(Montana State University - Bozeman, College of Agriculture, 2007) McColley, Samuel David; Chairperson, Graduate Committee: Bok F. Sowell.
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. Beaver promote aspen suckering through their dam and lodge building activities. In 2005, I assessed the long-term effects of beaver on aspen stands and the associated riparian area in the Eagle Creek Drainage. Aerial photographs taken in 1990 and 2005 were used to compare changes in riparian area vegetation where beaver were reintroduced. Aspen canopy cover decreased (P<0.05) from 43% to 25% on Eagle Creek (29 ha) between 1990 and 2005. Willow (Salix spp.) cover increased (P<0.05) from 10% to 14% and alder (Alnus incana) cover and water surface area doubled during the same period. Aspen recovery was estimated by comparing vegetative changes among control sites with <10% beaver use (n = 5), active beaver sites (n = 6), sites abandoned for 1-3 years (n = 7), sites abandoned for 4-6 years (n = 4), and sites abandoned for 7-11 years (n = 5).
