Cheatgrass (Brotnus tectorum) was introduced to the sagebrush (Artemisia) ranges of western North America largely during the 20th century. It has become a significant portion of the forage base for the range livestock industry in the Intermountain Area. The introduction of cheatgrass has changed secondary plant succession on most of the sagebrush ranges. The dominance of cheatgrass is closely related to the increased frequency and changed periodicity of wildfires that occur following establishment of this annual grass. Cheatgrass communities are open to invasion by other weed species that may not support grazing.