B41C-0443
Long-term data on δ13C-CH4 emissions elucidate drivers of CH4 metabolism in temperate and northern wetlands
Thursday, 17 December 2015
Poster Hall (Moscone South)
Carmody K McCalley, Rochester Institute of Technology, Rochester, NY, United States, Joanne H Shorter, Aerodyne Research Inc., Billerica, MA, United States, Patrick M Crill, Stockholm University, Dept. of Geological Sciences, Stockholm, Sweden, Suzanne B Hodgkins, Florida State University, Tallahassee, FL, United States, Jeffrey Chanton, Florida State Univ, Tallahassee, FL, United States, Scott R Saleska, University of Arizona, Tucson, AZ, United States and Ruth K Varner, University of New Hampshire Main Campus, Durham, NH, United States
Abstract:
Methane flux from wetlands is both a critical component of the global CH4 budget, and highly sensitive to global climate change. Gaps in our knowledge of the biological processes that underlie CH4 fluxes from natural ecosystems limit our ability to scale flux estimates as well as predict future emissions. To address these gaps, we used quantum cascade laser technology linked to automated chambers to quantify the isotopic composition of CH4 fluxes from a high latitude (68° N) wetland underlain by discontinuous permafrost (Stordalen Mire, Sweden) and a temperate wetland (43° N) undergoing shrub encroachment (Sallie’s Fen, NH). Changes in plant communities and hydrology during permafrost thaw result in both large increases in CH4 emissions as well as shifts in the CH4 production pathway, from hydrogenotrophic to increasingly acetoclastic mechanisms. In contrast, shrub encroachment that replaces sedge species in the temperate wetland reduces CH4 emissions, but doesn’t effect δ 13C-CH4, with predominantly acetoclastic production occurring across plant communities. Multi-year data sets identify temperature and hydrologic variability as key contributors to annual and interannual patterns in δ 13C-CH4. Fully-thawed fens at Stordalen had consistent δ13C-CH4 across years, with an annual pattern suggestive of more hydrogenotrophic production early and late in the growing season. In contrast, intermediate-thaw sites, where the water table was more dynamic, had large variations in δ13C-CH4 across years. At Sallie’s Fen, patterns in δ13C-CH4 suggest an abrupt shift in CH4 transport and metabolism at the beginning of the growing season and then more stable δ13C-CH4 during the growing season. Together these results provide insights into how plant communities and variable environmental conditions interact to influence the microbial metabolisms that drive CH4 production and consumption in diverse wetland ecosystems.
