estoration of Skjern River and its valley — Short-term effects n river habitats , macrophytes and macroinvertebrates orten

The lower 19 km of the Skjern River was restored and transformed into a 26 km long meandering river. Three survey reaches and one control reach upstream of the restoration area were surveyed to assess the short-term effects of the restoration on river habitats, macrophytes and macroinvertebrates. The reaches were surveyed before the restoration in 2000 and again after the restoration in 2003. Morphological adjustments were evident in the re-meandered river and the habitat structure (depth, current velocity and substratum) became more diverse. The macrophyte coverage was 34% before the restoration. Restoration included removal of dense near bank vegetation stands of Glyceria maxima, and in 2003 recolonization of the restored reaches had resulted in 24% macrophyte coverage. Species composition and growth patterns changed significantly in the edge habitat and the dominant macrophyte G. maxima was replaced by Elodea canadensis and Sparganium sp. Macroinvertebrates rapidly colonized the restored reaches and increased the community diversity. Only acroinvertebrate diversity acrophyte coverage one taxon, Heptageniidae, significantly increased in abundance after the restoration and a more even distribution of taxa developed on the restored reaches. Biological communities will continue to develop over the coming years as the river becomes more physically stable. Hence the macroinvertebrate and macrophyte communities will adjust and colonization from upstream sources and other systems will probably increase biodiversity. functional return to a pre-disturbance state”, sensu Cairns . Introduction tream and rivers constitute a dense network of flowing water ith a large interface to the surrounding landscape. For this eason they are highly susceptible to various anthropogenic ressures and this has significantly affected biodiversity and aused the extinction of some species (Sand-Jensen, 2001). atural morphological characteristics and the biota of streams Please cite this article in press as: Pedersen, M.L. et al., Restoration of macrophytes and macroinvertebrates, Ecol. Eng. (2007), doi:10.1016/j.ecole nd their riparian areas have been strongly altered and in any cases lost due to human manipulation of the landscape e.g. Phillips, 1995; Sparks, 1995). One way of counteracting the ∗ Corresponding author. Present address: Aalborg University, Departme enmark. Tel. : +45 96 35 80 80; fax: +45 98 14 25 55. E-mail address: mlp@civil.aau. dk (M.L. Pedersen). 925-8574/$ – see front matter © 2006 Elsevier B.V. All rights reserved. oi:10.1016/j.ecoleng.2006.08.009 © 2006 Elsevier B.V. All rights reserved. morphological degradation of streams and rivers is to restore the lost physical features (e.g. Mitsch and Jørgensen, 2003; Ormerod, 2003; Pedersen et al., 2006a). This has been widely applied in the US and Western Europe on different scales and with the use of a multitude of approaches (Holmes, 1998; Hansen, 2000; Bernhardt et al., 2005). Restoration can be defined as “a complete structural and Skjern River and its valley—Short-term effects on river habitats, ng.2006.08.009 nt of Civil Engineering, Sohngaardsholmsvej 57, DK-9000 Aalborg, (1991). Many river restoration projects in lowland areas aim at re-creating morphological features and thus increase habitat diversity. Because lowland streams are usually located in IN ECOENG-1099; No. of Pages 12