Analysis Of Soil Methane Emission Flux In Typical Ecosystem Of Ebinur Lake Region During The Growing Season

Methane is a recognized as an important greenhouse gas after carbon dioxide;its infrared absorption capacity is20～30times that of carbon dioxide; the average lifetime of methane is up to10years, much higher than carbon dioxide in theatmosphere. Although its concentration in the atmosphere is much less than carbon dioxide, the growth rate is much greater, resulting in the ability of global warming is2times of carbon dioxide. Wetlands are in great importance of a site for absorption and emission of greenhouse gases. There is15～22%of methane which discharged into the atmosphere in global are from the wetlands. Estimates of methane emissions and the analysis of its environmental impact factors is an important substance of wetland research. It has drawn wide attention both at homeand abroad.In recent years, because of the pressure of large human population and rapideconomic development, the Ebinur Lake in the protected areas of natural wetland are narrowed year after year, The wetland ecological processes which included the wetland soil carbon storage and greenhouse gas emissions has been greatly affected by the changing of Land use type of the wetlands. As one of the concentrated areas of wetland in Xinjiang, Ebinur Lake wetland has a greater representation and research value.Therefore, the soil methane emission of the most typical ecosystem（such asdesert ecosystem,farmland ecosystem and wetland ecosystem） are observed in July-August2011in this region.And soil samples are taken back to the laboratory test,too. Acrroding to these, we can get the following conclusions:（1） In farmland ecosystem, cotton field and abandoned land had obviously diurnal variation dynamic of soil methane emission, their peak appeared at about9:00am. During the observation time, the average methane flux of10a cottonfield is0.02mg﹒m^-2﹒h^-1, the average methane flux of10a abandoned land is ^-1.63mg﹒m^-2﹒h^-1. The10a cotton field soil is a weak source of the soil methane, the flux changes in volatility is not obviously and showed double peak curve;10a abandoned land soil within the observation time is a weak sinks of methane. soiltemperature of10cm,15cm,20cm depth and soil methane emission of10a cottonfield showed a significant negative correlation, While soil methane emission of10a abandoned land and the soil temperature of15cm,20cm depth showed a very significant negative correlation, its also have a significant or very significant correlation to wind speed of surface10cm,150cm. The influence of water and temperature factors which impact soil methane emission change of. are not significant inthis ecosystem.（2）In desert ecosystem, Populus euphratica land and deserted grasslandhad obviously diurnal variation dynamic of soil methane emission, their peak appeared at about10:00am. The trend of the xerophytic reed land is more quietly.Within the observation time, the average methane flux of Populus euphratica land is^-16.52mg.m^-2.h^-1; deserted grassland of the average methane flux is^-2.28mg.m^-2.h^-1; the average methane flux for the xerophytic reed land is0.52mg.m^-2.h^-1. Populus euphratica land and deserted grassland consume large amountsof methane, both of them are sinks of methane.The xerophytic reed land is a weak source of methane. Subject to only soil temperature of20cm depth and methane emission from Populus euphratica land had negative correlation, each layer of the remaining plots of soil temperature and soil methane emission is significant or very significant negative correlation. Found by observation, the impactof temperature, humidity, water and heat factors on soil methane emissions ofthis ecosystem is also not notable, content of soil organic matter and soil porosity and its methane emissions have a certain relevance.（3）In wet aquatic ecosystem, the diurnal variation of the floodplain sandland soil methane flux emission is more smoothly, and the diurnal variation of t he wet reed grassland soil methane flux emission changes in volatility. Within the observation time, the average methane flux for the wet reed grassland is11.19mg.m^-2.h^-1; the average methane flux for the floodplain sand land is-0.18mg.m^-2.h^-1. The weather is cloudy, light intensity weakening may result in reducingmethane emission flux of wetland. As this study at the time of observation the floodplain sand land is continuous cloudy and windy weather, as a consequence the flux value is negative, make it become a sink of methane. The wet reed grassland is a source of methane emission. Methane emission from soil of the floodplain sand land and its soil temperature of15cm,20cm depth are in significant or very significant negative correlation, while every layer of soil temperature is not relevant to methane emission from the wet reed grassland soil. Because of the observation time is shorter and the limits of observation method itself, this study concludes that water、heat factors and soil properties of methaneemission from soils in this ecosystem is not apparent correlation.（4）We defined May to October as the growing season, estimating methane emission flux of all the ecosystems in growing season, the results are following:The methane emission flux of deserted grassland and10a abandoned landare-9.97g. m^-2and-7.10g. m^-2, respectively;The methane emission flux of Populus euphratica land during growing season is g. m^-2;The methane emissionflux of the floodplain sand land （Bird Island） and10a cotton field in growingseason is0.08g. m^-2and-0.79g. m^-2, respectively;The methane emission fluxof two different values of Reed community is2.26g. m^-2and48.86g. m^-2, respectively.