The Potential to Save Agrestal Plant Species in an Intensively Managed Agricultural Landscape through Organic Farming—A Case Study from Northern Germany

Intensive agriculture is among the main drivers of diversity decline worldwide. In Central Europe, pressures related with agriculture include habitat loss due to the consolidation of farming units, pesticide and fertilizer use, and shortened crop rotations. In recent decades, this development has resulted in a severe decline of agrestal plant communities. Organic farming has been suggested as a biodiversity friendly way of farming, as it strongly restricts the use of synthetic pesticides and fertilizers and relies on longer crop rotations. It may thus help in saving agrestal plant communities in the future. In this study, we assessed the long-term effects of three types of arable field management (conventional farming, organic farming, and bio-dynamic farming) on three farms in the federal state of Schleswig-Holstein, Northern Germany. We collected data on above-ground plant communities and seed banks and analyzed them with regards to the impact of the farming system and their position in the field using nonmetric multi-dimensional scaling (NMDS) and linear mixed effects models (LME) combined with ANOVA and Tukey contrast tests. Plants in organically or bio-dynamically managed fields differed in their composition and traits from those occurring in conventionally managed fields, i.e., they showed a preference for higher temperatures and were dominated by insect-pollinated species. While conventional farming had negative effects on vegetation and the seed bank, organic and bio-dynamic farms had neutral or slightly positive effects on both. This highlights the potential of the latter two to conserve species even in an intensively managed landscape. In addition, this may halt or even reverse the decrease in arthropod, bird, and mammal species, since agrestal plants constitute an important component of food-webs in agricultural landscapes.