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

本文采用了三种高度相互关联但独立的方法[a)木质部流量测量，b)稳定同位素分析/建模，c)水动力模型系统PLATHO/Expert-N]，在整个植物水平上评估树木和共生植被在不同时间尺度上的水分关系。利用液流传感器、叶片水平气体交换以及追踪潜在水源和木质部水分中的（18O）和(D)，将对植物内部的水流/运动和物种之间的分配进行建模和分析。评估不同翻代时间有机池的(18O, (D)和（13C），以表征气孔导度（gs）和蒸腾(T)对环境条件的响应。此外，同位素特征将用于预测gs和T应用面向过程的模型。基于模型系统Expert-N和植物功能结构生长模型PLATHO，建立了山毛榉的树木水动力模型。该模型将用于模拟土壤-植物-空气系统水分关系，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到生态系统尺度模型中。同位素方法和水动力学模型都将在三个实地地点进行校准和验证。将在其他地点进行两种独立方法之间的交叉验证。

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.