An investigation into the effects of forest fragment structure and spatial context on rainfall redistribution and solute flux within a city and along an urban to rural gradient
Date
2018
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Publisher
University of Delaware
Abstract
Urban green space has increasingly been utilized as a natural means by which to mitigate the negative environmental impacts of expansive and often unchecked urbanization. Much effort has been placed on increasing urban forest cover, as trees have been found to provide an array of cultural, supporting, provisioning, and regulating ecosystem services that collectively help to sustain, and in some respects, improve both human life and environmental function. There remains, however, a knowledge gap with respect to our understanding of subcanopy hydrologic and solute fluxes that occur within remnant metropolitan forest patches. Filling this gap is crucial for better identifying the threats and aids to the sustainable management of urban wooded ecosystems, in addition to aiding in the development of more strategic initiatives for the management and expansion of urban forest cover. ☐ This dissertation utilizes in situ measurements from remnant forest fragments in the Wilmington, Delaware, USA metropolitan region to quantify and characterize the hydrologic and solute fluxes that take place within them. It is the first study to utilize the flux-based enrichment ratio for stemflow in relation to throughfall to determine the degree to which net precipitation chemistry is altered due to its interaction with the canopy, with specific emphasis on the relative contributions of stemflow and throughfall to subcanopy nutrient cycling. Flux-based enrichment ratios for stemflow were consistently found to be higher for Quercus rubra than Quercus alba (due to variability in bark morphology between the two species), and in urban rather than non-urban remnant forests. Additional quantification of throughfall fluxes determined that within highly developed portions of a metropolitan region, throughfall solute flux is governed largely by intensity of urban land use and related emissions, rather than solely by location along an urban to rural gradient (i.e., within city limits vs. within a suburban community). Knowledge of the biotic and abiotic factors that govern both water and solute fluxes within these metropolitan forest ecosystems was used to develop a prescriptive guide upon which urban land managers may base tree selection and management strategies to optimize the yield of select hydrologic and hydrochemical ecosystem services.
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Keywords
Biological sciences, Social sciences, Earth sciences, Flux-based enrichment ratio, Nutrient cycling, Stemflow, Throughfall, Urban forestry, Urban planning