A plant hydraulic scheme (PHS) integrated into Noah-MP improves the simulation of hydrological processes, yet its impacts on key variables remain unclear. This study employs a global sensitivity analysis method (the Sobol’ indices) to identify the key parameters in the PHS scheme that affecting evapotranspiration (ET), soil moisture (SMC), gross primary productivity (GPP), and water flux absorbed by the plant roots (Qroot). By combining model simulations, stations measurements and satellite data, this study conducts a systematic analysis of the sensitivity of each parameter to various variables and evaluates the spatial variability of the sensitivity. Additionally, the influence of three climate-related factors—aridity index, precipitation, and vapor pressure deficit—on the regional sensitivity pattern of parameters was investigated. The results indicate that the Sobol’ indices of individual parameters show noticeable differences depending on the data source. Overall, (leaf turgor loss water potential) and (xylem saturated water conductivity) exert a significant influence on ET and GPP, while the simulation of SMC and Qroot is jointly affected by multiple parameters, with (root distribution parameter) and (stem volume specific water capacitance) taking the leading roles, respectively. Although the dominant parameters vary across regions, their sensitivity indices show no strong correlation with the three climate factors examined. Furthermore, the model’s simulation accuracy was validated against observation data from both stations and satellite. The evaluation indicates that ET, GPP, and Qroot are simulated with relatively high accuracy, although the performance declines in arid regions. In contrast, the simulation accuracy of SMC exhibits greater spatial variability and performs worse in areas with dense vegetation cover. The findings suggest that identifying region-specific sensitive parameters can provide valuable guidance for model parameter optimization. Targeted parameter optimization or the integration of new schemes can significantly enhance the simulation of specific variables.
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