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.