A pulse-label experiment to determine the biophysical kinetics of different carbon pools for methane emissions in a Carex aquatilis dominated wetland

Methane is a greenhouse gas that is produced by microbes under anoxic conditions. Previous work has coupled photosynthesis and methane emissions using stable and radio isotopes of Carbon Dioxide. However, a full understanding of the transfer and conversion of fixed carbon from the plant, through the rhizosphere, and to the atmosphere as methane is lacking. The coupling of the methane and belowground carbon cycles within model simulations will allow for a finer understanding of the role of ecosystem production in methane emission and the potential effects of a changing climate. In order to parameterize this model, flux rates and pool half-lives need to be measured in situ. Using 13C-CO2, 13C-Acetate, and 13C-CH4, we conducted a pulse-chase experiment in a high alpine wetland dominated by Carex aquatilis to determine the temporal importance of different pools within the methane cycle on emissions. Using a field-based Methane Carbon Isotope Analyzer we measured the flux and isotopic composition of methane from the labeled plots at a high temporal resolution (~ every 2 hours). Flux of 13C-CH4 from the plots amended with dissolved 13C-CH4 peaked approximately 5 hours after addition and decreased significantly within 24hours. Flux of labeled methane from the plots amended with dissolved 13-Acetate peaked 13 hours after injection and decayed very slowly. Flux of labeled methane from plots amended with 13C-CO2 appeared around 13 hours after addition and was not detectable within another 12 hours. We will present an analysis of how the varying turnover times of these labeled materials reflect differences in pool sizes and biophysical kinetics.