http://hdl.handle.net/1903/2797 2013-06-18T22:16:49Z http://hdl.handle.net/1903/13664 Title: TRANSMISSION OF CYMBIDIUM MOSAIC VIRUS IN ONCIDIUM ORCHIDS BY PERIPLANETA AUSTRALASIAE Authors: Allen, Carol Dianne Abstract: ABSTRACT Title of Thesis: TRANSMISSION OF <italic>CYMBIDIUM MOSAIC VIRUS</italic> IN ONCIDIUM ORCHIDS BY <italic>PERIPLANETA AUSTRALASIAE</italic> Carol Dianne Allen, Master of Science. 2012 Thesis Directed by: Gary Coleman, Ph.D. Department of Plant Science and Landscape Architecture <italic>Cymbidium mosaic virus</italic> is the most common disease in orchids infecting a large number of cultivated orchids found in all phases of the industry and around the world. Its transmission occurs through contact by contaminated cutting tools, human hands, or water. Although insects known to transmit plant viruses have been exposed to orchid viruses, none have been found to successfully transmit <italic>Cymbidium mosaic virus</italic>. <italic>Periplaneta australasiae</italic>, the Australian cockroach, is a common greenhouse pest that is known to feed on orchid plants. In controlled conditions Australian cockroaches were given inoculation access through feeding activity on known CymMV positive orchid plants and then allowed to feed on virus free plants. The virus free plants were isolated from subsequent insect exposure and after a period of time samples from the feeding damage sites were analyzed for the presence of virus RNA through nested and hemi-nested PCR techniques. A statistically significant number of samples were positive demonstrating that with high population numbers and long term exposure, virus transmission is possible. 2012-01-01T00:00:00Z http://hdl.handle.net/1903/13252 Title: Genetic consequences of habitat fragmentation and restoration Authors: Lloyd, Michael Warren Abstract: The objective my dissertation was to assess the effects of habitat loss and fragmentation on genetic diversity and landscape connectivity. I focused on <italic>Vallisneria americana</italic> Michx. (Hydrocharitaceae), a submersed aquatic plant species found in the Chesapeake Bay. <italic>Vallisneria americana</italic> has undergone dramatic changes in abundance and distribution throughout its range and has been targeted for restoration, which makes it ideal for examining the effects habitat loss and fragmentation. I examined the naturally occurring genetic diversity across the Chesapeake Bay and its major tributaries. Sites were genetically diverse, but had a range of genotypic diversities. There were four genetic regions, corresponding with geographic regions in the Bay. <italic>Vallisneria americana</italic> has been the target of restoration, and restoration techniques could be influencing genetic diversity and potentially lowering overall success. I examined various restoration techniques across eight restoration sites, and found that technique did not greatly influence genetic diversity. However, small population size, significant inbreeding coefficients, and low overlap of allele composition among sites provide cause for concern. Measures of functional and potential connectivity provide insights into the degree of contemporary gene flow occurring across a landscape. Pollen dispersal distance was measured using indirect paternity analysis, and is spatially restricted to only a few meters. Dispersal at this scale imposes small genetic neighborhoods within sites, evidenced by high seed relatedness within mothers. I used a graph theoretic approach to examine the distribution and potential connectivity of historic and current patches of <italic>V. americana</italic>. There was a high turnover in the distribution of patches, and connectivity varied through time, but even if all habitat were occupied, increases in overall network connectivity would not necessarily be observed. I developed an individual based model that I used to test the ability of measures of genetic differentiation to detect changes in landscape connectivity. Genetic differentiation measures became significant after two generations, but the magnitude of change in each was small in all cases and extremely small when population sizes are greater than 100 individuals. These results suggest that genetic differentiation measures alone are inadequate to rapidly detect changes in connectivity. 2012-01-01T00:00:00Z http://hdl.handle.net/1903/13071 Title: Redox and Soil Manipulation Effects on Ditch Soil Phosphorus Processing Authors: Ruppert, David Emmanuel Abstract: Ditches increase the connectivity of landscapes to open water systems, potentially facilitating the degradation of downstream waterways. A treatment and an observational experiment were conducted to identify processes behind phosphorus (P) cycling in ditch soils. If the ditch had not undergone recent dredging soils were observed in the treatment experiment to release P to surface water whether the soil system was iron (Fe)-oxidizing or Fe-reducing. Also in the treatment experiment, Fe was released to surface water in appreciable amounts only if the soil system was Fe-reducing. From the observational experiment P release due to mineralization was inferred due to a positive trend with temperature. Also in the observational experiment Fe-reducing conditions were weakly correlated with diminished P concentrations in the ditch water. It was inferred that emergent Fe(II) released from within the soil through reductive dissolution captures P from ditch surface water upon oxidation. In the treatment experiment dredging and saturated conditions resulted in similar effluent P concentrations as drained soils that were undredged. This may explain a lack of dredging effect that was observed in the field. 2012-01-01T00:00:00Z http://hdl.handle.net/1903/13043 Title: COMMUNITY BASED APPROACHES TO STORMWATER DESIGN IN A BALTIMORE NEIGHBORHOOD Authors: Clarkwest, Jennifer Zoe Abstract: This interdisciplinary research-design thesis explores the role of resident engagement in developing a design criteria for urban stormwater runoff design solutions, urban greening, and activating public spaces in the urbanized McElderry Park neighborhood of Baltimore. Drawing upon stakeholder and resident interviews, community workshops, resident working groups, and site observations and analysis the designer developed design criteria for site interventions as well as neighborhood-wide programming elements. Residents identify jobs, safety and health as primary concerns. Beyond harvesting stormwater, site interventions must provide safety, education, entrepreneurial opportunities, exercise, etc. Building on community input, the design interventions proposed by the designer are site specific, but the intervention types are readily adaptable. The overall design process and programming strategies apply to a variety of urban sites. Given the amount of stormwater managed by the interventions, the potential jobs created by the interventions, and other benefits provided to residents, the model merits field testing at the neighborhood scale. 2012-01-01T00:00:00Z