崇明东滩芦苇湿地温室气体排放通量及其影响因素

通过静态箱-气相色谱法对崇明东滩芦苇群落在生长周期内的3种温室气体——CH₄、N₂O和CO₂的排放、吸收特征进行研究. 结果表明:芦苇群落湿地CH₄排放通量受温度影响较大,夏季排放通量明显高于其他季节,年均排放通量为74.46μg/(m2·h)；N₂O年均排放通量为2.22μg/(m2·h),冬季排放通量最大；CO₂的吸收率季节变化明显,年均排放通量为-101.93mg/(m2·h). 温度、芦苇植株光合作用及呼吸作用是影响CH₄产生和排放的主要因素；而沉积物氮素不足和限制,则是促使芦苇群落表现出对N₂O吸收的原因；芦苇的光合作用及土壤呼吸作用随温度和季节的变化是控制芦苇湿地CO₂的排放和吸收的主要因素. 芦苇植株发达的通气组织是CH₄和N₂O由大气向沉积物扩散的通道,同时分子扩散过程也是沉积物产生的CH₄、N₂O和CO₂扩散到大气中的途径和方式. 

Greenhouse Gases Fluxes at Chongming Dongtan Phragmites australis Wetland and the Influencing Factors

Methane(CH₄), nitrous oxide(N₂O)and carbon dioxide(CO₂)are primary greenhouse gases, many recent studies indicate that wetland is one of the major atmospheric greenhouse gases sources in the world. In order to understand the mechanisms and factors that influence greenhouse gases production in and emission from reed(Phragmites australis)wetland during its growth cycle, static closed chamber combined with a gas chromatograph technique was used to investigate the flues of three greenhouse gases(CH₄, N₂O and CO₂)at a Phragmites australis wetland in Chongming Dongtan. The results showed that the flux of CH_4was greatly influenced by temperature, which the fluxes were significantly higher in summer than in other seasons. Annual average flux of CH_4is 74.46μg/(m2·h). The maximum flux of N₂O is in winter and the annual average flux of N₂O is 2.22μg/(m2·h). There is obviously seasonal change in CO_2absorption with the annual average flux as -101.93mg/(m2·h). The production and emission of CH_4were also affected by the photosynthesis and respiration of Phragmites australis, while the Phragmites australis communities showed consumption of N₂O because of the shortage and limitation of nitrogen in sediment. The emission and consumption of CO_2were mainly controlled by the photosynthesis of Phragmites australis and the soil respiration which was influenced by temperature seasonal change. The developed aerenchyma of Phragmites australis provides a channel which makes CH_4and N₂O diffuse from atmosphere to sediments, meanwhile molecular diffusion process is also a way and methods that makes CH₄, N₂O and CO_2diffuse form sediments to atmosphere.