不同干扰强度下三江平原湿地土壤温室气体排放对冻融作用的响应

Response of Greenhouse Gas Emission to Freeze-Thaw with Different Disturbance Intensity of the Sanjiang Plain Wetland

为评估季节性冻融作用对不同干扰强度湿地温室气体产生机制的影响,采用静态箱/气相色谱法,原位观测三江平原洪河国家自然保护区内未受干扰的常年积水的小叶章湿地(undisturbed Deyeuxia angustifolia wetland,UDAW)、保护区外受人类活动干扰导致湿地含水量减少的季节性积水的小叶章湿地(disturbed Deyeuxia angustifolia wetland,DDAW)以及由小叶章湿地开垦10年以上的水稻田(rice paddy,RP)的温室气体排放通量,分析季节性冻融作用对3种湿地温室气体排放的影响特征.结果表明:3种湿地在冻融期均有CO2和CH4排放,且在春季冻融初期CO2和CH4均出现短期的高排放现象,随着冻融温度升高,温室气体排放通量均逐渐增加.其中,CO2排放通量表现为UDAW>DDAW>RP,CH4排放通量却表现为DDAW>RP>UDAW;DDAW的CH4排放速率与冻融温度的相关性最高(P<0.01,R2=0.647 5),UDAW中二者的相关性最低(P<0.01,R2=0.424 7).相关性分析显示,DDAW和RP土壤中CO2与CH4的排放通量均呈正相关(P均小于0.01,R2分别为0.749 1、0.574 4),而UDAW土壤中CO2与CH4的排放通量表现为弱相关(P<0.05,R2=0.303 8),可见冻融温度会影响CO2和CH4的排放通量.季节性冻融作用影响了3种湿地土壤N2O的排放通量,秋季冻融期UDAW和DDAW表现为N2O的汇,而在春季冻融期3种湿地均表现为N2O的源,表明不同干扰湿地N2O的排放通量对冻融作用的响应不同,但均随土壤温度的升高其排放通量不断增加.研究显示,三江平原的冻融作用降低了湿地温室气体排放,干扰强度越大,冻融作用影响越小,且秋季冻融作用大于春季.

This study aims to evaluate the effects of seasonal freeze-thaw on greenhouse gas emission mechanisms and determine the control factors for different interference intensities of the wetlands in the Sanjiang Plain of Northeast China. Static chamber technique and gas chromatography were used to study greenhouse gas fluxes of undisturbed Deyeuxia angustifolia wetlands (UDAW) in Honghe National Nature Reserve,disturbed D. angustifolia wetland (DDAW) and rice paddy reclaimed by D. angustifolia wetland (RP) outside the Honghe National Nature Reserve in the Sanjiang Plain. The results revealed that CO2 and CH4 emissions occurred during the freezing period in the three wetlands. Further,CO2 and CH4 emissions were high during a short period of time in the early stage of thawing. The greenhouse gas emission flux was positively correlated with temperature in the three wetlands. The CO2 emission flux showed UDAW >DDAW > RP. The CH4 emission rate showed DDAW > RP > UDAW. The CH4 emission rate of DDAW had the highest correlation with temperature (P< 0. 01,R2= 0. 6475). Meanwhile,the lowest correlation occurred in UDAW (P < 0. 01,R2= 0. 4247). Correlation analysis showed that DDAW and RP were significantly correlated with the emission flux of CO2 and CH4 (P<0. 01,R2= 0. 7491 and R2=0. 5744). However,the correlation between UDAW results and the release of CO2 and CH4 was weak (P < 0. 05,R2= 0. 3038). This indicated that temperature affected the emission flux of CO2 and CH4. In addition,seasonal freeze-thaw affected the release of N2O in different wetlands. UDAW and DDAW served as sinks of N2O during the freezing period. The three wetlands acted as the sources of N2O during the thawing period,indicating that the emission flux of N2O had different responses to freeze-thaw wetlands with different interference intensities. However,the emission flux increased with increasing soil temperature. The results showed that the freeze-thaw effect reduced greenhouse gas emissions in the wetlands: the greater the interference intensity,the less significant the influence of freezethaw. The freeze-thaw effect was more obvious in autumn than in spring.