Biodiversity of a perennial wild flower mixture for biogas production

Abstract

Due to an expected high biodiversity wildflower mixtures for biogas production may perform a reasonable ecological alternative to maize cropping, while they at the same time suppress weeds. To test the development of biodiversity and weed abundance in three years, in 2014 field trials were established at two sites in North-East Germany. The wild flower mixture „BG 70” (Saaten Zeller) was sown, a perennial mixture containing 23 species developed especially for the use of biomass in biogas plants. From 2014 until 2016 wild flowers and weed species and densities were counted on eight plots per site. The assessment was done each year from late May until mid June. The diversity of the wild flower mixtures decreased over the years, as described with three indices for diversity. The sown species common mugwort (Artemisia vulgaris), common knapweed (Centaurea nigra) and common tansy (Tanacetum vulgare) increasingly dominated starting in the second year after sowing. However, the number of individual wild flower plants was constant over the years and led to a decreasing weed density. The increased biodiversity by wild flower cultivation may enhance ecosystem services with the positive side effect of biomass production for biogas plants. At least in the first years of wild flower cultivation, growers should not fear increasing weed densities.