Sammendrag
Large herbivores are important drivers in ecosystems
worldwide. Changes in herbivore densities are
predicted to especially affect herbs that are strongly
preferred by herbivores. The persistence of herbs could
be challenged by enhanced grazing, but also grazing
cessation may affect persistence, especially for prostrate
herbs, which might be out-competed. To test how different
herbivore densities (high, low, and no sheep) affect
grazing frequency and plant responses (plant height,
flowering frequency, and plant density) at the herb
community and species level, we conducted a fully replicated,
landscape-scale experiment in an alpine environment.
We found that none of the herb species
changed their densities after 5 years with experimental
changes in grazing pressure. Sheep density affected
grazing and flowering frequency at the herb community
level. Eight herb species were more grazed at high sheep
density as compared to enclosures with no sheep. Herb
height decreased at high sheep density as compared to
no sheep for the two species with the highest grazing
frequency. Increased height and flowering frequency
were found for small herbs at high sheep density. Our
experiment clearly shows that herbs do not constitute a
homogeneous functional group and that, in particular,
tall and small herbs are affected in contrasting ways but
all species (n = 15) tolerated changes in grazing regimes
as densities were maintained at both enhanced grazing
Climatic effects, Herbivory, Plant density,
Plant height,Reproduction
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