河口湿地具备不同于其他生态系统的典型的生物化学特征.利用开路式涡度相关系统,对长江口崇西湿地净生态系统CO2交换(NEE)进行了初步研究.结果表明,生长季CO2交换呈V字型特征,平均CO2交换量为-0.06 mg/(m2·s);非生长季无明显特征,平均CO2交换量为0.025 mg/(m2·s).这与其他生态系统CO2交换特征相符合.主要是生长季的植被光合固碳作用所致.非生长季的净生态系统CO2交换比生长季受土壤温度的影响更大.大潮期和小潮期的CO2交换表明,无论是生长季还是非生长季,小潮期从生态系统释放到大气的CO2均高于大潮期,潮汐高度与CO2释放量呈负相关,暗示着高水位抑制生态系统呼吸和阻碍CO2的传输.从而减少了CO2的释放.通过分析大潮期和小潮期的植被净光合速率发现,同一地点的植被固碳过程受潮汐的影响不很明显.潮汐对净生态系统CO2交换的影响主要是减少了土壤呼吸释放CO2的过程.总体而言,崇西湿地在年周期内表现为CO2的汇.%Estuarine wetlands have unique biochemical characteristics different from other ecosystems. The net ecosystem exchange (NEE) of carbon dioxide was studied preliminarily by open-path eddy covariance at the Chongxi Wetland, Yangtze Estuary. The results showed that during the growing season, the NEE of carbon dioxide showed a distinct V-like diel course, with a mean emission rate of -0.06 mg/( m2·s). The NEE lacked a diurnal pattern, and it fluctuated above zero with an average emission rate of 0. 025 mg/(m2·s) during the non-growing season. It conformed to carbon exchange characteristics of other ecosystems mainly due to plant photosynthesis and carbon fixation in the growing season. The NEE in the non-growing season was more largely affected by soil temperature than that in the growing season. Carbon dioxide emissions from ecosystem to atmosphere during neap tides were higher than those during spring tides in both the growing and non-growing seasons, which indicated an inverse correlation between carbon dioxide emissions and tidal height, and that high water level inhibited ecosystem respiration and the transport of carbon dioxide and therefore further reduced carbon dioxide emission. The net photosynthetic rate of plants during the neap tides was similar with that during the spring tides, suggesting that the tide had little influence on plant photosynthesis and carbon fixation at the same site. The tide affected the net ecosystem exchange of carbon dioxide mainly by reducing carbon dioxide emissions from soil respiration. In summation, the Chongxi Wetland is a carbon sink in whole year period.
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