Recruitment of Target Species in the Drentsche Aa Reserve

It is a well known problem in restoration efforts that one or more important species are missing in the area. In this study three possible reasons for the absence of 13 I target species are investigated. First, it could be that the abiotic ranges that are present in the fields are still not suitable for these species. Also, dispersal limitation could be a problem since most of the dispersal vectors of these plants are missing. Lastly, there I could be an insufficient amount of gaps or microsites in the area, a feature necessary for some species to establish or remain present in their vegetation community. To find the reason(s) for these species, fieldwork has been done on a running sowing I experiment in the area Anlooer Diepje located in the Drentsche Aa Reserve. Seeds of target species were sown in three different treatments (bare ground, moss removed, ' control). Treatments were applied in 15 plots, divided over two fields containing the same plant community. In total four plant communities were used in the experiment. Soil samples, germination conditions and vegetation recordings have been taken of all 60 plots. Soil samples were analysed for moisture content, pH and organic matter I content. Out of the 13 species Succisa pratensis, Crepis paludosa, Pedicularis palustris, Cirsium oleraceum, Rhinanthus angustfolius and Bromus racemosus germinated in I the field and the first five survived the summer, all of which had a high seed weight. Between treatments only Crepis had statistically less seedlings in the control than in bare ground and raked. On the other species, especially Succisa and Pedicularis, the I measures had no effect on germination. Between the fields the differences in seedling number of Succisa, Cirsium and Crepis were statistically significant. Succisa was negatively affected by a high percentage of living plants in its vicinity, but not by moss, so in sites where living plants were abundant, bare ground became more important for Succisa than in sites with more moss. In four out of the six species it is mainly dispersal limitation that prevents them from I colonizing an area, while in two of them microsite limitation may also play a role. Bromus could not be tested, since it died out due to unfavourable weather, but as it did germinate it may also be inhibited by dispersal limitation and, perhaps, microsite I limitation. For the other species no answers have been found.