Forage Values on a Mountain Grassland-Aspen Range in Western Colorado

Abstract

West of the Continental Divide in the southern Rocky Mountains, open parks within the sprucefir forests are occupied by a diverse herbaceous vegetation (Fig. 1). Intermingled are sites dominated by aspen (Populus tremuloides Michx.) that support a luxuriant understory of grasses and forbs. Thurber fescue (Festuca thurberi Vasey), a large bunchgrass, often characterizes the general aspect of the parks as well as the aspen understory. Hence, the grass-forb openings frequently are categorically referred to as Thurber fescue grasslands. Langenheim (1962) described the Festuca thurberi of the Crested Butte area in western Colorado as a community with a wide elevational range that is found on deep soils and xeric exposures. Thurber fescue has been reported at elevations of 8,000 to 12,000 ft from southern Wyoming, Colorado, northern New Mexico (U.S. Forest Service, 1937), and westward in the Abajo Mountains of Utah3 and the Graham Mountains of Arizona (Kearney and Peebles, 1942). In many respects these grasslands are similar to other high-elevation grasslands of the mountainous West. For example, in the Big Horn Mountains in Wyoming, grassland openings are dominated by Idaho fescue (Festuca idahoensis Elmer) (Hurd, 1961), which is an important species in western Colorado. In eastern Oregon and Washington,