Restoration of calcareous grasslands: The early successional stage promotes biodiversity

Abstract

Land-use change has been identified as the most important factor responsible for the recent loss of biodiversity. One major problem is the abandonment of management, especially in semi-natural grassland ecosystems. Numerous restoration projects were, therefore, launched to counteract this development. However, the effects of restoration are not yet fully understood. Especially the early successional stage, i.e. the composition of the vegetation in the first years after the restoration measures, has received little attention probably due to its supposedly low conservation value. As study area, we selected the largest area of calcareous grasslands at the northern edge of the German uplands. About 35 ha of formerly abandoned calcareous grasslands have been restored by cutting shrubs here in the last eight years. Within the restored sites, 50 randomly chosen vegetation surveys were made and the results were compared to 50 control plots. Our study revealed that the value of the early successional stage for biodiversity conservation was previously underestimated. Even though the target state - calcareous grassland - is far from being reached, the early successional stage enhances the conservation value of calcareous grasslands by (i) increasing diversity at the landscape scale, (ii) hosting numerous target species as well as (iii) contributing to a higher habitat quality and heterogeneity. Future restoration of calcareous grasslands should focus on sites with low nutrient content of the soil, a shallow topsoil, and a warm microclimate. At such sites, the chances are greatest that species with a high nature conservation value, i.e. characteristic species of calcareous grasslands as well as thermophilous fringe and ruderal species, will re-establish.