三江平原毛果苔草湿地CH_4排放研究

Methane Emission From Carex Lasiocarpa Wetland in The Sanjiang Plain,China

用密闭不透明箱 -气相色谱法对三江平原毛果苔草湿地进行了近两年的观测研究 ,结果表明 :三江平原毛果苔草湿地全年甲烷排放通量有着明显的季节变化 ,在非冰冻期 (5～ 10月 )CH4通量范围在 4 .6 4～ 2 1.4 8mg·m-2 ·h-1之间 ,平均值为 11.15mg·m-2 ·h-1;冰冻期 (11月到次年 4月 )CH4通量范围在 0 .4 6～ 4 .30mg·m-2 ·h-1之间 ,平均值是 1.6 9mg·m-2 ·h-1。经估算 ,三江平原毛果苔草湿地全年CH4排放总量为 0 .2 32 4Tg/a-1。

Methane is one of very important greenhouse gases. Although CH 4 concentration is considerably lower than that of CO 2 in the atmosphere,it is 21 times effect of radiated heat than CO 2 per molecule (IPCC 2001). Increasing Methane concentration in the atmosphere has been stimulated in studies of CH 4 emission from terrestrial and aquatic environments. Wetlands are regarded as one of the major sources,about 21% of global methane emission came from natural wetlands. Marsh wetland is a synthetic natural ecosystem with rich carbon,especially in the high latitude region,one third of global carbon are stored in it. The Sanjiang plain is the largest and most concentrated marsh wetland region in China. The plain is located in the Northeast of Heilongjiang province,the 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). The mean annual precipitation was 550-600 mm and the mean annual temperature was 1.9°C. The vegetation types are marsh and wet meadow plants,the main soil types are marsh soil,meadow soil and peat soil. Typical and the perennial waterlogged Carex lasiocarpa wetland was selected to be the study sample. The methane fluxes was measured by closed opaque chamber made of non-stained steel and gas chromatography system (Agilent 4890). The experiment lasted from June 2002 to Feb. 2004,measured twice a week,and once daily change per month in no frozen season; measured once a month in frozen season,three repeats at each sampling site. Meanwhile,the inside and outside chamber air temperature,surface and 5cm,10cm depth soil temperature were also measured at the same time. By more than one year's experiment,the results was shown that there was a obviously seasonal variety in the methane emission from the perennial waterlogged Carex lasiocarpa marsh,the methane fluxes was 4.64-21.48 mg·m -2 ·h -1 in no frozen season (from May to October),average 11.15 mg·m -2 ·h -1 ; and 0.46- 4.30 mg·m -2 ·h -1 in frozen season,average 1.69 mg·m -2 ·h -1 . It was calculated that the total annual methane fluxes amount is 0.2324 Tg/a from the Carex lasiocarpa wetland in the whole Sanjiang plain.