Grassland Research Institute, Chinese Academy of Agricultural Sciences, Hohhot 010010, China.
Center for Global Change and Earth Observations, Michigan State University, East Lansing, MI 48823, USA.
Science. 2023 Aug 11;381(6658):672-677. doi: 10.1126/science.adf5041. Epub 2023 Aug 10.
The ratio of carbon assimilation to water evapotranspiration (ET) of an ecosystem, referred to as ecosystem water use efficiency (WUE), is widely expected to increase because of the rising atmospheric carbon dioxide concentration (). However, little is known about the interactive effects of rising and climate change on WUE. On the basis of upscaled estimates from machine learning methods and global FLUXNET observations, we show that global WUE has not risen since 2001 because of the asymmetric effects of an increased vapor pressure deficit (VPD), which depressed photosynthesis and enhanced ET. An undiminished ET trend indicates that rising temperature and VPD may play a more important role in regulating ET than declining stomatal conductance. Projected increases in VPD are predicted to affect the future coupling of the terrestrial carbon and water cycles.
由于大气中二氧化碳浓度（）的上升，生态系统碳同化与水蒸散发（ET）的比例（即生态系统水利用效率（WUE））有望普遍提高。然而，人们对上升的和气候变化对 WUE 的交互影响知之甚少。基于机器学习方法的扩展估计和全球通量网观测，我们表明，由于蒸散压亏缺（VPD）增加的非对称影响，全球 WUE 自 2001 年以来并未上升，因为 VPD 抑制了光合作用并增强了 ET。蒸腾趋势的持续表明，上升的温度和 VPD 可能比下降的气孔导度在调节 ET 方面发挥更重要的作用。预计 VPD 的增加将影响未来陆地碳和水循环的耦合。
