Influence of competition by sown grass, disturbance and litter on recruitment of rare flood-meadow species

As a response to the sharp decline in species-rich flood-meadows along the northern Upper Rhine during the past decades, large-scaled restoration projects have been started recently. For the implementation of restoration measures knowledge about the effects of topsoil disturbance, litter and simultaneously sown grasses on seedling recruitment are of special interest. This applies in particular to the role of sown of grasses that may accelerate sward development and ease the incorporation of newly created meadows into local farming systems. As study species we selected six typical, but rare or declining flood-meadow species which differed in seed size, since this may influence the impact of the applied treatments. We studied effects of simultaneously sown grasses on germination and recruitment success of these flood-meadow species in two former arable fields situated in the functional and fossil floodplain along the northern Upper Rhine. The effects of litter and topsoil disturbance in an existing grass sward on the recruitment of the six flood-meadow species were experimentally assessed in a species-poor grassland in the functional floodplain. The individual fate of emerging seedlings was followed over two years. The effects of the applied treatments were species-specific and rather inconsistent. Responses towards disturbance and litter application corresponded to differences in seed size, with large-seeded species showing a lower susceptibility to the influence of treatments. In addition, simultaneous sowing of grass did not hamper seedling recruitment in most cases, and thus seems to be a feasible measure to accelerate the integration of newly created flood-meadows into farming systems.