Document Type

Dissertation

Date of Award

7-2018

Keywords

Biological sciences, Invasive species, Seed bank, Urbanization

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

First Advisor

John E. Titus

Subject Heading(s)

Biological sciences; Invasive species; Seed bank; Urbanization; Biology

Abstract

Urban wetlands are important ecosystems that moderate flooding risks and improve water quality. Vegetation is a key component of urban wetlands; plants promote sedimentation, play critical roles in biogeochemical cycling, and provide food and habitats for other organisms. My research focuses on the standing vegetation and seed banks of urban wetland plant communities. Urban wetlands in south-central New York had a higher percent cover of invasive species in the standing vegetation and significantly lower species richness; however, native species were also common in urban flora. These sites had a high percentage of obligate wetland species, and most closely resembled emergent wetlands in their vegetation composition. Like the standing vegetation, urban wetland seed banks were dominated by obligate wetland species. Although these seed banks may be viable and can contribute to the revegetation of disturbed sites, a high percentage of invasive species may limit the establishment of native populations. We evaluated the effects of a complete regrade and expansion of an urban retention wetland on its seed bank and standing vegetation. The density and species composition of seedlings that emerged from the seed bank were determined under drawdown and flooded conditions from sediment cores collected before (2011) and after (2014) the regrade. The standing vegetation composition was recorded just prior to the regrading, and twice in each growing season (2012-2014) after the regrade. Seedling densities were reduced nearly 66% after the regrade, and seedling density significantly decreased in the drawdown treatment. Species richness in the standing vegetation decreased immediately after the regrade and rebounded over three years. This indicates that a regrading project can substantially reduce seedling density of an urban wetland seed bank, but standing vegetation can show signs of recovery within a short time span, perhaps due to the presence of a prolific bud bank. My work shows that urban wetlands are different from natural wetlands in south-central upstate New York. Although invasive species are common in urban wetlands, some native species can establish and survive under urban conditions, and these species should strongly be considered in planting schemes of wetland creation or rehabilitation projects in urban landscapes.

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