三江平原湿地CH4、N2O的地-气交换特征
摘要
Methane and nitrous oxide are the very important greenhouse gases.Although CH_(4) and N_(2)O concentrations are considerably lower than that of CO_(2) in the atmosphere,however they are more effective on a molar basis than CO_(2) in resulting in radiative heating.Increasing CH_(4) and N_(2)O concentrations in the atmosphere have stimulated studies on CH_(4) and N_(2)O emissions from terrestrial and aquatic environments.Wetlands are regarded as one of the major sources of CH_(4),about 21% of global methane emission come from natural wetlands. The Sanjiang plain,the largest and most concentrated marsh-wetland region in China,is located in the northeast of Heilongjiang province.Its total marsh-wetland area is about 83.5×10~(4) hm~(2)with rich carbon resources. There are many rivers and lakes in this region and wide flood plain were formed along the river.The study was carried out at the Ecological Experimental Station of Mire-Wetland in the Sanjiang Plain,Chinese Academy of Sciences(47°35′ N,133°31′ E;56 m above sea level),center of the Sanjiang plain.The mean annual precipitation is 550-600 mm and the mean annual temperature 1.9 ℃.The vegetation types are marshes and wet meadows.The main soil types are marsh soil,meadow soil and lessive soil.Three typical types of wetlands of perennial waterlogged Carex lasiocarpa marsh,seasonal waterlogged Deyeuxia angustifolia wet meadow and perennial non waterlogged brushy wetland are selected as samples of study.The methane and nitrous oxide fluxes were measured by sealed stainless steel chamber and gas chromatography(Agilentilent 4890) system. The experiment lasted from June 2002 to August 2004,measurement was done twice a week in growth season,once a month in winter,and daily change observation was performed several times at the clear day during growth season and three repeats were practised at each sample site.Meanwhile,the inside and outside chamber air temperature,surface and 5 cm deep soil temperature were measured at the sa