As recognized here, glades are bedrock communities associated with horizontally-bedded sedimentary rock exposures found in wide valleys, toe slopes, benches on side slopes, along riversides, and occasionally on clifftops. In Tennessee glades are found in the Western Valley, Highland Rim, Nashville Basin, Cumberland Plateau, and Ridge and Valley. They are generally level to slightly sloping and are dominated by herbaceous plants, graminoids, bryophytes, and lichens and may have scattered shrubs and trees. The vegetation of glades depends on a variety of features, including rock type, soil chemistry, depth, and moisture, and substrate composition. Some glades may have smooth unbroken masses of bedrock, others may be gravelly or covered with flagstone or scattered seasonally water-filled depressions.
Outcrops are distinguished from glades by the fact that they typically are located on strong side slopes or summits of ridgelines or mountains. They may have flat or convex faces and many also have scattered large complexes of boulders or ledge systems. Outcrops on steep side slopes may grade into cliff communities though cliffs usually are on nearly vertical slopes. The vegetation of outcrops is similar to glades in that they are dominated by herbs, graminoids, bryophytes, and lichens. Shrubs and trees are often stunted and are limited to soil pockets and cracks or to the edges. Outcrop communities as defined here primarily are found in the Cumberland and Crab Orchard Mountains, on higher ridges of the Ridge and Valley, and in the Blue Ridge.