ELK WINTER FORAGE ENHANCEMENT BY HERBICIDE CONTROL OF SPOTTED KNAPWEED

Spotted knapweed (Centaurea maculosa) is an exotic forb that aggressiv ely invades grassland and early-successional forest sites in the North ern Rocky Mountains of the United States and Canada. Reduced vigor of native bunchgrass populations on spotted knapweed-infested winter elk ranges is potentially decreasing the forage value of these sites. We a nalyzed standing crop data collected 1 and 3 years after spraying for spotted knapweed control at 3 experimental sites in western Montana. P lant species biomass estimates were scaled by numerical indices quanti fying the selection behavior of elk on winter range, and then summed o ver all species in each experimental plot. By the third year after spr aying, herbicide plots averaged 47% greater (P < 0.05) elk winter fora ge than the no-spray check plots. Implications for management of elk w inter range sites in the Northern Rockies are discussed.