Effects of Increased Rainfall on Native Forage Production in Eastern Montana

Abstract

Basal area data, collected from five sites in 1963 and 1976, were compared to determine the effects of 13 years of above-average rainfall in the growing season (April through September) on native range vegetation of the northern Great Plains. Changes in basal area, composition, and forage production were analyzed for five major grass and grass-like species. During the 13-year above-average rainfall period, western wheatgrass (Agropyron smithii), needleandthread (Stipa comata), and prairie junegrass (Koeleria cristata) established or increased on all sites. Threadleaf sedge (Carex filifolia) increased on the silty thin hilly range sites but decreased on the sandy range sites. Blue grama (Bouteloua gracilis) decreased on all sites. Calculated forage yield of these five species more than doubled on the silty (110%) and thin hilly (109%) range sites and increased 61% on the sandy range sites. The increase in forage yield decreased the amount of land needed for grazing by 1.6, 0.7, and 2.4 ha/cow-month for the silty, sandy, and thin hilly range sites, respectively.