Date of Award

5-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Forest Resources

Advisor

Wang, Geoff

Committee Member

Layton , Patricia

Committee Member

Gerard , Patrick

Abstract

Chinese privet (Ligustrum sinense Lour.) is a non-native invasive shrub that has become ubiquitous throughout the southeastern United States. There is a large infestation of privet at Congaree National Park in South Carolina, and the National Park Service is interested in controlling it with dormant-season foliar herbicide treatments. The primary objective of this study was to determine which combination of herbicide and applicator provides the most effective control of privet, while minimizing damage to non-target plants. Another objective was to document impacts of privet invasion on Congaree's plant communities.
Seven vegetation plots were installed in each of five large privet populations, and one plot outside of each population in a similar un-invaded area. Herbicide treatments were applied in January of 2012, and consisted of the herbicides glyphosate, metsulfuron, and a combination applied with both backpack sprayers and mistblowers. Measurement plots were set up using the protocols of the Carolina Vegetation Survey.
Chinese privet invasion significantly affected native plant communities at Congaree National Park. Density of canopy tree stems from 1-5cm dbh was lower in invaded than un-invaded plots, suggesting that privet may inhibit canopy regeneration. Invaded areas had a lower density of native shrubs and understory trees and lower cover of sedges. A significant negative correlation was found between privet abundance and species richness, herbaceous cover, and density of canopy tree stems. However, cover of Microstegium vimineum was higher in un-invaded plots, suggesting that Chinese privet may also inhibit the establishment of other invasive species.
The efficacy of Chinese privet control did not differ among herbicide types, but it did differ between the two applicators. Mistblowers achieved more effective control of privet, in part due to their greater height of spray. All treatments appeared to be highly effective below the maximum height of spray. The height of some privet stems exceeded the reach of both applicator types.
Tests for non-target impacts showed that for most variables, no treatments differed from control plots. The greatest non-target impacts detected were to sedges and winter-green species from treatments containing glyphosate. The backpack-metsulfuron treatment showed a significant decrease in tree and shrub cover (<50cm >height), and the mistblower-glyphosate treatment showed a small decrease in fern cover as compared to the control. Mistblowers showed fewer impacts overall. No treatments significantly impacted species richness.
No single combination of herbicide and applicator met all objectives. However, mistblowers showed a number of advantages for both privet control and non-target impacts. Glyphosate, despite greater impacts to some graminoid species, may be preferred for its soil-binding properties. Height of privet must be considered in planning treatments. Benefits from the removal of privet are expected to outweigh the negative impacts of herbicide application.

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