鄱阳湖南矶湿地净生态系统CO2交换量的日变化特征

摘要

利用涡度相关技术分未淹水期和淹水期对2015年4月—2016年10月鄱阳湖南矶湿地净生态系统CO2交换量(net ecosystem CO2 exchange,NEE)进行观测,分析其日变化特征和影响因子.结果表明:在未淹水期,湿地NEE日变化呈现"U"型分布特征,日间最大CO2吸收量为18.24μmol·m-2·s-1,夜间最大CO2释放量为24.92μmol·m-2·s-1.在淹水期,除较高洲滩及湖岸高地外,植被被水面覆盖,湿地NEE日变化无明显特征,日间最大CO2吸收量为2.29μmol·m-2·s-1,夜间最大CO2释放量为12.66μmol·m-2·s-1.相关分析和主成分分析表明在未淹水期南矶湿地日间NEE月平均日变化与光量子通量密度相关性最高,与气温、降水、土壤含水量和土壤温度的相关性次之,夜间NEE月平均日变化与气温、土壤温度和土壤含水量相关性较高.在淹水期,南矶湿地日间NEE月平均日变化与光量子通量密度、土壤含水量有关,夜间变化与土壤温度、土壤含水量和气温有关.%With the aid of the eddy covariance technique, monitoring was carried out of net ecosystem CO2 exchange ( NEE) of the Nanji Wetland National Nature Reserve, sitting in the south of Poyang Lake, for analysis of diurnal variation of NEE and its affecting factors, during non-flooding and flooding periods of April, 2015-October, 2016. Results show that during the non-flooding period, diurnal variation of NEE exhibited a typical "U" shaped curve. In the day, CO2 up-take peaked up to 18. 24 μmol·m-2 ·s-1 , while at the night CO2 release did up to 24. 92 μmol·m-2 ·s-1 . During the flooding period, the vegetation in the area was submerged by water, except for the parts in shoals and high lands around the lake. Diurnal variation of NEE in this period didn′t have any distinct characteristics, and was much narrower in ampli-tude than that in the non-flooding period. In daytime, CO2 uptake peaked up to 2. 29μmol·m-2 ·s-1 while at night CO2 release did up to 12. 66μmol·m-2 ·s-1 . Correlation analysis and principal component analysis show that during the non-flooding period, monthly mean daily NEE variation in daytime was the most closely related to photosynthetic photon quanta flux density, and then to air temperature, precipitation, soil moisture content and soil temperature, whereas at night, it was closely related to air temperature, soil temperature and soil moisture content. During the flooding period, monthly mean daily NEE variation in daytime was related to photosynthetic photon quanta flux density and soil moisture content, whereas at night, it was related to soil temperature, soil moisture content and air temperature.