The interrelation of carbon and water balance in beech-dominated forests - from leaf level water use efficiency to stand and area scale assessments

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The interactions between the carbon (C) balance and the water relations in beech and competing vegetation as affected by climate and climate-related environmental conditions are assessed. Spanning this characterisation from the leaf level to the area scale we will combine (a) natural abundance stable isotope analysis and modelling, (b) water and C flux analysis and (c) a tree hydrodynamic model supplemented with a carbon transport module. On the leaf level we focus on the effects of mesophyll conductance and its importance for water use efficiency strategies on the one hand and its effects on isotope fractionation models on the other hand. On the plant level we will assess C and water transport and metabolite fluxes applying stable isotope tracers. The tree hydrodynamic model developed in the research group FOR 788 will be coupled to a phloem flow and C transport model and isotope fractionation modules will be incorporated. For upscaling the physiological information encoded in tree rings to the ecosystem and area scale we will combine isotopic landscape (isoscape) approaches with oxygen and C stable isotope modelling. The experimental and model-based assessments of the water and C balance and of competitive interactions on the leaf, tree and landscape level will be closely related and coupled to the mechanistic stand modelling approach MoBiLE developed by the 2nd project of this application bundle.