For Some Trees, Climate Change Could Worsen Recovery After Fires

Published: Monday, August 31, 2020 - 2:54pm
Updated: Tuesday, March 16, 2021 - 12:31pm
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Arizona is home to the country's largest contiguous area of Ponderosa pines, some of which burn each year during wildfire season.

Fire activity has worsened across the western United States since the 1980s. Experts largely blame the uptick on drier summers and rising aridity due to human-caused climate change.

Now, a new study in the journal Global Ecology and Biogeography examines how those trees recover or decline under an uncertain climate future.

Beyond bringing wildfire conditions, climate change alters species' life cycles, ecologies and death rates.

Sensitive seedlings make better coal-mine canaries than hardier adult trees, which more closely reflect climate conditions from their youth than those that exist at present. So researchers studied tree rings from young Ponderosa pines (Pinus ponderosa var. scopulorum) and Douglas firs (Pseudotsuga menziesii var. glauca) that grew after fires.

Their database included 717 samples from 1,301 plots in post-fire environments across a range of topographies and climates.

Computer models simulating moderate and extreme future carbon emissions predicted moderate or bleak futures, subject to moisture availability. The deeper the drought, the less likely seedlings would establish themselves after fires.

Lead author Kyle Rodman of University of Colorado Boulder said the outcome depends in part on society's response to climate change.

"I think it's an important point to make. A lot of this is still unknown, and we still have some agency in what happens over the upcoming decades," Rodman said.

Either way, the evergreens could fare worse in Arizona, which is at the warmer and drier edge of their ranges.

"Arizona is a place that could be affected in very similar ways to the sites that we were looking at in Colorado and, in fact, climate projections generally are sort of more stark for the Southwest," said Rodman.

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