Seasonal methane dynamics in three temperate grasslands on peat

Abstract

Drained peatlands are considered to be insignificant CH4 sources, but the effect of drainage on CH4 dynamics has not been extensively studied. We investigated seasonal dynamics of CH4 in two fen peat soils and one bog peat soil under permanent grassland in Denmark. Soil CH4 concentrations were measured several times throughout the year in parallel to a one year CH4 flux monitoring campaign with static chambers. Additionally, CH4 production potentials were determined in a laboratory incubation assay for the bog soil. Methane fluxes were generally negligible, even though soil CH4 concentrations of up to 155 and 1000 μmol CH4 dm−3 were measured in one of the fen peats and in the bog peat, respectively. Significant CH4 concentrations were observed above the water table. Methane production assays confirmed the presence of viable methanogens in the upper parts of the bog peat soil. The aerenchymous plant Juncus effusus L. liberated CH4 from the peat at rates of up to 3.3 mg CH4 m−2 h−1. No CH4 dynamics were observed in the second fen peat which, in contrast to the other two sites, had high sulfate concentrations. Peat type and the distribution of aerenchymous plants should be considered before dismissing grasslands on peat as CH4 sources.