Yu Guirui, Song Xia, Wang Qiufeng, Liu Yunfen, Guan Dexin, Yan Junhua, Sun Xiaomin, Zhang Leiming, Wen Xuefa
Synthesis Research Center of Chinese Ecosystem Research Network, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China.
New Phytol. 2008;177(4):927-937. doi: 10.1111/j.1469-8137.2007.02316.x. Epub 2007 Dec 6.
Carbon (C) and water cycles of terrestrial ecosystems are two coupled ecological processes controlled partly by stomatal behavior. Water-use efficiency (WUE) reflects the coupling relationship to some extent. At stand and ecosystem levels, the variability of WUE results from the trade-off between water loss and C gain in the process of plant photosynthetic C assimilation. Continuous observations of C, water, and energy fluxes were made at three selected forest sites of ChinaFLUX with eddy covariance systems from 2003 to 2005. WUE at different temporal scales were defined and calculated with different C and water flux components. Variations in WUE were found among three sites. Average annual WUE was 9.43 mg CO(2) g(-1) H(2)O at Changbaishan temperate broad-leaved Korean pine mixed forest, 9.27 mg CO(2) g(-1) H(2)O at Qianyanzhou subtropical coniferous plantation, and 6.90 mg CO(2) g(-1) H(2)O at Dinghushan subtropical evergreen broad-leaved forest. It was also found that temperate and subtropical forest ecosystems had different relationships between gross primary productivity (GPP) and evapotranspiration (ET). Variations in WUE indicated the difference in the coupling between C and water cycles. The asynchronous response of GPP and ET to climatic variables determined the coupling and decoupling between C and water cycles for the two regional forest ecosystems.
陆地生态系统的碳（C）循环和水循环是两个相互耦合的生态过程，部分受气孔行为控制。水分利用效率（WUE）在一定程度上反映了这种耦合关系。在林分和生态系统水平上，WUE的变异性源于植物光合碳同化过程中水分损失和碳获取之间的权衡。2003年至2005年，利用涡度相关系统在中国通量的三个选定森林站点对碳、水和能量通量进行了连续观测。利用不同的碳和水通量分量定义并计算了不同时间尺度下的WUE。发现三个站点的WUE存在差异。长白山温带阔叶红松混交林的年平均WUE为9.43毫克二氧化碳/克水，千烟洲亚热带针叶人工林为9.27毫克二氧化碳/克水，鼎湖山亚热带常绿阔叶林为6.90毫克二氧化碳/克水。还发现温带和亚热带森林生态系统在总初级生产力（GPP）和蒸散量（ET）之间存在不同的关系。WUE的变化表明了碳循环和水循环耦合的差异。GPP和ET对气候变量的异步响应决定了两个区域森林生态系统碳循环和水循环之间的耦合和解耦。
