Floodplain meadow plant species are particularly adapted to the specific environmental conditions (e.g., the interplay of flooding and drought) in the floodplains of Europe s large rivers. Numerous species of this set of species often jointly occur at floodplain grassland despite their ecological heterogeneity. The traits that cause the joint distribution pattern still have hardly been studied. This thesis deals with the flooding tolerance of selected floodplain meadow species with a focus on different key factors of floods. Furthermore, the spatial distribution of species based on (mainly hydrological) environmental variables was studied. Two experiments showed that increases in flooding duration, flooding depth and the combination of the two factors (i.e., intensity of the flooding effect) as well as the occurrence of a flooding event at young plant age (younger than ~4-6 weeks) result in severe limitation to seedling establishment. The combined effect of flooding duration and depth and often interactions in general have been underestimated in experimental studies so far. Hence, the results of these studies are difficult to compare. Using an interdisciplinary approach (disciplines: hydrology and ecology) a habitat model of 23 floodplain meadow species was developed. The species distribution was modeled by relating occurrence of species to several environmental variables (i.e., morphological, meteorological, hydrological). The hydrological predictor variables (e.g., flooding depth and duration) were generated from a hydrological model, which simulates the surface water-groundwater interactions with a high temporal resolution. Habitat models that include hydrological parameters from the hydrological model show better results for floodplain meadow species distribution than models based on simple hydrological parameters. Habitat-suitability maps based on the habitat modeling were computed for the 23 target species. These maps could serve as a baseline for the target site selection of upcoming restoration projects (e.g., the reestablishment of typical floodplain meadow species). That enables an estimation of the restoration success in advance. Consequently, false investments of limited resources (e.g., freshly-cut, seed containing plant material, financial resources) through the restoration on unsuitable sites can be prevented.
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