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Abstract
Sporophore abundance of putatively ectomycorrhizal fungi was compared in a mature mixed hardwood/conifer forest inside of (+) versus outside of (−) Rhododendron maximum thickets (RmT). Experimental blocks (1/4 ha) were established inside of (3) and outside of (3) RmT at the Coweeta Hydrologic Laboratory in Macon County, North Carolina, USA. Litter and organic layer substrates were removed, composited and redistributed among 90 2 × 2m plots within the blocks. Plots received either +RmT or −RmT litter, and either +RmT or −RmT organic layers, or were unmanipulated for controls. Sporophores of 67 putatively ectomycorrhizal species were collected from the blocks. Species diversity and overall community structure were similar inside of and outside of RmTs, and no grouping was detected by substrate type. Differences within the ectomycorrhizal fungus community were associated only weakly with environmental parameters, as indicated by ordination. In light of these results, recent observations of ectomycorrhizal suppression and strong shifts in the proportions of morphotypes on tree seedlings inside of RmT do not appear to be related to differences in sporophore distributions. The changes in seedling mycobiont dominance in relation to RmT and the influence this has on seedling health should be examined directly from root tips.
This study was conducted in partial fulfillment for an MS degree in biology at Virginia Polytechnic Institute and State University by the first author. Funding for this project was provided by the National Research Initiative Competitive Grants Program of the USDA, grant number 95371011902, and USDA/CSREES grant number 9502486. The Coweeta Hydrologic Lab provided logistical support. We also thank Dr. J. K. Stone and two anonymous reviewers for their constructive comments regarding the manuscript.