Due to multiple global change factors, wildfires are increasing in size, severity, and frequency, impacting nearly all ecosystem processes. While wildfire is ubiquitous across almost all terrestrial ecosystems, there is a relative scarcity of fire-related microbial ecology research. Here, we report work from two projects that singularly evaluate the effect of fire on the soil or plant microbiome:
- To assess the impact of fire on the soil microbiome, we used biogeochemical, amplicon, and metagenomic analyses from soils collected in burned mixed-conifer forests of the Sierra Nevada (California, USA). Using a chronosequence-based study design, we assessed the long-term (44 y) impact of high-severity fire on microbial community composition and function.
- To assess the impact of fire on the plant microbiome, we sampled aspen (Populus tremuloides) saplings less than three months after a high-intensity prescribed burn from areas varying in burn severity in central Utah, USA. We sequenced archaeal, bacterial, and fungal amplicons from the soil, rhizosphere, root, rhizome, stem, and leaf microbiomes, and used statistical models to determine changes in endosphere colonization patterns.
Results/Conclusions
From our work on the soil microbiome, we show that high-severity mega-fires can result in multidecadal changes to the soil microbial community structure and genetic potential leading to large changes in carbon and nitrogen cycling process rates. Additionally, we extracted 206 metagenome assembled genomes (MAGs) from soils at these sites and characterized these MAGs as positive or negative fire responders. Positive fire responders were primarily Actinobacteria and were predictable based on their functional genes using random forest modelling. In particular, positive fire responders were enriched in genes encoding for proteasomes, which degrade mutated proteins. This suggests that these bacteria are well-adapted to stressful post-fire soil environments.
Work on the fire response of the aspen microbiome is on-going. However, we detected significant changes in the composition of the leaf microbiome. By incorporating both plant and soil microbiome responses to fire, it is our goal to holistically understand the impact of fire on the microbial community and uncover links among soils, plants, and microbes in post-fire landscapes. Such insights may allow for future microbiome interventions that encourage plant regeneration, enhance soil nutrient availability, maintain soil carbon, and aid ecosystem recovery post-wildfire.