Water Relations of Beech and Interacting Vegetation in Beech-Dominated Forests

三种既相互联系又相互独立的方法[a)木质部流量测量，b)稳定同位素分析/模拟，c)水动力模型系统PLATHO/Expert-N]被用于在整个植物水平上在不同的时间尺度上评估树木和共生植被的水分关系。将使用树液流量传感器、叶片水平气体交换和示踪(18O和(D))对植物内的水流/运动和物种间的分配进行建模和额外分析。(18O，(D)和(13C)在不同周转时间的有机库中将被评估，以表征气孔导度(GS)和蒸腾作用(T)对环境条件的响应。此外，同位素特征将被用于应用面向过程的模型来预测GS和T。在模型系统Expert-N和功能结构植物生长模型PLATHO的基础上，建立了山毛榉树木水动力模型。该模型将用于模拟土壤-植物-空气系统的水分关系，包括菌根对土壤水分吸收的影响，并将作为树木水流子模型插入生态系统尺度模型。同位素方法和流体动力学模型都将通过三个现场的测量进行校准和验证。这两种独立办法之间的交叉验证将在更多地点进行。

Three highly interconnected though independent approaches [a) xylem flow measurements, b) stable isotope analysis/modelling, c) a hydrodynamic model system PLATHO/Expert-N] are applied for assessing water relations of trees and co-occurring vegetation on different time-scales on a whole plant level. Water flow/movement within the plant and partitioning between species will be modelled and additionally analysed using sap flow sensors, leaf level gas exchange and by tracing (18O and (D in potential water sources and in xylem water. (18O, (D and (13C in organic pools with different turn over-times will be assessed to characterise responses of stomatal conductance (gs) and transpiration (T) to environmental conditions. In addition, isotopic signatures will be used to predict gs and T applying process-oriented models. Based on the model system Expert-N and the functional-structural plant growth model PLATHO a tree hydrodynamic model for beech will be developed. The model will be applied to simulate soil-plant-air system water relations including mycorrhiza effects on water uptake from soil and will be inserted as tree water flow sub-model to the ecosystem-scale model. Both, the isotopic approach and the hydrodynamic model will be calibrated and validated with measurements at the three field sites. Cross-validation between the two independent approaches will be carried out at additional sites.