Rehabilitation of alluvial landscapes along the River Hase (Ems river basin, Germany).

Abstract

Extensive alluvial pasture landscapes with high biodiversity were for centuries characteristic of the northwestern German lowland plains, but for 50 years nearly all have been replaced by intensive agricultural management systems. As part of a rehabilitation project an alluvial pasture landscape along the River Hase (Ems river basin) was to be redeveloped. The dikes were set back and soil and sand were rearranged, creating a wetland-river dune complex low in nutrients. Hardly any plant species were present in the seed bank. Without any further assistance mainly hydrochoric wetland plant species were expected to colonize the area, whereas anemo- and zoochoric river dune plant species and those of dry grassland growing today only on fragmented sites would not be in a position to reach the rehabilitated area in the near future. Therefore, the areas have been inoculated with diaspores from mown and raked plant material taken from special source areas (Spergulo-Corynephoretum, Diantho-Armerietum). Results after two vegetation periods indicate that the plant species composition at the inoculated plots develop in the desired direction in contrast to non-inoculated plot. A long-term cattle grazing scheme was set up to prevent vegetation succession and guarantee a dynamic system of pioneer communities.