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Ecology – Thinning forests

Pine trees in the Tuolumne Valley of Yosemite National Park show the effects of drought and fire. Credit: Anthony Walker/Oak Ridge National Laboratory, U.S. Dept. of Energy

A multi-institutional research team found that changing environmental conditions are affecting forests around the globe, leading to increasing tree death and uncertainty about the ability of forests to recover.

Increases in atmospheric carbon dioxide, temperature, drought and extreme events such as wildfires are causing more frequent tree mortality and triggering intense competition among saplings for resources. This competition contributes to forest thinning, which limits the amount of carbon captured and held in tree trunks, branches and roots.

“There’s a lot of nuance just in the carbon dioxide response,” said Anthony Walker of Oak Ridge National Laboratory who contributed carbon dioxide analyses for the study published in Science. “We are examining the many tradeoffs and feedbacks. For instance, elevated carbon dioxide can spur tree growth while also increasing the risk of mortality associated with faster growth rates.”

The study concluded that pervasive shifts in forest vegetation are likely to accelerate in the future.