Within Wind Cave National Park you can find an excellent example of a mixed grass prairie. A mixed grass prairie is an ecotone characterized by a mixture of the tall grass species of the eastern tall grass prairie and the short grass species of the western high plains. It is a meeting place, an area that is constantly changing. The dominance of the different types of grasses depends on the amount of moisture received in any given year. With abundant rainfall the tall grasses will dominate because they need more moisture. They are generally found in the valleys of the park. The short grasses are adapted to less moisture. These grasses are found on the dryer, south facing slopes of the park.
Of all of the flowering plants of the prairie, grasses are often overlooked. They are the main component of the prairie, making up about 80% of the biomass. Forbs constitute the other 20%.