Aspen Restoration Using Beaver on the Northern Yellowstone Winter Range under Reduced Ungulate Herbivory

摘要: Ungulate browsing and lack of overstory disturbance have historically prevented aspen regeneration on the Northern Yellowstone Winter Range (NYWR). Aspen clones regenerate if sprouts are produced that grow into recruitment stems (>2 m tall) replace mature overstory. Beaver reintroduced in 1991 to Eagle Creek NYWR facilitated restoration by removing trees increasing sprouting. However, intense ungulate browsing, primarily from elk herd, was preventing as 2005. Since 2005, wolf predation has contributed a 56% decrease this herd. We investigated effects beaver reintroduction, herbivory, predator-mediated declines numbers 1997 2012. Aerial photos 2005 2011 showed not been replaced 21 years after reintroduction (p > 0.05). Sprouting were using 4-m radius circular plots (n = 31) established throughout monitored annually until activity stimulated sprouting 71% these plots. In 2012, 77% had ≥1 stem 75% paired associated with exclosures 16) an average height ≥2 m. Recent increases indicate communities regenerating. This likely resulted decreased pressure saplings These findings consistent predictions density-mediated trophic cascade following reintroduction.