Each of the four unions can be found on the three types of range sites. However, the relative abundance and dominance of characteristic species changes with the range site and with environmental conditions. Soil moisture is the principal factor in Nebraska sandhills prairie vegetation distribution. The more mesic species, such as the bluestems, switchgrass, and indiangrass, can be supported in the valleys of Nebraska sandhills prairie. A characteristic feature of the Nebraska sandhills prairie is the blowout, an area denuded of vegetation due to rapid wind erosion.
Blowouts occur where the vegetation is depleted due to fire or overgrazing.
A blowout can be active for many years, and can reach a depth of 100 feet and a circumference of more than 600 feet. The vegetation remains sparse even after several years.