research Highlight: Assessing fuel treatments and burn severity using global and local analyses
Authors: Astrid Sanna, Caden Chamberlain, Susan J. Prichard, C. Alina Cansler, Andrew T. Hudak, Craig Bienz, L. Monika Moskal & Van R. Kane
This research highlight summarizes an article recently published in Fire Ecology that examines herbivory as a supplement to prescribed fire in the Missouri Ozarks where fire use can be limited.
THE IMPORTANCE OF FUEL TREATMENTS
As U.S. dry forest structure has increasingly departed from historic conditions — mostly due to fire suppression and the exclusion of Indigenous fires — restoring forests by reducing fuel accumulation through thinning and broadcast burning is critical to promote beneficial wildfires.
THE CHALLENGE AND OPPORTUNITY
Understanding the effect of fuel treatments on burn severity, as well as their interaction with fire suppression operations relative to other drivers, is often challenged by the availability and accuracy of fuel treatment data, limited local knowledge, and the confounding influence of variable fire weather conditions.
MANY STUDIES HAVE INVESTIGATED THE ROLE OF FUEL TREATMENTS ON BURN SEVERITY — WHAT SETS THIS STUDY APART?
Focusing on an 1800-ha section of the Bootleg Fire near Sycan Marsh (south-central Oregon), where pre-fire LiDAR data were available, we isolated and investigated the effects of broadcast burning, thinning, both treatments combined, and fire-suppression operations — alongside other environmental predictors — under constant severe fire-weather conditions. We also leveraged local knowledge provided by land and fire managers, as well as accurate fuel treatment data representing 41 treatment units.
To interpret the results of our Random Forest model, we employed Shapley Additive exPlanations (SHAP) analysis, which provided both a global overview of mean predictor effects and a spatially explicit assessment of local variability. This approach captured complex predictor interactions and revealed spatially variable relationships at the scale of individual observations that would have otherwise been overlooked.
THE CRITICAL EFFECT OF BROADCAST BURNING AND FUEL ON BURN SEVERITY
Units that received broadcast burning had the highest percentages of area burned at low severity. Broadcast burning was the single most important driver of burn severity. It served as a proxy for surface fuel loads and reduced the influence of canopy cover. The other top drivers were related to fuel accumulation, structure, and continuity — underscoring the key role of fuel, which is often confounded by fire weather variability and diluted among bioclimatic and topographic factors.
Key Messages:
Fuel treatments involving broadcast burning were disproportionately more effective in mitigating burn severity than thinning alone or untreated forests.
Broadcast burning alone was as effective as thinning combined with broadcast burning, reducing management costs and soil disturbance.
Under constant severe fire weather conditions, fuel characteristics — including fuel treatments and their local variability — played a central role in influencing burn severity.
This study provides a reproducible framework for explaining burn severity at both global and local scales.
