Agroscope, Institute for Plant Production Sciences IPS, 1260 Nyon, Switzerland

Complex seed mixtures increase species diversity on wildflower strips

Wildflower strips, sown with different seed mixtures, were established on contrasting soil types of arable land on the Swiss plateau. The objectives were to develop seed mixtures which support plant species diversity on wildflower strips over a considerable period of time, and to investigate factors which could potentially cause a decrease in species diversity. After three years a rapid decrease of species diversity and flowering intensity was detected in strips of seed mixtures with high proportions of competitive herbs and grasses, but not in strips of complex mixtures with various wildflower species. Unlike poorer mixtures, species-rich wildflower mixtures were able to compete against invasive, competitive grasses such as Agropyron repens. The best persistence of species diversity was observed at sites with poor, skeletal soils. A diverse flora could be established on most of the typical soil types in arable land. However, in many cases species-rich plant communities failed to establish on high nutrient soils.

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