淡水沼泽湿地CO2、CH4和N2O排放通量年际变化及其对氮输入的响应

利用静态暗箱-气相色谱法自2002～2004年连续3a观测了三江平原淡水沼泽湿地CO₂、CH₄和N₂O 3种主要温室气体排放特征及外源氮素输入条件下温室气体通量的变化.结果表明,三江平原CO₂、CH₄和N₂O 3种主要温室气体排放具有明显的季节及年际变化规律.其中生态系统呼吸CO₂排放的最大值779.33～965.40 mg·(m·h)^-1]出现在7、8月份,CH4通量最大值19.19～30.52 mg·(m·h)^-1]出现在8月,N₂O通量最大值0.072～0.15 mg·(m·h)^-1]出现在5月和9月,3种温室气体通量最小值CO₂为2.36～18.73 mg·(m·h)^-1;CH₄为-0.35～0.59 mg·(m·h)^-1;N₂O为-0.032～-0.009 mg·(m·h)^-1大都出现在冬季,且冬季淡水沼泽湿地表现为N2O的吸收.对气候因子的分析发现,温度条件是影响淡水沼泽湿地温室气体排放通量季节性变化的主要因子,而降水和积水水位变化是影响其排放年际变化的关键因素,特别是降水对CH₄排放通量的影响较其它2种温室气体更显著,且冬季雪融水对夏季CH₄的排放起重要作用.CO₂和CH4排放与土壤温度(5cm)呈显著的指数相关关系,而N₂O排放通量与土壤温度和水深相关性不显著.氮输入促进了三江平原CO₂、CH₄和N₂O 3种主要温室气体的排放,与对照处理相比,其排放通量分别升高了34%,145%和110%.

Annual Dynamics of CO2, CH4, N2O Emissions from Freshwater Marshes and Affected by Nitrogen Fertilization

Annual dynamics of CO2, CH4, N2O emissions from freshwater marshes and affected by nitrogen fertilization were studied in situ in Sanjiang Plain of Northeast China from June 2002 to December 2004, using the static opaque chamber-GC techniques. The results showed that there was significant seasonal and annual variation in the CO2, CH4 and N2O emissions. The ecosystem emission of CO2 reached a maximum of 779.33- 965.40 mg x (mxh)(-1) in July and August, CH4 reached a maximum of 19.19-30.52 mg x (mxh)(-1) in August, N2O reached a maximum of 0.072-0.15 mgx (mxh)(-1) in May and September, respectively. While the minimum of the CO2, CH4, N2O emission was 2.36-18.73 mg x (mxh)(-1), - 0.35 - 0.59 mg x (mxh)(-1), - 0.032- 0.009 mg (mxh)(-1), respectively, which occurs in winter. The freshwater marsh was the sink of N2O in winter. Temperature was a primary factor, controlling greenhouse gas seasonal emissions in freshwater marshes; while the precipitation and floodwater depth were the dominating influencing factors, affecting the greenhouse gas annual variations. Especially, the influence of precipitation on CH4 emissions was more obvious, comparing with the CO2 and N20 emissions. And the summer higher CH4 emission was mainly induced by the ice and snow thawing water in winter. Respiration of the ecosystem and CH4 emission were exponentially dependent on soil temperature of 5cm depth, while the N2O emission was not related to the soil temperature and water depth. The greenhouse gas (CO2, CH4, N2O) emissions were significantly influenced by nitrogen fertilization in Sanjiang Plain. The CO2, CH4, N2O flux of fertilization increased 34% , 145% , 110% , respectively, comparing to the control treatment.