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NMSU Researchers Examine Benefits of Forest Thinning Techniques

LINCOLN NATIONAL FOREST - New Mexico State University scientists are using a ready-made lab in the forest near Cloudcroft to study tree thinning's effects on wildlife, plants, soil and watersheds.

New Mexico State University researchers, from left, wildlife specialist Jon Boren, research associate Glenn Mason and riparian management specialist Terrell T. (Red) Baker examine plant life growing in a thinned area of the forest near Cloudcroft. (07/25/2005) (NMSU Agricultural Communications Photo by Darrell J. Pehr)

The scientists are piggybacking on the U.S. Forest Service's Rio Peņasco II thinning project to reduce wildfire danger in overgrown forests.

"It's a neat opportunity," said Jon Boren, a wildlife specialist for NMSU's Cooperative Extension Service. "From a research standpoint, we couldn't cover the costs of putting these treatments in."

Boren and Terrell T. (Red) Baker, an Extension riparian management specialist for NMSU's Range Improvement Task Force, are leading a team of about a dozen students, staff and faculty. They are examining the changes in wildlife, vegetation, soil and watersheds on plots that represent several thinning techniques. The researchers are collaborating with the Forest Service's Rocky Mountain Research Station in Flagstaff, Ariz.

Devastating forest fires in the Southwest in 2000 and 2002 led to more public support for thinning forests and examining the best ways to thin.

"A lot of attention was generated about forest conditions and what the Forest Service can do to reduce fuels and reduce wildfire danger," Baker said.

Mechanical thinning, followed by prescribed burning, results in fewer trees per acre. Then, when the next fire starts, managing it will be simpler and less expensive, or it can be allowed to burn without the risk of raging out of control and threatening people and property.

"We're not suggesting that fire needs to be taken out of the system," Baker said. "In fact, it's an important part of the system. While wildfire certainly represents a disturbance to the ecosystem, we've learned that taking fire out of the ecosystem represents an even bigger disturbance."

Now that thinning is under way, researchers are looking at the complex process of ecological forest recovery. Boren said less sunlight reaching the forest floor in overgrown forests meant less plant diversity. Thinning will open the forest canopy, allowing a variety of plants to grow, bringing in animals attracted to the new food source and developing new habitats. But those processes have not been closely studied.

"There have been lots of discussions on this, but not enough quantitative data to hang your hat on," Boren said.

Already, the forest is changing. Green shrubs growing in a recently thinned area make a meal for deer and elk. Tiny, wild strawberries and foot-high aspen sprouts are beginning to appear in some of the open spaces between trees, in vivid contrast with a nearby stand of untreated trees where no plants grow in the dense shade of giant Douglas firs. The distinction between these plots is obvious, but various thinning techniques produce more subtle differences.

"We're really trying to pull together a puzzle based on what the Forest Service is doing up here," Baker said. He is particularly interested in learning about mixed-conifer forests of spruce, fir and pine trees, which haven't been as closely studied as the more common ponderosa pine forests of the Southwest.

Researchers are examining three thinning techniques as well as a control site that has not been thinned. On two "precommercial thin" sites, trees up to nine inches in diameter are removed. At one of the two sites, thinned trees are lopped into shorter lengths and placed in slash piles. At the other, cut trees are left on the ground where they fall, scattered across the site. Piled-up slash creates different microhabitats for small animals than scattered slash, Boren said.

At the third site, commercially useful timber (trees up to 24 inches in diameter) have been harvested.

Boren and Baker first discussed the project with Forest Service officials about two years ago. The preliminary work began in 2004. The project will conclude in 2007, but researchers plan more research for a more complete analysis of thinning impacts. In the meantime, the researchers appreciate the close working relationship with the Forest Service.

"It's good for the university, good for the Forest Service, good for the community," said Glenn Mason, a research associate working on the project. "They've been as helpful as they can be in working with us and giving us the opportunity to do our work."