From text of...'Summary: Deep-soil savannas of the Midwest occupied a transitional area between eastern deciduous forest and tallgrass prairie. These savannas included oak openings and barrens/brush prairie that tended to merge floristically and structurally with each other and with forest and prairie communities. Oak openings tended to have an open, parklike appearance with widely scattered trees and an understory of high floristic similarity to tallgrass prairies. Barrens/brush prairies apparently were derived from forested areas and had a woody undergrowth of trees and shrubs that was maintained in scrubby condition by repeated burning. Because of the transitional nature of barrens, brush prairie, and oak openings. there are relatively few species of plants that characterize these vegetation types. Maintenance of these savannas was strongly dependent upon periodic fire. In the later part of the 19th century, barrens and oak openings were rapidly converted to closed forest following cessation of fires associated with European settlement. Agricultural activities, including overgrazing, degraded most of the remaining savannas, and consequently there are few extant examples of this vegetation type.'