Master of Science (M.Sc.)
Virginia Institute of Marine Science
As created wetlands are becoming more common due to compensatory mitigation under section 404 of the Clean Water Act, it has become important to understand how the vegetation community and the soil nutrient availability develop over time. For a created wetland to replace the function of the destroyed natural wetland, the biogeochemical cycling and vegetation community must replicate the natural system. In this study, I sampled the vegetation community as well as the soil and porewater nutrient availability in four created wetlands in southeastern Virginia, constructed and managed by the Virginia Department of Transportation. All the sites used in this study had areas of dense Typha spp. stands, which had been identified as problem areas by the site managers,based on inferences from previous research indicating Typha are invasive in other types of wetlands. In many of these sites, the Typha populations were removed by cutting and herbicide spraying, due to the assumption that the dense Typha stands hinder the biodiversity and therefore reduce the functionality of the created wetlands. As part of this study, I sampled the composition of the vegetation community both within Typha stands and in areas dominated by other species. I was able to show that the dense Typha stands do not lower the species richness or the Shannon diversity index of the vegetation community. I also measured the nutrient availability associated with Typha stands and areas dominated by other vegetation and found no consistent significant differences in soil nutrient availability. However, I did observe a change in nutrient concentration across all vegetation communities and in all study sites from 2006 to 2007. The soil a range of 20 and 55 in 2007. These results may indicate that as created wetlands mature the amount of soil total phosphorus (TP) decreases and the amount of total nitrogen (TN) increases, resulting in a steady state of P limitation relative to N as the site matures. Since these conclusions are based on only two years of data, longer-term research is needed in created wetlands to verify trends in soil TP and TN dynamics as these sites mature.
© The Author
Bevington, Azure E., "Environmental Factors and Typha spp Dominance in Created Wetlands" (2007). Dissertations, Theses, and Masters Projects. William & Mary. Paper 1539617851.