Changes in Net Primary Production of Calcareous Grasslands through Nutrient Input from Adjacent Farmland

Calcareous grasslands are semi-natural, nutrient-limited plant communities. Because of their high species richness they are of great interest for nature conservation. During the second half of this century the utilization of these areas became uneconomic and so they decreased considerably in area due to the abandonment of great parts of these formerly widespread plant communities. Nowadays the areas which have been set aside as nature reserves are also undergoing undesirable changes. Today the most severe threat to the existence of calcareous grassland communities is eutrophication. The main sources of nutrient input are the atmosphere and agroecosystems. Eutrophication causes changes in species composition and phytomass production. In this article it is shown that a gradient in nutrient availability along transects from farmland into calcareous grasslands corresponds to a gradient in aerial net primary production of the plant stands and a decrease in plant number.