EXPLORING LINKS BETWEEN BIOGENIC GAS DYNAMICS AND CRITICAL ZONE ARCHITECTURE FROM TWO BOREAL PEATLANDS IN MAINE, USA

Boreal peatlands are natural producers of greenhouse gases that contribute significantly to the pool of stored carbon in organic soils, and therefore may directly influence future climate patterns. Previous work has shown how differences in the architecture of the critical zone, particularly along the peat-mineral sediment interface, may influence peatland surface patterning (i.e., vegetation and landform distribution) and hydrological conditions (i.e., groundwater discharge). Some studies have also suggested that this influence may extend to specific hydrogeochemical properties affecting biogenic gas distribution in peat bogs, however this correspondence is unclear. In this study, we investigated a series of suspected biogeochemical hot spots (5 sites in total) in two boreal peatlands in Maine, defined from winter thermal infrared surveys showing areas of snowmelt in areas of increased temperature. The two sites, Meddybemps Heath and Sawtelle Heath, are positioned in somewhat contrasting locations with reference to the inland limit reached by the sea during the last ice sheet retreat in Maine. Field measurements using ground-penetrating radar (GPR) surveys confirmed the presence of a distinct glacial geology architecture beneath the peat in both locations, and sharp differences in peat thickness and several physical properties, including moisture content, soil temperature, and gas flux releases. Field scale investigations were also combined with laboratory measurements of peat soil monoliths collected at each of the five study sites (three at Meddybemps Heath and two at Sawtelle Heath) where soil gas content and biogenic gas fluxes are currently being investigated. While measurements are currently ongoing, preliminary results show some correspondence between higher biogenic gas releases in areas where peat soils are thinner, have less moisture content variability over time (perhaps due to a decreased ability to retain gases), and are potentially corresponded to highly permeable mineral soil deposits. These results may have implications for better understanding how subsurface geology and peat basin morphology may influence gas distribution and dynamics in peat soils.