Vegetation and Topographic Controls on Post‐Fire Snowpack: Evidence From the 2021 Caldor Fire

The increase in wildland fires in recent decades due to long‐term fire suppression policies and increasingly favourable climate factors has also increased the elevation range of wildland fires. In the mountainous western United States, this has led to an increasing influence of fire on landscape‐level vegetation patterns in snow‐dominated ecosystems. The resulting hydrological implications of these fire‐driven changes in vegetation patterns are being studied. In forests, fires consume surface fuels and understory vegetation, reduce tree canopy cover, darken tree boles and deposit black carbon. Together, these impacts alter snow accumulation and persistence in burned areas compared to pre‐fire conditions. In this study, we use field measurements and remote sensing of snow and fire conditions within the footprint of the Caldor Fire, a large wildland fire in the central Sierra Nevada, California, that burned in 2021. In this work, we explain the variability in snow accumulation and persistence and compare these findings to measurements at snow pillow and course stations within and near the Caldor Fire boundary. We show that north‐facing slopes at mid‐ to high‐elevation see snowpack accumulation benefit from fire, especially in areas burned at low and moderate severity. Other elevations, aspects and fire severity classes experienced decreases in snowpack. Compared to established snow measurement sites, this response to fire led to deviations in the behaviour of snowpack within the burned area. This work shows how the locations of established monitoring sites differ from the surrounding basin in their response to a major disturbance and can inform the interpretation of snow measurements in post‐fire landscapes.