Re-Meandering German Lowland Streams: Qualitative and Quantitative Effects of Restoration Measures on Hydromorphology and Macroinvertebrates |
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Authors: | Armin W Lorenz Sonja C Jähnig Daniel Hering |
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Institution: | 1.Applied Zoology/Hydrobiology,University of Duisburg-Essen,Essen,Germany;2.Limnology and Conservation,Senckenberg, Research Institute and Natural History Museum,Gelnhausen,Germany |
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Abstract: | We investigated the effects of two river restoration projects on hydromorphology and macroinvertebrate fauna in two German
lowland rivers, the Schwalm and the Gartroper Mühlenbach. The stream channels were re-meandered and the floodplain levels
were lowered to better connect the streams to their floodplains. The restoration was performed 10 years ago in the Schwalm
and 2 years ago in the Gartroper Mühlenbach. We compared the restored reaches to nearby anthropogenically straightened reaches.
Twenty-five hydromorphological parameters were recorded on twenty transects; between nine and 23 substrate-specific macroinvertebrate
samples were taken per reach. Several hydromorphological parameters, such as the number and width of channel features and
the number of substrate types, were significantly higher in the restored reaches compared to nearby anthropogenically straightened
reaches. Total numbers of invertebrate families, genera, and taxa were also higher in the restored reaches than in the anthropogenically
straightened reaches. Biotic substrates like dead wood or macrophytes were more abundant in the restored reaches, and these
substrates hosted 28 taxa not found in the straightened reaches. While diversity was high in both restored reaches, overall
abundance increased only in the river that was restored 10 years ago. Using NMS-analysis, substrate-specific faunistic samples
of the restored reaches were compared to those of the straightened reaches. Our results revealed different invertebrate communities
on the same substrates in the recently restored river. In the 10-year-old restoration, however, the same substrates were similarly
inhabited. This comparable colonization of substrates may reflect succession in the macroinvertebrate community. The results
are discussed according to the re-colonization potentials of the upstream and downstream reaches and the dispersal capacity
of taxa. |
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