## 5 Conclusions  
In this study, we used the latest version of Noah-MP to evaluate the impact of plant-water interactions on hydrological processes in the \(R\). _pseudocacia_ plantation located in the southern Chinese Loess Plateau. By introducing actual soil thickness and new subsurface and water table schemes, we evaluated the sensitivity of the leaf area index, soil water content, vertical root fraction to soil stratification schemes, and vertical carbon allocation determined by parameter \(a\). We then quantified plant-water interactions by comparing simulations with dynamic and static vegetation representations. Our sensitivity experiments underscored the critical role of soil stratification schemes in regulating soil water dynamics. Dividing the root zone uniformly into 0.1 m soil layers yielded the most realistic soil water content because of lower infiltration and higher surface  
Figure 12: Evapotranspiration, precipitation, and soil water storage within 2 m soil (**a**) during the growing season and (**b**) at the annual scale. \"\" means significance at 95% level. runoff. The soil water content and root fraction were particularly sensitive to vertical carbon allocation. As parameter \(a\) increased from 0.1 to 3.0, the root profiles transitioned from uniform to exponential distributions, leading to better agreement with observations. As a result, lower \(a\) values exhibited higher root water uptake from deeper soil layers (>2 m). Overall, the improved model enhanced the simulation accuracy of the soil water content and vertical root fraction. The dynamic experiment revealed a more realistic relationship between the leaf area index and transpiration. Plant-water interactions led to lower soil moisture in the root zone as deep roots extracted soil water to meet transpiration. Shallow root water uptake (<2 m) contributed 92% of the total transpiration, while deep water uptake (>2 m) accounted for 0.3-20.5% of the transpiration during the growing season, with higher contributions in dry years. The simulated transpiration and water uptake remained in a dynamic equilibrium, fluctuating around the long-term average, indicating that water availability did not limit vegetation growth between 1980 and 2020. The simulated evapotranspiration was significantly influenced by soil water storage within the upper 2 m during the growing season and at the annual scale. However, an insignificant relationship was found between precipitation and evapotranspiration. Excluding plant-water interactions led to unrealistically deep infiltration in the soil profile. In this case, rainfall infiltration could replenish soil moisture below 5 m, leading to an elevated soil water content, 3.9% higher evapotranspiration, and 18.0% greater transpiration compared to the dynamic experiment. These findings highlight the crucial role of plant-water interactions in regulating water availability for extensive plantation areas with deep-rooted vegetation across the Loess Plateau, particularly under changing environmental conditions. It is important to note that the conclusions drawn in this study are based on observations from a single site in the southern Loess Plateau, which may limit the spatial representativeness of the findings. Given the substantial heterogeneity in climate regimes, soil properties, and vegetation restoration practices across the Loess Plateau, further research is needed to assess the generalizability of the findings to broader areas. Comparative studies at multiple sites with varying environmental conditions would help to verify the robustness of the modeled plant-water interactions and support more region-wide ecological restoration strategies. Methodology, H.F.; formal analysis, H.F.; writing--original draft preparation, H.F.; writing--review and editing, J.J. and G.N. ; supervision, J.J. All authors have read and agreed to the published version of the manuscript. This research was funded by the State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, CAS, and the grant number is SKILLQG205.