Prescribed fire selects for a pyrophilous soil sub‐community in a northern California mixed conifer forest

• Published in: Environmental microbiology Vol. 25; no. 11; pp. 2498 - 2515
• Main Authors: Fischer, Monika S., Patel, Neem J., Lorimier, Phillip J., Traxler, Matthew F.
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01-11-2023; Wiley Subscription Services, Inc; Wiley-Blackwell
• Subjects: Assembly; Community structure; Coniferous forests; Conifers; Controlled burning; Disturbance; Fires; Forest fires; Fungi; Microbial activity; Microbiomes; Microorganisms; Mixed forests; Prescribed fire; Soil; Soil microorganisms; Soils; Temporal resolution; Wildfires; United States > US; California
• ISSN: 1462-2912; 1462-2920
• DOI: 10.1111/1462-2920.16475

Prescribed fire is a critical strategy for mitigating the effects of catastrophic wildfires. While the above‐ground response to fire has been well‐documented, fewer studies have addressed the effect of prescribed fire on soil microorganisms. To understand how soil microbial communities respond to prescribed fire, we sampled four plots at a high temporal resolution (two burned, two controls), for 17 months, in a mixed conifer forest in northern California, USA. Using amplicon sequencing, we found that prescribed fire significantly altered both fungal and bacterial community structure. We found that most differentially abundant fungal taxa had a positive fold‐change, while differentially abundant bacterial taxa generally had a negative fold‐change. We tested the null hypothesis that these communities assembled due to neutral processes (i.e., drift and/or dispersal), finding that >90% of taxa fit this neutral prediction. However, a dynamic sub‐community composed of burn‐associated indicator taxa that were positively differentially abundant was enriched for non‐neutral amplicon sequence variants, suggesting assembly via deterministic processes. In synthesizing these results, we identified 15 pyrophilous taxa with a significant and positive response to prescribed burns. Together, these results lay the foundation for building a process‐driven understanding of microbial community assembly in the context of the classical disturbance regime of fire.
Prescribed fire is crucial for mitigating catastrophic wildfires. We studied the impact of prescribed fire on soil microorganisms in a mixed conifer forest. Our high‐resolution sampling over 17 months post‐fire revealed significant changes to the community structure. We found that neutral processes dominated community assembly. However, a dynamic sub‐community of positively responding taxa also emerged, likely as a result of deterministic processes. This work lays the foundation for a process‐driven understanding of post‐fire community assembly.