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Nitrogen enrichment and the structure and function of ectomycorrhizal communities.

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Call No.	QK604.2.M92 E28 2000
Author	Eaton, Gregory Kent, 1959-
Title	Nitrogen enrichment and the structure and function of ectomycorrhizal communities.
Date	2000
Abstract	The ectomycorrhizal symbiosis between temperate forest trees and some soil fungi is an adaptation to resource limitations of both symbionts. Nitrogen enrichment of historically N-limited forest ecosystems may change this symbiosis through direct and indirect impacts on the availability of either symbionts most limiting resources. This study addressed the impacts of resource alterations associated with nitrogen enrichment on (1) fungal phenotypic properties that should be important to community and ecosystem properties of soil microbes, (2) the richness, diversity and structure of ectomycorrhizal fungus communities, and influences of community structure on important ecosystem functions, and (3) the potential for alterations in fungal community structure to influence the responses of an important host tree to nitrogen enrichment. I utilized pure culture studies of fungal growth and nitrogen mineralization capacity, surveys of ectomycorrhizal fungus communities and soil properties across sites of different N status, and an experimental test for effects on young paper birch (Betula papyrifera) trees of inoculation with the different communities of ectomycorrhizal fungi that inhabited sites of different soil N status. Fungal species differed widely in their growth and mineralization responses to N enrichment. These differences indicate that N enrichment of forests is likely to impact competitive interactions between fungi and ecosystem mineralization processes. Nitrogen fertilization of forests tended to alter the community structure of ectomycorrhizal fungi and reduce species diversity. Measures of mineralizing enzymes in soils did not differ markedly with N enrichment, but soil phosphatase enzyme activity was strongly correlated with the community composition of ectomycorrhizae. Different ectomycorrhizal communities provided similar benefits to plant performance suggesting considerable redundancy in their symbiotic function. Colonization of paper birch roots by an assemblage of several species of ectomycorrhizal fungi provided greater benefit to growth and nutrition than colonization by a single opportunistic fungus. I conclude that ectomycorrhizal fungi respond to N enrichment in ways that benefit paper birch trees, and may contribute to increased abundance of this tree in nitrogen-enriched forests. While changes in ectomycorrhizal communities at the level of individual trees can affect mineralization processes, redundancy of function within those communities may also stabilize some ecosystem properties of forest systems.
Description	1 online resource (ix, 141 leaves) : illustrations
Format	application/pdf
Advisor	Ayres, Matthew P.
Subject	Ectomycorrhizas -- Ecology. ; Ectomycorrhizas -- Physiology. ; Ectomycorrhizal fungi -- Ecology. ; Ectomycorrhizal fungi -- Physiology. ; Fungal communities. ; Plants -- Effect of nitrogen on. ; Plant-fungus relationships. ; Paper birch. ; Forest ecology.
College	Dartmouth College -- Department of Biological Sciences.
Issuing Body	Dartmouth Dissertations are made available through the Dartmouth Digital Library.
Degree	Thesis (Ph.D)--Dartmouth College.
Copyright	In Copyright. This material is protected by copyright and/or related rights. You are free to use this material in any way that is permitted by copyright law that applies to your use. For other uses, you need to obtain permission from the rights-holder(s). http://rightsstatements.org/page/InC/1.0/
DOI	https://doi.org/10.1349/ddlp.2711

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