Hyper-diverse microbial communities in soil mediate nutrient cycling processes and ecosystem productivity, yet we have a limited understanding of the environmental factors shaping their composition. To an even greater extent, identification of the metabolically active microbial community and environmental influences structuring its composition are lacking. As such, we investigated the influence of environmental factors on the diversity and composition of total and active bacterial and fungal communities across an expanse of northern hardwood forest in Michigan, USA, which spans a 500-km climatic gradient. We sought to understand how these total and active communities differ from one another and which environmental factors drive compositional differences within communities. We quantified the composition of soil bacterial and fungal communities using high-throughput DNA sequencing technology on co-extracted rDNA (total community) and rRNA (active community), and explored how a suite of ecologically relevant environmental characteristics shaped their diversity.
Results/Conclusions
Among both Bacteria and fungi, we found that differences in composition between total and active communities reflected changes in relative abundance between study sites and did not indicate undiscovered biodiversity in the active community. Compositional variation within the total bacterial community was driven by subtle changes in soil pH and N content across sites. Changes in soil moisture shaped the composition of metabolically active bacteria and fungi and positively increased the active bacterial phylum Bacteroidetes (+1%) and active fungal classes Dothideomycetes (+4%) and Agaricomycetes (+7%) across the gradient. Our results indicate metabolically active taxa are an expression of species present in the total community that are differentially shaped by soil moisture availability. As such, we emphasize the importance of discerning how environmental determinants influence the metabolically active taxa of the total community to better understand how soil microbial communities will respond under future climate scenarios.