Plant communities of conventional lawns and their transformation into species-rich grasslands – a review of the German lawn research project

Conventional (frequently mowed) lawns are the most widely distributed type of urban grasslands. Due to the high cutting frequency, lawns generally support lower plant biodiversity and provide less value for wildlife than meadows. Since the beginning of the 21st century, interest in managing lawns in a more biodiversity-friendly way has increased. However, studies on sustainable lawn management aimed at enhancing biodiversity have been conducted in Germany date back to the 1980s. The German Lawn Research Project initiated in 1982, addressed two main research questions: 1) What are the plant community features of conventional lawns in Germany? And 2) How can conventional lawns be transformed into species-rich grasslands? A floristic comparison of 800 park lawn plots (relevés) in German cities identified lawns as an independent type of grassland community, which can be classified into different types according to soil and water conditions. We detected a domination of native plant species in lawns originating from European pastures and meadows which have specific ecological characteristics adapted to high mowing frequency. To clarify the 2nd question, 100 permanent plots were established in urban parks of Augsburg (Southern Germany), across 8 test facilities representing different lawn types (dry, damp, old, and young) and different mowing regimes: one cut per year (October), two cuts per year (June and October), and three cuts per year (June, August, and October), with clipping removal. The target habitats for this experiment were species-rich, low-productivity meadows, which were typical for the European cultural landscape until the middle of the last century. After five years of monitoring, the results showed that vegetation succession was determined by the species already present in the plots. In the absence of mowing or under a once-yearly mowing regime, all lawn types tended to develop species-poor communities. However, with mowing twice or three times a year, old lawns can be transferred to species-rich meadows. Species-poor, younger lawns can be enriched by sowing meadow species and by mowing two or three times per year. The significance of this project lies in its long-term monitoring, from 1982 to 1986, and in part until 1992. Some parks are still being observed today. Based on these long-term research observations, we provided recommendations for the design and management of species-rich urban grasslands.