The benefits of thinning in whitebark pine forests
Can thinning help save a species? For decades, researchers and foresters have been studying the effects of thinning in whitebark pine forests to help answer that question. Whitebark pine is a threatened tree species that grows in high elevation forests throughout the western U.S. and Canada. The intent of thinning in whitebark pine forests is to remove competing tree species like subalpine fir. Past thinning treatments have had mixed success in whitebark pine forests, partly due to factors such as fire, bark beetle outbreaks, and the exotic fungus white pine blister rust. But promising results from a recent study in the Caribou-Targhee National Forest in Idaho show that thinning might be an effective restoration tool.
The focus of the study was to see how whitebark pine trees responded to the removal of competing tree species. Researchers measured whitebark pine growth and the response of resin ducts, an important defense mechanism to bark beetles, over nine years following the thinning treatments. They found that whitebark pine tree ring width and resin duct area increased by about 50 percent compared to trees in areas that were not thinned. This response was more dramatic in small whitebark pine, which saw a 74 percent increase in tree ring width. Thinning created conditions that are better for whitebark pine seedlings, and did not increase whitebark pine tree mortality.
These positive results provide strong evidence that thinning can be a useful tool to help restore and conserve whitebark pine forests.