New research has suggested that a change in the forests in the Eastern United States' composition is not a result of climate change.

According to a Penn State University (PSU) news release, the new study appears in the journal Global Change Biology. Study co-author Marc Abrams, a PSU professor of forest ecology and physiology, said the nation's eastern forests still in a "disequilibrium" state since the mass cuttings and burnings in the late 1800s and early 1900s.

"Looking at the historical development of Eastern forests, the results of the change in types of disturbances - both natural and man-caused - are much more significant than any change in climate," Abrams said in the release. "Over the last 50 years, most environmental science has focused on the impact of climate change. In some systems, however, climate change impacts have not been as profound as in others. This includes the forest composition of the eastern U.S."

Gregory Nowacki, a scientist with the U.S. Department of Agriculture (USDA) Forest Service and the other author on the study, said he and Abrams compared ancient and modern vegetation in the region.

"Many ecological phenomena combine to direct vegetation trends over time, with climate and disturbance playing prominent roles," Nowacki said in the release. "To help decipher their relative importance during Euro-American times, we employed a unique approach whereby tree species/genera were partitioned into temperature, shade tolerance and pyrogenicity classes and applied to comparative tree-census data."

However, the composition of the forests has been in a transitional phase since the 1930s, a time when forest fire prevention first became prevalent in the U.S.

"In both cases, these shifts were attributed to fire suppression rather than climate change," Abrams said. "Because mesophication is ongoing, eastern U.S. forests formed during the catastrophic disturbance era followed by fire suppression will remain in climate disequilibrium into the foreseeable future.

"Land-use change often trumped or negated the impacts of warming climate, and this needs greater recognition in climate change discussions, scenarios and model interpretations."