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Citation. Bakker, E.S.; Ritchie, M.E.; Olff, H.; Milchunas, D.G.; Knops, J.M.H. 2006. Herbivore impact on grassland plant diversity depends on habitat productivity and herbivore size. ECOLOGY LETTERS 9:780-788.
Abstract. Mammalian herbivores can have pronounced effects on plant diversity but are currently
declining in many productive ecosystems through direct extirpation, habitat loss and
fragmentation, while being simultaneously introduced as livestock in other, often
unproductive, ecosystems that lacked such species during recent evolutionary times. The
biodiversity consequences of these changes are still poorly understood. We
experimentally separated the effects of primary productivity and herbivores of different
body size on plant species richness across a 10-fold productivity gradient using a 7-year
field experiment at seven grassland sites in North America and Europe. We show that
assemblages including large herbivores increased plant diversity at higher productivity
but decreased diversity at low productivity, while small herbivores did not have consistent effects along the productivity gradient. The recognition of these large-scale, cross-site patterns in herbivore effects is important for the development of appropriate biodiversity conservation strategies.