Date of Award

Winter 2012

Project Type

Thesis

Program or Major

Microbiology

Degree Name

Master of Science

First Advisor

Serita D Frey

Abstract

This study documents soil fungal communities at the Harvard Forest Chronic Nitrogen Addition experiment, which was established in 1989 to test the effects of long-term nitrogen fertilization on ecosystem processes. Researchers at this site have observed an accumulation of soil carbon in the nitrogen fertilized plots and a decrease in fungal biomass, ligninolytic enzyme activity, and rates of litter decay. We hypothesized that decreased decomposition rates in nitrogen-fertilized plots were due to changes in the structure of the fungal community, especially Basidiomycetes, the primary decomposers of lignin in this ecosystem. We performed a marker gene study of fungal communities in the organic soil horizon using 454 high-throughput sequencing of three separate loci. The dominant OTU increased significantly in relative abundance in the highest N treatment. Additionally, Basidiomycete community composition was altered by N additions. These results suggest that changes in fungal community structure may contribute to decreased decomposition rates.

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