Title page for ETD etd-42198-15118


Type of Document Master's Thesis
Author Walker, John F.
Author's Email Address jowalker@vt.edu
URN etd-42198-15118
Title The Inhibitory Effect of Rhododendron maximum L. (Ericaceae) Thickets on Mycorrhizal Colonization of Canopy Tree Seedlings
Degree Master of Science
Department Biology
Advisory Committee
Advisor Name Title
Miller, Orson K. Jr. Committee Chair
Hilu, Khidir W. Committee Member
Nilsen, Erik T. Committee Member
Keywords
  • Ectomycorrhizae
  • Mycorrhizal colonization
  • Fungus community
  • Rhododendron
  • Tree seedling
Date of Defense 1998-04-28
Availability restricted
Abstract
THE INHIBITORY EFFECT OF RHODODENDRON MAXIMUM L. (ERICACEAE) THICKETS ON MYCORRHIZAL COLONIZATION OF CANOPY TREE SEEDLINGS

John F. Walker

(ABSTRACT)

Thickets of Rhododendron maximum (Rm) in the southern Appalachians impose severe limitations on the regeneration of hardwood and coniferous seedlings. Interactions between Rm thickets and ectomycorrhizal colonization were examined to explain seedling inhibition. Experimental blocks were established in and out of Rm thickets in a mature, mixed hardwood/conifer forest in Macon County, North Carolina. Planted seedlings of red oak (Quercus rubra) and hemlock (Tsuga canadensis) were harvested at the end of the first and second growing seasons. Litter manipulation had no effect on total mycorrhizal colonization. Mycorrhizal colonization and ramification index (# mycorrhizae cm-1) were depressed and colonization by Cenococcum geophilum increased in blocks with versus without Rm. After the first year, percent colonization of T. canadensis not in Rm thickets (62 %) was three times higher than in Rm thickets (19%), and the ramification index was increased by more than a factor of four (2.83 versus 0.61). Mycorrhizal colonization levels were correlated with root weight and shoot weight in both hemlock and oak seedlings, but did not explain most of the variation observed. Sporocarps of 69 putatively ectomycorrhizal species were collected on the blocks. Species diversity and overall community structure was similar in and out of Rm thickets. Individual species, i.e. Lactarius speciosus and Russula krombholzii, were significant indicators of forest without Rm thickets. Rhododendron maximum thickets probably affect the process of mycorrhization. The reduced level of mycorrhizal capacity under Rm thickets could be a factor in the increased seedling failure in Rm thickets.

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