Master of Science (M.Sc.)
Randolph M Chambers
Doug A DeBerry
Invasive plant species can alter natural communities and degrade ecosystem function, yet the factors influencing species invasion are poorly understood. Understanding how environmental factors affect plant invasion on compensatory wetland mitigation sites would allow wetland managers to approach invasive species management using a proactive approach (prior to invasion), thus minimizing the likelihood of invasive plants colonizing the system and degrading ecosystem function. In Chapter 1, I introduce the concepts and relevant literature used repeatedly in my project. In Chapter 2, I examine which key environmental factors are associated with altered plant community structure and invasive species prevalence on compensatory wetland mitigation sites. In Chapter 3, I look further into the plant community assemblage at each of my study sites and examine differences in the plant community at varying levels of invasive plant prevalence. For this study, Arthraxon hispidus (small carpet grass), Microstegium vimineum (Japanese stilt grass), and Typha spp. (cattail) were selected as representative invasive plants due to their abundance on non-tidal wetland mitigation sites, as well as their relative differences in ecological tolerance for environmental conditions (e.g., light availability or flooding). Within populations of these species, transects consisting of five 4m2 plots were established on 34 wetland mitigation sites within the Coastal Plain and Piedmont physiographic provinces in Virginia. Along transects, plots were randomly assigned to locations that captured the gradient from completely invaded (invasive species dominant) to uninvaded (invasive species absent or nearly so). For each plot, vegetation abundance data, soil samples, and canopy imagery were obtained for analysis. In Chapter 2, Canonical Correspondence Analysis (CCA) reveals iron, phosphorus, calcium, carbon:nitrogen ratio, canopy cover, and hydrology as correlates with variation in plant community composition across the invasion gradient. In Chapter 3, Spearman rank correlation results show no significant relationship between native species richness and invasive species abundance for any of the three species examined. Further analysis using Sørensen indices of similarity and species accumulation curves corroborate this result. Further study is required to determine causality in the relationships between invasive species and environmental variables, but results demonstrate the need for function-based criteria regarding invasive species management on compensatory wetland mitigation sites. Current standards encourage the use of non-specific herbicides, which may increase the risk of damaging native plant communities and perpetuating the cycle of disturbance and re-invasion on wetland mitigation sites.
© The Author
Hunter, Dakota, "Invasive Species Research in Compensatory Wetland Mitigation: Investigating Plant Community Composition and Environmental Correlates with Three Invasive Plants" (2019). Dissertations, Theses, and Masters Projects. William & Mary. Paper 1563899036.