Macrophytes respond to reach-scale river restorations: River restoration enhances macrophytes

Published source details Lorenz A.W., Korte T., Sundermann A., Januschke K. & Haase P. (2012) Macrophytes respond to reach-scale river restorations: River restoration enhances macrophytes. Journal of Applied Ecology, 49, 202-212.
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Summary

Action: Restore/create rivers (multiple interventions)

A replicated, paired, site comparison study in 2005–2008 of 40 rivers in Germany (Lorenz et al. 2012) found that restored reaches typically contained a greater richness, diversity and abundance of submerged macrophytes than degraded reaches, after 1–13 years. In both upland and lowland rivers, restored reaches contained more submerged macrophyte taxa (3–5 taxa/100 m; vs degraded: 2–4), had greater submerged macrophyte diversity (data not reported) and contained more submerged macrophyte growth forms (4 forms/100 m; vs degraded: 2). In three of four comparisons based on a semi-quantitative index, submerged macrophytes were more abundant in restored than degraded reaches. In the other comparison, within lowland rivers, there was no significant difference (data reported as Kohler values and derived volume). None of the metrics significantly varied with the age of restored sites (data not reported). Results were similar for analyses based on submerged and emergent macrophytes combined: restored > degraded for all metrics in both upland and lowland rivers, and no significant variation with age. Methods: In summer 2005, submerged and emergent macrophytes were surveyed in two reaches in each of 40 rivers (24 upland, 16 lowland). In each river, one downstream reach had been restored 1–13 years ago (average: 5 years) and one reach (around 500 m upstream) remained degraded. Restoration involved a combination of 1–8 specific engineering measures/river along a 0.1–8.0 km reach (e.g. increasing depth, reconnecting backwaters, installing flow deflectors, or adding coarse woody debris). This study included the rivers in Lorenz et al. 2009, but examined different reaches of those rivers.