Integrating soil genomics into the study of biosphere-atmosphere trace gas fluxes

International audience; Microorganisms play a significant role in shaping the composition of Earth’s atmosphere. Soils host rich microbial communities whose biogeochemical processes have both leading-order impacts on climate variability and susceptibility to global change feedbacks. Yet, the microbial actors and genetic diversity driving trace gas cycling in soils remain poorly understood, challenging attempts to model microbial contributions to biosphere-atmosphere interactions. New methods for integrating soil genomics into the study of biosphere-atmosphere trace gas fluxes are needed. Here, we present our approach for uncovering the genetic underpinnings of the microbe-mediated biogeochemical transformations in soils that drive significant trace gas fluxes. In past work, we constrained soil microbial contributions to biosphere-atmosphere exchange of carbonyl sulfide (COS or OCS)—a promising photosynthetic tracer—through controlled laboratory studies. This approach revealed microbial groups and types of carbonic anhydrase enzymes driving COS consumption by soil microbes,1 and identified coupled biological-abiotic processes driving soil COS emissions2, helping to build genome-informed constraints to biosphere-atmosphere interactions. We will present current efforts to extend this approach to constrain microbial contributions to trace gas fluxes in the Biosphere 2 tropical rainforest. We use the experimental ecosystem to control environmental drivers and amplify biosphere-atmosphere interaction within the enclosed structure. Using a suite of trace gas analyzers (concentrations and isotopomers) and measurement tools (probes, chambers) in key ecosystem locations (soil, stem, leaf, atmosphere) we constrain ecosystem fluxes across drought and rewet conditions. By integrating trace gas measurements and soil genomics data, we will test current understanding of the microbial genomics behind soil N2O emissions and develop new hypotheses regarding microbes and pathways driving soil VOC cycling.