科尔沁沙丘-草甸梯级生态系统CO2,CH4和N2O通量特征

Characteristics of CO2, CH4 and N2O Fluxes in Horqin Dune-Meadow Cascade Ecosystem

为了明确科尔沁沙丘—草甸梯级生态系统中不同生态系统生育期内温室气体通量变化规律及其影响因素,采用静态箱—气相色谱法,于2017年5—10月对呈梯级分布的半流动沙丘、半固定沙丘、人工林地、农田(玉米)和草甸湿地CO2,CH4和N2O通量进行了原位观测,并同步测量取样点的土壤温度、土壤含水量、土壤总有机质含量、总磷含量和总氮含量。对温室气体通量及其影响因子之间进行了相关分析,结果表明:科尔沁沙丘—草甸梯级生态系统上温室气体通量均具有明显的季节性变化,温室气体通量受到土壤含水量和土壤温度的显著影响,二者共同作用促进了温室气体通量的吸收或排放。在干旱半干旱地区,土壤含水量显著影响着土壤温室气体通量对土壤温度的敏感性,土壤温室气体通量随着温度的增加而增大,同时土壤含水量超过田间持水率时,土壤温室气体通量又会随着土壤含水量的增大而降低,从而影响土壤温室气体通量对土壤温度的响应。CO2通量的温度敏感性(Q10)表现为:农田(4.18)>草甸湿地(2.87)>人工林地(2.51)>半固定沙丘(2.41)>半流动沙丘(2.36)。CO2排放峰值出现在水热条件较好的7月、8月,其中8月22日附近的排放峰值明显高于7月21日附近的排放峰值。3种温室气体通量均值呈现出梯级变化(换算为CO2):半流动沙丘[181.65 mg/(m2·h)]<半固定沙丘[242.16 mg/(m2·h)]<人工林地[348.33 mg/(m2·h)]<农田[405.72 mg/(m2·h)]<草甸湿地[(487.63 mg/(m2·h)]。试验区土壤总有机质含量、总磷含量也呈现出相同的梯级变化,生育期CO2通量与土壤中总有机质含量和总磷含量呈极显著正相关(p<0.01)。生育期内N2O通量的变异对土壤温度的响应更强烈。

In order to study the variation pattern of greenhouse gas fluxes and the influencing factors in different areas of Horqin sand dune-meadow cascade ecological belt,we used the static chamber-GC technique and conducted in situ observations of CO2,CH4 and N2 O fluxes in semi-mobile dunes,semi-fixed dunes,artificial forest land,farmland(maize)and meadows from May to October,2017,and simultaneously measured soil temperature,soil moisture,total carbon,total phosphorus and total nitrogen.Correlation analysis on greenhouse gas fluxes and the influencing factors showed that the greenhouse gas fluxes in the Horqin sand dune-meadow ecological belt had obvious seasonal changes,which was significantly affected by soil moisture and soil temperature.The combination of the two promoted the absorption or emission of greenhouse gas fluxes.In arid and semi-arid regions,the sensibility of soil greenhouse gas fluxes to soil temperature is highly dependent on soil moisture.The soil greenhouse gas fluxes increase with the increase of the temperature.When soil moisture exceeds the field water holding capacity,the soil greenhouse gas fluxes will decrease with the increase of soil moisture,which affects the response of the soil greenhouse gas fluxes to soil temperature.Temperature sensitivity of CO2(Q10)decreased in the order:farmland(4.18)>meadow(2.87)>artificial forest land(2.51)>semi-fixed sand dune(2.41)>semi-mobile dune(2.36).The peak of CO2 emission appeared in July and August when the hydrothermal condition was better,and the peak around August 22 was significantly higher than that around July 21.The average roll of three greenhouse gas fluxes(converted to CO2)increased in the order:semi-mobile dunes[181.65 mg/(m2·h)]<semi-fixed dunes[242.16 mg/(m2·h)]<artificial forest land[348.33 mg/(m2·h)]<farmland[405.72 mg/(m2·h)]<meadows(487.63 mg/(m2·h))Organic matter and total phosphorus of the soil in the test area also showed the same change.The CO2 flux in the growing season showed significantly positive correlation with organic matter and total phosphorus of the soil(p<0.01).Soil N2O flux is more responsive to soil temperature in the growing season.