Bouncing back from burn: Examining asynchrony in soil microbial responses to wildfire over time

Kendall Beals, Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN, Joe Bailey, Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Knoxville, TN and Jen Schweitzer, Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, Knoxville, TN

Background/Question/Methods
Wildfire can substantially alter soil properties, including microbial abundance and diversity, and research has identified specific taxa that are particularly abundant or sparse after fire. However, it is largely unknown how individual microbial taxon responses contribute to recovery of soil microbial communities after wildfire disturbance and how soil microbial communities recover from wildfire over time. One way to determine the instability or resistance of soil microbial communities to disturbance is to examine asynchrony of species’ responses. Here we investigated the response of soil bacterial and fungal communities annually for five years after a wildfire in Great Smoky Mountains National Park, Tennessee. We collected soil from multiple undisturbed and severely burned sites and conducted amplicon metagenomic sequencing. We identified sensitive, opportunistic, and resistant microbial response strategies to wildfire by measuring differential expression of bacterial and fungal taxa between undisturbed and burned soils. We then assessed if the proportion of each response strategy shifted with time since wildfire.
Results/Conclusions
We found that fire substantially altered bacterial and fungal composition, but that composition did not change significantly over time. We identified similar response strategy profiles among soil bacteria and fungi. We found that 95% of bacterial taxa and 98% of fungal taxa were resistant to wildfire, 3% of bacterial taxa and 1% of fungal taxa were facilitated by wildfire, and 2% of bacterial taxa and less than 1% of fungal taxa were sensitive to wildfire. These results provide insights into the mechanisms that contribute to soil microbial community recovery from wildfire. Findings from the work will facilitate more accurate predictions of the amount of the soil microbiome that is highly vulnerable to and resistant to wildfire disturbance.