## 5 Conclusions  
This study integrated multi-source remote sensing and meteorological observation data from 2000 to 2020, combined with the SPEI and improved CASA model, systematically analyzed the spatiotemporal response law of the Yellow River basin vegetation NPP to extreme drought events, and quantified the regulation effect of vegetation coverage change on the drought sensitivity of the ecosystem. Among the 101 drought events identified based on the 3D clustering algorithm, the high-intensity drought event with DI of more than 0.7 resulted in an average NPP loss of \(-23.2\) gC\(\cdot\)m\({}^{-2}\). However, the NPP reduction was significantly reduced to \(-9.03\) gC\(\cdot\)m\({}^{-2}\) through artificial irrigation regulation in the Hetao irrigation area. Large-scale afforestation projects were driving basin NDVI to a \(3.45\times 10^{-4}\) month\({}^{-1}\) rate of sustained growth, with a contribution rate of 78%, but the high-density vegetation soil moisture competition caused carbon-sink benefit attenuation. The core of TNSP in the central loess plateau \"Three North Shelterbelt\" presented significant exceptions, in which local carbon sink gain was realized through the mixed forest structure optimization, which revealed the vegetation configuration regulation can effectively alleviate the pressure of water competition. Drought amplifies the Suppressive Effect of Afforestation through stomatal conductance-photosynthesis coupling mechanisms, inducing additional NPP losses of 7.45-31.00 gC\(\cdot\)m\({}^{-2}\), yet the April-July 2008 event exhibited reversed suppression effects due to immature artificial communities during the 2000-2004 baseline period. Our work elucidates nonlinear inhibitory mechanisms of vegetation-climate interactions on carbon sequestration in semi-arid ecosystems, providing critical insights for optimizing ecological restoration strategies and climate-adaptive management in the Yellow River Basin.  
There are still two limitations in this study. First, the coupling mechanism of vegetation physiological processes and drought stress needs to be further analyzed, combined with in situ observation data. Second, the response threshold of ecosystem resilience to composite climate stress needs to be verified by long-term monitoring. Future research should focus on the spatial and temporal sustainability of ecological engineering benefits in the context of climate change to provide a scientific basis for ecological protection and high-quality development in the Yellow River Basin.  
Conceptualization, F.W., Z.Z. and M.D.; methodology, F.W.; software, F.W.; validation, F.W. and Z.Z.; formal analysis, F.W., data curation, F.W., Z.Z. and M.D.; writing--original draft preparation, Z.Z. and M.D.; writing--review and editing, Z.Z., M.D. and J.L.; visualization, F.W.; supervision, F.W., J.L. and Z.Z.; project administration, Z.Z., J.L. and X.C.; funding acquisition, J.L. and X.C. All authors have read and agreed to the published version of the manuscript.  
This study was funded by the National Natural Science Foundation of China (42371367, 42271354), the Key Research and Development Program of Jiangxi Province in China (20243 BBH81033), and the LIESMARS Special Research Funding.  
The original contributions presented in this study are included in the article. Further inquiries can be directed to the corresponding author.  
During the preparation of this manuscript, the authors used Deepseek for the purposes of enhancing article readability. The authors have reviewed and edited the output and take full responsibility for the content of this publication.  
The authors declare no conflicts of interest.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} NPP & Net Primary Productivity \\ CASA & Carnegie-Ames-Stanford Approach \\ STL & Seasonal-Trend Decomposition using Loess \\ SPEI & Standardized Precipitation Evapotranspiration Index \\ TNSP & Three-North Shelterbelt Forest Program \\ PAR & Photosynthetically Active Radiation \\ \end{tabular}