<p> While urban ecosystems can host surprisingly high levels of biodiversity, there are still many shifts in the characteristics of the biotic communities found in cities. My dissertation explores patterns of plant community assembly in urban residential vacant lots. Firstly, I reviewed the literature to describe how various components of urban ecosystems impact vegetation diversity and composition and presented a novel conceptual model of spatiotemporal variation in plant community composition. Secondly, I described how spatially heterogeneous legacies of human land use within vacant lots structured plant community diversity and composition, relative to spatial and environmental variation. Plant community compositional variation was primarily explained by differences in human land use legacies, compared to local environmental variation (abiotic soil characteristics) and environmental context (lot area, proximity to other vacant lots and tree canopy). Thirdly, I examined how successional processes interacted with spatial variation in land use by constructing a chronosequence of vacant lot properties. I found no evidence of changes in plant community diversity over time but demonstrated significant shifts in functional composition in building footprint sections over time, primarily related to seed dispersal. Finally, I conducted a greenhouse experiment to uncover the interaction between local biotic and abiotic pressures on community structure. I replicated each seed mix across three soil environments (urban soils, soil from an unmanaged suburban lawn/field area, and greenhouse potting mix) and crossed soil and seeded species assemblages with a treatment to remove individuals emerging from the soil seed bank. I found that soil environment had the strongest impact on seeded species establishment. Weeding reduced overall community diversity in vacant lot soils but increased seeded species diversity.Overall, my dissertation results described patterns of community assembly of spontaneous plant communities in vacant lots at a spatial scale appropriate for guiding urban ecological management decisions. </p>
| Identifer | oai:union.ndltd.org:PROQUEST/oai:pqdtoai.proquest.com:3707286 |
| Date | 15 July 2015 |
| Creators | Johnson, Anna L. |
| Publisher | University of Maryland, Baltimore County |
| Source Sets | ProQuest.com |
| Language | English |
| Detected Language | English |
| Type | thesis |
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