On August 3rd, 2021, the Antelope Fire reached the Goosenest Adaptive Management Area (GAMA) on the Klamath National Forest in Siskiyou County. For six days, the fire burned through the predominately ponderosa pine and white fir forest, exhibiting mild, moderate, and extreme fire behavior. Fortunately for Pacific Southwest Research Station Scientists, the fire offered a unique opportunity to study the effectiveness of fuel treatments on wildfire behavior and severity.
Prior to the Antelope Fire's arrival, twenty-three study plots at GAMA had received four different fuel treatments: 1) Thin-only (emphasis on pine retention), 2) Thin-only (emphasis on big tree retention), 3) Thin (emphasis on pine retention) plus Prescribed Fire (two broadcast burns, nine years apart), and 4) Fire-only (two broadcast burns nine years apart). Untreated control plots provided a baseline for the study. “I think what's incredible about the Goosenest data set is that because of the number of replicated treatments that we had, and because they were laid out in a randomized experiment before the fire came through, we really had this incredible and to our knowledge unprecedented opportunity [to assess fuel treatment effectiveness],” said Emily Brodie, Forest Monitoring Scientist with CAL FIRE, Former Postdoctoral Scholar at the Pacific Southwest Research Station, and one of the paper's co-authors.
When researchers returned to the site post-fire, they found more than just a black forest. Overall, fuel treatments resulted in lower fire severity across all four metrics examined: tree mortality, average bole char-height, percent crown volume consumed (PCVC), and percent crown volume affected (PCVA). All treatments were found to lower fire severity, with thinning plus prescribed fire being the most effective.
“I was most excited about these areas where the road went through and on one side you had a treatment that had received thinning and burning and the trees were totally green,” said Brodie. “And on the other side, there was a control where no treatment action had occurred. Those trees were completely charred.”
The study also demonstrated that fuel treatments can be effective over a decadal or multi-decadal time period – it had been ten years since prescribed fire and twenty years since mechanical thinning had been implemented at the study plots. Importantly, treatments were still effective under extreme weather conditions.
“In a nutshell, what our study showed is that fuel treatments changed outcomes, even under the most extreme weather conditions,” said Eric Knapp, Research Ecologist at the Pacific Southwest Research Station and one of the paper's co-authors. “Fuels really do matter. When the winds were the strongest and the humidity was super low, only the trees in the treated areas really had a chance. Going forward in a time of increasing fire activity, if we want forests that are resilient to these types of fires, it's going to become increasingly important to keep both the canopy fuels and the ground fuels low and keep them managed.”
For more details and insights on the paper, please refer to the following resources:
Brodie, Emily G.; Knapp, Eric E.; Brooks, Wesley R.; Drury, Stacy A.; Ritchie, Martin W. 2024. Forest thinning and prescribed burning treatments reduce wildfire severity and buffer the impacts of severe fire weather. Fire Ecology. 20(1): 11770. https://doi.org/10.1186/s42408-023-00241-z.
An Interview with Emily Brodie and Eric Knapp: Through The Fire | US Forest Service Research and Development (usda.gov)