Post-fire Logging Means Less Woody Fuel for Forest Fires

By Dana Kobilinsky

Post Fire Logging Two ponderosa pine trees stand in an eastern Oregon forest. Researchers sampled forest stands mostly dominated by ponderosa pines and Douglas-fir, to determine how post-fire logging potentially impacts the likelihood of future wildfires.
Image Credit: Sam Beebe via Flickr

Forest managers have much to contend with when it comes to tackling wildfires that can destroy endless acres of wildlife habitat.

But, based on a recent study published in Forest Ecology Management, researchers found that logging fire-killed trees in regenerating forests reduced woody or forest fuels for up to 40 years.

“We started this study because of discussions with forest managers who were concerned with the need to reduce fuel, and who felt they had observed a number of situations where fires were burning through old fire areas,” said Dave Peterson, a research forester with the Pacific Northwest Research Station who led the study. “We designed the study to go back and look at forests in eastern Oregon and Washington between 1970 and 2007.”

While weather and topography are big factors in the creation of wildfires, Peterson said fuel loading, or the amount of flammable material in a particular space, is the most measurable aspect of wildfires for researchers to study. Big wildfires leave fire-killed trees that tend to fuel future wildfires, he said. Although post-fire logging is usually done for the economic benefit, Peterson and his team found post-fire logging also provides a long-term fuel reduction benefit.

In a retrospective analysis, Peterson and his team sampled woody fuels from 255 coniferous forest stands killed by wildfires from the past 40 years in Oregon and Washington. They sampled 96 logged stands and 159 unlogged stands. The researchers then compared and analyzed logged and unlogged stands and found logged stands had higher fuels the first five years after the fire and logging, but had lower fuels seven to 40 years after the fire.

The research revealed with unlogged stands, woody fuel levels were low right after the wildfire, peaked 10 to 20 years later, and then gradually declined 39 years after the fire. Peterson said when trees are not logged, wood is in contact with soil, which makes it rot faster. And when wood gets rotten, it has more air which makes it easier to burn. In logged stands, fuels reached their highest levels shortly after the wildfire and declined in the following years.

“There have been short-term studies that showed fuels were higher in logged than in the unlogged areas,” Peterson said. “Those studies are not wrong, but ours put it in a larger time frame, and looks at longer term fuel reduction benefits.”

Fuel reduction is an important part of management where fire is a hazard for wildlife, Peterson said. The study provides forest managers with a scientific basis when deciding when and where to use post-fire logging, he said. Forest managers must take into consideration fuel management goals, economic recovery and wildlife habitat concerns.

“Forest managers have to decide where on a recently burned landscape to make fuel reduction a priority and where to prioritize other objectives like providing snags and down woody debris for wildlife habitat,” Peterson said. “But, now we know that post-fire logging can be an effective long-term fuel reduction treatment.”

Dana KobilinskyDana Kobilinsky is a science writer at The Wildlife Society. Contact her at dkobilinsky@wildlife.org with any questions or comments about her article. You can follow her on Twitter at @DanaKobi.

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