Characteristics Of CH₄Emission From A Typical Carex Dominated Wetland In Poyang Lake

Wetlands are the largest natural sources of emissions of the global methane（CH₄）. With the change of global climate, especially in the context of global warming,the emission of greenhouse gases CH₄in the wetland has become the focus attentionof the world’s governments and scientists. However, the study on China’s largestfreshwater lake-Poyang Lake with its unique characteristics is still empty. In fact, itcan provide the basic data for estimating the emissions of CH₄in China’s lakes andwetlands, deepen the understanding of the mechanism of emission process of CH₄inlakes and wetlands. The researchers selected a typical Carex wetlands in theNanjishan wetlands Nature Reserve in Poyang Lake from May2009to June2011, andset up two treatments, one is TC, which maintains the natural state of Carex soil-plant system; The other called TJ: cut off the ground from aerial parts of plants, andrepeat three times. Then, the researchers observe the flux distribution of CH₄in carextypical wetlands and its impact factor with gas chromatography static box. The mainresults are as follows:（1） The emission flux of CH₄of the wetland in Carex wetland during theflooding period shows the obvious diurnal variation law. The emission of CH₄lasts allthe day, and its CH₄flux is higher than the overall flux in the night. The maximum ofemission flux is5.625mg·m^-2·h^-1, which happens around13:00; While the minimumis2.637mg·m^-2·h^-1. Water temperature is one of the most important environmentalfactors that control the the diurnal variation of CH₄emissions in Carex wetland. Thediurnal variation of CH₄release rate and water temperature keep a significant positivecorrelation （r=0.76, n=10, P <0.01）.（2） Changes of water level in Poyang Lake comprise an important factor ofWetland CH₄release. There are two experiments treating CH₄release rate before andafter the flooding of the soil. The release of CH₄after the flooding is nearly a hundredtimes of that before the flooding.（3） The two methods of CH₄emission treatment showed obvious seasonalvariation: CH₄release during spring and summer was significantly higher than thatduring the fall and winter seasons. The negative emissions of CH₄（absorption ofatmospheric CH₄） appeared continuouslyduring TC treatment from November2010toFebruary2011. And the absorptive amount was up to0.18mg·m^-2·h^-1. The entireobservation during the TJ treatment gave priority to with CH₄release. （4） The correlation between the seasonal variation of CH₄emission flux duringnon-flooding period and the Influencing factors of air temperature, soil temperature,the surface temperature reached a significant level. The temperature becomes the maincontrol factor of CH₄emissions during the non-flooded period.（5） The annual CH₄emission flux of Nanjishan Carex wetland in Poyang Lakeis about19.51gCH₄·m^-2·a^-1.