Comparison of Hydrologic and Hydraulic Characteristics of the Anacostia River to Non-Urban Coastal Streams

Streams in urban areas often utilize channelization and other bank erosion control measures to improve flood conveyance, reduce channel migration, and overbank flooding. This leads to reductions in evapotranspiration and sediment storage on floodplains. The purpose of this study is to quantify the evapotranspiration and sediment transport capacity in the Anacostia Watershed, a large Coastal Plain urban watershed, and to compare these processes to a similar sized non-urban watershed. Times series data of hydrologic and hydraulic changes in the Anacostia, as urbanization progressed between 1939-2014, were also analyzed. The data indicates lower values of warm season runoff in the non-urban stream, suggesting a shift from evapotranspiration to runoff in urban streams. Channelization in the Anacostia also increased flow velocities and decreased high flow width. The high velocities associated with channelization and the removal of floodplain storage sites allows for the continued downstream transport of sediment despite stream bank stabilization.

The Ecology of Urbanization: A Study of Soil Microbial Community Rosponse

Urbanization is associated with global biodiversity loss of macrophauna and flora through direct and indirect mechanisms, but to date few studies have examined urban soil microbes. Although there are numerous studies on the influence of agricultural management on soil microbial community composition, there has been no global-scale study of human control over urban soil microbial communities. This thesis extends the literature of urban ecology to include soil microbial communities by analyzing soils that are part of the Global Urban Soil Ecology and Education Network (GLUSEEN). Chapter 1 sets the context for urban ecology; Chapters 2 addresses patterns of community assembly, biodiversity loss, and the phylogenetic relationships among community members; Chapter 3 addresses the metabolic pathways that characterize microbial communities existing under different land-uses across varying geographic scales; and Chapter 4 relates Chapter 2 and 3 to one another and to evolutionary theory, tackling assumptions that are particular to microbial ecology.