THE INFLUENCE OF WATER TABLE LEVELS ON METHANE AND CARBON DIOXIDE EMISSIONS FROM PEATLAND SOILS

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Abstract
The evolution of carbon dioxide and methane was measured from laboratory columns packed with surface (0-30 cm) materials representing a fen, a bog and a swamp and with varying water tables and treated with water containing 10 mg L-1 dissolved organic carbon. Carbon dioxide evolution increased in a linear relationship as the water table was lowered, ranging from 0.3-0.5 g CO2 m-2 d-1 to 6.6-9.4 g CO2 m-2 d-1 for the water table at 10 cm above and 70 cm below the peat surface, respectively. Methane evolution decreased in a logarithmic relationship as the water table was lowered. The fen showed the highest rates of methane flux (28 mg CH4 m-2 d-1 when inundated) and the bog the lowest (0.7 mg CH4 m-2 d-1 when inundated). These differences appeared to be related to the acidity of the soils and their microbial characteristics. Molar ratios of carbon dioxide:methane evolution increased from 4 to 173 under inundated conditions to > 2500 when the water table was at a depth of 70 cm.