The Cedar Glades of Middle Tennessee

Abstract

In the eastern United States there are perhaps not more than a dozen well-marked types of rock-outcrop vegetation, if we leave out of consideration precipitous cliffs. Rocks are common enough in most states, but where the individual outcrops are not more than a few feet wide-as in the case of glacial boulders-they are likely to be overshadowed by surrounding trees, and also to have too few crevices to support any vegetation but mosses and lichens. Or if in grass-land or open forests any vegetation that might tend to establish itself on them is likely to be destroyed in a year or two by fire sweeping through the grass.' And, in order for a given type of rock to support any vegetation peculiar to it, the outcrops must not only be of substantial width, but also be scattered over a considerable area. For if a rock different from anything else in the world should have an area of only an acre or so, any peculiar species that might tend to develop on it would be likely to be exterminated by vicissitudes of weather, erosion, or herbivorous animals long before it could become fixed as a distinct form. But if a peculiar type of rock (or soil) is scattered over several hundred square miles, then any species confined to it, if destroyed in one spot may persist in others and re-establish itself through natural agencies. One of the most interesting types of flat rock vegetation is that of the cedar glades of Middle Tennessee. These have been visited by a few botanists, but nearly all of them were interested in flora rather than vegetation To this day no adequate description of a cedar glade seems to have ever been attempted, and apparently no one has ever thought it worth while to publish a photograph of such a place. What little descriptive matter is available is more in geological than in botanical literature. Dr. J. M. Safford, who was state geologist of Tennessee from i854 to 1860 and i871 to I899, published several interesting notes on the subject, the most accessible of which are probably those in the American Journal of Science (62: 354, 357. i851 4) and the Tenth Census of the United States (5: 400-401, 459, 46i. i884). Additional details by other non-botanical writers can be found in some of the government soil surveys of Middle Tennessee counties, and on pages 13-i6 of Bulletin 22 (i919) of the present Tennessee