Browsing by Author "George Hess, Committee Co-Chair"

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    Can Urban Greenways Provide High Quality Avian Habitat?
    (2003-09-09) Hull, Jamie Rebekah; Heather Cheshire, Committee Member; George Hess, Committee Co-Chair; Christopher Moorman, Committee Co-Chair
    As natural areas are converted to urban or suburban development, landscape and urban planners are pressed to integrate wildlife habitat into a rapidly changing landscape. Urban greenways provide a broad range of social, economic and environmental benefits, and consequently are enjoying worldwide popularity as a developing form of urban openspace protection. One of the goals of greenway development often is to provide habitat for wildlife. If landscape and urban planners are to strategically design greenways so as to maximize their value to wildlife, they need information on the specific environmental characteristics in and surrounding urban greenways that contribute to their value as wildlife habitat. I investigated how forested corridor width, land use context, and greenway composition and vegetation structure affected avian community composition in urban greenways in Raleigh and Cary, North Carolina, USA. I surveyed breeding bird communities at 34 greenway study sites using 50-m fixed-radius point counts located at the center of 300m long greenway segments. Each greenway segment's forested corridor width and surrounding land use were determined in ArcGIS. Greenway composition (proportion of mature forest, young forest, managed area, and stream in the greenway study site) and vegetation structure were measured in the field. Total bird abundance increased with increasing canopy cover in the adjacent landscape and increasing shrub cover within the greenway. Neotropical migrant, insectivore and forest-interior species richness decreased with increasing amounts of managed area, such as trail and other mowed or maintained surfaces, within a greenway. Neotropical migrant species richness and forest-interior species richness and abundance decreased with increasing amounts of building in the adjacent landscape. Insectivore species richness increased with increasing lawn cover in the adjacent landscape, and insectivore abundance increased with increasing amounts of canopy in the adjacent landscape. White-eyed Vireos were recorded only in greenways wider than 300m; Wood Thrushes and Indigo Buntings were recorded only in greenways wider than 100m; and Blue-gray Gnatcatchers, Downy Woodpeckers and Red-eyed Vireos were recorded only in greenways wider than 50m. Urban-adaptors such as Common Grackles and European Starlings were more common in narrower greenways. Landscape and urban planners can maximize native bird diversity and abundance by minimizing the width of the greenway trail and associated mowed and landscaped surfaces adjacent to the trail, maintaining vegetative structure within the greenway, and giving priority to the protection of greenways in areas of lower development intensity. Greenways wider than 50m provide habitat for a diversity of bird species, but many species of conservation concern require much wider greenways.
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    Composition and Estimated Value of Selected Benefits of Trees in Parking Lots in Raleigh, NC
    (2010-02-04) Keto, Evan; Bronson Bullock, Committee Member; Melissa McHale, Committee Co-Chair; Gary Blank, Committee Member; George Hess, Committee Co-Chair
    Trees are often planted in parking lots to reduce the environmental and visual impacts created by these paved surfaces. I used a two-phase cluster sampling scheme to assess the composition of trees within parking lots in Raleigh, NC, USA. These parking lots contain discrete unpaved areas, called inclusions, which I classified into four types by size and shape: inclusions smaller than 1,000 ft2 were categorized as compact “islands†or linear “slivers†, and inclusions larger than 1,000 ft2 were categorized as compact “chunks†or linear “rows†. I measured more than 1800 trees in 502 inclusions within 110 parking lots to determine the overall composition of trees and how this composition varied among different inclusion types. Raleigh’s parking lots were found to contain 44,000 ± 24,000 trees (with 95% confidence). These trees were estimated to provide benefits valued at more than one million dollars annually. Inclusions containing trees that appear to have existed before construction (“preserved†inclusions) were found to have more trees, canopy, and basal area per acre than other (“designed†) inclusions. Significant differences in tree composition and the proportion of trees meeting Raleigh’s mature shade tree size goals were associated with the size and shape of the inclusion used. A disproportionately high number of willow oaks and trees in larger inclusions were observed meeting Raleigh’s size goals for mature shade trees. Additionally, using GIS, parking coverage was found to vary greatly between different zoning classes, with the greatest coverage in commercial and industrial areas. These results indicate that the distribution and coverage of parking lots in Raleigh, and the composition and resulting benefits of trees within these lots, may depend upon planning and design decisions made before a parking lot is constructed. This study provides a methodology for assessing the composition of trees in a city’s parking lots, which allows comparisons to be made among different types of parking lots, inclusions, and trees. While few studies have addressed the composition of trees in parking lots, this area of research has both practical and scientific value. With additional research, we may better understand how to maximize the ecosystem services provided by trees in limited growing spaces, and use this knowledge to design parking lots with improved environmental impacts.