La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Titre :	Trophic cascades involving cougar, mule deer, and black oaks in Yosemite National Park
Auteurs :	William J. Ripple, Auteur ; Robert L. Beschta, Auteur
Type de document :	Article
Dans :	Biological Conservation (141(5) MAY 2008)
Article en page(s) :	1249-1256
Langues:	Anglais
Résumé :	Using a historical reconstruction, we discovered a potential trophic cascade involving cougar (Puma concolor), mule deer (Odocoileus hemionus), and California black oak (Quercus kelloggii) in the Yosemite Valley of Yosemite National Park in California. Our objective was to determine whether large deer populations in the absence of a top-level carnivore were suppressing tree regeneration. As human visitation increased in the early 1900s and cougar became increasingly scarce, the mule deer population irrupted in the 1920s. In August 2006, we undertook a retrospective study of black oak recruitment (i.e., growth of seedling/sprouts into tall saplings and trees) by inventorying all black oaks in stands accessible to deer and greater than 0.5 ha in size (18 stands, 2921 trees). We similarly inventoried oaks within sites representing refugia from deer browsing (4 stands, 481 trees). While significantly diminished oak recruitment has occurred since the 1920s in stands accessible to deer (p

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