Recovering aspen follow changing elk dynamics in Yellowstone: evidence of a trophic cascade?

摘要: To investigate the extent and causes of recent quaking aspen (Populus tremuloides) recruitment in northern Yellowstone National Park, we measured browsing intensity height young 87 randomly selected stands 2012, compared our results to similar data collected 1997-1998. We also examined relationship between recovery distribution Rocky Mountain elk (Cervus elaphus) bison (Bison bison) on ungulate winter range, using fecal pile densities annual count data. In 1998, 90% were browsed none taller-than 200 cm, at which begin escape from browsing. only 37% east 63% west portions range browsed, 65% had taller than cm. Heights inversely related intensity, with least greatest heights eastern portion corresponding changes density distribution. contrast historical (1930s-1990s), recently (2006-2012) have been north park boundary (approximately 5 elk/km2), western part (2-4 relatively few (<2 even mild winters. This redistribution decrease inside park, overall reduction numbers, explain why many begun recover. Increased predation pressure following reintroduction gray wolves (Canis lupius) 1995-1996 played a role these changing population dynamics, interacting other influences including increased by bears (Ursus spp.), competition an expanding population, shifting patterns human land use hunting outside park. The resulting new is evidence landscape-scale trophic cascade resurgent large carnivore community, combined ecological changes, has benefited through effects prey.