Applied Vegetation Science 15 (2012) 290–298 SPECIAL FEATURE: VEGETATION RESTORATION Enhancing plant biodiversity in species-poor grassland through plant material transfer – the impact of sward disturbance Ralf Schmiede, Annette Otte & Tobias W. Donath Keywords Alluvial meadows; Floodplain; Grass sward; Grassland restoration; Hay transfer; River Rhine Nomenclature Wisskirchen & Haeupler (1998) Received 21 February 2011 Accepted 6 October 2011 Co-ordinating Editor: Thierry Dutoit Schmiede, R. (corresponding author, Ralf.Schmiede@umwelt.uni-giessen.de), Otte, A. (Annette.Otte@umwelt.uni-giessen. de) & Donath, T.W. (Tobias.W. Donath@umwelt.uni-giessen.de): Department of Landscape Ecology and Resource Management, Interdisciplinary Research Centre, Justus-Liebig-University Gießen, Heinrich-Buff-Ring 26-32, DE-35392, Gießen, Germany Abstract Questions: Is the transfer of plant material a feasible measure for the enrich- ment 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 mead- ows. 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 suc- cessfully 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 mate- rial 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 dis- turbance 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. Introduction In most parts of Central Europe a serious decline in species-rich grasslands, caused either by intensification of land use or abandonment, has placed them as a focus for conservation and restoration activities (Joyce & Wade 1998). As a consequence, species-rich flood- plain meadows are protected by the Fauna Flora Habi- tat Directive of the European Union (Council of the European Union 1992). In our study area at the northern upper Rhine, Ger- many, remnant stands of species-rich alluvial grasslands are mostly small and fragmented (Bo ¨ger 1991). After sev- eral major floods in the early 1980s, large areas of arable fields in the study area were converted into grassland via spontaneous succession and subsequent non-intensive management for hay production (Bissels et al. 2004). Although site conditions were favourable for the establish- ment of species-rich plant communities, i.e. bare soil sur- faces and a near-natural flooding regime, typical species and plant communities of alluvial meadows did not re- occur (Donath et al. 2003; Bissels et al. 2004). Similar to other studies on grassland restoration (Bakker et al. 1996), target species have not re-established due to seed and Applied Vegetation Science 290 Doi: 10.1111/j.1654-109X.2011.01168.x © 2011 International Association for Vegetation Science