The Significance of Nitrogen Uptake and Metabolism by Beech Roots for the Competition for Nitrogen in the Rhizosphere

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This project is aimed (1) to quantify the uptake of inorganic and organic nitrogen sources by beech roots and to elucidate the competition between beech roots and soil microorganisms for these nitrogen sources, (2) to analyse the mechanisms of competition, and (3) to characterise their dependency on environmental factors, particularly on drought, in natural beech regeneration of nitrogen-limited, beech-dominated deciduous forests on calcarious soil. For this purpose, the physiological principles and patterns of competition between beech and soil microorganisms will be studied in experiments under field conditions and in the greenhouse. In the field, short-term and long-term consequences of differences in water availability will be analyzed in microcosms exchanged between a cool/moist (NE aspect) and a warm/dry (SW aspect) slope. Under controlled conditions, the significance of colonisation of beech roots with mycorrhizal fungi for the uptake of inorganic and organic nitrogen will be quantified at different levels of water availability and different temperatures. These studies include the determination of uptake rates and uptake kinetics of NH4+, NO3-, and amino compounds combined with N metabolite profiling in beech roots.