Spatial variability of methane emissions from Swiss alpine fens

Wetland ecosystems are a major natural source of the important greenhouse gas methane (CH₄). Among these ecosystems, fens have been shown to release high quantities of CH₄. Data on CH₄ emissions from alpine fens are scarce and mainly limited to the United States and China. Therefore, static chambers were used to quantify CH₄ emissions from 14 fens located in the Swiss Alps. The aims of this study were to determine the spatial variability of the emissions and to identify potential key factors which influence CH₄ turnover. The fens were located at altitudes between 1,800 and 2,600 m a.s.l., the pore water varied from acidic to slightly acidic (pH 4.5–6.4) and the vegetation was dominated by plants of the genus Carex. In addition, the underlying bedrock was either siliceous or calcareous. Methane emissions ranged from 74 ± 43 to 711 ± 212 mg CH₄ m⁻² day⁻¹. The type of bedrock, the plant biomass above the water table and the CH₄ pore water concentrations at depths from 0 to 20 cm were the main factors influencing CH₄ emissions. Detailed measurements in three selected fens suggested that more than 98 % of the total CH₄ emissions are due to plant-mediated transport.