Wind Cave National Park is located where the grasslands meet the ponderosa pine forests of the uplifted Black Hills. Here, there is a blending of the tall grass prairie species of the eastern Great Plains and the short grass species of the western Great Plains. These eastern and western prairies are differentiated by the types of grasses and forbs found there. Each type reflects the amount of available moisture which decreases from the east to west. The species composition is determined by climate, fire frequency, and the degree and frequency of grazing. The mixed grass prairie is an ecotone that results where species composition is constantly shifting between the tall and short grass prairies.