The quality of oak stands in Arkansas forests can be degraded by pests or by “high-grading” — a timber practice in which the best or biggest trees are removed, leaving only inferior or undesirable trees. Scientists in the University of Arkansas' Division of Agriculture are evaluating techniques for rehabilitating degraded forests to increase the value of timber and improve wildlife habitat.
Matthew Pelkki, forest economist at the Arkansas Forest Resources Center in Monticello, Ark., is lead scientist for the study. He said the goal is to evaluate the effectiveness and economics of techniques that remove less desirable trees that compete for soil, sunlight and other resources needed to establish healthy oaks.
The study is being conducted in forest plots at the Savoy Research Unit, west of Fayetteville, Ark.
Chris Stuhlinger, forest manager, said high-value trees were harvested from the area several years ago, leaving only poor-quality oaks and other species with little or no commercial value.
In some plots, controlled burns kill undesirable trees and open the canopy for new growth of oak seedlings. Pelkki said only one burn is used in some plots, and others will have multiple burns about three years apart. In other plots, low-value trees will be killed with herbicide. Some tests will include a combination of single- or multiple-controlled burns and herbicide application.
“Prescribed fire offers a number of benefits,” Pelkki said. “Oaks are particularly well adapted for fire. The stem may burn up or die, but the root system survives and a new tree will sprout from the roots.”
All the controlled burns in the study are conducted under supervision of the Washington County office of the Arkansas Forestry Commission.
Pelkki said a burn costs about $20 an acre, and herbicide application costs about four times more. Initial results show that oaks are responding better to a single herbicide application than to a single burn or combination of burning and herbicide. A combination treatment with a single burn followed by herbicide application to kill non-oak regrowth costs about $100 an acre.
“The long-term results may be quite different,” Pelkki said. “It will take another six or seven years of research to know which treatment is most effective.”
Other elements of the study include studying the effects of varying fire temperatures on different species and diameters of oaks. Temperatures can vary widely in different areas of a burn, Pelkki said. The study uses temperature-indicating liquids — disks of paint in varying colors that melt at different temperatures.
The goal of the research is to have a forest with straight, healthy oaks at different ages. “Once you have a good forest, it's easier to maintain,” Stuhlinger said.
“A healthy stand of oaks offers landowners high commercial value,” Pelkki said. “More than that, it improves wildlife habitat because oaks provide hard mast in the form of acorns that drop in the fall, which is an excellent food source for deer, squirrels and wild turkey.”
Pelkki would like to see oak forests managed to be more open. “It's a very different look from what people are used to.”
Maintaining dense forests at high quality requires more human intervention. An “ideal” forest can take different forms depending on how a landowner wants to manage it. A forest where trees are selectively harvested according to size can have a rotation of 10 years between harvests. Conversely, a clear-cutting requires about an 80-year rotation.
Pelkki recommends that landowners always call their local office of the Arkansas Forestry Commission before harvesting. They will evaluate the value of trees for free and create a forest management plan that meets the landowner's goals.
Landowners who manage their forests well using resources like Forestry Commission evaluations get higher quality forests for commercial, aesthetic and wildlife uses, Pelkki said.