Date of Award

2023

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Natural Resources

First Advisor

Kristine Stepenuck

Abstract

ABSTRACT

In riparian areas of the northeastern United States, well-established reed canary grass (Phalaris arundinacea) stands are common and have proven to be a challenge for the success of tree plantings during riparian forest restoration projects. The impacts of reed canary grass (RCG) on the habitats it invades are numerous. Reed canary grass reduces biological diversity by homogenizing habitat structure, richness, and environmental variability. Its rapid growth rate and invasive nature limits tree regeneration in riparian forests by shading and crowding out seedlings. Riparian forests improve water quality, wildlife habitat, flood control, and provide a variety of other ecosystem services. As such, there is interest in restoring riparian areas that have been inundated by RCG stands to forest. A critical step to promoting and ensuring widespread adoption of riparian forest restoration efforts is to identify best practices for site preparation and maintenance at locations where RCG has become well-established. Due to its invasive nature, the time, labor and cost of managing plantings to encourage high percent survival, have made restoration efforts challenging. To ease the restoration process, the herbicide glyphosate is commonly used to eliminate RCG prior to tree planting. Recent research has suggested that glyphosate may have sublethal and chronic impacts on wildlife and people, with particular impact on birds. To address the opportunity for widespread forest restoration and the challenge of RCG infestations, the purpose of this experiment was to assess survival of native trees subject to glyphosate, till and mowing management techniques (treatment B) vs. herbicide-free till and mowing management techniques (treatment A), and to compare RCG density between plots over time. To accomplish this, two treatment plots of ten species of native tree stems were planted at eight sites and stem survival was assessed over two growing seasons. In addition, percent cover of RCG was recorded at each site. Chi Square, independent T-test and binary logistic regression statistics were used to assess tree stem survival and the relationship between tree stem survival and percent cover of RCG between treatment A and treatment B plots. Preparing plots by tilling and the application of herbicide (glyphosate) combined with two mowing events in each of the two growing seasons did not result in higher tree stem survival rates than the treatment A plots that were prepared by tilling only and were mowed four times in each of the two growing seasons. As was expected, treatment B plots (glyphosate use) significantly reduced RCG density in the first growing season. However, after the second growing season the percent cover of RCG in the treatment A and treatment B plots was not statistically different. This suggests that the treatment A prescription was as effective at RCG suppression as the treatment B, during the second year. Furthermore, the odds ratio produced by the binary logistic regression models in this study, can be useful to practitioners and landowners when considering which methods of management to use in restoration projects.

Language

en

Number of Pages

92 p.

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