Restoring the alluvial landscape of the Hase river - Resulting structural complexity and colonization by flora and fauna [Renaturierung der Hase-Aue - Folgen für die Strukturkomplexität und die Besiedlung durch Flora und Fauna]

Abstract

The fundamental aim of the 'Hasetal' testing & development project was to restore a wider area of alluvial pasture landscape. Realization of the project started in 1999 by removing dikes and suspending common maintenance measures as well as switching to extensive agricultural management. This led to a rapid increase of semi-natural structures in both the littoral zones and the direct surroundings of the water. Dynamic processes were initiated by more frequent and longer-lasting flooding of the alluvial landscape. Moreover, the stream course was extended by reactivating old branches. Compared to the initial situation an expansion of the total alluvial area resulted, as well as increasing differentiation of the vegetation characteristic of sandy alluvial landscapes in specific areas. In the littoral zones, initial gallery forests as well as willow areas had already established during the project period. By 2012 these areas had developed completely and have, for example, become a food source for the beaver populations which have established there in the meantime. In addition, intensively managed areas have been converted successfully into extensively managed grassland. The integration of areas of alluvial pasture landscapes has proven to be one of the most successful revitalization methods for running waters. Changing runoff characteristics due to changing flood retention in the total drainage area remains a problem which still has to be resolved.