Microbial δ13C profiles in Peat soils Under Warming

Background/Question/Methods: Many of the world’s peatlands are located in northern ecosystems where the climate is changing at a rapid pace, creating concern over the fate of these carbon rich ecosystems. The microbial community is a crucial aspect of biogeochemical functioning of these peatland ecosystems ¹³CPLFA analysis was used to characterize the microbial community and provide isotopic information about microbial carbon use through peat depth profiles taken from the Spruce and Peatland Responses Under Climatic and Environmental Change (SPRUCE) Project; an extensive study of the response of peatlands to climatic manipulation in northern Minnesota. SPRUCE warming treatments range from 5 temperatures from 0 to +9° C. Samples were taken from an initial direct peak warming treatment in 2014-2015 and a time series of whole-ecosystem warming treatments across the growing season in 2016.

Results/Conclusions: We found both strong vertical stratification and variation over time, both in bioindicator abundance and in isotopic carbon use profiles. In addition, the microbial community in the surface of the peat profile is more responsive to external conditions than deeper peat. Deep peat warming enhanced the existing sensitivity of surface peat communities. Warming was related to increased fungal relative abundance, and decreased anaerobic bacterial and actiobacterial relative abundance. Fungi also used newer carbon under warming. In summary, fungal communities could be the main drivers of change in peatlands under warming, and their use of new carbon either suggests that peat profiles may remain undecomposed under warming, or that fungal communities will eventually prime decomposition of older peat.