HR: 1340h
AN: B53A-0925    [Abstracts]
TI: Seasonal Variation in Net Ecosystem Methane Flux in a Moderately-Rich Fen in Northern Alberta: Comparison Between Measurements and Model Calculations
AU: * Flanagan, L B
EM: larry.flanagan@uleth.ca
AF: University of Lethbridge, Department of Biological Sciences 4401 University Drive, Lethbridge, AB T1K 3M4, Canada
AU: Long, K
EM: long.long@uleth.ca
AF: University of Lethbridge, Department of Biological Sciences 4401 University Drive, Lethbridge, AB T1K 3M4, Canada
AU: Cai, T
EM: tiebo.cai2@uleth.ca
AF: University of Lethbridge, Department of Biological Sciences 4401 University Drive, Lethbridge, AB T1K 3M4, Canada
AB: We conducted measurements of seasonal variation in net ecosystem methane flux using the eddy covariance technique in a moderately-rich fen in northern Alberta, Canada during May-October 2007 as part of the Canadian Carbon Program (a follow-on program to the Fluxnet-Canada Research Network). Mid-day fluxes increased from near zero in May to a peak of approximately 4.3 mg m^-2 h^-1 in July and then declined through the rest of the growing season. There was a strong diurnal pattern in the concentration of methane (measured above the canopy at 10 m) and net methane flux, with low fluxes at night and peak fluxes occurring near mid-day. The diurnal pattern in concentration and flux had two primary causes. First, consistently low winds at night resulted in lack of turbulent exchange and a large build up in methane concentration below the eddy covariance sensors and the inlet for the methane analyzer. Second, model calculations suggested that stomatal closure at night limited methane flux through vascular plants. During the day open stomatal pores apparently allowed some methane flux through vascular plants thereby avoiding oxidation in aerobic layers near the surface of the peatland. The model calculations suggested that in July the net methane flux was a result of the difference between a maximum methane production rate of 6.3 mg m^-2 h^-1 and a maximum methane oxidation rate of 2.3 mg m^-2 h^-1 (both rates normalized to 10 degrees C), with 60 percent of methane production passing through vascular plants and being affected by stomatal control.
DE: 0400 BIOGEOSCIENCES
DE: 0428 Carbon cycling (4806)
DE: 0476 Plant ecology (1851)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting