1. Species-rich grasslands are highly endangered habitats in Central Europe. To halt their ongoing loss, many sites have become subjects of restoration efforts. Traditionally, restoration success is measured using target species or by comparing similarity in species composition. Here, we suggest to additionally use functional community composition to assess restoration success as functional traits might offer mechanistic insights into restoration processes. 2. In a 5-year restoration experiment, we annually evaluated the responses of (i) floristic composition and species diversity, (ii) number and cover of target species, (iii) functional identity and (iv) functional diversity to four different methods of assisted recolonization through species introduction: hay transfer and application of threshing material from a local provenance, combined with and without addition of regional seed mixtures of target species, as well as to a control treatment. 3. Across all treatments, floristic composition, species diversity, and number and cover of target species approached the values of reference sites. In the last observation year, Shannon diversity was still lower in all treatment plots than in the reference plots, while the number of target forb species had reached or exceeded the reference levels. We demonstrated that the community was also restored functionally in many aspects, but not in all studied traits. Calculated community-weighted means (CWMs), specific leaf area (SLA) and leaf dry matter content (LDMC) in experimental plots did not differ significantly from the reference plots, thereby indicating that productivity of restored sites had reached target values. In contrast, CWMs of strategy types and pollination modes revealed significant differences, showing that biotic interactions among plant species and with other trophic levels have not yet been fully restored. However, almost all CWMs showed a trajectory towards the reference, thus giving a positive prospect for the future development. With respect to functional diversity (FD), we found steadily increasing FD values for almost all traits analysed. 4. Synthesis and applications. We demonstrated that all applied restoration measures were appropriate to achieve the restoration aim in terms of species composition of a given community and the establishment of target species. With respect to many functional traits, the restored meadows were already as functional as communities from the reference sites. Hence, including functional criteria did not only corroborate traditional criteria of restoration success but also allowed identifying those floodplain meadow's functions that can be quickly and less quickly restored.

Questions: Is the transfer of plant material a feasible measure for the enrichment of species-poor alluvial grassland? Which is the proper degree of grass sward disturbance to enhance germination and establishment of plant material species? Does the establishment success depend on soil nutrient status of the restoration sites?Location: Northern Upper Rhine valley, southwest Germany.Methods: Seed-containing plant material was transferred to species-poor meadows. We tested two methods of sward disturbance: rotovation or ploughing before the transfer of plant material vs. a control, i.e. no disturbance but transfer of plant material. We studied vegetation development on nine sites for 3 yr.Results: Three years after the transfer of plant material, 101 species were successfully re-established on the restoration sites, including 28 Red List species. In contrast to our expectations, establishment was similar on rotovated and ploughed plots, both harbouring higher numbers and abundances of plant material species than the control plots. In contrast, the cover of resident grassland species differed significantly between ploughed plots (lowest cover), rotovated plots (intermediate cover) and control plots (highest cover) in the last 2 yr of vegetation recording. While elevated phosphorus was in line with reduced establishment of plant material species, potassium and total nitrogen had no negative effect. Conclusions:The transfer of plant material is an appropriate method to enhance plant biodiversity in species-poor grasslands. We show that a sward disturbance by rotovation or ploughing is crucial for species to re-establish. Our results suggest that ploughing is the more promising disturbance measure because it more persistently suppresses grassland vegetation.

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