Patterns of permafrost microbial community structure

Understanding drivers of permafrost microbial community composition is critical for understanding permafrost microbiology and predicting ecosystem responses to thaw, however studies describing ecological controls on these communities are lacking. We characterized patterns of environmental variation and microbial community composition in permafrost collected across an Alaskan boreal forest landscape. We used null modeling to estimate the relative importance of dispersal and selection on community composition, and identified environmental factors influencing selection through regression and structural equation modeling (SEM). The strongest process influencing composition was dispersal limitation. Fe(II) content was the most important factor explaining variable selection. SEM supported a model in which Fe(II) content mediated influences of the Gibbs free energy of the organic matter pool and organic acid concentration on total selection. These findings suggest that permafrost communities are shaped by a balance between dispersal limitation and deterministic selection, with soil redox conditions being the most important factor deterministically influencing community composition.