Abstract
Methane fluxes were measured on vegetated surfaces (2003) and pools (2004) of three peatlands (LG1‐LG2‐LG3) located 30, 100, and 200 km along a transect from the James Bay coast, in the La Grande Rivière watershed, James Bay lowland, Quebec, Canada. Fluxes were measured with static chambers at sites chosen to represent the biotypes characteristic of each peatland, from hummocks with a water table 35 cm below the surface to pools 100 cm deep. Average CH4 fluxes for the biotypes on vegetated surfaces sampled during summer 2003 ranged from 3.5 to 197 mg m−2 d−1, while summer 2004 average floating chamber pool fluxes ranged between 6.2 and 3165 mg CH4 m−2 d−1. Seasonal average daily CH4 fluxes on vegetated surface were strongly correlated with average water table depth, greater fluxes occurring where the water table was close to the surface, and with vegetation cover, particularly the aboveground biomass of sedges. Within the summer, increasing CH4 fluxes from vegetated surfaces were correlated with rising peat temperature. Pool fluxes from the LG1 and LG2 peatlands decreased with increasing pool depth, but not at LG3. Estimated growing season CH4 emissions for the three peatlands were of 44 ± 21 (standard error), 21 ± 9.4 and 52 ± 17 mg CH4 m−2 d−1 for the LG1, LG2, and LG3 peatlands, respectively. Estimated annual release of CH4 is 3.8 g m−2 with the winter contributing to 13% of the overall emission, based on winter‐time measurements at LG2.
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