Greenhouse gas emissions related to landscape elements in the subarctic environment at Churchill, Manitoba

The relationship between greenhouse gas (GHG) emissions, landscape elements and major environmental regulators was studied. The hydrologic regimes of the Hudson Bay Lowlands are expected to change along with the extent of permafrost and composition of vegetation due to increased levels of GHGs associated with global warming. Two transects were created at a Polygonized-Peat Plateau (PPP) and a Spruce Forest (SF) site in 2005. A sub-set on 4 dominant landscape elements of each transect were used to estimate emissions of carbon dioxide (CO2), methane (CH4), and nitric oxide (N2O) on a weekly basis from June to August. In order to obtain a good sampling representation of environmental conditions and of the gradients in plant communities, the entire transect at PPP was sampled monthly. In order to examine the role of soil conditions on the production and consumption of GHG leading to surface fluxes, soil gas samplers were installed at 2 depths at both sites. N2O production and consumption were found to be inconsequential at both sites. However, high methane emissions were observed when the volumetric moisture content (VMC) rose higher than 80 per cent at the edge of the ponds. Methane consumption was found to be related to low VMC values (20-40 per cent) for the tops of peat polygons. Soil atmosphere concentrations for CO2 and CH4 at PPP were typically much higher at depths of 23-32 cm compared to depths of 5-9 cm. Some of the wettest landscape elements had very high CH4 content, but had no corresponding CH4 flux from the soil surface, suggesting that the gas was consumed under aerobic conditions at the soil surface. It was concluded that GHG emissions from both sites were altered by both landscape elements and environmental regulators such as temperature and moisture. Future work will focus on identifying the association of these relationships to processes responsible for GHG emissions in subarctic environments. The impact of global warming on these emissions will also be examined