AbstractsBiology & Animal Science

During climate change rising mean air temperatures will be accompanied by climatic extremes such as drought. The frequency and magnitude of those extreme weather events are expected to increase in the future. Additionally, climatic extremes may have stronger effects on plants than a gradual temperature shift. Therefore, investigations of plant response to extreme weather events are needed to understand ecological and economic implications better. Apart from the consequences of climate change for plants, this thesis also asks the question: Can we simulate global warming reliably with our available warming techniques? In particular, the work in hand is intended to give answers to four research questions in this context (corresponding to four manuscripts). 1. How reliable are our experimental evidences and techniques (passive warming versus warming by transplantation) (manuscript 1)? 2. Is the leaf palatability of Quercus pubescens influenced by warming and drought (manuscript 2)? 3. Does drought response of Fagus sylvatica differ between central and marginal provenances (manuscript 3)? 4. Does stress response of plant communities and species (heath and grassland) differ if drought reoccurs (manuscript 4)? Concerning the first of the above stated research questions, the comparison of the two warming techniques "passive warming" and "warming by transplantation" revealed that the reliability of the experimental results and therefore the resulting predictions for future plant response depend on the chosen technique. Experimental passive warming techniques are complicated in execution and should consider further parameters besides temperature increases such as: evapotranspiration, photosynthetically active radiation, and wind speed in order to improve the knowledge of warming technique effects (manuscript 1). The climatic manipulations "warming" and "drought" were simulated in the EVENT 3 experiment to investigate their impact on the leaf palatability of Quercus pubescens of four European provenances from Germany, Bulgaria, Hungary, and Italy (second research question). This was done in a palatability experiment using the leaf consumption of the forest pest Lymantria dispar (gypsy moth) as response parameter (manuscript 2). Surprisingly, "warming" and "drought" did not effect the leaf palatability. However, leaf palatability was negatively correlated with an increasing density of trichomes (i.e. leaf hairs) and Bulgarian leaves were preferred compared to Hungarian and Italian oak leaves. This study suggests that the attractiveness of the four tested European Q. pubescens provenances might be stable in a changing climate at least as far as L. dispar is concerned. Regarding the third research question, beech seedlings originating from three marginal (Bulgaria, Spain, and Poland) and three central (Germany) Fagus sylvatica provenances out of its geographic range were exposed to drought in two different soil types (sand, loam) (manuscript 3). Drought had a negative impact on all tree growth parameters,…