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Carbon dioxide and methane exchange in a boreal wetland
Detailed information on carbon exchange in northern wetlands is needed to improve our understanding of global carbon cycle and predictions of future climatic conditions. For this reason, fluxes of carbon dioxide and methane were measured in a boreal wetland in central Saskatchewan as part of the Boreal Ecosystem Atmosphere Study (BOREAS) in 1994 and 1995. Seasonal patterns of midday CO2 flux were comparable in the two years. Peak midday CO 2 uptake (about 0.5 to 0.6 mg m−2 (ground area) s−1) occurred in early July concurrent with peak LAI (≈1.3). The relationship between CO2 flux (normalized by leaf area) and incident photosynthetically active radiation was similar in both years. High vapor pressure deficit (1.5 < D < 3.2 kPa) and air temperature (20 < Ta < 30°C) reduced CO2 flux significantly. Integrated net ecosystem CO2 uptake was 89 and 108 g CO2-C m−2 (890 and 1080 kg CO2-C ha−1 ) in the 1994 and 1995 growing seasons, respectively. Periods of high vapor pressure deficit and air temperature, a brief interval of cloudy/cool conditions, and a brief temporary rise of the water table in 1994 were likely associated with the lower carbon uptake. ^ Seasonal trends of methane emission showed some similarities in the two years. Maximum seasonal methane emission was of comparable magnitude (19.5 and 16.5 mg m−2 h−1 in 1994 and 1995, respectively) and occurred about the same time as the highest peat temperatures and water tables. However, peak methane emission occurred much earlier (5 to 6 weeks) in 1995: this was probably linked to the contrasting seasonal trends of peat temperature and water table between years. Peat temperature and water table also reached their peak values later in the 1994 season. Sensitivity of methane emission to changes in peat temperature and water table was consistent between the two seasons. Seasonally integrated methane emission of 16.3 and 17.9 g CH4-C m−2 (163 and 179 kg CH4 -C ha−1) in 1994 and 1995 respectively, was 15–20% of the net ecosystem CO2 exchange. Thus, for a productive wetland as studied here, carbon loss through methane emission is significant in the overall carbon budget. ^
Biology, Ecology|Biogeochemistry|Physics, Atmospheric Science|Environmental Sciences
Suyker, Andrew Edward, "Carbon dioxide and methane exchange in a boreal wetland" (2000). ETD collection for University of Nebraska - Lincoln. AAI9992010.