Cold season CH4, CO2 and N2O fluxes from freshwater marshes in northeast China.

Cold season (winter and thaw) CH4, CO2 and N2O fluxes from freshwater marshes (47 degrees 35'N, 133 degrees 31'E, Northeast China) were measured, using the static chamber method. The mean CH4 and CO2 fluxes from Carex lasiocarpa (Cl) were 0.5+/-0.19 and 6.23+/-1.36 mgCm(-2)h(-1), respectively, and those from Deyeuxia angustifoli (Da) were 0.18+/-0.15 and 5.22+/-2.48 mgCm(-2)h(-1), respectively in winter. There was no significant difference between Cl and Da (p > 0.05). The contributions of winter CH4 fluxes were about 5.5% and 3% in the Cl and Da, respectively. Marshes are an important potential N2O sink in winter season in northeast China. During thaw, the CH4 and CO2 emissions rapidly increased, 4.5-6 times of winter emissions. Wetland became a source of N2O. Cold season gases flux from northern wetlands play an important role in the seasonal gas exchange.