Diversity change of mountain hay meadows in the Swiss Alps

We investigated changes in plant diversity in the traditionally fertilised and species-rich Golden Oat meadows by repeating historic grassland relevés from the 1940s in two agricultural areas in the Swiss Alps. The effects of time on alpha and beta diversity at plot level were analysed within the study areas. The specificity of the two study areas was investigated by comparing the variability of species composition within and between study areas.In both regions, species richness at plot level (alpha diversity) was found to be lower in the recent relevés than in the historic ones. However, the variability of species composition within the study areas (beta diversity) was higher between the recent relevés than between the historic relevés. There was a significant floristic differentiation between the two study areas sixty years ago but not today.Plant diversity in Golden Oat meadows has changed significantly during the last sixty years. The decrease in species richness at plot level was anticipated, but not the increase in beta diversity between plots, which may indicate individualised management regimes of modern farmers. The loss of specificity between the study areas revealed an important and as yet hardly considered further dimension of biodiversity change, which leads to a homogenisation of plant diversity at a regional level.