Hopkins, J. R. | bioRxiv Science

bioRxiv2025

Fire limits soil microbial dispersal and differentially impacts bacterial and fungal communities

Fire is a globally pervasive force reshaping ecosystems, yet its influence on the ecological processes structuring soil microbiomes remains poorly understood. Using a meta-analysis of >2,600 amplicon sequencing samples across 19 global studies, we tested whether fire alters soil microbiome assembly processes, diversity, and ecological selection for pyrophilic specialists. Contrary to prevailing assumptions, we found that fire did not significantly shift ecological selection processes in bacteria or fungi but instead constrained dispersal, particularly reducing dispersal in bacterial and fungal communities, and increasing ecological drift in fungi. Despite limited evidence for ecological selection, fire consistently filtered for specialist taxa, increasing their relative abundance across microbial communities. Fire also reduced fungal diversity and evenness, while bacterial communities exhibited greater dominance and loss of rare taxa. These findings support the idea that fire promotes microbial post-fire niche specialization while disrupting dispersal pathways. Our results indicate that increasing fire frequency and severity under climate change may homogenize soil microbial communities, reduce microbial resilience, and constrain ecosystem recovery.

ecology↗

bioRxiv2024

Fuel buildup shapes post-fire fuel decomposition through soil heating effects on plants, fungi, and soil chemistry

Forty percent of terrestrial ecosystems require recurrent fires engineered by feedbacks between fire and plant fuels. Fuel loads control fire intensity which alters soil nutrients and shapes soil microbial and plant community responses to fire. Changes to post-fire plant fuel production are well known to feed back to future fires, but post-fire decomposition of new fuels is poorly understood. Our study sought to quantify how pre-fire fuel loading impacted post-fire fuel decomposition through soil abiotic properties, plant and soil fungal communities. In a longleaf pine savanna, both near and away from overstory pines, we manipulated pre-fire plot fuel loads to modify soil heating. We then assessed how fuel load and soil heating influenced post-fire plant fuel decomposition through changes to soil chemistry, vegetation, and fungi. Larger fuel loads, particularly beneath pines, increased soil heating and reduced decomposition of newly deposited fuels during the eight months following fire. Fire intensity effects on soil nutrients had the most consistent effects on decomposition with plant and fungal communities playing secondary roles. This demonstrates how fuel load and soil heating influence post-fire decomposition through fire-driven changes to soil abiotic properties, plant communities, and soil fungi. Further, since fire effects on decomposition and fire-fuel feedbacks were temporally dynamic this illustrates the importance of considering fire-fuel feedbacks across time. Understanding the importance of these feedbacks among ecosystems can help increase our predictive ability to manage fuels and the effects of repeated fires.

ecology↗