Hay and seed transfer to re-establish rare grassland species and communities: How important are date and soil preparation?

European floodplain grasslands are threatened by land use intensification or abandonment. Hay transfer using plant material from species-rich reference communities may be a valuable tool to restore such grasslands. However, large differences in seed production periods and strong competition are still obstacles that limit the efficiency of hay transfer. Using continental Cnidion meadows (FFH habitat type 6440) as a model system, we tested the effect of cutting date and of soil disturbance intensity on community and target species for eight years in a full-factorial hay transfer experiment. The cutting date treatments were early (June), late (October), combined and no hay. Soil disturbance included shallow, deep and no tillage prior to hay transfer. We estimated the plant cover on donor and restoration sites before and after hay transfer. We additionally counted the individual number of seven specialist species of Cnidion meadows considered as target species. In a sowing experiment, seedling establishment was recorded for a subset of target species and compared to establishment in the hay transfer experiment. Hay transfer was successful in transferring target species but community structure was still quite different from the reference grassland. Target species were only transferred with late hay but early hay added several nonspecialist species of Cnidion meadows. Strong competition by pre-existing vegetation prevented target species from establishing without soil disturbance but differences were small between shallow and deep tillage. In conclusion, a combination of early and late hay and moderate soil disturbance were the most appropriate treatments to restore Cnidion meadows.