Dynamics of methane emissions from a freshwater marsh of northeast China

In this paper, CH4 flux was measured from Nov. 2002 to Oct. 2005, to estimate CH4 emissions in winter and during freeze– thaw period, and interannual variation in CH4 emissions in freshwater marsh in northeast China. The results showed that there was an obvious CH4 emission (0.1–2.3 mg m−2 h−1) in the freshwater marsh in winter. Flux of CH4 in winter (November to March the next year) was about 3.8%, 5.5%, and 2.2% of the whole year in 2003, 2004, and 2005, respectively. Emission of CH4 significantly increased during the freeze–thaw period (April–June), and was about 30.8%, 20.9%, and 20.6% of the whole year in 2003, 2004, and 2005, respectively. Standing water depth greatly governed interannual variation of CH4 emissions from marshes during the thaw–freeze period. Interannual variation of CH4 emissions was significant during the growing season ( pb0.05). Standing water depth during April to June was a primary factor, which affected the interannual variation of CH4 flux during the growing season. Precipitation during the preceding non-growing season affected CH4 emission indirectly via standing water depth.