Riparian vegetation recovery in Yellowstone: The first two decades after wolf reintroduction

摘要: During the seven decades of gray wolf (Canis lupus) absence in Yellowstone National Park intensive browsing by Rocky Mountain elk (Cervus elaphus) suppressed growth young deciduous woody plants within park's northern ungulate winter range. Since reintroduction, 24 assessments riparian areas have been published, including eleven on willow (Salix spp.), six aspen (Populus tremuloides), five cottonwood angustifolia and Populus trichocarpa), one each berry-producing shrubs thinleaf alder (Alnus incana spp. tenuifolia). All but two these studies found increases plant height, stem diameter, establishment, canopy cover, or recruitment. More than half measured and, all instances, increased growth/cover over time occurred concurrently with a decrease browsing. Almost also compared observed community changes to climatic/hydrologic variables results analyses were often inconsistent. Although long-term warming drying trends underway appear unlikely contributed occurrence improved communities during last decades, vegetation consistent reestablishment tri-trophic cascade involving an intact large predator guild, elk, species. This early stage recovery Yellowstone, although not occurring everywhere, represents major departure from wide-spread suppression that when wolves absent.