Year of Award

2013

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Wildlife Biology

Department or School/College

College of Forestry and Conservation

Committee Chair

Ragan M. Callaway

Commitee Members

Cory Cleveland, John L. Maron, Laurie Marczak

Keywords

Bromus tectorum, Centaurea stobe, Euphorbia esula, grasslands, invasion, nitrate, potential nitrification, Potentialla recta

Abstract

Invasion is associated with unexpected increases in aboveground net primary productivity and altered ecosystem function, including increased nitrogen availability and cycling. These shifts are well documented, however many previous studies have been observational, focused on a single plant species, or have not examined belowground microbial communities. I combined field and experimental techniques to examine changes in productivity and ecosystem function, and the abundance of ammonia- oxidizing bacteria (AOB) for the exotic invaders Bromus tectorum, Centaurea stoebe, Euphorbia esula, and Potentilla recta. To quantify effects of these invasive species on N cycling and AOB abundance we compared soil from invaded and native communities in the field and in an experimental garden. AOB are bacteria responsible for a rate-limiting step in nitrification. We found that invasion was associated with increased abundance of AOB across all species of invader. For other variables, the magnitude of response to invasion varied by species, but we found in general invasion was associated with increased aboveground net primary productivity and soil nitrogen cycling. In addition results from the experimental garden suggest some species of invader may drive increases observed in the field. Finally we report on a novel relationship between aboveground net primary productivity and soil NO3-N indicating that invaders may drive ecosystem processes in ways different from native communities.

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© Copyright 2013 Morgan Marie Luce