三江平原旱田土壤甲烷氧化的初步研究

Primary Study of Methane Oxidation from Dryland in the Sanjiang Plain

透气性良好的旱田土壤是大气CH4的主要吸收汇,对于降低大气CH4浓度具有非常重要的意义.本研究在三江平原选择两块旱田,分别于1987年和1993年由沼泽湿地开垦而成(分别简写为87D和93D),种植方式均为大豆-冬闲,利用静态暗箱/气相色谱法对2003年和2004年两个生长季的CH4排放进行了野外观测,发现不同垦殖年限的两块旱田在CH4氧化速率上没有明显差异,但它们均具有显著的年际变化特征,2003年大豆生长季内87D旱田表现为向大气排放CH4,排放量为0.68 kg/hm2,而2004年则表现为吸收大气CH4,吸收量为1.29 kg/hm2;93D旱田在2003年和2004年大豆生长季内均表现为吸收大气CH4,吸收量分别为0.57和1.07 kg/hm2,旱田CH4排放上的这种年际变化主要是由大气降水的年际差异造成的.土壤水分状况是控制CH4氧化速率的主要因素,二者呈负相关关系.植物参与能够显著提高土壤氧化CH4的能力,2004年,在植物的参与下,93D旱田和87D旱田土壤与无植物处理相比对CH4的氧化能力分别提高了197.2%和268.6%.

Well-aerated dryland soils are net atmospheric CH4 sinks,which play a significant role in decreasing atmospheric CH4 concentration.Two drylands reclaimed from freshwater marsh were selected in the Sanjiang Plain,northeast China.One dryland was reclaimed in 1987 and the other in 1993（hereinafter referred to as 87D and 93D,respectively）.The cropping system of both drylands was soybean-fallow.Methane fluxes were monitored in the field with static opaque chamber method/gas chromatography（GC） during the growing seasons in 2003 and 2004.The results showed that there was no remarkable difference in CH4 emissions between these two drylands.But there was significantly inter-annual variance in CH4 emissions from both drylands,which was mostly controlled by the inter-annual changes of precipitation.87D acted as a CH4 source and emitted 0.68 kg/ha CH4 from the soil to the atmosphere in the growing season of 2003.However,it became a CH4 sink and took up 1.29 kg/ha CH4 from the atmosphere in the growing season of 2004.93D dryland always acted as a CH4 sink and took up 0.57 and 1.07 kg/ha CH4 in the growing seasons of 2003 and 2004,respectively.Inter-annual differences in precipitation were mainly responsible for this inter-annual variation in CH4 flux from drylands.Soil water content was the dominant factor controlling CH4 flux from drylands.In this study,CH4 oxidation rate was negatively correlated with soil water content.Additionally,soybean plants also significantly influenced the oxidation of CH4.They enhanced CH4 uptake about 2.0 and 2.7 times compared with the plots without plants during the growing season of 2004 in 93D and 87D drylands,respectively.