The barrens in Tennessee are small openings in the forest; the openings are dominated by perennial grasses which are usually the same grass taxa that dominate the Tallgrass Prairies of the Middle West. The flora of the barrens comprises nearly 40 percent of the presently known Tennessee flora. The taxa are mainly intraneous but there are significant northern, southern and western elements. There are few or no barrens endemics, but the number of taxa listed in Tennessee as rare exceed, for example, the numbers of rare taxa in the Great Smoky Mountains. Barrens today appear to be successional and are chiefly those maintained as open communities by human action. Maintenance before arrival of European settlers was presumably due to periodic drought, especially on shallow soils, and grazing-browsing-trampling, and fire. Although known areas are few, they are still being found and opportunities for their study are great.