Satellite-Observed Hydrothermal Conditions Control the Effects of Soil and Atmospheric Drought on Peak Vegetation Growth on the Tibetan Plateau  
[PERSON]  
1 School of Traffic & Transportation Engineering, Changsha University of Science & Technology, Changsha 410114, China; [EMAIL_ADDRESS] (Z.Q. ); [EMAIL_ADDRESS] (L.T. ); [EMAIL_ADDRESS] (Y.Z. ); [EMAIL_ADDRESS] (J.T. ); [EMAIL_ADDRESS] (S.X)  
[PERSON]  
1 School of Traffic & Transportation Engineering, Changsha University of Science & Technology, Changsha 410114, China; [EMAIL_ADDRESS] (Z.Q. ); [EMAIL_ADDRESS] (L.T. ); [EMAIL_ADDRESS] (Y.Z. ); [EMAIL_ADDRESS] (J.T. ); [EMAIL_ADDRESS] (S.X)  
[PERSON]  
2 The Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 1001101, China [EMAIL_ADDRESS]. peak vegetation growth also being perceived globally [12], which has significantly changed the carbon-water cycles within terrestrial ecosystems [16; 17]. Research has demonstrated that climatic factors such as precipitation, temperature, and radiation dominate peak vegetation growth [18; 19; 20; 21; 22]. Furthermore, CO\({}_{2}\) and nitrogen deposition are crucial in controlling peak vegetation growth [12]. Ongoing global warming is leading to increasingly frequent and prolonged drought events, placing significant stress on ecosystems and potentially resulting in severe ecological imbalances, which profoundly affect vegetation growth [23; 24; 25; 26; 27; 28]. Existing research has shown that the sensitivity of phenology to drought has significantly increased in recent decades. Under future climate change scenarios, drought is expected to become more severe and frequent, exacerbating its impact on vegetation [29; 30]. Insufficient soil moisture (SM) and elevated atmospheric water requirements, characterized by vapor pressure deficit (VPD), are recognized as the two major factors contributing to drought stress in plants [31]. Soil drought can occur when soil moisture (SM) is insufficient. SM typically refers to the soil humidity or soil water content, which is one of the key factors determining plant growth and hydrological processes. Vapor pressure deficit (VPD) describes the difference between the moisture content in the air and the potential evaporation, characterizing the degree of air dryness, which is crucial for plant transpiration and water exchange. The effects of moisture stress may be exacerbated in the context of ongoing climate warming, complicating our understanding of how the coupling of SM and VPD influences vegetation [32]. Several studies have demonstrated the importance of SM in mediating the exchange of water, energy, and carbon between soil and vegetation, thus influencing the growth conditions of plants [31; 33]. However, other research has indicated that VPD, instead of SM, dominates the efficiency of the ecosystem production at more flux sites and on a greater scale globally [34]. For example, [PERSON] et al. [35] revealed the important role of VPD in terrestrial ecosystems and indicated that increasing VPD would threaten high-latitude ecosystems in the context of continuing global warming. The relative roles of SM and VPD in influencing ecosystem productivity remain highly controversial. Recent studies have indicated that SM is the primary moisture constraint on the productivity of terrestrial vegetation ecosystems in most regions of China, with the rate of increase in SM's impact on vegetation productivity outpacing that of VPD [36]. Conversely, other researchers have found that VPD exerts a greater influence on the productivity of terrestrial ecosystems in China than SM, suggesting that VPD has a stronger and more widespread effect on the trends and variability in ecosystem productivity in the region [37].