摘要：Aspen (Populus tremuloides) on the Gardiner Ranger District, Gallatin National Forest, have declined over the last half-century. In an attempt to reverse this trend, beaver (Castor canadensis) were reintroduced in Eagle Creek in 1991. In 2005, we assessed the long-term effects of beaver on aspen stands and the associated riparian area in the Eagle Creek drainage. Aspen recovery was estimated by comparing vegetative changes among control sites with (n = 5), active beaver sites (n = 6), sites abandoned for 1 to 3 years (n = 7), sites abandoned for 4 to 6 years (n = 4), and sites abandoned for 7 to 11 years (n = 5). Aspen stem densities in active sites and sites abandoned by beaver for 1 to 3 years were similar (2.6/m2) and greater (P = 0.01) than the remaining sites. Sprout and sapling densities were greater (P = 0.01) on active and sites abandoned for 1 to 3 years compared to the other sites. Aspen suckers were not able to grow taller than 2m on sites without beaver activity for 4 to 1 years, which prevented aspen recovery. Beaver activity stimulated the growth of aspen sprouts and saplings, but ungulate herbivory prevented successful aspen recovery in Eagle Creek.
