Conclusions
In summary, herbivore impact on grass vegetation depends on water and nutrient availability. In our system, grass cover decreased with water availability towards perennial rivers, where most animals were recorded and was higher on more fertile soils on basaltic bedrock. Our main finding is that the relationship between grass species richness and herbivore species richness changes with water and nutrient availability. Grass species richness increases with herbivore species richness on basalts and on crests, where dominant grass species are suppressed by grazing but decreases on granites and by seasonal rivers. In plots where grasses were dominant, grazing and other animal activities further increase microsite heterogeneity, which provides more niches and supports grass species richness. This suggests that it is necessary to critically assess resource availability in protected areas that aim to support grass species richness. Depending on the context, the same herbivore abundance may lead to different outcomes and both overgrazing as well as low grazing pressure may lead to grasslands dominated by a few species. Grass species richness is important not only per sebut because more grass species form a more heterogenous environment that supports the diversity of other species of animals and plants. Such a mosaic of species-rich grasslands offers a broad fodder supply and contain species of different successional stages, making them more resistant to different scenarios, such as fluctuation of grazing pressure, fire or drought.