Effects of glyphosate and replanting treatments on plant diversity in an urban wetland
Grundy, M. 2022.
Abstract
Urban ecosystems experience complex and compound disturbances that facilitate biological
invasion. Urban proximity has led many wetlands to experience invasion by the nonnative species
Phragmites australis (common reed). Treatment for invasion by Phragmites is often limited to the
application of herbicide followed by passive plant regeneration. However, such restoration
treatments do not typically achieve diversity and community composition similar to reference
areas, and the efficacy of additional treatments should be considered. My research looks at the
impact of varied treatments for control of Phragmites on native plant communities in a disturbed
wetland. Specifically, I aimed to answer: what are the effects of glyphosate (herbicide) and
replanting treatments on taxonomic plant diversity in an urban wetland?
I found that there were significant differences in community composition, richness, and diversity
among sites that received different restoration treatments. My findings suggest that spraying with
glyphosate followed by native replanting led to a community that was most similar in composition
to uninvaded control site. Plant communities that were treated with glyphosate alone also differed
compositionally from the invaded control community but had lower diversity and richness
compared to the glyphosate and replanting treatment. Community composition was also
significantly associated with nitrate nitrogen, boron, and aluminum as well as distance to Typha
spp. and Phragmites stands, and plot level water depth. However, treatment was the strongest
predictor of diversity. Overall, my research demonstrates the potential benefit of adding replanting
treatment to Phragmites restoration plans. The inclusion of replanting native species following
glyphosate treatment can lead to plant communities that more closely reflect reference conditions.
Key Words
Wetland restoration, Phragmites australis, native plants, biodiversity, biological invasion
