Evolution of the vegetation of mown field margins over their first 3 years

Early succession of newly created sown/unsown margin strips on ex-arable land, managed by two cuttings per year with/without removal of cuttings, was characterised by the replacement of annuals in favour of perennials, a steady increase in the importance of monocotyledons and a decrease in non-nitogen-fixing dicotyledons. Mowing with removal of cuttings delayed this succession pattern. Sorensonʹs qualitative similarity index revealed that species composition of the sown communities in terms of species occurrence became increasingly similar to the unsown plots. Furthermore, convergence in vegetation composition between sown and unsown plots occurred also in terms of species importance as assessed by Sorensonʹs quantitative index. Similarity, in species, importance was significantly enhanced by cutting with removal of cuttings. During the first three successional years, species diversity of sown and unsown communities converged in time, irrespective of mowing regime or location. The decrease in species diversity, number and density of sown wildflowers was more pronounced under a mowing regime without removal of cuttings. The annual addition of mown roadside herbage significantly enhanced species-richness, but not the importance of dicotyledons.