Are wolves saving Yellowstone's aspen? A landscape-level test of a behaviorally mediated trophic cascade

摘要: Behaviorally mediated trophic cascades (BMTCs) occur when the fear of predation among herbivores enhances plant productivity. Based primarily on systems involving small-bodied predators, BMTCs have been proposed as both strong and ubiquitous in natural ecosystems. Recently, however, synthetic work has suggested that existence may be by predator hunting mode, whereby passive (sit-and-wait) predators much stronger effects than active (coursing) predators. One BMTC for a wide-ranging system involves reintroduction wolves (Canis lupus) to Yellowstone National Park, USA, which is thought leading recovery trembling aspen (Populus tremuloides) causing elk (Cervus elaphus) avoid foraging risky areas. Although this generally accepted highly popularized, it never adequately tested. We assessed whether influence obtaining detailed demographic data stands using tree rings monitoring browsing levels experimental exclosures arrayed across gradient risk three years. Our study demonstrates historical failure regenerate varied widely (last recruitment year ranged from 1892 1956), our do not indicate an abrupt cessation recruitment. This pattern appears more consistent with gradual increase numbers rather rapid behavioral shift following wolf extirpation. In addition, estimates relative survivorship young browsable are currently recovering Yellowstone, even presence large population. Finally, test hypothesis we found impacts demography diminished sites where at higher wolves. These findings suggest need further evaluate how predator-prey life history ecological context.