PNNL

Abstract

Forest soil microbiomes play critical roles in carbon (C) storage, biogeochemical cycling, and rhizosphere processes. However, climate-driven increases in wildfire season length and the frequency and size of severe fires threatens to modify soil microbiomes and microbially-mediated biogeochemical processes, potentially altering post-fire ecosystem recovery. Here, we characterized functional shifts in the soil microbiome (bacteria, fungi, and viruses) across burn severity gradients one year post-fire in coniferous forests (Colorado and Wyoming, USA), revealing severity-dependent increases of Actinobacteria that encode genes for heat resistance, fast growth, and pyrogenic C utilization that may enhance post-fire survival. Conversely, the near complete loss of ectomycorrhizal fungi and less tolerant microbial taxa contribute to lost key ecosystem services with increasing burn severity. Active viruses influenced C cycling via turnover of biomass and encoded ecosystem-relevant auxiliary metabolic genes. These genome-resolved analyses link post-fire soil microbial taxonomy with function and reveal the complexity of post-fire soil microbiome activity.