Title: Methane production and oxidation potentials in relation to water table fluctuations in two boreal mires

Authors: Kettunen A., Kaitala V., Lehtinen A., Lohila A., Alm J., Silvola J. and Martikainen P.J.

Status: Soil Biology and Biochemistry, Vol. 31 No. 12, 1999, pp. 1741-1749

We studied the response of methane production and oxidation potentials in a minerotrophic and an ombrotrophic mire to water table fluctuations. In profiles where water table had not varied, the water saturated layers showed significant potentials while the unsaturated layers did not. The production potentials in the saturated layers below water level ranged from 0.1 to 2.4 mg CH₄ h^-1 (g dw)^-1 and oxidation potentials (first order reaction rate constants) between -0.010 and -0.120 h^-1 (g dw)^-1. In profiles with constant water level, the maximal production potential occurred 20 cm and maximal oxidation potential 10 cm below water level. When water table varied only little, production potentials slightly increased towards the autumn. After a water level draw-down, in the profiles from the dry microsites, production and oxidation potentials were detected in layers that had been unsaturated up to six weeks. The maximal oxidation zone was shifted downwards during low water periods. In a wet microsite, a two weeks period of unsaturation eliminated the production potential and decreased the oxidation potentials. After a rise in the water level, the potentials were reactivated more rapidly in the wet than in the dry microsites.