荒漠灌丛碳通量对极端水分和温度的响应研究

Assessing impacts of extreme water and temperature conditions on carbon fluxes in two desert shrublands

利用位于中国北方半干旱区的两个观测站(陕西榆林站和内蒙古通辽站)的碳通量及气象数据,获得荒漠灌丛生态系统碳通量的季节动态特征,并定量估算环境因子的极端状况对该生态系统各碳通量的影响。结果表明:(1)榆林站2011—2012年和通辽站2015年的净碳交换量(NEE)分别为-132.8 gC/m^2/yr和-59.6 gC/m^2/yr,表明榆林站碳汇功能更明显;(2)极端水分状况对NEE的影响大于极端温度状况的影响。以生长季平均而言(4—10月),水分和温度的极端状况对榆林站(和通辽站)的NEE的影响最大值分别为0.51 gC/m^2/s(0.26 gC/m^2/s)和0.17 gC/m^2/s(0.20 gC/m^2/s);(3)生长旺盛期(6—8月),高温(榆林站>27℃;通辽站>29℃)状况会抑制植被的光合作用能力,导致榆林站和通辽站的总初级生产量(GPP)相较于正常温度状况分别减少0.37 gC/m^2/s和0.53 gC/m^2/s。

We study the seasonal patterns of carbon fluxes in two desert shrublands of North China, Yulin Station in Shaanxi Province and Tongliao Station in Inner Mongolia Autonomous Region, using the eddy covariance technique, and qualitatively estimate the impact of extreme temperature and water conditions on carbon fluxes. Our findings show that （1） during 2011-2012, the total net ecosystem exchange （NEE） of Yulin and Tongliao were -132.8 and -59.6 gC/m2/yr respectively, indicating that the shrub ecosystem carbon fixation capacity in Yulin was obvious. （2） Extreme water and temperature conditions have significant effects on carbon fluxes, especially extreme water conditions. On an average over the growing period （April-October）, the differences of NEE relative to normal conditions at Yulin and Tongliao are 0.51 and 0.26 gC/m2/s in the extreme water condition and 0.17 and 0.20 gC/m2/s in the extreme temperature condition, respectively. （3） In the peak growing period （July-August）, the extreme high temperature （above 27 ~C at Yulin and above 29 ~C at Tongliao） effectively inhibits vegetation photosynthesis, decreasing gross primary production （GPP） by 0.37 and 0.53 gC/m2/s respectively, relative to the normal temperature condition.