【摘要】 植被蒸腾（Tc）是水循环的重要组成部分。土壤水分（SM）和饱和水汽压差（VPD）是Tc的关键驱动因素，探讨其对Tc的影响有助于加深生态系统对气候变化响应机制的认识。然而有关VPD和SM对Tc变化的相对贡献尚不清楚，主要原因在于SM和VPD通过陆地—大气相互作用强烈耦合，阻碍了SM、VPD对Tc独立影响程度的量化。本文基于气象再分析资料、遥感土壤水分、蒸腾以及土地覆盖数据等多源数据，采用当前较为先进的“分箱解耦法”，分析2003—2018年中国亚热带植被蒸腾主导驱动力。通过对SM和VPD数据相关性解耦发现，研究区Tc随SM增加呈现出先上升后保持稳定的趋势，而随VPD增加Tc变化幅度较小；总体而言，SM对Tc变化的相对贡献更高，约为VPD对Tc相对贡献的5倍；不同植被类型Tc对SM和VPD的敏感性有所差异，尽管4种植被类型Tc对SM的敏感性均大于VPD的敏感性，但4种植被Tc对SM响应的阈值不同，其中森林（常绿阔叶林除外）的阈值最低（约为35%），短木植被的阈值最高（约为55%），表明不同植被生态对策的差异。此外，为验证结论的可信性，本文基于光合与蒸腾的强耦合关系，利用太阳诱导叶绿素荧光（SIF）指征Tc变化，经上述分析得到一致的结果。通过解耦SM-VPD对Tc的定量影响，本文进一步完善了气候变化生态水文效应的认知，为区域水循环模拟优化提供理论依据。更多还原

【Abstract】 Transpiration(Tc) is a critical component of the global water cycle. Soil moisture(SM) and vapor pressure deficit(VPD) are key regulators of Tc, and exploring their contributions to changes in Tc can deepen our understanding of the mechanisms of water cycling in terrestrial ecosystems. However, the driving roles of VPD and SM in Tc changes remain debated because of the coupling of SM and VPD through land-atmosphere interactions which restrict the quantification of the independent effects of SM and VPD on Tc. By decoupling the correlations between SM and VPD using a novel binning approach, this study analyzed the dominant drivers of vegetation transpiration in subtropical China from 2003 to 2018 based on multi-source data, including meteorological reanalysis, remotely sensed soil moisture, transpiration, and land cover data. The results show that Tc first increased and then remained stable with an increase in SM across the study area but changed slightly with increasing VPD. Overall, the relative contribution of SM to the change in Tc was approximately five times that of VPD. The sensitivities of Tc to SM and VPD differed among vegetation types. Although the sensitivity of Tc to SM was greater than that of VPD for all four vegetation types, the thresholds of Tc in response to SM were different, with the lowest threshold(approximately 35%) for the other forests and the highest threshold(approximately55%) for short wood vegetation. We infer that this is associated with the differences in ecological strategies. To verify the reliability of our conclusions, we used solar-induced chlorophyll fluorescence(SIF) data as a proxy for Tc based on the tight coupling between photosynthesis and transpiration. Consistent results were obtained by repeating the analyses.The results of this study, in which the impacts of SM and VPD on Tc were decoupled, are beneficial for further understanding the critical processes involved in water cycling in terrestrial ecosystems in response to climate change.更多还原