Despite the spatial significance of Canada's boreal forest, there is very little known about CH4and N2O emissions from non-peatlands within it. The primary objective of this project was to study the atmosphere-soil exchange of CH4and N2O at three sites in the boreal forest of central Saskatchewan. In the summers of 2006 and 2007, CH4and N2O emissions were measured along transects in three different mature forest stands (aspen, black spruce and jack pine) using a sealed chamber method. At the aspen site, the gross rates of mineralization and nitrification, and the relative contribution of nitrification and denitrification to N2O emissions, were also measured using the15N isotope dilution technique. Results indicated that the jack pine and black spruce sites were slight sinks of CH4(-0.123 g CH4-C m-2yr-1and -0.017 g CH4-C m-2yr-1respectively in 2006 and -0.095 g CH4-C m-2yr-1and 0.045 g CH4-C m-2yr-1respectively in 2007), whereas the aspen site was a net source (4.40 g CH4-C m-2yr-1in 2006 and 19.60 g CH4-C m-2yr-1in 2007). The high CH4emissions at the aspen site occurred at depressions that were water-filled due to above-average precipitation levels in 2005-2007. All three sites had very low cumulative N2O emissions, ranging from -0.002 to 0.014 g N2O-N m-2yr-1in both years. The15N results indicated that N cycling at the aspen site was very conservative, allowing little N to escape the system as N2O; the emissions that did occur were due primarily to a nitrification-related process. © 2009 Elsevier B.V. All rights reserved.
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