Long-term effect of sheep and goat grazing on plant diversity in a semi-natural dry grassland habitat

摘要

Semi-natural dry grassland sites are of great importance for nature conservation because they support high species diversity and the abundance of “Red-List” species. Grazing has proved to be a successful management tool in terms of maintenance and restoration of biodiversity. For a deeper understanding of the effects of different grazers on species biodiversity in dry grasslands, it is necessary to study the long-term effects of major changes in grazing management. In a semi-natural dry grassland habitat, which was formerly grazed by cattle, we investigated the changes in plant species composition due to long term grazing by sheep and goats. Specifically we asked: a) How does long-term grazing by sheep and goats change the composition of all plant species and particularly those that are on the Red-List? Are changes caused mainly by species turnover? b) How does long-term grazing by sheep and goats influence the fertility and acidity of the soil? To address these questions, we compared the composition and diversity of plants as well deriving Ellenberg indicator values of the species. Long-term grazing by sheep and goats subsequent to a year-round cattle grazing changed the plant species composition of the dry grasslands resulting in a high species turnover rate. It did not, however, lead to an increase in plant species diversity even though Red-List species were considerably more abundant in 2013. Overall, the grazing regime studied positively influenced vegetation composition. The effects on local species composition due to species turnover might further be influenced by local factors like soil nitrogen availability.