Our natural prairie vegetation is dominated by grasses such as spear grasses, wheat grasses and blue grama grass. Drier sites in the southwest support sparser grass cover with abundant prickly pear and sagebrush. Northward and eastward from the mixed grassland, moisture deficits can be less severe and droughts less prolonged. Here “mid-grass”-dominated mixed grasslands alternate with plains rough fescue grasslands, more extensive shrublands, aspen grove woodlands, and wetlands. The aspen parkland, the northern transition zone to the boreal forest, has expanded south into former grassland areas since European settlement effectively stopped prairie fires.