油蒿灌木荒漠光能利用效率季节动态研究

Seasonal dynamics of light-use efficiency in Artemisia ordosica shrubby desert

【目的】光能利用效率(LUE)是表征植被通过光合作用将所吸收的能量转化为有机干物质效率的指标,也是估算生态系统生产力的重要参数,为了提高油蒿灌木荒漠生产力的估算和预测精度,本文研究了油蒿灌木荒漠LUE的季节动态以及环境因子对其的调节机制。【方法】本研究于2014年5—10月通过涡度协方差法观测了宁夏盐池典型油蒿灌木荒漠生态系统的净碳交换、光合有效辐射、温度和水分等因子,分析油蒿灌木荒漠生态系统LUE的昼夜和季节变化及与其主要环境因子的关系。【结果】在日尺度上,LUE在14:00时达到最低值(0.000 8~0.002 4μmol/μmol)。LUE的日变化主要受到冠层导度(gs)和光合有效辐射的影响。在季节尺度上,LUE从5月份开始迅速升高,9月份达到最大值(0.002 5 g/MJ),而后逐渐降低。LUE月平均值介于0.000 9~0.002 5 g/MJ之间。LUE的季节变化主要受土壤氮含量(Nsoil)、冠层导度(gs)和光合有效辐射(PAR)的影响。【结论】通过以上研究,发现在季节尺度上,通过增加土壤中的氮含量可以促进生态系统总生产力(GEP),从而增大油蒿灌木荒漠的光能利用效率。研究结果可以为提高半干旱区油蒿灌木荒漠生态系统生产力提供一定的理论指导,也为区域植被恢复重建提供重要参考。

[Objective]Light-use efficiency(LUE)is a key parameter to evaluation the ecosystem productivity,which shows the efficiency of vegetation photosynthesis transforming absorbed energy into organic dry matter.In order to improve the ecosystem productivity estimation and prediction accuracy of Artemisia ordosica shrubby desert,this paper studied the seasonal dynamics of LUE and the regulation mechanism of environmental factors for Artemisia ordosica shrubby desert.[Method]We used eddy covariance measurements in growing season(from May to October)in 2014 to analyze the net carbon exchange,photosynthetically active radiation,temperature,and moisture dynamics and the relationship between influential factors and light-use efficiency at different temporal resolutions of Artemisia ordosica shrubby desert in northern China.[Result]At diurnal scale,LUE showed a significant trough trend,reaching the lowest(0.000 8-0.002 4μmol/μmol)at 14:00.Canopy conductance(gs)and photosynthetically active radiation were the main factors in affecting LUE at diurnal scale.At the seasonal scale,LUE began to rise rapidly in May and reached its peak(0.002 5 g/MJ)in September,then gradually decreased.The monthly average of LUE was between 0.000 9 and 0.002 5 g/MJ.Soil N content,canopy conductance and photosynthetically active radiation were the most factors in regularizing LUE at seasonal scale.[Conclusion]The light-use efficiency for Artemisia ordosica shrubby desert has obvious diurnal and seasonal dynamics.At seasonal scale,increasing soil N content can promote the ecosystem primary productivity(GEP),so as to increase LUE.The results can improve the accuracy of ecosystem productivity model and provide an important reference for the sustainable management of the desert ecosystem and the restoration of the sandy area.