胡杨林净生态系统CO_2交换特征

Diurnal and seasonal variations in net ecosystem CO_2 exchange of a desert riparian Populus Euphratica forest

文中使用2014年生长季两个胡杨林通量观测样地的数据,分析了黑河下游荒漠河岸胡杨林净生态系统CO_2交换(F_(NEE))的变化特征、影响因素以及冠层内CO_2储存通量(F_S)对F_(NEE)的贡献。结果表明:(1)2014年生长季总的F_(NEE)为-198.85g·C·m^(-2),5-10月F_(NEE)分别为-24.45,-46.10,-60.48,-50.70,-34.30和17.18g·C·m^(-2)·mon^(-1)。日最小F_(NEE)为-2.97g·C·m^(-2)·d^(-1),日最大F_(NEE)为1.69g·C·m^(-2)·d^(-1)。(2)各月F_(NEE)的日变化过程明显不同,白天吸收和夜间释放CO_2的强度随生长过程而变化,7月F_(NEE)的日变化幅度最大。(3)各月冠层内CO_2储存通量(FS)的日变化过程基本一致且季节变化不明显,半小时尺度上FS对F_(NEE)的影响较大,然而在月、季节尺度上FS对F_(NEE)的贡献太小,可以忽略不计。(4)F_(NEE)主要受光合有效辐射(PAR)和叶面积指数(LAI)的影响:日尺度上F_(NEE)与PAR在0.01的显著性水平上呈显著负相关关系,月尺度上F_(NEE)的值随着LAI的增大(降低)而降低(增大)。

The sound and steady progress of the Populus Euphratica forest is not only conductive to prevent the further desertification, but also can help to maintain ecological security of Ejina oasis. So far, the process and change characteristics of the net ecosystem CO2 exchange are still unknown and the amount of carbon assimilation and release need to be quantified. Thus, the characteristics of net ecosystem CO2 exchange in the P. euphratica forest was analyzed in this study. And the data was derived from two eddy covariance flux observation sites in the P. euphratica forest in 2014. Accordingly, some conclusions were given as follows. （1） In the growing season, from May to October the monthly FNEE were 24.45, -46.10, - 60.48, - 50.70, - 34.30 and 17.18g · C ·m -2 · mon^-1 , respectively. The total value of FNEE was - 198. 858 · C · m in the whole growing season. （2） The diurnal course of FNEE was obviously different at monthly level. The amount of earbon assimilation in daytime and carbon release in night varied as the P. euphratica growing. The highest uptake in the midday （10：00 - 15：00） and release in night of CO2 were occurred in July. （3） The diurnal course of Fs was similar in differ- ent months, whereas the contribution of Fs to FNEE was significant. However, the ratio of Fs to FNEE was less than 3.2% in month and the contribution of Fs to FNEE could be neglected under monthly or seasonal scale. （4） Pho- tosynthetic Active Radiation（PAR） and Leaf Area Index （LAI） were the main drivers in variation of net ecosystem exchange at daily or monthly scale.