Microbial CO2 exchanges in peatlands: contribution to the peatland carbon pool and response to climate change – MICE

Soil microorganisms are globally seen as a source of carbon (C) because of their central role in releasing greenhouse gases such as carbon dioxide (CO2) and methane. Certain bacteria and protists can consume atmospheric CO2 using diverse metabolic pathways, but they are presumed either to be rare community members or with insignificant CO2 assimilation capacities compared to plants. Yet emerging evidence shows that microbial CO2 uptake can contribute significantly to terrestrial primary productivity. Given that both microbial CO2 uptake and release coexist in soils, an enduring question is to which extent and under which conditions these microbial C processes counterbalance each other. Particularly, any decoupling among these coexisting microbial processes resulting from climate change is likely to have consequences for the whole-soil C balance, with unforeseen consequences for future climate conditions. MICE will tackle these questions in peatland ecosystems— a major terrestrial C pool. We will test how microbial CO2 exchanges with the atmosphere modulate peatland C dynamics under climate change. Specifically, this project aims to 1) probe the metabolic rates that underpin microbial CO2 exchanges; 2) Examine the biotic and environmental controls of microbial CO2 exchanges across space and time to make annual microbial CO2 budgets; 3) Perform experimental and modelling studies to reveal how climate change alters microbial CO2 exchanges and how these shifts could impact whole peatland C balance. To fulfil these aims, this work will utilize a powerful approach that harnesses multi-omics microbial analyses, microbial and ecosystem CO2 flux measurements, and biogeochemical analyses with geospatial and Land Surface modelling. The response of soil C to warming is still one of the great uncertainties in global C cycling. The achievement of this project will mark a step-change in understanding microbial processes surrounding the projections of peatland C emissions to the atmosphere, and address a critical research challenge of the Anthropocene in a key natural ecosystem: how climate change will impact soil C cycling by the soil microbiome?