Prescribed Fires Reduce Tree Death from Drought

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Fighting Drought with Fire

THREE RIVERS, Calif. — A new study from the U.S. Geological Survey and National Park Service shows that thinning forests with prescribed fire can reduce the effects of drought. Climate change is expected to amplify drought conditions in California so using science to better understand the impacts of drought is of great importance to resource managers such as the National Park Service.

Photo depicting drought-related tree mortality in Sequoia National Park
Drought-related tree mortality at a low elevation forest in Sequoia National Park. Public domain

“There is a lot of research showing that climate change is already increasing drought frequency and severity,” said Phillip van Mantgem, USGS forest ecologist and lead author of the study. “Our study indicated that when some trees were removed using prescribed fire, the remaining trees were more likely to survive during the drought. The use of prescribed fire prior to drought may help forests by allowing the remaining trees to have more water during times of stress.”

Researchers studied low elevation conifer forests in areas that had recently experienced severe drought in Sequoia, Kings Canyon and Yosemite National Parks, examining data from almost 10,000 individual coniferous trees, including familiar species such as ponderosa pine, white fir and Douglas fir. They used this information to estimate the risk factors involved in tree mortality, and found greater tree mortality in forests that were not burned before the onset of drought in 2012. The study is published in the journal Fire Ecology.

“If current warming trends continue, we can expect to see more frequent tree deaths following drought, which can lead to substantial changes in forests,” said Dr. van Mantgem. “But managers may be able to blunt the effects of drought by using prescribed fire as a tool for forest health.”

The analysis only considered the impacts of drought in 2012 and 2014, and future research is planned to include the continued effect of drought in 2015 and an understanding of how lower numbers of trees might influence tree survival. This ongoing research addresses key uncertainties facing future forests, and will include areas outside of the southern Sierra Nevada.

“Understanding the relationship between drought, fire, and tree mortality from fires adds some important wrinkles to how we manage forests,” said Tony Caprio, a fire ecologist with Sequoia and Kings Canyon National Parks and study co-author. “One of our goals is to reduce risks of undesirable wildfire using prescribed fire. Maybe prescribed fire can also help prepare these forests for a drier future.”

tree, fire, landscape
Comparison of Upper Lewis Creek previously treated with prescribed fire. The top photo was taken on July 8, 2015 prior to the Rough Fire. The bottom photo was taken on Sep. 29, 2015 after the Rough Fire came through. Notice the still standing live trees.  Photo: NPS/ K.HowardPublic domain

The study was conducted by researchers from and funded by the USGS Western Ecological Research Center and the Sequoia and Kings Canyon National Parks, with operational support from the National Park Service and the Southwest Climate Science Center, which is managed by the USGS National Climate Change and Wildlife Science Center. This study is part of the long-term collaboration between USGS, NPS, and academic scientists to understand and mitigate the potential effects of climate change on our national parks.