季节性冻融期沼泽湿地CO2、CH4和N2O排放动态

三江平原季节性冻-融时间长达7～8个月,对沼泽湿地温室气体排放有重要影响.采用静态箱/气相色谱法研究了三江平原冻、融期沼泽湿地温室气体排放特征,表明三江平原不同类型沼泽湿地冬季都有明显的CH₄和CO₂排放,且冬季沼泽湿地CH₄排放量在全年CH₄排放中占有重要份额.融冻期沼泽湿地出现明显的CH₄和CO₂排放峰值,季节性积水沼泽化草甸CH₄和CO₂排放量大于常年积水沼泽湿地,而冬季常年积水沼泽湿地CH₄排放通量大于季节性积水沼泽化草甸.融冻期CO₂排放通量与土壤温度(5cm)呈指数相关关系(R²=0.912,p<0.001),沼泽湿地CO₂排放通量与CH₄通量间也呈显著正相关关系(R²=0.751,p<0.001).冬季三江平原沼泽湿地是N₂O的汇,融冻期随着土壤温度升高逐渐成为N₂O的源,且在5月份沼泽湿地表层土壤(0～20cm)融冻期间N₂O排放通量明显增大.三江平原土壤冻、融期间沼泽湿地温室气体的排放特征,反映了冬季微生物活性的存在及融冻作用对土壤碳矿化和氮硝化、反硝化作用有重要影响.

Dynamics of CO2,CH4 and N2O Emission Fluxes from Mires During Freezing and Thawing Season

In the Sanjiang Plain, the freezing and thawing phase have 7 - 8 months and play important role in the greenhouse gases emission. The characters of the greenhouse gases emission during freezing and thawing season in the Sanjiang Plain were studied, using the static chamber and gas chromatogram method. The results observed show that there were obvious CH4 and CO2 emissions in winter and the CH4 emission made a relatively large contribution to the total CH4 flux from the different type mires during the winter in the Sanjiang Plain. And there were significantly CH4 and CO2 emission peak values during thawing time. The CH4 and CO2 emissions fluxes from seasonal flooded mire were larger than that from continuously flooded mire during thawing time. On the contrary, the CH4 and CO2 emissions from continuously flooded mire were larger than that from seasonal flooded mire in winter. During thawing, there was exponential relationship between CO2 fluxes and the soil temperature (5cm) (R2 = 0.912, p< 0.001). Meanwhile, CO2 fluxes was obviously correlated with the CH4 emission fluxes (R2 = 0.751, p < 0.001). The mires are N2O sink in winter and gradually become N2O source, with increasing temperature during thawing time. The characters of the greenhouse gases emission, during freezing and thawing in the Sanjiang Plain respond to the microbial activity in winter and the effects of thawing on soil carbon mineralization, nitrification and denitrification.