A resampling approach for evaluating effects of pasture abandonment on subalpine plant species diversity

The decline of species-rich semi-natural calcareous grasslands is a major conservation problem throughout Europe. Maintenance of traditional animal husbandry is often recommended as an important management strategy. However, results that underpin such management recommendations were derived predominantly from lowland studies and may not be easily applicable to high mountain areas. In this study we analyse the importance of traditional low-intensity summer farming (cattle grazing) for vascular plant species diversity of a subalpine region in the northern calcareous Alps in Austria by resampling from an existing dataset on its vegetation. Results indicate a significant long term decline of plant species diversity following abandonment at the landscape scale. In contrast, within-community effects of pasture abandonment on plant species diversity are equivocal and strongly depend on the plant community. We suppose these differences to be due to diet preferences of cattle as well as to the differential importance of competition for structuring the respective communities. From our results we infer that the main mechanism by which pasture abandonment affects vascular plant species diversity, at least during the first ca. 100 yr documented here, are not local-scale competitive exclusion processes within persisting communities. Instead, post-abandonment successional community displacements that cause a landscape scale homogenization of the vegetation cover seem to be primarily responsible for a decline of species diversity. We conclude, that successful management of vascular plant species diversity in subalpine regions of the Northeastern Calcareous Alps will depend on the maintenance of large scale pasture systems with a spatially variable disturbance regime.Nomenclature: Adler et al. (1994).Abbreviations: DEM == Digital Elevation Model; GIS == Geographical Information System; WET == Topographic Wetness Index; EROS == Topographic Erosion Index; GLM == Generalized Linear Model; S == Species Richness; H == Shannon Index of diversity; E == Evenness; CC == Number of plant communities; dC == Berger-Parker Index of community diversity.