Effects of floodplain dynamics on richness, abundance, composition and functional diversity of grasshopper assemblages in the Donau-Auen National Park (Austria)
Demetz Agnes, University of Vienna (AT)
Flooding events are an important factor shaping arthropod communities on riverine meadows. We investigated to what extent species richness, abundance, species composition and functional diversity of grasshopper assemblages on meadows in the Donau-Auen National Park (Lower Austria) are affected by annual floods. Grasshoppers were sampled between June and September 2012 on 12 meadows prone to yearly summer inundations, and 13 meadows protected from such floods by a levee. All acoustically and visually detected individuals were counted. Excluding one stray species not associated to meadows and representatives of the genus Tetrix, which could not be recorded reliably with our sampling method, a total of 24 grasshopper species were recorded. Grasshopper abundance was negatively affected by flooding. Species richness was nearly identical on both meadow types. However, species composition differed prominently between regularly flooded and non-flooded meadows. While the relative abundance of xerophilous species was higher on non-flooded meadows, in hygrophilous species and grasshoppers with indifferent habitat preferences no significant differences were found. Further, flooding did not prove to affect functional diversity. This study shows that natural floodplain dynamics still have a high and significant impact on grasshopper assemblages of meadows in the Donau-Auen National Park. The perpetuation of high hydrological dynamics, like annual floodings, is a precondition to maintain the existing grasshopper fauna and to provide habitats for regionally threatened hygrophilous species.