Seasonal and Diurnal Net Methane Emissions from Organic Soils of the Eastern Alps, Austria: Effects of Soil Temperature, Water Balance, and Plant Biomass

Abstract

ABSTRACTAlthough the contribution of methane emission to global change is well recognized, analyses of net methane emissions derived from alpine regions are rare. Therefore, three fen sites differing in water balance and plant community, as well as one dry meadow site, were used to study the importance of soil temperature, water table, and plant biomass as controlling factors for net methane emission in the Eastern Alps, Europe, during a period of 24 months. Average methane emissions during snow-free periods in the fen ranged between 19 and 116 mg CH4 m−2 d−1. Mean wintertime emissions were much lower and accounted for 18 to 59% of annual flux. The alpine dry meadow functions as a methane sink during snow-free periods, with mean flux of −2.1 mg CH4 m−2 d−1 (2003) and −1.0 mg CH4 m−2 d−1 (2004). Seasonal methane emissions of the fen were related to soil temperature and groundwater table. During the snow-free periods the water table was the main control for seasonal methane emission. The net methane flux related to water table was much higher for the distinctly drier year 2003 than for the wetter year 2004. Methane emissions differed diurnally at sites where the water table position was high or very low. The influence of total above-ground plant biomass on methane emission was apparent only for those sites with high water table positions. Seasonal and diurnal methane uptake of the dry meadow was related to soil temperature and water-filled pore space, whereas plant biomass did not significantly influence methane fluxes. Our studies gave evidence that fens in the Eastern Alps act as a source of methane throughout the whole year and that a dry meadow site acts as a net methane sink during snow-free periods.