Influence of mowing and seed mixture composition on the vegetation of wildflower strips and rotational fallows

Wildflower strips and rotational fallows are areas planted with indigenous wildflowers and are intended for ecological enrichment of cultivated areas. They promote diversity of plant and animal species. Within the scope of a long term experiment in the vicinity of Frauenfeld (Switzerland), we examined the influence of six seed mixtures differing in species composition on the biodiversity and the cover of spontaneous plant species during the year of sowing. Spontaneous growth on unplanted plots and plots planted with a seed mixture for ley were examined for comparison. Moreover, we studied the influence of one early mowing on the vegetation. The lowest plant diversity was observed on the unplanted plots with spontaneous growth. Plant diversity in the field increased with increasing number of species included in the seed mixture. The number of spontaneous plant species growing after the sowing of the different seed mixtures was similar in all plots except for the plots planted with the seed mixture containing the least species, where more spontaneous species were observed. The wildflower strips where Festuca pratensis was included, showed about the same cover with spontaneous plants as the wildflower strips containing no planted grass species. Noticeably only by late summer, a reduced share of Medicago sativa in the mixture increased the spontaneous plant cover. Mowing induced an increase in spontaneous plant cover and especially promoted the growth of creeping plants. Except for the plots planted with grass-rich seed mixtures, the amount of dead plant material in autumn was much lower in the mowed plots than in the unmowed ones.