Ecosystem Services and Western U.S. Rangelands

摘要: Rangelands are expansive, unimproved lands located in arid or semi–arid regions, spanning a variety of landscapes including savannahs, high and low altitude deserts, mountain meadows, tundra. generally unsuitable for crop production due to aridity, topography, extreme temperatures. support varying mixtures native nonnative grasses, grass–like plants, forbs, shrubs which provide forage free–ranging domestic animals (Stoddart, Smith Box, 1975). There more than 760 million acres rangelands the United States, Alaska, comprising 33% nation’s total land base (USDA–USFS, 1989a). While exact determinations unavailable, it is estimated that 50% U.S. privately owned, 43% owned by federal government, with remainder state local governments (National Research Council, 1994). Approximately 262 controlled Forest Service (USFS) Bureau Land Management (BLM) leased private individuals purpose land– extensive livestock grazing (CAST, 1996). Many 11 western states1 government agencies grazing, all these states having degree intermingled public ownership rangelands. Arid States characterized variable precipitation, evaporative demand, nutrient poor soils, spatial temporal variability plant production, net primary (Havstad et al., 2007). These often subject desertification invasion other woody plants as result drought, resilience, past management practices. Increased