Causes and consequences of juniper browsing in Kiskunsági National Park, Hungary
Abstract
We have observed local differences in the vegetation-herbivore interaction pattem in the Juniper shrublands of Kiskunsági National Park, Hungary. The density of herbivorous mammals differs in the Bugac, Bocsa and Orgovány forests, and their diet composition varies seasonally and spatially. We have found juniper browsing by the rabbits at Bugac, by the sheep at Orgovány, but no one fed on juniper at Bocsa. We studied whether juniper shrubs deter browsing via enhanced aromatic oil production or via specific chemicals reducing digestibility, and how chemical interaction is reflected in the age distribution of local stands.
By analyzing the chemical composition of shmbs in the three forests we found some significant differences both in the yield and the composition of essential oils related to the damage level. The shrubs produced the highest yield at Bugac and during the winter season when their consumption was most probable.
As we have shown that rabbits avoid junipers with high oil content and there are local traditions in diet composition due to social learning, these mechanisms might have contributed to the selective survival of juniper seedlings during the past decades. Such local interactions could be reflected by the skewed age distribution of junipers at Bugac where density of young age classes is much lower than expected.
Thus we found that selective feeding by herbivores contributes to the vegetation pattemeven at the landscape level.
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