NMSU Researchers Study Impact of Forest Thinning
by Darrell J. Pehr
When it comes to studying the forests in New Mexico and Arizona, everything is on a large scale, from the towering pine trees and vast, forested countryside to the length of time it takes for change to take place in mountain meadows and hillsides. Now, New Mexico State University scientists are tackling their study of forest thinning impacts on a big scale, too.
The latest project will cover two 100-acre plots in the Lincoln National Forest near Cloudcroft. In coordination with the U.S. Forest Service, scientists are examining the process of thinning forests to reduce the possibility and intensity of forest fires, with a particular interest in the effects of tree thinning on wildlife, plants, soil and watersheds.
“By setting up these plots, we have the ability to control the setting,” said Terrell T. (Red) Baker, a Cooperative Extension Service riparian management specialist for NMSU’s Range Improvement Task Force.
The Lincoln National Forest is an especially good laboratory for the research because of the close working relationship with the Forest Service, the nearness to NMSU, the need for research-based information and the makeup of the forest – a mixed conifer combination of spruce, fir and pine – which means research conducted there has statewide implications. Baker and Extension wildlife specialist Jon Boren are leading a team of almost two dozen students, staff and faculty working on four research projects.
The new location includes a 100-acre south-facing plot across a meadow from a 100-acre north-facing plot. Neither plot was treated by the Forest Service, so researchers can examine the thinning process from start to finish. Each section will be divided into 25-acre pieces that include a control site, a burn-only site, a thin-only site and a burn/ thin combination.
Because the plots are so large, researchers will be able to use prescribed fire in their experiments.
“The larger the scale, the more reallife it is,” said Doug Cram, a fire ecologist with NMSU’s Extension animal resources department. The large-plot project dovetails with research Cram spearheaded on national forests in New Mexico and Arizona, where he studied wildfire damage to treated and untreated forests. Cram’s research showed far less extensive damage on forests that had been thinned prior to the fire.
“Because fire was taken out of the system, the natural thinning mechanisms have been eliminated,” Cram said. Forests protected from fire for decades become unnaturally dense. “At some point, fire is going to come into the system, as it has for millennia, and if it’s been out a long time, it’s going to burn very severely.”
Forest managers, therefore, may not be able to use fire by itself, especially in dense forests, to return to natural conditions because of the risk of a catastrophic crown fire. Some mix of mechanical thinning and prescribed fire is more likely.
The big plots also will be studied in coordination with research already under way on smaller, nearby sites where several thinning techniques have been used. The scientists are piggybacking on the Forest Service’s Rio Peñasco II thinning project, which is intended to reduce wildfire danger in overgrown forests. The researchers are collaborating with the Forest Service’s Rocky Mountain Research Station in Flagstaff, Ariz., and some funding for the research is coming from the Joe Skeen Institute for Rangeland Restoration.
On the small sites, researchers led by graduate student and research associate Glenn Mason are looking at the complex process of ecological forest recovery. Less sunlight in overgrown forests meant less plant diversity on the forest floor, Boren said. Thinning will open the forest canopy, allow a variety of plants to grow, bring in animals attracted to the new food source and develop new habitats.
On the big plots, researchers hope to get a better feel for tree-thinning impacts on wildlife on a larger scale. They also hope to learn from the meadows between the large plots.
“Meadows are a small portion of the landscape, but they involve a disproportionate amount of the wildlife,” Baker said.
Outside Ruidoso, scientists examined the impact of new forest-thinning equipment used to remove small-diameter trees. At the request of the Forest Service’s Southern Research Station, NMSU researchers studied the effectiveness of a specialized eight-wheel machine – called a harvester/forwarder – that was used in a 200-acre thinning project at Eagle Creek, northwest of Ruidoso. The machine uses an arm to grasp and cut a tree, which is then moved into an attached truck bed. That eliminates the need to drag logs from thinned areas. Scientists focused on soil disturbance, runoff and erosion.
Baker expects the various research projects to generate useful information for forest managers and others.
“We’re really trying to pull together a puzzle based on what the Forest Service is doing up there,” he said. “We’re interested in not only the research, but also in making this information available to stakeholders across the state, and providing educational opportunities for students.”