Modification of mixed-conifer forests by ruminant herbivores in the blue mountains ecological province

Secondary plant succession and the accumulation of biomass and nutrients we re documented at seven ruminant exclosures in Abies and Pseudotsuga forests variously disturbed by logging, burning, and grass seeding. Long-term (25 or more years) foraging by Rocky Mountain mule deer (Odocoileus hemionus) a nd Rocky Mountain elk (Cervus elaphus) suppressed the development of decidu ous shrubs. Ruminant herbivores influenced vegetation to extents equal to t hose of the initial episodic disturbances. Food preferences of elk were lin early correlated with longterm development of plant taxa. Accumulations of understory and forest floor biomasses were greater inside exclosures than o utside. Accumulations of nitrogen, phosphorus, calcium, magnesium, and pota ssium were greater inside exclosures than outside.