Abstract
Biodiversity conservation is currently one of the greatest challenges of the Anthropocene. Negative impacts on biodiversity are prevalent worldwide. Currently, land use change, impacts of human management, and increasingly climatic changes are considered major causes of biodiversity loss in all ecosystems. Maintaining high levels of biodiversity is a difficult but critical goal to preserve ecosystem functioning in all habitats. Grasslands are among the most negatively affected habitats. In particular, small and spatially as well as genetically isolated grassland communities are at risk of complete habitat conversion and extinction of highly specialized species, such as the inner-alpine dry grasslands. However, the sparse past environmental information available makes it difficult to assess the extent of conversion of these plant communities precisely. This thesis aims at unraveling the key environmental factors (such as land use, human management, and climate) that have caused community and species changes to gain insights into the future potential for conservation of dry grasslands in the inner-alpine dry valley of Val Venosta (autonomous province of Bolzano, South Tyrol, IT). By developing a mixed machine learning approach to classify historical (more than 70 years ago) and recent land cover, the influence of land use on the extent of inner-alpine dry grasslands was assessed. The increasingly fragmented grassland areas that today offer only little core area were further assessed by re-sampling historical relevés surveyed by J. Braun-Blanquet in the first half of the 20th century to quantify direct changes at community and species level. To estimate future conservation potential, the patterns of change in species composition were related to the respective environmental conditions, differentiating between protected and non-protected areas. Results show that dry grassland sites have changed markedly over time regardless of their current protection status. While the presence of shrubs has increased significantly on non-grazed sites, the effects of eutrophication are visible on sites that are largely surrounded by intensive agriculture (i.e. apple monocultures). Species composition has shifted toward less specialized species that tolerate elevated nutrient levels. Although climate has changed since the historical survey, the current species composition does not yet reflect this pattern. Further, differences in functional traits of species were assessed between three regions featuring the same habitat type: Aosta Valley, Tuscany and the Marches (IT). The differences in plant functional traits again indicate a significant influence of local environmental factors that determine diversity and variation in plant functional traits. This shows that plant species within their community have a certain adaptive capacity of functional traits to environmental conditions. Overall, this work significantly contributes to the understanding of the environmental pressures on dry grasslands, especially in the context of the II effectiveness of current conservation efforts on protected sites. Current management approaches need to be adapted to ensure the conservation of dry grassland habitats in the long-term. In this context, transdisciplinary approaches that raise the awareness about the importance of these humanshaped dry grasslands across sectors could be a key element for their long-term conservation.