An empirical approach to developing and testing a traits-based fire ecology framework for bacterial response to wildfires

Abstract

Globally, wildfires represent major disturbances, burning millions of hectares annually. Wildfires can restructure soil microbial communities via changes in soil properties and microbial mortality. Fire-induced changes in bacterial communities may influence soil carbon cycling, and recovery to pre-burn community composition and function may take years. We investigated carbon cycling, soil properties, and the importance of three fire-adaptive strategies – fire survival, fast growth, and affinity for post-fire soil environmental conditions – in structuring soil bacterial communities following burns of varying temperatures in boreal forest soils. To identify taxa with each strategy, we simulated burns and incubated soils, tracking respiration and sequencing DNA and rRNA. We then quantified their abundances in the field following wildfires of varying burn severities. The importance of these strategies varies over time and with burn severity. Fire survival has a small but persistent effect on structuring burned soil communities. Fast growing bacteria rapidly colonize the post-fire soil but return to pre-burn relative abundances between one and five years post-fire. Taxa with an affinity for the post-fire environment thrive post-fire, but the effect of this strategy declines by five years post-fire, suggesting that other factors such as vegetation recovery or bacterial dispersal may influence community composition over decadal timescales.Graphical Abstract