| Abstract: | In this study nutrient supply along transects from farmland to calcareous grasslands was investigated. The aim was to assess a gradient in nutrient supply parallel to the change in species composition. Net nitrogen mineralization was measured under field conditions and in a laboratory incubation experiment. The seasonal course of net N mineralization was determined by the increase of soil temperature in spring and changes in soil moisture during summer. In the farmland soils fertilization was also an important factor. Annual net N mineralization was highest in the moderately acid soils of the Rosenberg on the Lower Devonian schist. It was lowest in the soils of the transect near Erdorf on limestone. Two transects on dolomite took an intermediate position. At all study sites net N mineralization and the mineral nitrogen contents were higher in the peripheral zones of the calcareous grasslands than in the centre of the grasslands. In the base-rich soils of the three transects on limestone and dolomite annual net N mineralization varied in the calcareous grasslands between 4.6 and 61 mg/kg, in the peripheral zones between 35 and 190 mg/kg and in the farmland between 117 and 350 mg/kg. In the base-poor soils of the transect on Rosenberg it was 96 mg/kg in the calcareous grassland, 115–130 mg/kg in the boundary zone and 165 mg/kg in the meadow. It is presumed that the increase in nitrogen supply was caused by nutrient input from the adjacent farmland. |
