Methane flux in grassy marshlands near Kolyma River, north-eastern Siberia

The relationships between vegetation types and methane flux were evaluated in north-eastern Siberia in the summer of 1995. Based on 71 50×50-cm plots, the vegetation was divided into three types by TWINSPAN cluster analysis: (1) Eriophorum grassland where species richness was high and moss well-established (Eriophorum grassland), (2) horsetail grassland with moss cover and (3) Carex grassland without moss. Vascular plant cover in all vegetation types was less than 50%. The methane flux was measured by a static chamber method. Horsetail grassland emitted the highest amount of methane, 165.5 mg CH4/m2/d, while diverse-sedge grassland emitted less methane, i.e., −1.9 mg CH4/m2/d. Methane flux positively increased with electric conductivity (EC), water depth, thaw depth, and soil humidity. Of those, EC was strongly correlated to methane emission (Spearmanʹs rank correlation, r2=0.630). The difference in methane flux between horsetail grassland and sedge-dominated grassland suggested that the morphological characteristics of vascular plants were important on methane transport, probably because vascular plants, such as horsetail, that developed aerenchyma and intercellular gas space promoted methane transport from soil to air while mosses do not.