Prescribed Fire Mitigates Climate‐Driven Aboveground Carbon Losses From Wildfire in High Elevation Ecosystems of the Sierra Nevada

Abstract

Extreme wildfires are becoming more common in California's Sierra Nevada, increasing the need for fuel management to protect ecosystem services such as carbon storage. Because mechanical treatments can be costly or inaccessible in steep or remote terrain, prescribed fire, particularly broadcast burning, provides a cost‐effective strategy for treating large, forested areas. However, managers must weigh the immediate carbon costs of treatment against the longer‐term benefits of reduced fire severity. These trade‐offs are difficult to estimate from historical data alone, as climate change is actively reshaping fire regimes. We used the coupled ecohydrological‐fire regime model (RHESSys‐WMFire) to examine how climate change and prescribed fire influence future fire regimes and carbon dynamics in a high‐elevation, mixed conifer watershed. We simulated historical conditions and three future climate scenarios, each with and without prescribed fire, in a factorial design. Climate change increased watershed aridity, producing smaller but more frequent fires. Untreated locations that were historically mesic experienced higher future fire hazard because they had accumulated high fuel loads while simultaneously becoming more arid. In these locations, prescribed fire effectively reduced fire size and hazard. However, under the hottest and driest climate scenario, climate‐driven increases in fire hazard exceeded reductions achieved through prescribed burning. Prescribed fire also reduced wildfire‐driven carbon losses, particularly in scenarios with greater precipitation variability. Overall, our findings suggest that prescribed fire can reduce fire hazard and enhance carbon retention in fire‐prone, climate change‐impacted landscapes, though its effectiveness may be limited under extreme warming and drying.