Supervisor: Sonja VOSPERNIK

Project assigned to: Anita ZOLLES

Climate scenarios for Europe predict a rise in temperature for the medium and extreme greenhouse gas emission scenarios in the range of 1-4.5 °Celsius for RCP4.5 and 2.5-5.5 C for RCP8.5 (Jacob et al. 2014). The increase in temperatures in Europe will be particularly pronounced in the South and the temperature increase is associated with shifts in precipitation patterns. Models predict a decrease in precipitation in Southern Europe and an increase in Central and Northern Europe (Jacob et al. 2014). As a result of climate change, drought is expected to increase in Europe. Drought is a stochastic natural hazard that is instigated by a temporal shortage of precipitation (Wilhite 2000), and varies in intensity and duration.

Extreme events, such as the length and frequency of drought episodes, are thought to have the greatest long-term impact on forest ecosystems (Overpeck et al., 1990; Lombardero et al., 2000; Hanson and Weltzin,2000) leading to irreversible negative effects such as lower productivity, increased pest vulnerability, and higher subsequent mortality (Bréda et al., 2006; Ciais et al., 2005; Zweifel et al., 2021; Scharnweber et al.,2020; Zhang et al., 2021) and consequently compromising the important role of forests as natural carbon dioxide sinks. Tree growth is a crucial indicator of tree health and hence the ability to store carbon. Growth dynamics and the underlying physiological mechanisms are highly complex since they depend on local meteorology, hydrology, geology, and forest management.

Understanding and explaining tree growth is essential for optimizing carbon partitioning and climate adaption in forest ecosystems. Furthermore, the identification of key parameters for growth dynamics is crucial for the design of future monitoring programmes. A major focus of the presented research will be on drought events as they can become a major threat for forest ecosystems. Tree growth might not only be altered by lacking water availability in the current growing period but moreover might also be influenced by drought spells that occurred already before the start of the present growing season (carrying over effects). To take this into account long- and short-term effects of drought need to be analysed.

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