UNIVERSITY PARK, Pa. — Warmer and drier climate conditions in western U.S. forests are making it less likely that trees can regenerate after wildfires, according to a new study published in the Proceedings of the National Academy of Sciences, which includes researchers from Penn State.
Importantly, the research shows that ecologically based forest management can partially offset climate-driven declines in tree regeneration by limiting fire-caused tree death, but only if action is taken quickly. This study provides key information for sustainably managing forests across millions of acres of Western forests in the face of climate change, according to Alan Taylor, professor of geography and ecology at Penn State and co-author on the paper.
Forests are adapted to different types of fire across the West, but hotter and drier conditions in recent decades have increased fire severity which kills more trees. Fewer trees mean fewer seeds available for forests to regenerate after wildfires. Even when seeds are available, a warming climate is reducing the chances that seedlings can establish and grow, according to the researchers.
“We have a chance to buffer these climate effects,” said Taylor. “By reducing fire severity across the landscape and reducing the potential for large, high-severity fires, we can better equip our forests for the future.”
The research examined how the severity of a fire — the number of trees it kills — in combination with the climate conditions after the fire affected the chances of tree seedlings regenerating to establish a new forest. It is the most extensive study to date, assessing regeneration of eight major conifer tree species after 334 wildfires across the West, using information from over 10,000 field plots collected by more than 50 research teams.