Date of Award

3-1957

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Botany

Major Professor

Royal E. Shanks

Committee Members

A. J. Sharp, Fred H. Norris, L. F. Seatz, James T. Tanner

Abstract

Summary: (1) Prior to the beginning of this century, chestnut (Castanea dentata) was one of the most important forest trees in the eastern United States. It ranged from New England to Georgia, reaching greatest abundance and best form in the mountains of Tennessee and North Carolina. In 1904, the chestnut blight was discovered in New York. Within the next 40 years, the causal fungus (Endothia parasitica) introduced from Asia on blight-resistant species of chestnut, virtually eliminated chestnut as a member of the deciduous forest complex of the eastern United States.

(2) Being a great distance from the center of spread, chestnut trees in the forests of the southern Appalachians were among the last to be attacked by the blight. To determine what tree species are replacing chestnut in the Great Smoky Mountains of North Carolina and Tennessee, 2569j openings in the forest canopy created by the death of the trees and 79 stands, in which chestnut had been a component, were studied.

(3) A total of 5046 trees of 51 species were found in the 2569 openings studied. The most abundant species replacing chestnuts in the Great Smokies were found to be Quercus prinus (17% of all individuals), Q. rubra (16%), Acer rubrum (13%), Tsuga canadensis (6%), Halesia carolina var. monticola (5%), Oxydendrum arboreum (4%), Robinia pseudoacacia (4%), Quercus coccinea (4%), Liriodendron tulipifera (4%), Betula lenta (3%), Quercus alba (2%), Fagus grandifolia (2%), Cornus florida (2%), Pinus rigida (2%), and Quercus velutina (2%). The three leading species, Quercus prinus, Q. rubra, and Acer rubrum comprised 46 per cent of the total individuals. Quercus, comprising a total of 41 percent of all replacement, was the most abundant genus.

(4) In some stands, especially the very mesic cove types, the removal of chestnut resulted in more mesic forest types, genearally including Tsuga canadensis and often Liriodendron tulipifera, Magnolia fraseri, Halesia carolina var. monticola, Tilia heterophylla and Acer saccharum. On the dry slopes and ridges chestnut is usually being replaced by species more xeric than itself.

(5) The death of chestnuts attacked by the blight was not sudden, but gradual. Occupation of the canopy and soil space once filled by chestnut was usually begun by canopy expansion of co-dominants, growth of advance reproduction, or seedling growth even before the blighted trees were dead. Increment cores revealed that suppressed trees generally took nine to 15 years to reach maximum yearly growth increment following release. Increased annual growth began in approximately 1925-1926, indicating the arrival date of the fungus in the Great Smoky Mountains.

(6) No indication was found that the chestnut will "recover" or regain its former position as a dominant. Forest management practices in regions which once contained chestnut should be predicated on this premise.

(7) The results of this study are in general agreement with those obtained in New England, Pennsylvania, and eslewhere in North Carolina. The unifying taxa that welded the former oak-chestnut association into a unit were Castanea dentata, Quercus prinus, Q. rubra, Q. alba, Q. coccinea, Acer rubrum, and Carya supp. Carya was of minor importance in the forests of the Great Smoky Mountains. Because Chestnut is being replaced mainly by various species of oak, mainly Quercus prinus and Q. rubra, it is believed that the former oak-chestnut forest association will eventually develop into an oak association -complex.

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