Flood meadows of the alliance Cnidion are among the most endangered plant communities of Central Europe. Due to agricultural intensification there were large losses of this vegetation type also along the northern Upper Rhine. As a consequence, large scale measures were undertaken to restore this type of meadows at the beginning of the 1980s.
The objectives of the present thesis were:
i. To evaluate the potential of re-colonisation of formerly arable fields and species-impoverished grassland by rare flood-meadow species,
ii. to assess the capability of the seedbank of arable fields to contribute to the restoration of species-rich flood meadows,
iii. to evaluate the influence of different treatments possibly applied in the course of restoration measures on the process of seedling emergence and early establishment, and
iv. to assess the potential of species-rich flood-meadows to be incorporated into local farming systems and its main factors of influence.
No active introduction of target species was done in the course of flood meadow restoration along the northern Upper Rhine since it was thought that re-colonisation could take place from the seed bank or from remnant stands nearby. But after 10 years of restoration management it is apparent that despite favourable site conditions re-colonisation took mostly place close to remnant stands of target species. This shows that dispersal limitation is the main factor limiting restoration success.
In addition, it is shown that also the seed bank has very little potential for the reestablishment of rare target species. The current seed bank of former habitats of flood meadows which are today under arable use was dominated by agrestal species and those typical to ephemeral wetlands.
The influence of measures often applied during restoration (such as simultaneously sown grass, disturbance and the application of litter) on germination, survival and establishment of six typical flood meadow species (Arabis nemorensis, Iris spuria, Serratula tinctoria, Silaum silaus, Pseudolysimachion longifolium, Viola pumila) were explored.
Most species reacted positive towards disturbance and negative to the application of litter. The effect of simultaneously sown grass was much more species specific. In general, when certain precondition were fulfilled all typical flood meadow species showed successful establishment under all treatments. This suggests that in the course of restoration measures seed- and dispersal limitation are the most important factors that need to be addressed.
After the successful re-establishment of flood-meadows, their long-term preservation is best secured by integrating them into local farming systems. In fact, meadows of the alliance Cnidion yielded highest quantities and qualities in case of the species-rich meadows of highest nature conservation value. Thus species-rich flood meadows are easily integrated into local farming systems and the requirements of both agriculture and conservationists can be fulfilled.
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