Centralia diversity Preprint available on PeerJ

ShadeLab is pleased to share a new preprint available on PeerJ!

The paper, "Stochastic extremes but convergent recovery of bacterial and archaeal soil communities to an ongoing subterranean coal mine fire", is authored by Sang-Hoon Lee, Jackson Sorensen, Keara Grady, Tammy Tobin, and Ashley Shade. This will be our "debut" paper on our lab's research efforts in Centralia, PA, where an underground coal mine fire has been burning since 1962. This work was most recently presented at the 2016 ISME Meeting last month.

In this work, we used cultivation-independent 16S rRNA gene sequencing to investigate surface soil microbial community responses to the ongoing underground coal mine fire in Centralia, Pennsylvania, which has been burning since 1962. The fire burns 40-69 m below ground, but heats surface soils to as high as 80 degrees Celsius, creating an extreme press stressor that persists for years and impacts on multiple microbial generations. As a result of the fire, active vents form at the surface, where steam and coal combustion products escape. Interestingly, as the fire advances slowly along the coal seams (5-7 m/yr), previously hot soils can recover to ambient temperature, creating a chronosequence of fire impact that has proven to be advantageous for investigating decadal soil community resilience. We conducted a soil survey of the chronosequence and then applied the Vellend 2010 and Nemergut et al. 2013 conceptual framework of community assembly to interpret Centralia community responses.

We found that soil context (selection processes) had high explanatory value for understanding differences between recovered, reference, and currently fire-affected soils. In fact, recovered soils approached reference soil community structure within 10-20 years post-fire, suggesting a tremendous capability for soil resilience given an extreme and unnatural stressor. We also observed unexplained divergences in microbial community structure among fire-affected soils that could not be attributed to any measure soil properties, neutral models of assembly, or local dispersal. We ultimately found that the fire-affected soils harbored the same community compositions but very different dominant memberships, such that rare members in one soil were among the top ten most prevalent in another. Given that high temperatures select for mesothermophiles and thermophiles in these soils, we suggest that the divergences in community structure at temperature extremes is due to differences in thermophile seed bank transitions, possibly due to priority effects from different waking spores.

We welcome feedback on the work (it is being submitted to a journal for formal peer review) and also note that all of the data and the analysis workflows are public.