Beech forest resilience against drought and high-intensity rainfall in the Rosalia Forest

Climate change increases the frequency and severity of droughts and rainfall events in Austria. The drought-related soil water deficit and the change in rainfall patterns poses a risk for forests, leading to increased tree mortality and loss of ecosystem services. The complex interplay of climate change impacts on trees and the associated response of hydrological components such as precipitation, soil moisture, or runoff is difficult to entangle under temporally-varying, natural conditions. However, detailed knowledge of forest and water interactions are urgently needed in promoting tree-resistance against climate change. Here, we propose controlled manipulation experiments using rain-out shelters and sprinklers to simulate drought and heavy rainfall events in a highly-instrumented, long-term measurement network located in a beech stand of the mountainous Rosalia forest (Lower Austria). We will quantify the percentage of summer and winter precipitation that beech trees transpire, and fluxes of evaporation, transpiration, and groundwater recharge using stable water isotopes. To achieve this, soil and xylem samples will be taken and analysed in the laboratory, and the results of this analysis compared to in-situ high-resolution measurements of soil water and xylem water isotopes using liquid-vapor equilibrium techniques. Further, we will quantify hydrological components using water balance methods and fluorescence tracers. This project will result in estimates of changes in water fluxes under climate change using controlled manipulation experiments as repeated experiments. We will gain insights into forest hydrological changes of Austrian, mountainous beech trees, from which suggestions for forest managers for strategies to promote beech health threatened by increased droughts and heavy rainfalls can be derived.