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

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. Key words: Methane, carbon dioxide, water table, organic soils, peatlands