Seasonal and spatial variations of methane emissions from montane wetlands in Northeast China

To evaluate the seasonal and spatial variations of CH4 emissions and understand the controlling factors, we measured CH4 fluxes and their environmental variables from seven natural wetlands in mountainous regions in northeast China using a static chamber technique during a growing season from May to October in 2008. Four sites were significant atmospheric CH4 sources, ranked in order from highest to lowest according to their seasonal mean CH4 release; these sites were a marsh (34.18 mgCH4 m−2 h−1), two deciduous forested swamps (0.83–18.21 mgCH4 m−2 h−1) and a thicket swamp (0.43 mgCH4 m−2 h−1). Coniferous forested swamps, forested fens and bogs are unique wetlands in northeast China and represent large wetland coverage in this zone, but they were observed to be weak sinks of atmospheric CH4 (−0.08 to −0.01 mgCH4 m−2 h−1). Similar seasonal variations can be observed at marsh, thicket swamp and two deciduous forested swamps sites, with peaks were observed during the summer and early autumn (July to early September). However, no seasonal pattern was found at the other three sites. Seasonal variations of CH4 fluxes were primarily affected by the soil temperature. However, spatial variation among wetlands was mainly controlled by the water table, the soil temperature, plant aboveground biomass and potential CH4 production. A high water table and herb-dominant sites had high potential CH4 production rates and thus induced high CH4 fluxes. In contrast, a low water table and tree- or moss-dominant sites had low potential CH4 production rates and induced low CH4 fluxes.

Research highlights
► Wetlands could act as both atmospheric CH4 sources and sinks.
► CH4 fluxes were mainly controlled by water table, soil temperature and plant biomass.
► Spatial variations of CH4 fluxes were correlated with potential methane production.
► Herbs are better predictors for evaluating CH4 fluxes from wetlands than shrubs.