The effects of management practices and environmental variables on the biodiversity of Nardus grasslands in the national park Hohe Tauern, Austria

Sammanfattning: Introduction. A large part of the biodiversity of the Alps is linked to an interaction between the natural environment and traditional land-use practices. This study focuses on the priority habitat type of species rich Nardus grasslands (Natura 2000 Code 6230'), which is endangered, but continues to thrive in extensively managed subalpine pastures. I will specifically be looking at pastures within Austria’s Defereggen valley, situated in the outer region of the Hohe Tauern National Park. Aims. The purpose of this study is to classify the field-mapped relevés of Nardus grasslands, discern patterns within these plant communities, and assess the impacts of both management practices and environmental factors on the diversity and conservation status of this habitat type. Ultimately, my goal was to pinpoint the necessary measures to enhance biodiversity levels. Methods. The methods employed in this study include several steps. Initially, remote sensing was utilized to identify potential study sites. Subsequently, field surveys were conducted following the hierarchical, syntaxonomic system of the Braun-Blanquet approach for vascular plants. During these surveys, data of various parameters was gathered including management variables such as land use intensity and yield, environmental variables such as altitude and slope, and the conservation status of the sites. Furthermore, on-site interviews with local shepherds were conducted to gain insight into the farming practices and the relationship between biodiversity and agriculture. Biodiversity assessment included the calculation of the Shannon-Wiener Index and the determination of the Ellenberg Indicator values for all study sites, which served as additional parameters for the statistical analysis. To classify Nardus grasslands, Twinspan analysis was employed, and identification was based in established literature, particularly the work by Mucina et al. (1993). To understand the factors influencing changes in species composition, all collected parameters were subjected to gradient analyses and ANOVA to identify the drivers responsible for these variations. Results. All Nardus grasslands in the region were classified as the Sieversio-Nardetum strictae association, according to Lüdi 1948. My research found significant correlations between Nardus grassland biodiversity and Ellenberg indicator values for soil pH as well as type of bedrock, with higher diversity in areas with elevated soil pH. This challenges the European Habitats Directive’s definition of ‘species-rich’ communities on siliceous substrates, suggesting that calcareous bedrock areas host greater plant diversity. The second significant correlation was found for the indicator value of nitrogen as well as land use intensity, indicating that the highest biodiversity occurs with moderately extensive to moderately intensive land management and moderate nutrients levels. Additionally, an analysis based on ecological characteristics and indicator species led to the classification of Nardus grasslands into five subgroups within the Sieversio-Nardetum strictae category. This subgroup analysis suggests that insufficient pasture use is the key factor contributing to lower Nardus grassland diversity. Discussion. To prevent degradation and restore the balance of Nardus grasslands, I recommend implementing a comprehensive management strategy. This study underscores that Nardus grasslands can be effectively maintained through consistent and early grazing as well as dividing pastures into subunits to enable controlled grazing, which reduces the growth of dwarf shrubs (e.g., Rhododendron ferrugineum), weed growth (e.g., Deschampsia cespitosa), and the encroachment of grasses (e.g., Nardus stricta). Notably, there is a growing interest among shepards and contemporary literature in utilizing small ruminants for grazing, which holds a promise for biodiversity conservation efforts.