Coupled soil-plant water dynamics - Environmental drivers and species effects

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The predicted climate and land-use changes could have dramatic effects on the water balance of the soil-vegetation system in particular under drought conditions. However, information is scarce on temporal and spatial dynamics of soil water in the rooted soil horizons, the dynamics of plant water acquisition and on transpiration from plant leaves that will allow characterizing the effects of the predicted changes. The central aim of the planned project is to quantitatively characterise the interaction between plant water use – as affected by rooting patterns and physiology of different plant functional groups – and the hydrological water balance of an ecosystem. A main emphasis will be put on the effects of droughts and rewetting on this interaction. We will focus on the morphological and physiological parameters and on functional adaptations of plants to changes in soil water supply and stand specific proprieties, which drive water uptake capacity and actual water uptake. The effect of plants and vegetation on preferential flow paths, soil water storage, hydraulic redistribution and water infiltration capacity is in the second focus of this project. Until present short-term spatial and temporal dynamics of soil water movement and plant water uptake have never been characterised continuously in high temporal resolution. Such high-resolution approaches are, however, a prerequisite for understanding the water balance in ecosystems subjected to drought-rewetting transitions. As a consequence a methodological focus of this project is the further development and application of new innovative techniques that allow the continuous tracing of isotope signatures in soil water and transpiration.