Successional trajectories of soil nematode and plant communities in a chronosequence of ex-arable lands

Conversion of arable land into semi-natural grassland or heath land is a common practice for restoring and conserving plant diversity. However, little is known about the effectiveness of land conversion for restoring and conserving taxonomic and functional diversity in the soil. We studied soil nematode community development in a chronosequence of abandoned fields and related this to plant community development. The taxonomic and functional composition of the soil nematode community was analyzed to detect changes in soil food web structure, using semi-natural sites and theoretical plant and soil communities as references. While plant communities clearly developed towards the semi-natural references, there was less direction in succession of nematode taxa. The number of fungal feeding nematodes increased after land abandonment. Numbers of omni-carnivorous nematodes expanded only during the first years, after which there were no substantial changes for the next three decades. Plant communities on the ex-arable fields developed towards the theoretical reference plant associations Galio hercynici-Festucetum ovinae and Genisto anglicae-Callunetum. Nematode communities developed away from a theoretical community indicative of arable land, but there was no clear development towards a theoretical (semi-)natural reference. Our results show that restoration and conservation of plant communities is of limited indicative value for developments belowground: successful restoration of plant diversity does not necessarily imply successful restoration of belowground diversity. Assessing the impact of conservation measures on restoring soil biodiversity requires information on belowground community composition of (semi-)natural areas in order to establish proper references for restoration sites