Spatial variation of soil methane and nitrous oxide emissions in subarctic environments of Churchill, Manitoba

Abstract

Global warming, associated with elevated levels of greenhouse gases is expected to alter hydrologic regimes, permafrost extent and vegetation composition in the Hudson Bay Lowlands (HBL). Greenhouse gas (respiration, CH4 and N2O; GHG) emissions and soil gas concentrations were determined over the growing seasons of 2005 and 2006 from numerous habitats within three dominate ecosystems within the HBL, a polygonized-peat plateau, northern fringe boreal forest and palsa fen, near Churchill, Manitoba. Nitrous oxide emissions and soil concentrations were near zero however, a trend for very slight production of N2O was observed at dry aerobic sample positions while very slight consumption occurred at very wet sample locations. “Hot-spots” of intense CH4 emissions and soil concentrations occurred in the sedge-dominated areas of high moisture and plant productivity, whereas areas of low moisture and plant productivity resulted in slight CH4 consumption. Of all the ecosystems studied, the palsa fen had the greatest CH4 production, with carbon losses from CH4 occurring at rates of approximately 50 g C m-2 during the growing season. A peat plateau ecosystem site was also used to compare GHG emissions using a similar vegetation type (Cladina stellaris) and under differing soil conditions. Based on the results, slight gradients in soil conditions such as moisture content, peat accumulation and active layer depths altered respiration emissions but did not significantly affect CH4 and N2O fluxes. The differences in GHG emissions were not as great as those between different plant community types, which suggest plant community types could be used to predict GHG emissions in similar environments.