High Plant Diversity of Grasslands in a Landscape Context: A Comparison of Contrasting Regions in Central Europe

Some regions and habitats harbour high numbers of plant species at a fine scale. A remarkable example is the grasslands of the White Carpathian Mountains (Czech Republic), which holds world records in local species richness; however, the causes are still poorly understood. To explore the landscape context of this phenomenon and its relationships to diversity patterns at larger scales, we compared diversity patterns in grasslands and other vegetation types in the White Carpathians with those in nearby regions lacking extremely species-rich grasslands, using data from vegetation plots and flora grid mapping of entire landscapes. Although small-scale species richness of grasslands and ruderal/weed vegetation of the White Carpathians was higher than in the nearby regions, the number of grassland and ruderal/weed species in the regional flora of the White Carpathians was not. Diversity of forests was not higher in this region at any scale. Thus the remarkably high local species richness of the White Carpathian grasslands does not result from a larger grassland species pool in the region, but from the fine-scale co-occurrence of many grassland species in this landscape, which results in the formation of grassland communities that are locally rich but with similar species composition when comparing different sites (i.e. high alpha but low beta diversity). This pattern can be partly attributed to the large total area of these grasslands, which reduces random extinctions of rare species, low geological diversity, which enables many species to occur at many sites across the landscape, and high land-cover diversity, which supports mixing of species from different vegetation types.