HR: 16:30h
AN: B22D-02 INVITED     [PDF]
TI: Methane Emission and Net Ecosystem Exchange in Melt and Permafrost-Plateau Bog Features Within the Discontinuous Permafrost Zone of Northern Alberta, Canada
AU: * Whiting, G J
EM: gwhiting@cnu.edu
AF: Christopher Newport University, Dept. Biology, Newport News, VA 23606 United States
AB: Recent evidence indicates northern latitude permafrost is degrading in response to changing climate conditions (elevated temperatures and changing moisture input) which may significantly alter the processing of peatland carbon. As the permafrost melts, the bog surface subsides to the level of the surrounding water table creating a collapse scar with saturated surface conditions. Previously frozen peat is now available for decomposition and may become part of methanogenic processes elevating methane pools and emissions. Increased primary production in the collapse scar provides a sink for carbon dioxide and may counterbalance the greenhouse effect of a greater methane emission from these sites. However, increased primary production may stimulate methanogenesis and provide a positive feedback to even greater methane emissions. It is this balance of methane (CH$_{4}$) and CO$_{2}$ exchange that was examined within 7 melt features in northwestern Alberta during the growing season of 2002 (May to October). To measure CH$_{4}$ and CO$_{2}$ exchange, clear phytochambers (0.28 m$^{3}$) were placed on sampling frames (0.43m$^{2}$) inserted into the peat surface. Each site had 4 sampling frames (plots) in the melt feature and 4 plots in the permafrost plateau. Methane emission was measured by headspace grab samples analyzed on a FID-GC and net ecosystem CO$_{2}$ exchange (NEE) was estimated utilizing a LiCor 6200 portable photosynthesis system. During peak methane emission in late August, melt scars ranged between 2 to 10 mg CH$_{4}$ m$^{-2}$h$^{-1}$ as compared to the highly variable (near zero) permafrost plateau maximum exchange of 0.15 (emitted) to -0.15 (oxidized) mg CH$_{4}$ m$^{-2}$h$^{-1}$. Along a transect within the melt at two sites, methane emission and NEE peaked 2 meters from the permafrost plateau edge as compared to plots adjacent to the edge or near the middle of the melt feature (20m from the permafrost plateau). During late August, NEE during full sunlight ranged from a low uptake of 80 mg CO$_{2}$ m$^{-2}$h$^{-1}$ in permafrost plateau plots to a high of 1000 mg CO$_{2}$ m$^{-2}$h$^{-1}$ in melt plots near the permafrost edge. Highly productive sites for both NEE and CH$_{4}$ emission were related to the amount of vascular plants present.
DE: 0315 Biosphere/atmosphere interactions
DE: 1615 Biogeochemical processes (4805)
DE: 1823 Frozen ground
DE: 1851 Plant ecology
DE: 1890 Wetlands
SC: Biogeosciences [B]
MN: 2003 Fall Meeting