Marian Gratzer

Gratzer

Marian.Gratzer@gmx.at

PDF im Hochschulschriften-Service der Universit├Ąt Wien

Impact of flooding on bug communities (Heteroptera) on meadows of the Morava River floodplains, Eastern Austria.

Lowland floodplains in Europe have been altered radically by human activities during the last century. One of Central Europe`s last semi-natural lowland floodplains remained along the Morava River on the border between Austria and Slovakia. In this riparian landscape the annual flood dynamics still represent a determining factor in shaping different habitats. Especially terrestrial arthropods of the soil and herb layer are permanently exposed to flooding events. In this study we quantified effects of flooding on richness, abundance and composition of terrestrial bug assemblages (Heteroptera), considering feeding guild affiliation, host plant specialization of herbivorous species and flight ability, on floodplain meadows in the nature reserve "Untere Marchauen" (Lower Austria) and its close proximity. Bugs were sampled by sweep netting on meadows with different flooding regimes ranging from meadows only occasionally flooded by a rising ground-water level to meadows usually flooded for several weeks per year. A total of 11,950 individuals, 5,312 of them adults belonging to 118 species, were collected. Species richness and abundance of bugs were negatively affected by flooding duration and species composition differed between meadows of different flooding regimes. Meadows flooded for longer periods of time were characterized by a higher relative abundance of predacious species. Relative species richness and abundance of host plant specialists (mono- and oligophagous bugs) and relative abundance of brachypterous bug species increased towards meadows with lower flooding intensity. Our study proved that flooding does not only affect abundance, richness and species composition of bug assemblages but also has an impact on the relative importance of trophic guilds and negatively affects species with lower dispersal abilities. Therefore, river restoration measures changing the hydrological dynamics of adjacent floodplains do not only affect diversity of terrestrial arthropods but may have a significant ecological impact. It remains to be studied to what extent such changes in the feeding guild composition and the trophic structure of arthropod communities are capable to affect ecosystem processes in the entire floodplain ecosystem.