Image 3_Sensitivity of transpiration to influencing factors at varying drought levels in Schima superba.jpeg
Introduction<p>Uneven rainfall distribution alters tree water use patterns, ultimately influencing plantation establishment.</p>Methods<p>Based on monthly rainfall, six drought levels were classified. Whole-tree sap flux and meteorological variables were monitored across these leve...
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2025
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| Summary: | Introduction<p>Uneven rainfall distribution alters tree water use patterns, ultimately influencing plantation establishment.</p>Methods<p>Based on monthly rainfall, six drought levels were classified. Whole-tree sap flux and meteorological variables were monitored across these levels from 2010 to 2013 in a pure Schima superba plantation in South China. The relationships between daily transpiration (T<sub>t</sub>) and the influencing factors were modeled using the Support vector regression (SVR) method. Shapley additive explanations (SHAP) values were employed to characterize the sensitivity and contributions of four environmental variables to T<sub>t</sub>.</p>Results<p>The results indicate that monthly rainfall (RF<sub>t</sub>) significantly influences the sensitivity of these four environmental variables to T<sub>t</sub> when RF<sub>t</sub> exceeds 300 mm (Level 6). Furthermore, when RF<sub>t</sub> is 300 mm or less (Levels 1–5), the sensitivity of these factors and their total contributions to T<sub>t</sub> are independent of tree size.</p>Discussion<p>Our findings indicate that the decoupling between T<sub>t</sub> and environmental factors may be a significant characteristic of ongoing water stress during high rainfall months. Additionally, these findings enhance the predictive capability of machine learning models in assessing tree water use.</p> |
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