Large Predators Limit Herbivore Densities in Northern Forest Ecosystems

摘要: There is a lack of scientific consensus about how top-down and bottom-up forces interact to structure terrestrial ecosystems. This especially true for systems with large carnivore herbivore species where the effects predation versus food limitation on herbivores are controversial. Uncertainty exists whether driven by carnivores common, if so, their influences vary predator guild composition primary productivity. Based data information in 42 published studies from over 50-year time span, we analyzed guilds prey densities across productivity gradient boreal temperate forests North America Eurasia. We found that mammalian carnivores, sympatric gray wolves (Canis lupus) bears (Ursus spp.), apparently limits herbivores. cervid densities, measured deer equivalents, averaged nearly six times greater areas without compared wolves. In wolves, density increased only slightly increasing These consistent exploitation ecosystems hypothesis appear occur broad range net productivities. Results also theory trophic cascades, suggesting widespread forcing forest biomes northern hemisphere. findings have important conservation implications involving not management but plant communities.