Date of Award
Master of Science
Royal E. Shanks
A. J. Sharp, A. C. Cole
The unglaciated Appalachian Plateaus, as part of the more extensive Appalachian highlands, represent some of the oldest land area in North America with respect to continuous land masses suitable for occupancy by terrestrial plants. These plateaus, along with the Blue Ridge Province and the Ozark and Ouachita highlands, had long been above marine waters when the Coastal Plain emerged, probably during the Miocene Epoch (Fenneman 1938). With the formation and southward advance of the great ice sheets of the Pleistocene, the existing plant life of the glaciated region was destroyed, thereby drastically reducing the botanical age of the otherwise ancient land area north of the glacial boundary (Fernald 1931; Harshberger 1911).
The character of the forest which occupied the Southern Appalachian region (including the present Blue Ridge Province and the Cumberland Plateau) since Cretaceous time and the effect of the period of glaciation upon this forest have been of considerable interest to phytogeographers (Braun 1938, 1947, 1950, 1955; Core 1938; Harshberger 1911; Sharp 1941). Harshberger described the mixed forest south of the glacial border as a remnant of the Tertiary forest which persisted during the Pleistocene with its greatest density in the region drained by the Tennessee River and its tributaries. Braun (1950) considered the Tertiary forest to be the progenitor of the present-day Mixed Mesophytic Forest. She described this modern forest as coextensive with the unglaciated Appalachian Plateaus"... except the northeast arm of the Unglaciated Allegheny Plateau, and the southernmost end of the Cumberland Plateau." She further stated: "The Mixed Mesophytic association . . . is the most complex and the oldest association of the Deciduous Forest Formation . . . and from it or its ancestral progenitor, the mixed Tertiary forest, all other climaxes of the deciduous forest have arisen."
The ancestral nature of the Southern Appalachian flora and the unique characteristics of the Mixed Mesophytic Forest in general make this area exceedingly interesting to plant geographers. This interest may be indicated by the following quotation from Mohr (1901) concerning Lookout Mountain in northeast Alabama:
. . . along the low, damp banks of Little River, there occurs a strong mingling of [Southern Appalachian] types . . . with plants of the lower ranges within the Carolinian area, giving rise to a varied flora, the like of which has not been observed in any other part of the mountainous region of Alabama. When the low elevation of this extremely limited spot is considered . . . , the suffusion of types from different life zones admits of no explanation on the ground of climate or local influences controlling plant distribution, but points clearly to a disjunction of floral conditions due to geological changes.
A number of papers concerning the composition of the forests of the unglaciated Appalachian Plateaus and the affinities of the species which occur in the region have been written by various authors. Perhaps the most thorough discussions are contained in a series of articles by Braun (1938, 1940, 1942, 1947) and in her book on the deciduous forests of eastern North America (1950). Work of a more intensive nature, but more limited in scope, has been completed by Caplenor (1954) and partial results have been published by him in a paper on the Fall Creek Falls system of gorges in Tennessee (1955).
Most of the work by Braun was done in the northern portion of the Cumberland Plateau (especially in Kentucky), in the Unglaciated Allegheny Plateau and in the Cumberland Mountains. The work by Caplenor apparently represents the only systematic study of any of the gorges of the southern district of the Cumberland Plateau. However, several of the protected ravines of the plateau outlier section (Warrior Tablelands) of northern Alabama have received some attention in the literature (Harper 1919, 1937, 1943a; Harvill 1949, 1950, 1951; Segars et al., 1951), mostly because of the occurrence of hemlock at or near its southern limit in this region. Few of these papers provided a comprehensive list of the species occurring in the gorges. Rather, attention was focused on the dominant canopy and understory species and a few others of special interest.
This paper presents further information concerning the vegetation and floristics of the gorges of the Cumberland Plateau of Tennessee, Georgia, and Alabama. An attempt has been made to characterize the vegetation of five of these gorges, and to provide lists of woody species known to occur in each. Information concerning the continental affinities of the species involved is included, and a number of general distribution maps have been prepared with the help of the curators of various herbaria. A review of the history of the Southern Appalachian region in so far as it is pertinent to this study has been provided.
Sherman, Harry L., "The Vegetation and Floristics of Five Gorges of the Cumberland Plateau. " Master's Thesis, University of Tennessee, 1958.