Root water uptake (RWU), as an important process in the terrestrial water cycle, can help us to better understand the interactions in the soil–plant–atmosphere continuum. We conducted a field study monitoring soil moisture profiles in the rhizosphere of beech trees at two sites with different soil conditions. We present an algorithm to infer RWU from step-shaped, diurnal changes in soil moisture. While this approach is a feasible, easily implemented method for moderately moist and homogeneously textured soil conditions, limitations were identified during drier states and for more heterogeneous soil settings. A comparison with the time series of xylem sap velocity underlines that RWU and sap flow (SF) are complementary measures in the transpiration process. The high correlation between the SF time series of the two sites, but lower correlation between the RWU time series, suggests that soil characteristics affect RWU of the trees but not SF.

中文翻译：

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从土壤水分剖面动态估算树根吸水量

根吸收水（RWU）作为陆地水循环中的重要过程，可以帮助我们更好地了解土壤-植物-大气连续体中的相互作用。我们进行了实地研究，监测了两个土壤条件不同的山毛榉树根际土壤水分状况。我们提出了一种从土壤水分的阶梯状，昼夜变化推断RWU的算法。虽然这种方法对于中度潮湿和质地均质的土壤条件是一种可行且易于实施的方法，但在较干燥的状态和较不均一的土壤环境中仍存在局限性。与木质部树液速度时间序列的比较表明，RWU和树液流量（SF）是蒸腾过程中的补充措施。两个站点的SF时间序列之间的相关性很高，