suffered from a "hands-off" approach to forestland management.
"Consequently, there has been little practice of forest or wildlife habitat management," says Demarais.
Often, a midstory of hardwood trees has grown up in and among the pine trees—10 to 40 feet high. Depending on the region, these may consist of sweet gum, maple, poplar, hickory, green ash or other species that have limited commercial value. But they take up nutrients from the pine trees.
In addition, there has been a buildup of pine straw and other leaf material that retards the growth of food plants and does not provide nesting material for game birds. This, according to Demarais, is due in large part to the suppression of natural wildfires that in previous times periodically cleaned out both the hardwood midstory and the leaf buildup.
The MSU researchers developed a three-pronged approach to resolving these problems:
1. Thin pine trees where a dense overstory of pines doesn't allow enough sunlight penetration to the ground. Typically, pine stands are thinned two or three times during their lifetime to remove small-diameter, lower-quality trees for pulpwood and other products.
2. Use a selective herbicide to control hardwoods. Mississippi researchers have obtained excellent control with applications of imazapyr made in late summer or early fall (August to October), while target species are still actively growing.
Imazapyr is sold as Arsenal, Chopper and ChopperGEN2 by BASF Inc. It also is available as a generic product.
Harry Quicke, BASF market development specialist, says Arsenal may be applied over the top with an aircraft. Chopper and ChopperGEN2 may be applied under the canopy using ground equipment. BASF uses the term "quality vegetation management" to describe the practices needed to improve timber stands and wildlife habitat.
3. Do prescribed burning the following January to March, prior to green-up of plants. This gets rid of the buildup of pine straw and other litter that retards the emergence of desirable plants.
"A secondary benefit of prescribed burning," Demarais points out, "is that many naturally occurring seeds in the soil that we want to encourage to emerge have very hard coats. Fire helps break those coats so that they will absorb moisture and emerge. These include members of the pea family, lespedezas, desmodiums and others."
MSU's Demarais reports that studies comparing treated versus untreated plots in various regions of Mississippi showed a three- to 20-fold increase in nutritional carrying capacity for deer for a program of midstory thinning, followed by herbicide treatment and prescribed burning.
Researchers have observed an increase in bird species where a lush understory of native grasses, legumes, forbs and shrubs has replaced hardwoods that have been removed.
The program also can improve timber growth. A large-scale study showed the combination of thinning, removal of hardwoods with imazapyr and prescribed fire resulted in a growth in height of pine trees of 9 to 15%, and an increase in diameter growth of 2 to 7% compared to untreated areas.
BASF's Quicke notes that elimination of the hardwood understory in a pine stand also facilitates easier management and harvest. This may result in higher per-unit timber prices.
"This is not a one-size-fits-all program," Demarais concedes. "It needs to be adjusted depending on ages of pine stands, species of hardwoods that need to be controlled, environmental conditions and wildlife objectives.
"For example, older stands of pine may not require thinning," he notes. "If you are trying to develop quail habitat, you may have to do prescribed burning every other year to promote more grasses and fewer wood vines and shrubs. For deer and turkey, prescribed burning every three or four years will promote the production of more forbs and young browse."