Influence of plant water relation on ecosystem function and quantification of soil water fluxes for nutrient and carbon budgets

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The goal of this research is to understand the role of biodiversity for water relations within grassland communities established in the Jena Experiment by the DFG Research Group. In particular we want to investigate if biodiversity contributes to efficient soil water use, and hence higher ecosystem productivity. Furthermore, we will study the capability of a given plant community to gain access to water, when water becomes limiting in summer. We hypothesize that the occurrence of deep rooted plants is higher in diverse communities than in less diverse ones, and that in diverse communities the use of deeper water resources will alleviate water stress. Furthermore the results concerning vertical water flow will be useful for the calculation of nutrient and carbon budgets.To test our hypothesis we propose to calculate transpiration and water uptake profiles from soil moisture data in high spatial and temporal resolution. With the cost of equipment for the soil moisture measurements and the data load in mind, we will only instrument selected plots and a limited diversity gradient (2, 4, 16 species). The measurements will be combined with inverse hydrological modelling, a setup that is dedicated particularly for quantification of subsurface fluxes and transpiration at the Jena Experiment.This project will contribute to understanding the role of biodiversity on efficiency of water use and resource partitioning. In particular, this project sheds light on the question, what are the driving factors for the perceived increase in transpiration with increase in biodiversity.