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Abstract

Wildfires produce substantial carbon emissions and are increasingly causing forests to transition from carbon sinks to net carbon sources. Across forests of western North America, legacies of fire suppression and extensive timber extraction have disrupted historical surface fire regimes, resulting in the accumulation of hazardous fuel loads and denser, more homogenous forest landscapes. Fuel treatments are often implemented to proactively reduce the risk of severe wildfire and resulting emissions; however, the effects of these treatments on forest carbon storage and stability are not well characterized in British Columbia, Canada. To better understand the role of carbon in wildfire mitigation efforts, I partnered with five community forests in southeastern British Columbia that implemented different types of fuel treatments between the summers of 2021 and 2022. I estimated differences in above-ground carbon stored on-site before and after treatment and across treatment types while also accounting for the utilization of biomass removed off-site during treatment. I then combined field data and fire effects modeling to quantify potential tree mortality and direct carbon emissions under three future wildfire scenarios in forest stands with and without fuel treatments. Fuel treatments resulted in immediate reductions in carbon storage primarily driven by live tree removals. Compared to pre-treatment conditions, fuel treatments consistently reduced potential tree mortality from wildfire, but they had a minor impact on potential direct carbon emissions. This work develops ecosystem-specific knowledge to critically evaluate the short-term effects of fuel treatments on forest carbon stocks in fire-prone landscapes. Ongoing research is needed to evaluate long-term dynamics of fuel treatments, wildfire, and carbon under climate change.