Recent changes in carbon source-sink relationships and greenhouse gas emissions in forest and peatland ecosystems along the Mackenzie Valley region of Canada

Permafrost is a critical component of northern landscapes, not only directly affecting soil processes, but its indirect affect on soil water and active layer depths (depth of surface soil thaw in the summer) also has a substantial influence on the ecosystem. Because of the vast carbon (C) reserves present in peatlands, thawing of peatland permafrost can potentially mobilize this C, leading to enhanced emissions of greenhouse gasses (GHGs) to the atmosphere and substantially augmenting the global atmospheric C cycle. The relationship between vegetation and permafrost is particularly interesting in northern ecosystems, with plant communities both affected by changes in permafrost conditions, yet also able to influence the permafrost environment. This project was designed to improve our understanding of the potential impacts of recent climate change, as well as anthropogenic and natural disturbances, on the total C storage and source-sink relationships of forest and peat ecosystems of the Mackenzie Valley. The four main objectives of the study include: 1. across the regional gradient, assess possible changes in the distribution and composition of forest and peatland ecosystems due to recent climatic changes, permafrost melting, and human impacts and to determine present and recent past changes in C storage; 2. develop regional and site level estimates of C storage as well as recent changes in C storage in Boreal and Subarctic ecoclimatic regions of the Mackenzie Valley; 3. characterize the GHG emissions by assessing interannual and seasonal variation, and key processes controlling CO2, CH4 and N2O dynamics along the latitudinal gradient of ecosystems along Mackenzie Valley; 4. develop models of C storage and associated dynamics in order to predict future changes in the C source-sink relationship due to climate change, and other natural and anthropogenic disturbances in forest and peatland ecosystems. This project is linked nationally to IPY Climate Change Impacts on Canadian Arctic Tundra Ecosystems Project (Project 2006-SR1CC-096) and internationally to the Global Carbon Project (GCP), the International Permafrost Association's Soil Carbon Project (CAPP) and The North American Carbon Budget and Implications for the Global Carbon Cycle Project (SOCCR).