Effects of Spring and Fall Grazing by Sheep on Vegetation of the Upper Snake River Plains

Abstract

S AGEBRUSH-GRASS range plays an important part in the western sheep industry. Because of its topographical location between low wintering areas and high summer ranges it receives use during two separate periods of the year. This use occurs in the spring prior to readiness of the summer range, at which time ewes with young lambs require abundant succulent feed, and again in the fall when ewes need conditioning for breeding. This study of the effects of spring and fall grazing on sagebrush-grass range was conducted at the U. S. Sheep Experiment Station near Dubois, Idaho. It is based upon changes in vegetal composition over a 25-year period (1924-49). A similar comparison was made by Craddock and Forsling (1938) over a g-year period from 1924 through 1932. They not only found that heavy spring stocking reduced grasses and forbs while unpalatable shrubs greatly increased, but that heavy fall grazing alone caused an increase in palatable grasses and forbs while shrubs, chiefly threetip sagebrush (Artemisia tripartita), were slightly decreased. They concluded that fall stocking alone is a method of improving depleted sagebrush-grass lands without sacrificing current forage production. Besides covering changes over a much longer period than those described rather