不同类型河滨湿地甲烷和二氧化碳排放初步研究

Methane and Carbon Dioxide Emissions from Different Types of Riparian Wetland

湿地生态系统在全球碳循环中起着重要作用。湿地在低氧环境中促进碳累积的同时产出温室气体--甲烷（CH4）和二氧化碳（CO2），湿地的碳源和碳汇功能近来成为全球气候变化研究关注的重点问题。对于保护和修复湿地等生态工程措施与湿地温室气体排放量之间的关系还不明确。运用了静态箱-气相色谱法，对Olentangy河湿地研究中心的4种不同类型河滨湿地（人工种植人工湿地、自然演替人工湿地、半人工湿地和自然湿地）甲烷（CH4）和二氧化碳（CO2）排放时空规律进行了研究，探讨了湿地土壤温度、水文条件等环境因子对 CH4、CO2排放的影响。结果表明，不同类型河滨湿地的 CH4和CO2排放量具有显著的时空异质性，甲烷排放速率（中值）为：自然湿地（CH4-C 0.33-85.7 mg·m-2·h-1）〉人工湿地（CH4-C 0.02-20.5 mg·m-2·h-1）〉半人工湿地（CH4-C -0.04-0.09 mg·m-2·h-1）。CO2排放通量的中值（平均值）分别为9.8（19.2）、13.5（20.6）、24.7（36.0）和33.7（40.3）CO2-C mg·m-2·h-1。在湿地1、湿地2和河道边湿地中的CH4排放量与土壤温度显著性相关，相关系数分别为0.88、0.86和0.85；湿地1、湿地2和牛轭湖湿地CO2通量与土壤温度相关性显著，相关系数分别为0.63、0.54和0.67。土壤含水率与甲烷排放量具有一定的相关性；与二氧化碳排放通量具有显著负相关性。土壤碳含量与其相应的CH4和CO2排放量之间关联度都较高。在同一区域淡水河滨湿地中，自然湿地的CH4和CO2排放通量均大于恢复湿地，CH4和CO2排放的空间异质性是由于洪水冲击频率、土壤状况、地下水位及净初级生产力等因素决定的。

Wetlands are important ecosystems involved in global carbon cycle. Wetlands are both producers and consumers of the greenhouse gases. Controlling methane （CH4） and carbon dioxide （CO2） emissions from temperate zone wetlands created and restored for habitat replacement and water quality improvement is important. A field research by the method of static chamber-gas chromatography was conducted on the spatiotemporal pattern of methane （CH4） and carbon dioxide （CO2） from four riparian wetlands （planted and naturally colonizing experimental freshwater marshes, a river division oxbow, and the edge of a river） in the Wilma H. Schiermeier Olentangy River Wetland Research Park in Columbus, Ohio, USA, with the effects of soil temperature, hydrological condition on CH4 and CO2 emission approached. At ORWRP, CH4and CO2 emissions varied remarkably in both temporal and spatial terms. The range of median value methane emissions： riverside （CH4-C 0.33-85.7 mg·m-2·h-1） 〉 wetland 1 and wetland 2 （CH4-C 0.02-20.5 mg·m-2·h-1） 〉 oxbow （CH4-C -0.04-0.09 mg·m-2·h-1）; The median （average） values of CO2 emission rates for wetland 1, wetland 2, oxbow and riverside were 9.8（19.2）, 13.5（20.6）, 24.7 （36.0） and 33.7（40.3） mg CO2-C·m-2·h-1 respectively. Soil temperature had a significant relationship with CH4 emissions in wetland 1 （r2=0.88）, wetland 2 （r2=0.86） and riverside （r2=0.85）, while the relationship was not significant between CH4 emissions and soil temperature in oxbow site. Soil temperature had a significant relationship with CO2 emissions in wetland 1（r2=0.63）, wetland 2 （r2=0.54） and oxbow （r2=0.67） as well. There was a negative relationship between CO2 emissions and soil water content in different types of wetlands （r2=0.72）. Nature wetlands have the higher CH4and CO2 emission rates than created wetlands in river riparian zone here. Overall, our results showed that the edge of a river in a bottomland hardwood forest had the much higher CH4 and CO2 emissions than did created river diversion marshes. The spatial variation of the different types of riverine wetlands is caused by a combination of flood frequency, sediment organic carbon content, groundwater fluxes, and wetland productivity.