Plant responses to fire are mediated by the soil microbiome

Daniel P. Revillini, Christopher A. Searcy and Michelle E. Afkhami, Biology, University of Miami, Coral Gables, FL, Kevin Main, Archbold Biological Station, Lake Placid, FL, Eric S. Menges, Plant Ecology Program, Archbold Biological Station, Venus, FL, Aaron S. David, Agricultural Research Service, United States Department of Agriculture, Fort Lauderdale, FL

Background/Question/Methods
Environmental changes are drastically altering fire intensity and frequency in natural and managed systems, with many ecological impacts, but the mechanisms to explain post-fire plant community development remain elusive. In the face of these shifting fire regimes, it will be important to better understand the indirect effects of fire on plant communities through their interactions with the soil microbiome. Soil microbes are critical in plant establishment, performance, and persistence across many systems, and this is especially true after disturbances such as fire. In this study, we experimentally manipulated prescribed fire on the soil microbiome prior to a factorial grow room experiment with 11 plants that vary in their specialization to the Florida rosemary scrub habitat. We sequenced the soil microbiome, including archaea, bacteria, and fungi, to identify the ways that fire-induced shifts in microbial communities could then alter plant establishment and productivity, and relate these findings with plant strategies in the field.
Results/Conclusions
We found that fire significantly altered the composition of archaeal and bacterial, but not fungal communities. Overall, the post-fire microbiome decreased plant germination and productivity, but these responses were largely dependent on plant habitat specialization. Specifically, the relative increases of Actinobacteria and Alphaproteobacteria, decreases in Thaumarchaeota, and increased bacterial phylogenetic relatedness after fire were associated with the relative performance benefits of habitat specialist plants in the grow room, and also their frequency in the field. We show for the first time that fire-induced changes in soil microbial communities can alter plant performance, differentially benefitting plant habitat specialists. These findings highlight the importance of studying indirect effects of disturbance on plant-microbial interactions, which can ultimately affect the distribution of plants across the landscape.