WSB: High-severity forest fires provide diverse habitat

High-severity forest fires create a mix of trees and habitat for different species, according to new research, upending previous assumptions that held that these large, hot fires resulted in conversion to non-forest, or to a dominance of firs, rather than a mix of different types of trees.

“There’s been an assumption for a very long time that if you have large fires with large high-intensity patches you will not get natural regeneration of conifers within the interior of the patches,” said Chad Hanson, a research ecologist with the John Muir project of the Earth Island Institute and lead author of the recent study published in the Wildlife Society Bulletin. “But the problem is that assumption has not really been tested, and there’s very little data on it.”

In the study, Hanson created transects into the interior areas of the high-intensity fire patches and analyzed post-fire patterns in the patches within yellow pine and mixed-conifer forests in California where fires occurred from 1999 to 2013.

His findings showed significant natural conifer regeneration in the interior plots. “It doesn’t matter how big the high intensity fire patches were. It doesn’t matter how far into the interior of the patch you go. You still see natural conifer regeneration at significant levels,” he said.

The most regeneration occurred closer to the edges where the fire was low to moderate severity, but the interior areas where fire intensity was high were important, he said, with Ponderosa pine (Pinus ponderosa), sugar pine (Pinus lambertiana) and Jeffrey pine (Pinus jeffreyi) taking advantage of interior areas of high fire intensity. Fir and cedar dominated at the patch edges.

“These areas are ecological treasures of wonderful heterogeneous habitat for all sorts of different wildlife species getting what they need,” Hanson said. “Certain wildlife species like the pines more and certain wildlife species like the fir and cedar.”

Areas of lower-density conifer regeneration maintain montane chaparral — or shrub — habitat longer, which Hanson said would benefit rare and declining shrub-nesting birds that depend on it.

Hanson believes birds and small mammals are actively spreading seeds after these fires.

“We’re in a deficit of all fire intensities in the Western forests,” he said. “We have to stop suppressing backcounty fires and stop post-fire logging in our forests. Post-fire habitat is ecologically important and is naturally regenerating.”

Header Image: Jeffrey pine, which have larger cones than Ponderosa pines, inhabit the Sierra Nevada in California. Recent research shows both of these pine trees show up in the interior of forests after high-severity forest fires. ©Matt Lavin