Methane and carbon dioxide exchange potentials of peat soils in aerobic and anaerobic laboratory incubations

Samples (140) of peat collected from bogs, fens and swamps in boreal, subarctic and temperate regions of Canada were incubated at 15 or 20°C for 5 d in the laboratory to determine potential rates of CO2 and CH4 exchange under aerobic and anaerobic conditions. Rates of CO2 production ranged between 0.07 and 5.0 mg g−1 d−1, with means of 1.0 and 0.5 mg CO2 g−1 d−1 for aerobic and anaerobic production rates, respectively. Aerobic and anaerobic CO2 production rates were strongly correlated (r = 0.581, P < 0.001, log10 transformation) with the former an average of 2.5 times larger than the latter. CO2 production rates were greatest in the upper part of peat profile and appeared to be related to the botanical origin of the peat. Aerobic CH4 consumption and anaerobic CH4 production rates ranged from 0.01 to 100 μg CH4 g−1 d−1, with means of 13.1 and 3.1 μg CH4 g−1 d−1, respectively. Rates of CH4 exchange were positively correlated (r = 0.368, P < 0.001, log10 transformation). Within profiles, maximum CH4 consumption occurred in samples collected from beneath or at the water table, whereas CH4 production occurred mainly in samples collected from beneath the water table. There was no significant correlation between aerobic CH4 consumption and CO2 production, but anaerobic CH4 production was positively correlated with CO2 production (r = 0.36, P < 0.001).