HR: 0800h
AN: B51A-0927    [Abstracts]
TI: Environmental Control of Net Ecosystem Carbon Dioxide Exchange in Contrasting Peatlands in northern Alberta, Canada
AU: * Syed, K H
EM: kamran.syed2@uleth.ca
AF: University of Lethbridge, Department of Biological Sciences, 4401 University Drive, Lethbridge, AB T1K 3M4 Canada
AU: Carlson, P J
EM: peter.carlson@uleth.ca
AF: University of Lethbridge, Department of Biological Sciences, 4401 University Drive, Lethbridge, AB T1K 3M4 Canada
AU: Glenn, A J
EM: aaron.glenn2@uleth.ca
AF: University of Lethbridge, Department of Biological Sciences, 4401 University Drive, Lethbridge, AB T1K 3M4 Canada
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
AB: Peatlands cover about 21 per cent of the landscape and contain about 80 per cent of the soil carbon stock in western Canada. However, the current rates of carbon accumulation and the environmental controls on ecosystem photosynthesis and respiration in peatland ecosystems is poorly understood. As part of Fluxnet-Canada, we continuously measured net ecosystem carbon dioxide exchange (NEE) using the eddy covariance technique in a treed fen (main site) dominated by stunted black spruce and larch trees during August 2003 through July 2004. Additional NEE measurements were made at two auxiliary sites during intervals in the active growing season (May through September 2004). One auxiliary site was dominated by Sphagnum moss, while the dominant species at other site were Carex and brown mosses. The NEE measurements were used to develop statistical models to assess temporal variation in physiological parameters for ecosystem photosynthesis and respiration. Large seasonal changes occurred in maximum photosynthetic capacity and standardized ecosystem respiration rate at 10 degrees C (R$_{10}$). The mid-day NEE uptake rate during July averaged 10 $\mu$mol m$^{-2}$ s$^{-1}$ at the main site, while lower values of approximately 6 $\mu$mol m$^{-2}$ s$^{-1}$ were observed at the two auxiliary sites. No photosynthetic activity was observed during mid-November through mid-March. On an annual basis R$_{10}$ varied from less than 0.5 $\mu$mol m$^{-2}$ s$^{-1}$ in the winter to approximately 3 $\mu$mol m$^{-2}$ s$^{-1}$ during August at the main site. During much of the growing season, a distinct hysteresis was observed in the light (photon flux density, PFD) response curves for NEE between morning and afternoon periods. This was caused by large diurnal changes in temperature, which at times resulted in the light compensation point for NEE shifting from a PFD of 100 $\mu$mol m$^{-2}$ s$^{-1}$ in the morning to 350 $\mu$mol m$^{-2}$ s$^{-1}$ in the afternoon. The main site recorded a net annual gain of 160 g C m$^{-2}$ yr$^{-1}$, the result of a difference between gross photosynthesis of 648 g C m$^{-2}$ yr$^{-1}$ and total ecosystem respiration of 488 g C m$^{-2}$ yr$^{-1}$.
DE: 1694 Instruments and techniques
DE: 1600 GLOBAL CHANGE (New category)
DE: 1615 Biogeochemical processes (4805)
DE: 0315 Biosphere/atmosphere interactions
DE: 0394 Instruments and techniques
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting