Global plant transpiration (PT) is a crucial component of the Earth's hydrological cycle and plays a significant role in regulating the exchange of water and energy between the land surface and the atmosphere. However, the long-term trend and the underlying driver of global PT remain unclear due to the significant uncertainties in estimating PT on a global scale. This study uses two sub-Mixture Density Networks (MDN and MDN) to predict vegetation canopy resistance (r) and aerodynamic resistance (r), then the predicted r and r are imported into the Penman-Monteith-Leuning (PML) model to simulate PT. The observed PT at 112 SAPFLUXNET sites are used to validate the performance of hybrid MDN-PML model. The verified MDN-PML model is further applied to map the spatial distribution of global PT and reconstruct a long-term (1990–2020) global PT dataset. The results indicate that the long-term average global PT is 397.2 ± 63.1 mm. During the period 1990–2020, the global PT exhibit a significant upward trend (0.79 ± 0.28 mm/year ( < 0.05)), which equates to a 6.0% increase compared with the long-term average global PT. A widespread trend of elevated PT is observed in approximately 70% of the global land surface. The trend attribution analysis results show that the change in leaf area index (LAI) can explain 66.2% of the global PT trend, indicating that elevated LAI due to global greening is the dominant factor contributing to the upward trend in global PT. The elevated LAI can be largely attributed to the CO fertilization effect induced by elevated atmospheric CO concentration. Additional analysis reveals that the increased global PT is more sensitive to CO fertilization effect in high LAI areas than in low LAI areas. Projected climate scenarios indicate that global land surface PT will continue to rise from 2023 to 2100, and the rate of increase in the future will be higher than in historical periods. The rising rates of global PT under the three Representative Concentration Pathway scenarios (RCP) 2.6, RCP4.5, and RCP8.5 climate change scenarios are 0.86 mm/year, 1.16 mm/year, and 1.45 mm/year, respectively, during the period 2023–2100. Our results highlight the impact of global change and vegetation greening on the global PT and hydrological cycle. This study is of great significance for the scientific response to the challenges of climate change for regional water resource management.

中文翻译：

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全球绿化驱动植物蒸腾作用广泛增加

全球植物蒸腾作用（PT）是地球水文循环的重要组成部分，在调节陆地表面和大气之间的水和能量交换方面发挥着重要作用。然而，由于全球范围内的PT估算存在显着的不确定性，全球PT的长期趋势和潜在驱动因素仍不清楚。本研究使用两个子混合密度网络（MDN和MDN）来预测植被冠层阻力（r）和空气动力阻力（r），然后将预测的r和r导入Penman-Monteith-Leuning（PML）模型中进行模拟PT。在 112 个 SAPFLUXNET 站点观察到的 PT 用于验证混合 MDN-PML 模型的性能。验证后的MDN-PML模型进一步应用于绘制全球PT的空间分布图并重建长期（1990-2020年）全球PT数据集​​。结果表明，全球长期平均PT为397.2±63.1 mm。 1990-2020年期间，全球PT呈现显着上升趋势（0.79±0.28毫米/年（<0.05）），相当于全球长期平均PT的增长6.0%。在全球约 70% 的陆地表面观察到 PT 升高的普遍趋势。趋势归因分析结果表明，叶面积指数（LAI）的变化可以解释全球PT趋势的66.2%，表明全球绿化导致的LAI升高是全球PT上升趋势的主导因素。 LAI 升高主要归因于大气 CO 浓度升高引起的 CO 施肥效应。进一步的分析表明，高 LAI 地区比低 LAI 地区增加的全球 PT 对 CO 施肥效应更敏感。预测的气候情景表明，2023年至2100年全球陆地表面PT将持续上升，且未来的增长率将高于历史时期。三种代表性浓度路径情景（RCP）2.6、RCP4.5和RCP8.5气候变化情景下，全球PT上升速率分别为0.86毫米/年、1.16毫米/年和1.45毫米/年。 2023-2100 年期间。我们的结果强调了全球变化和植被绿化对全球水文温度和水文循环的影响。该研究对于区域水资源管理科学应对气候变化挑战具有重要意义。