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Aim: Species distribution models (SDMs) are commonly used to determine threats to biodiversity and opportunities under climate change. Despite SDMs being based on the assumption of complete knowledge of the climate space of the modelled species, truncated occurrence datasets (and hence truncated climate spaces) such as national inventories are often employed. This may lead to prediction errors, which have been proposed to stem from: (1) the degree of climate space truncation and/or (2) instability of the modelling algorithms. Our aim was to explore the potential causes of prediction errors in SDMs using truncated training datasets. Location: Europe 11° W–32° E, 34°–72° N. Methods: SDMs employing commonly used bioclimatic variables were applied to seven forest tree species. We created two model training datasets covering: (1) Germany only (significantly truncated climate space) and (2) Europe (minimally truncated climate space). Differences between the climate space represented by Germany‐only and European data were measured on two‐dimensional climate spaces obtained through principal component analysis of the bioclimatic variables. Seven SDM algorithms were run, and the stability of the response function and variable selection for each species and model type were analysed. Results: The degree of climate space truncation was less important for model performance than the instability of model algorithms and indiscriminate variable selection. The latter led to irrelevant relationships of species occurrence with bioclimatic variables. These instabilities caused pronounced prediction errors. Main conclusions: Our results strongly suggest that erroneous model predictions stem from instability and ecological irrelevance of the statistical functions relating the probability of a species' occurrence to bioclimatic variables, compounded by a lack of consistency in variable selection. Models displaying these characteristics showed lower overall performance when trained with truncated datasets. Further, commonly used ensemble approaches do not compensate for the shortfalls of individual models. Detailed model‐by‐model and species‐by‐species analysis of response functions and variable importance is recommended.

Conservation of biodiversity and sustainable resource use are central aims within ecology. This thesis focuses on the current data and environmental frameworks used to support these aims across different states in Europe. In particular, it examines the impact of geo-political boundaries on data-use, funding and planning for temporal movement of species in response to climate change. It also examines the current environmental framework agreements in Europe and their capacity to deal with trans-boundary aspects of biodiversity change. Through examination of European biodiversity datasets, undertaking species distribution modelling of forest taxa, examining economic data, palaeo-ecological data, and assessing international environmental framework agreements, this thesis identifies a number of important knowledge gaps. Probably unsurprisingly, the distribution of biodiversity in Europe mostly does not match political entities, all of which have individual aims, financial resources, and biodiversity management regimes in place. All have a significant impact on biodiversity conservation planning because i) the use of geo-politically truncated data influences modelling predictions, ii) financial commitment to biodiversity conservation varies between countries influencing success outcomes, iii) biodiversity persistence in current and future climate change does not recognise geo-political boundaries, and iv) many of the key environmental frameworks are implemented within countries and do not considering trans-boundary issues. Overall these findings significantly improve the understanding of conservation and resource management in Europe and fill a number of important knowledge gaps. They highlight the importance of appropriate trans-boundary ecological datasets and the need for more consistency across Europe in financial resources for biodiversity conservation. They also highlight the need for appreciation of areas of high-persistent biodiversity regardless of geo-political boundaries and environmental framework agreements that support cross-border conservation measures.

We present an overlapping generations model with two families who can guarantee old age support either by intra-family transfers from child to parent or via a tax-financed public pension system encompassing both families.We derive the individually and family-specific optimal decisions and present some more behavioristic hypotheses.Our experimental observations allow conclusions on (1) whether raising taxes crowds out voluntary transfers, (2) how income distributions influence family and public solidarity, and (3) whether participants prefer more to less public solidarity.

The adsorption ofkrypton, xenon and Krl-xXex-mixtures on Pt(111) and the system Al/Au(111) were studied with temperaturevariable scanning-tunneling-microscopy(STM). It is possible to detect the unoccupied xenon 6s- and 6p5d-states with STM via measuring the imaged height of the xenon islands as a function of bias. At negative tip bias upto U$_{T} \geq$ -5.5V the xenon islands are imaged with a constant height of 2.26$\mathring{A}$. With changing the bias to -5.5V $\geq$ U$_{T}$ $\geq$ -9V strong variations in the imaged height appear, that show a clear correlation on the xenon unoccupied state-levels. The results are explained in terms of resonant tunneling. The investigation of the monolayer krypton reveal beside the from TEAS-measurements well-known hexagonal R30° - and R0° -phase surprisingly a quadratic phase, which is interpreted to be an intermediar phase between the two hexagonal phases. Kr$_{1-x}$ Xe$_{x}$-mixtures adsorbed on Pt(111) were investigated as a function of molarfraction $\chi$ and sample-temperature T. After successive adsorption of the components at T = 17K krypton and xenon are separated because the mixing is kinetically hindered. Following annaeling to T = 27K leads to a mixing of the components. The mixing process is performed by a diffusion of xenon into krypton and not vice versa. At T = 36K a complete mixture is reached, which corresponds to a structure with small xe-rich and kr-rich islands. Further annaeling only leads to an increasing island size. The deposition of aluminum on Au(111) leads to a surfacealloy by replacing goldatoms by aluminum-atoms. Therefore, after aluminum-deposition gold-islands grow on the surface. The surprising solubility of aluminum in gold is attributed to the possibility of aluminum to reduce the surface stress of the Au(111)-surface because of its high electron-density. The incorporation of aluminum atoms into the Au(111)-surface involves a change and finally the disappearance of the Au(111)reconstruction. When the maximal solubility of the aluminum-atoms is reached, pure aluminum-islands start to grow.