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Traditional farming landscapes typically support exceptional biodiversity. They evolved as tightly coupled social-ecological systems, in which traditional human land-use shaped highly heterogeneous landscapes. However, these landscapes are under severe threats of land-use change which potentially pose direct threats to biodiversity, in particular through land-use intensification and land abandonment. Navigating biodiversity conservation in such changing landscapes requires a thorough understanding of the drivers that maintain the social-ecological system. This dissertation aimed to identify system properties that facilitate biodiversity conservation in traditional farming landscape, focusing specifically on birds and large carnivores in the rapidly changing traditional farmland region of Southern Transylvania, Romania. In order to identify these properties, I first examined the effects of local and landscape scale land-use patterns on birds and large carnivores and how they may be affected by future land-use change (Chapters II-V). Second, to gauge the role of particular traditional land-use elements for biodiversity I focused on the conservation value of traditional wood pastures (Chapters VI-VIII). Third, I took a social-ecological systems approach to understand how links between the social and ecological parts of the system affect human-bear coexistence (Chapters IV and IX). Bird diversity was supported by the broad gradients of woody vegetation cover and compositional heterogeneity. Land-use intensification, and hence the loss of woody vegetation cover and homogenization of land covers, would thus negatively affect biodiversity. This was especially evident from predictions on the distribution of the corncrake (Crex crex) in response to potential future land cover homogenization. Here, a moderate reduction of land cover diversity could drastically reduce the extent of corncrake habitat. Further results showed that the brown bear (Ursus arctos) would mainly be affected by land-use change through the fragmentation of large forest blocks, especially if land-use change would reduce habitat connectivity to the presumed source population in the Carpathian Mountains. Moreover, this dissertation revealed that large carnivores (brown bear and wolf, Canis lupus) may have important and often ignored roles in structuring the ecosystem of traditional farming landscapes by limiting herbivores. Wood pastures were found to have a high conservation value. The combination of low-intensity used grasslands with old scattered trees provided important supplementary habitat for different forest species such as woodpeckers and the brown bear. Worryingly, current management of wood pastures differed from traditional techniques in several aspects, which may threaten their persistence in the landscape. The majority of people had a positive perception on human-bear coexistence. The use of traditional sheep herding techniques combined with the tolerance of some shepherds to occasional livestock predation facilitated coexistence in a region where both carnivores and livestock are present. More generally, the genuine links between people and their environment were important drivers of people´s positive views on coexistence. However, perceived failures of top-down managing institutions could potentially erode these links and reduce people´s tolerance towards bears. Through the consideration of two different animal taxa, this dissertation revealed six important system properties facilitating biodiversity conservation in traditional farming landscapes. Similar proportions of the main land-use types (arable land, grassland, and forests) support species richness at the regional scale possible through habitat connectivity and continuous spill-over between land-use types. Heterogeneous landscapes can further support biodiversity through complementation and supplementation of habitat at the landscape scale. Gradients of woody vegetation cover and heterogeneity, supported biodiversity at both local and landscape scales possibly through the provision of a wide range of resources. The heterogeneous character of the landscape is tightly linked to traditional land-use practices, which also maintain specific traditional land-use elements and facilitate human-carnivore coexistence. Top-down limitation of large carnivores on herbivores possibly enhances vegetation growth and tree regeneration. The genuine links between humans and nature support human-bear coexistence, and these links may form the core of people´s values and sustainable use of natural resources.
The dissertation deals with the impact of nitrogen deposition on the functioning of heathland ecosystems. Special interests were the displacement of heather (Calluna vulgaris) by the purple moor-grass (Molinia caerulea) as well as the fate of nitrogen loads in dry heathland ecosystems. The results of the studies undertaken in the field and in the greenhouse are presented as five individual journal articles. The nature of nutrient limitation was studied by means of fertilisation experiments with nitrogen (N) and phosphorus for heather and purple moor-grass (Articles I and II). The impact of nitrogen deposition on the outcome of competition between these two species was analysed during a competition experiment in the greenhouse (Article III). The aim of a 15N tracer experiment was to determine the fate of nitrogen deposition as well as allocation patterns (Article IV). In addition, the response of purple moor-grass to the combined effects of nitrogen deposition and summer droughts was investigated in a second greenhouse experiment (Article V). The fertilisation experiments showed that the growth of heather as well as of purple moor-grass is predominantly limited by N (Articles I and II). However, the results of the competition experiment demonstrated that only purple moor-grass has the ability to benefit from additional N loads, which in turn gives the grass the opportunity to displace heather (Article III). Drought treatment resulted in strikingly reduced biomass production of purple moor-grass in N-fertilised pots, mainly as a result of dying aboveground biomass during dry periods (Article V). This striking susceptibility of purple moor-grass to the combination of nitrogen deposition and drought must be taken into account, when predicting future developments of dry heathlands. The results of the 15N tracer experiment showed that the investigated heath is still in an early stage of N saturation, as indicated by a high immobilisation capacity and negligible leaching losses of 15N (Article IV). The findings of the dissertation contribute to a better understanding of the processes underlying the encroachment of purple moor-grass in dry heathlands and can enhance heathland management. The results can also be used to to evaluate the current and future status of this ecosystem particularly with regard to the various stages of N saturation as well as in the determination of “Critical Loads”.