Do hoof prints actually serve as a regeneration niche for plant species in fens?

Plant species revegetation of hoof prints in a calcareous fen pasture and of artificially created hoof-print like gaps in an abandoned fen was investigated over two years and compared with the surrounding vegetation. The investigation of abiotic conditions showed that two hoof-print zones had to be distinguished: the steep, drained edge with good light conditions and the flat, dark, but wet bottom. Vegetative spreading and seedling recruitment were examined separately. After two years, hoof prints were not recolonized reasonably, indicating that both hoof-print zones did not offer good conditions for recolonization. Occurrence of frequent species and species numbers were similar in hoof prints, in the surrounding vegetation and in the seed bank. For many fen species germination from the seed bank was better in water-logged pots than in regularly-watered pots. Most species recolonized hoof prints both generatively and vegetatively. In the bottom zone more species germinated than spread vegetatively, but many seedlings died. At the edge, vegetative spreaders finally dominated in spite of high germination rates, because seedling mortality was also high. Overall, recolonization on the edges was more successful than on the bottom, probably because of better light conditions. Only few new species occurred inside hoof prints and only few species were frequent in hoof prints, but not in the surrounding vegetation. Those species were exclusively prostrate species germinating on the edges. The number of recolonizing species did not differ between pasture and abandoned site. Germination, however, was more severely limited in the abandoned fen due to low light availability, litter accumulation and competition by mosses. Altogether, our results show that the presumed importance of hoof prints for species recruitment has to be reconsidered for fen vegetation. On wet peat soil negative effects of soil compaction and changed water and light availability probably prevail over positive effects such as the promotion of subordinate species.