In the Shade lab, we want to understand the rules of resilience for microbial communities (microbiomes). Resilience is the capacity of a system to recover after it has been altered by a disturbance, and, with resistance, it is a key component of stability. We investigate the soil communities overlying the ongoing coal seam fire in Centralia, Pennsylvania as a model to understand how microbiomes respond to and recover from a “worst case scenario” disturbance: one that is extreme, unexpected, and prolonged. Previously we used soils collected along a fire-impact gradient in Centralia to quantify stark changes in community structure that was followed by near-complete recovery within ~10 years after the fire advanced. Moving forward from this field study, we considered two key microbial mechanisms that could support resilience: dormancy and dispersal. We hypothesized that microbial populations that are sensitive to disturbance can be either rescued by reactivated cells from the local dormant pool, or by immigrant cells dispersed from regional metacommunities. To understand the relative contributions of dispersal and reactivation to microbiome resilience, we designed a replicated, 45-week time-series experiment to quantify the responses of the active soil microbial community to a thermal press disturbance, including unwarmed control mesocosms, warmed mesocosms without dispersal, and warmed mesocosms with a dispersal event after the release of the stressor. We used 16S rRNA:rRNA gene ratios paired with qPCR to determine changes in active membership, community structure, and community size over the course of the experiment.
Results/Conclusions
We found that communities changed in structure within one week of warming. Though the warmed mesocosms did not fully recover within 29 weeks, resuscitation of thermotolerant taxa was key for the community transition during the warming, and both activation of opportunistic taxa and immigration contributed to community resilience. Also, mesocosms with dispersal were more resilient than those without. This work provides insights into the mechanisms that support microbiome stability at different points over a disturbance trajectory. It also highlights the potential importance of the local dormant pool for microbiome responses during a disturbance. Building a general framework for microbiome resilience will enable prediction and management of microbiomes towards stable functions. This work is supported by a National Science Foundation Early CAREER award.