Response of soil nutrient pools and microbiomes to recurrent wildfire disturbance and varying burn severities in a mixed conifer forest

As wildfires become more frequent with ongoing changes in global climate, we must deepen our understanding of soil’s physicochemical and biological changes driven by both severity and recurrence of these disturbances. After the 2022 Cerro Pelado wildfire, which affected 36,981 acres of the Santa Fe National Forest in New Mexico, we investigated the impact of fire disturbance on soil chemical and biological properties. Large portions of this most recent fire overlapped with previous fire extents, granting the opportunity to evaluate the effects of low to high burn severity and recurrence of zero to three fires over our 50-year record. We detected significant impacts to soil pH, DOC, TN, %N, as well as bacterial and fungal community composition from both fire recurrence and severity. The observed changes in fire-affected soils indicate fire recurrence may play a more important role than severity in soil chemical and biological dynamics in this system. The effect of burn severity was often significant only at sites that experienced one fire in our 50-year record, and less prominent at sites that experienced three fire events, signifying a progressive change in soil composition that must be further investigated in subsequent research.