Diversity loss in the macrophyte vegetation of northwest German streams and rivers between the 1950s and 2010

Abstract

This resampling study in 338 semi-permanent plots analyses changes in river macrophyte diversity in 70 water courses (small streams to medium-sized rivers) from four regions of the northwest German lowlands during the last six decades. The total macrophyte species pool decreased between the 1950s and 2010/2011 by 28% (from 51 to 37 species), mean plot-level species richness by 19% (from 4.7 to 3.8 species per relevé) and the number of red-listed species by 40% (from 30 to 18 species). Species loss was associated with marked change in species traits: species with presumably higher mechanical stress tolerance (indicated by low specific leaf area and short leaf longevity) are more abundant today. Nearly, half of the species present in the 1950s had either disappeared or been replaced by other species in the recent relevés. The dramatic impoverishment is likely a consequence of continued nutrient input that drove oligo-and mesotraphent species to extinction, and of restructuring and maintenance works in the water courses that reduced stagnant and undisturbed river habitats, where stress-intolerant species can persist. Efficient measures to reduce the nutrient load and to re-naturalise stream and river beds are urgently needed to halt and reverse the loss of macrophyte diversity.

Morphological forms of two macrophytes (yellow water-lily and arrowhead) along velocity gradient

“…Nuphar lutea tolerates high organic substrate and nutrient level (Rooney et al 2013). Free floating forms mange better in such limited light conditions of water (Steffen et al 2013). Differences in morphology of Sagittaria sagittifolia and Nuphar lutea result in the different rigidity of their tissues (Sukhodolova & Sukhodolov 2012;Steffen et al 2013).…”

“…Free floating forms mange better in such limited light conditions of water (Steffen et al 2013). Differences in morphology of Sagittaria sagittifolia and Nuphar lutea result in the different rigidity of their tissues (Sukhodolova & Sukhodolov 2012;Steffen et al 2013). Nuphar lutea produces very long rhizomes that make plants resistant to the flow pressure (Rooney et al 2013).…”

“…Nuphar lutea produces very long rhizomes that make plants resistant to the flow pressure (Rooney et al 2013). Furthermore, yellow water-lily was described in literature as mowing-tolerant species (Steffen et al 2013).…”

“…In the study of diversity loss in the macrophyte vegetation in Germany (Steffen et al 2013), authors indicate that apart from the changes in nymphaeids composition, also the number of lemnids increased. It is connected with their free-floating growth forms (Steffen et al 2013).…”

“…In the study of diversity loss in the macrophyte vegetation in Germany (Steffen et al 2013), authors indicate that apart from the changes in nymphaeids composition, also the number of lemnids increased. It is connected with their free-floating growth forms (Steffen et al 2013). Furthermore, Quinn et al (2011) in their study of preferences between the alien-native pairs of the same life form proved that alien species of macrophytes are better adapted to eutrophic conditions than native taxa.…”