Human forest modification is among the largest global drivers of terrestrial degradation of biodiversity, species interactions, and ecosystem functioning. One of the most pertinent components, forest fragmentation, has a long history in ecological research across the globe, particularly in lower latitudes. However, we still know little how fragmentation shapes temperate ecosystems, irrespective of the ancient status quo of European deforestation. Furthermore, its interaction with another pivotal component of European forests, silvicultural management, are practically unexplored. Hence, answering the question how anthropogenic modification of temperate forests affects fundamental components of forest ecosystems is essential basic research that has been neglected thus far. Most basal ecosystem elements are plants and their insect herbivores, as they form the energetic basis of the tropic pyramid. Furthermore, their respective biodiversity, functional traits, and the networks of interactions they establish are key for a multitude of ecosystem functions, not least ecosystem stability. Hence, the thesis at hand aimed to disentangle this complex system of interdependencies of human impacts, biodiversity, species traits and inter-species interactions. The first step lay in understanding how woody plant assemblages are shaped by human forest modification. For this purpose, field investigations in 57 plots in the hyperfragmented cultural landscape of the Northern Palatinate highlands (SW Germany) were conducted, censusing > 4,000 tree/shrub individuals from 34 species. Use of novel, integrative indices for different types of land-use allowed an accurate quantification of biotic responses. Intriguingly, woody tree/shrub communities reacted strikingly positive to forest fragmentation, with increases in alpha and beta diversity, as well as proliferation of heat/drought/light adapted pioneer species. Contrarily, managed interior forests were homogenized/constrained in biodiversity, with dominance of shade/cold adapted commercial tree species. Comparisons with recently unmanaged stands (> 40 a) revealed first indications for nascent conversion to oldgrowth conditions, with larger variability in light conditions and subsequent community composition. Reactions to microclimatic conditions, the relationship between associated species traits and the corresponding species pool, as well as facilitative/constraining effects by foresters were discussed as underlying mechanisms. Reactions of herbivore assemblages to forest fragmentation and the subsequent changes in host plant communities were assessed by comprehensive sampling of > 1,000 live herbivores from 134 species in the forest understory. Diversity was – similarly to plant communities - higher in fragmentation affected habitats, particularly in edges of continuous control forests. Furthermore, average trophic specialization showed an identical pattern. Mechanistically, benefits from microclimatic conditions, host availability, as well as pronounced niche differentiation are deemed responsible. While communities were heterogeneous, with no segregation across habitats, (smallforest fragments, edges, and interior of control forests), vegetation diversity, herbivore diversity, as well as trophic specialization were identified to shape community composition. This probably reflected a gradient from generalistic/species poor vs. specialist/species rich herbivore assemblages. Insect studies conducted in forest systems are doomed to incompleteness without considering ‘the last biological frontier’, the tree canopies. To access their biodiversity, relationship to edge effects, and their conservational value, the arboricolous arthropod fauna of 24 beech (Fagus sylvatica) canopies was sampled via insecticidal knockdown (‘fogging’). This resulted in an exhaustive collection of > 46,000 specimens from 24 major taxonomic/functional groups. Abundance distributions were markedly negative exponential, indicating high abundance variability in tree crowns. Individuals of six pertinent orders were identified to species level, returning > 3,100 individuals from 175 species and 52 families. This high diversity did marginally differ across habitats, with slightly higher species richness in edge canopies. However, communities in edge crowns were noticeably more heterogeneous than those in the forest interior, possibly due to higher variability in environmental edge conditions. In total, 49 species with protective value were identified, of which only one showed habitat preferences (for near-natural interior forests). Among them, six species (all beetles, Coleoptera) were classified as ‘priority species’ for conservation efforts. Hence, beech canopies of the Northern Palatinate highlands can be considered strongholds of insect biodiversity, incorporating many species of particular protective value. The intricacy of plant-herbivore interaction networks and their relationship to forest fragmentation is largely unexplored, particularly in Central Europe. Illumination of this matter is all the more important, as ecological networks are highly relevant for ecosystem stability, particularly in the face of additional anthropogenic disturbances, such as climate change. Hence, plant-herbivore interaction networks (PHNs) were constructed from woody plants and their associated herbivores, sampled alive in the understory. Herbivory verification was achieved using no-choice-feeding assays, as well as literature references. In total, networks across small forest fragments, edges, and the forest interior consisted of 696 interactions. Network complexity and trophic niche redundancy were compared across habitats using a rarefaction-like resampling procedure. PHNs in fragmentation affected forest habitats were significantly more complex, as well as more redundant in their realized niches, despite being composed of relatively more specialist species. Furthermore, network robustness to climate change was quantified utilizing four different scenarios for climate change susceptibility of involved plants. In this procedure, remaining herbivores in the network were measured upon successive loss of their host plant species. Consistently, PHNs in edges (and to a smaller degree in small fragments) withstood primary extinction of plant species longer, making them more robust. This was attributed to the high prevalence of heat/drought-adapted species, as well as to beneficial effects of network topography (complexity and redundancy). Consequently, strong correlative relationships were found between realized niche redundancy and climate change robustness of PHNs. This was both the first time that biologically realistic extinctions (instead of e.g.random extinctions) were used to measure network robustness, and that topographical network parameters were identified as potential indicators for network robustness against climate change. In synthesis, in the light of global biotic degradation due to human forest modification, the necessity to differentiate must be claimed. Ecosystems react differently to anthropogenic disturbances, and it seems the particular features present in Central European forests (ancient deforestation, extensive management, and, most importantly, high richness in open-forest plant species) cause partly opposed patterns to other biomes. Lenient microclimates and diverse plant communities facilitate equally diverse herbivore assemblages, and hence complex and robust networks, opposed to the forest interior. Therefore, in the reality of extensively used cultural landscapes, fragmentation affected forest ecosystems, particularly forest edges, can be perceived as reservoir for biodiversity, and ecosystem functionality. Nevertheless, as practically all forest habitats considered in this thesis are under human cultivation, recommendations for ecological enhancement of all forest habitats are discussed.

Membrane proteins are generally soluble only in the presence of detergent micelles or other membrane-mimetic systems, which renders the determination of the protein’s molar mass or oligomeric state difficult. Moreover, the amount of bound detergent varies drastically among different proteins and detergents. However, the type of detergent and its concentration have a great influence on the protein’s structure, stability, and functionality and the success of structural and functional investigations and crystallographic trials. Size-exclusion chromatography, which is commonly used to determine the molar mass of water-soluble proteins, is not suitable for detergent-solubilised proteins because the protein–detergent complex has a different conformation and, thus, commonly exhibits a different migration behaviour than globular standard proteins. Thus, calibration curves obtained with standard proteins are not useful for membrane-protein analysis. However, the combination of size-exclusion chromatography with ultraviolet absorbance, static light scattering, and refractive index detection provides a tool to determine the molar mass of protein–detergent complexes in an absolute manner and allows for distinguishing the contributions of detergent and protein to the complex. The goal of this thesis was to refine the standard triple-detection size-exclusion chromatography measurement and data analysis procedure for challenging membrane-protein samples, non-standard detergents, and difficult solvents such as concentrated denaturant solutions that were thought to elude routine approaches. To this end, the influence of urea on the performance of the method beyond direct influences on detergents and proteins was investigated with the help of the water-soluble bovine serum albumin. On the basis of the obtained results, measurement and data analysis procedures were refined for different detergents and protein–detergent complexes comprising the membrane proteins OmpLA and Mistic from Escherichia coli and Bacillus subtilis, respectively. The investigations on mass and shape of different detergent micelles and the compositions of protein–detergent complexes in aqueous buffer and concentrated urea solutions showed that triple-detection size-exclusion chromatography provides valuable information about micelle masses and shapes under various conditions. Moreover, it is perfectly suited for the straightforward analysis of detergent-suspended proteins in terms of composition and oligomeric state not only under native but, more importantly, also under denaturing conditions.