Geography
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Item THE UNCERTAINTY OF SPACEBORNE OBSERVATION OF VEGETATION STRUCTURE IN THE TAIGA-TUNDRA ECOTONE: A CASE STUDY IN NORTHERN SIBERIA(2015) Montesano, Paul; Dubayah, Ralph; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The ability to characterize vegetation structure in the taiga-tundra ecotone (TTE) at fine spatial scales is critical given its heterogeneity and the central role of its patterns on ecological processes in the high northern latitudes and global change scenarios. This research focuses on quantifying the uncertainty of TTE forest structure observations from remote sensing at fine spatial scales. I first quantify the uncertainty of forest biomass estimates from current airborne and spaceborne active remote sensing systems and a planned spaceborne LiDAR (ICESat-2) across sparse forest gradients. At plot-scales, current spaceborne models of biomass either explain less than a third of model variation or have biomass estimate uncertainties ranging from 50-100%. Simulations of returns from the planned ICESat-2 for a similar gradient show the uncertainty of near-term estimates vary according to the ground length along which returns are collected. The 50m length optimized the resolution of forest structure, for which there is a trade-off between horizontal precision of the measurement and vertical structure detail. At this scale biomass error ranges from 20-50%, which precludes identifying actual differences in aboveground live biomass density at 10 Mg•ha-1 intervals. These broad plot-scale uncertainties in structure from current and planned sensors provided the basis for examining a data integration technique with multiple sensors to measure the structure of sparse TTE forests. Spaceborne estimates of canopy height used complementary surface elevation measurements from passive optical and LiDAR to provide a means for directly measuring TTE forest height from spaceborne sensors. This spaceborne approach to estimating forest height was deployed to assess the spaceborne potential for examining the patterns of TTE forest structure explained with a conceptual biogeographic model linking TTE patterns and its dynamics. A patch-based analysis was used to scale estimates of TTE forest structure from multiple sensors and provided a means to simultaneously examine the horizontal and vertical structure of groups of TTE trees. The uncertainty of forest patch height estimates provides focus for improving spaceborne depictions of TTE structure patterns associated with recent change that may explain the variability of this change and the vulnerability of TTE forest structure.Item Analyze Municipal Annexations: Case Studies in Frederick and Caroline Counties of Maryland, 1990-2010(2012) Pomeroy, Jennifer Yongmei; Geores, Martha E; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Municipal annexations play an important role in converting undeveloped land to development, influencing landscape change. However, the existing literature does not explore the links between annexation and development. An additional inadequacy is the failure to consider environment/landscape aspect of annexation. Therefore, this dissertation proposes a new theoretical framework that is drawn upon political ecology and structuration theory to examine annexation phenomenon processes: environmental/landscape sensitivity and its causal social structures. Frederick and Caroline counties in Maryland from 1990 to 2010 were the two case-study areas because both counties experience increased annexation activities and are representative of suburban and exurban settings at rural - urban continuum of the United States. The data used in this qualitative research were collected from multiple data sources, including key-person interviews, a review of Maryland's annexation log, annexation applications and meeting minutes, and observations at public meetings. Triangulating content analysis, discourse analysis, and social network analysis, this research finds that environmental/landscape is not considered more widely in annexation practices. Although environmental mitigation measures are considered at site level if a property has site environmental elements, the overall environmental/landscape sensitivity is low. It is also found that the economic-centered space remains dynamic in the annexation processes determining annexation approvals and low-density zoning. In addition, the triangulated analyses reveal that current social structures are not conducive to environmental-conscious landscape planning because environmentally oriented non-profit organizations and residents are injected at a later stage of annexation process and is not being fully considered in the evaluation process. Power asymmetry in current annexation structures is due to a lack of environmental voice in annexation processes. The voice of such groups needs to be institutionalized to facilitate more tenable annexation practices.