Methane emission patches in riparian marshes of the inner Mongolia

Natural wetlands are an important methane (CH4) source. However, emission inventories of them are rather uncertain. One reason for this is the existence of ubiquitous wetland patches. Using a static-chamber technique, we performed field measurements in the inner Mongolia marshes to compare the CH4 fluxes between a sandy marsh and an organic marsh, and between a patch and the vicinity, and determine the seasonal variation of CH4 fluxes. For each marsh, the CH4 flux in the patch was significantly higher than that in the vicinity. Both marshes presented the similar patch pattern of CH4 emissions. Another remarkable result was the very high CH4 fluxes in the organic marsh, which averaged 1817.3 and 517.4 mg CH4 m−2 d−1 in the patch and the vicinity, respectively, during July–September 2004. The very high fluxes mainly resulted from the dense plants. It could be proposed that CH4 emission patches need to be accounted for in developing an accurate estimate of the global source strength of wetlands.