Sponsor
Portland State University. Department of Environmental Science and Management
First Advisor
Jeffrey Gerwing
Date of Publication
Winter 3-25-2013
Document Type
Thesis
Degree Name
Master of Science (M.S.) in Environmental Science and Management
Department
Environmental Science and Management
Language
English
Subjects
English ivy -- Environmental aspects -- Pacific Northwest, Pacific, Invasive plants -- Pacific Northwest, Nitrogen compounds -- Environmental aspects -- Pacific Northwest, Atmospheric deposition -- Pacific Northwest
DOI
10.15760/etd.680
Physical Description
1 online resource (vii, 57 pages) : illustrations (some color)
Abstract
Increased nitrogen deposition has been shown to promote the dominance of invasive species, and nitrogen deposition rates have steadily increased in most of the Western United States in recent years due to population increases. The purpose of this study was to determine if increased rates of nitrogen deposition are contributing to the success of Hedera helix in the Pacific Northwest. Plots were established in Lesser Park in Portland, Oregon and received monthly treatments of ammonium nitrate for one year. Growth, measured as change in percent cover, was compared between treated and untreated plots for both H. helix and native species. Additionally, a greenhouse experiment was employed wherein H. helix was grown in shared pots with two native species, Fragaria vesca and Polystichum munitum, and three treatment levels were compared; none, low, and high nitrogen. Relative growth rate was compared between treatments for each species after twelve weeks of treatment. Results from the greenhouse experiment were highly variable and no general conclusions could be drawn about the effects of increased nitrogen deposition on competition between H. helix and native species. In the field, treatment did not have a significant effect on growth but species did have a significant effect, as H. helix had a greater increase in percent cover than native species regardless of treatment. However, a marginally significant interaction was found between species and treatment. Native species cover actually increased in plots that received nitrogen addition and decreased in control plots, while H. helix had a slightly higher increase in cover in control plots. Though the growth of H. helix was significantly higher than the growth of native species in control plots, nitrogen addition caused the growth rates to converge towards more similar means in treated plots. Results indicate that increased nitrogen deposition may actually have a positive effect on the growth of native species by reducing the invasive potential of H. helix.
Rights
In Copyright. URI: http://rightsstatements.org/vocab/InC/1.0/ This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).
Persistent Identifier
http://archives.pdx.edu/ds/psu/9355
Recommended Citation
Dolan, Bianca Christine, "Effects of Increased Nitrogen Deposition on the Dominance of Hedera helix in the Pacific Northwest" (2013). Dissertations and Theses. Paper 680.
https://doi.org/10.15760/etd.680
Included in
Environmental Sciences Commons, Other Ecology and Evolutionary Biology Commons, Other Plant Sciences Commons, Weed Science Commons