Effect of Grazing by Sheep on the Quantity and Quality of Forage Available to Big Game in Oregon's Coast Range

Abstract

Effects of sheep grazing in Douglas-fir (Pseudotsuga menziesii) plantations in Oregon's Coast Range were studied in 1981 through 1983 to determine the impact of grazing on big game habitat. Biomass, dry matter digestibility, and crude protein content of forage present on grazed vs. ungrazed areas were determined in October and March both years. Sheep grazing reduced total current year's phytomass of browse and forbs (p<.10) in October. October phytomass of graminoids was not affected by grazing. Forage from grazed areas in October generally had higher crude protein levels and dry matter digestibility than forage from ungrazed areas in October. Few differences in either crude protein or dry matter digestibility of forage from grazed vs. ungrazed areas were evident in March. However, a greater quantity (p<.10) of new, succulent forage was generally present in grazed areas compared to ungrazed areas. These data suggest that sheep grazing can improve big game forage supply in Oregon's Coast Range by improving forage quality in the fall and by increasing the quantity of high quality forage in the spring.