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We examined controls on mineralization of carbon to methane (CH[sub 4]) and carbon dioxide (CO[sub 2]) in Sphagnum (moss)-dominated peatland ecosystems by transplanting surface (5 cm deep) and subsurface (40 cm deep) peat samples reciprocally among three sites for periods ranging from 4 to 25 months. The sites were Big Run Bog in West Virginia, USA, Bog Lake Bog in Minnesota, USA, and Bog 307 in Ontario, Canada. Immediately upon retrieval, we incubated the peat samples in the laboratory at 12 and 22°C under both anoxic and oxic conditions to estimate rates of carbon mineralization. Transplanting affected surface peat more than subsurface peat. Peat incubated within Bog Lake Bog in Minnesota had the highest rates of CH[sub 4] production, regardless of origin, whereas transplanting did not affect rates of CO[sub 2] production measured concomitantly. Peat that originated in Big Run Bog in West Virginia generally maintained higher rates of CH[sub 4] production and CO[sub 2] production than peat from the other two sites after incubation in the field. The temperature dependence (Q[sub 10]) of CH[sub 4] production and CO[sub 2] production varied among transplant sites, but not among peat origins, suggesting physiological adaptations of microbial communities to local environmental conditions. Differences in organic matter quality of the peat, particularly lignin chemistry, helped explain the results: (a) CH[sub 4] production correlated with fresher lignin derived from Carex sedges, and (b) CO[sub 2] production correlated with woody lignin. We concluded that, although both site conditions (climate, nutrient status, and microbial communities) and organic matter quality influence carbon mineralization in peat, interactive effects occur and may differ depending on peat temperature. Moreover, CH[sub 4] production and CO[sub 2] production respond differently to environmental regulators. [ABSTRACT FROM AUTHOR]

We measured seasonal patterns in the fluxes of CH4 and CO2 in a forested wetland in central New York State from 1992 to 1995. The site was a red maple-hemlock swamp with permanent pools (~30cm deep), except when the pools dried during severe drought in 1995. Annual CH4 emissions from the pools to the atmosphere averaged 4.3 (+/- 2.4) mol m-2 during 1993 to 1995 and ranged from 1.9 mol m-2 in 1993 to 6.7 mol m-2 in 1995. CO2 emissions from the pools during 1993 and 1994 were 10.5 and 11.9 mol m-2, accounting for 84.6% and 75.6% of the gaseous carbon export during 1993 and 1994, respectively. A combination of temperature and carbon availability influenced seasonal CH4 and CO2 fluxes more than other environmental factors (temperature, water column depth, O2, CH4, dissolved organic carbon, NH4+, or dissolved inorganic carbon). Based on an observed 12 C threshold temperature, linear regression models explained from 31% to 77% of seasonal gas flux variability. Compared with other forested wetlands, this site produced substantially greater CH4 fluxes, and the CH4 flux accounted for a greater proportion of the total carbon flux from the system. [ABSTRACT FROM AUTHOR]