Veränderung der Laufkäfergemeinschaften (Carabidae) in 15 Jahren Sukzession nach der Umstellung vom konventionellen auf ökologischen Landbau auf Hof Ritzerau

The study compiles the results of a fifteen years research on ground beetles after the conversion from conventional to organic farming on Ritzerau Manor (south-eastern Schleswig-Holstein, Germany). The results display the succession of the single ground beetle species and of the changes in the species diversity. The changes of the single ground beetle species can be differentiated into specific ecological groups. These are species (1) with declining abundance during the succession or retreat from the arable fields into marginal areas near their original source habitats. Among these are dominant species from conventional fields, e.g. Pterostichus melanarius, or (2) species orginating from woods, e.g. Carabus coriaceus. Among the ecological group that depends on open habitats (3), are species preferring high temperature from oligotrophic grassland or heath benefit from organic agriculture. Many species invaded into the organically managed arable fields, showed increasing abundance, or wider distribution. Aditionally, species from fallow grassland belong to this ecological group. Furthermore, characteristic species from (4) organic arable fields or nearly extinct species, which were common in the past under less intensive agriculture, e.g. Zabrus tenebrioides, have recently invaded and have highly increased their abundance, e.g. Carabus auratus. (5) Some species from moist grassland have also widened their resources into the organic fields in rainy years but certainly cannot inhabit the field permanently. In the specific case of the arable fields of Ritzerau Manor, species mainly invaded the arable area from the south-western direction, where dry and open grassland border the area or via the upper parts of the Duvensee-Creek channel in the Northeast. No invasion was observed from the Northwest, where large woods are adjacent to the arable area, and from the Southeast, where the wet area of the wide swampy area of the Duvensee-Creek or the shallow lake Duvensee operate