CARBON DIOXIDE PRODUCTION FROM PEATLAND SOIL PROFILES: THE INFLUENCE OF TEMPERATURE, OXIC/ANOXIC CONDITIONS AND SUBSTRATE

We incubated intact peat cores from depth intervals of 5-15, 15-25, 25-35, and 35-45 cm from ombrotrophic bog, poor fen, and beaver pond margin sections of a cool-temperate peatland. CO2 production was measured over 12-day incubation periods at 4 and 14 °C and under oxic and anoxic conditions. Rates ranged from 0.06 to 0.66 mg CO2 g−1 dry peat d−1 under oxic conditions and from 0.002 to 0.098 mg CO2 g−1 d−1 under anoxic conditions, and rates generally decreased with depth in the profiles. When expressed on a volumetric basis, production rates ranged from 0.3 to 23.4 g CO2 m−3 d−1, and there was much less variation in CO2 production rates within profiles because the bulk density of peat increased with depth. The Q10 quotient, between 4 and 14 °C, ranged from 1.0 to 7.7, depending on sample and incubation conditions, with an average of 2.0 for oxic and 2.7 for anoxic conditions. Oxic:anoxic ratios averaged 7:1, 16:1, and 12:1 for the bog, poor fen, and beaver pond margin samples, respectively. Degree of decomposition (von Post index) was the substrate property most strongly correlated with CO2 production. Based on temperature and incubation data for the peat profiles to a depth of 45 cm, annual decomposition values (k) ranged from 0.016 to 0.060 yr−1 under oxic conditions and from 0.001 to 0.007 yr−1 under anoxic conditions. A model of CO2 emission from the three sites, based on the incubation data and thermal and water table regime, gave good agreement with measured in situ CO2 emission rates (r2 = 0.72, n = 18), although summer emission rates were underpredicted, possibly because of the absence of a root production component in the incubations or because of underestimation of CO2 production rates in field conditions above the water table.