372 Arboricultural Abstracts DATA AND METHODS COMPARING SOCIAL STRUCTURE AND VEGETATION STRUCTURE OF URBAN NEIGHBORHOODS IN BALTIMORE, MARYLAND Morgan Grove, Mary Cadenasso, William Burch, Steward Pickett, Kirsten Schwarz, Jarlath O’Neil-Dunne, Matthew Wilson, Austin Troy, and Christopher Boone Recent advances in remote sensing and the adoption of geo- graphic information systems (GIS) have greatly increased the availability of high-resolution spatial and attribute data for examining the relationship between social and vegetation structure in urban areas. There are several motivations for understanding this relationship. First, the United States has experienced a significant increase in the extent of urbanized land. Second, urban foresters increasingly recognize their need for data about urban forestry types, owners and property regimes, and associated social goods, benefits, and services. Third, previous research has focused primarily on the distri- bution of vegetation cover or diversity. However, little is known about (1) whether vegetation structure varies among urban neighborhoods and (2) whether the motivations, path- ways, and capacities for vegetation management vary among households and communities. In this article, we describe novel data and methods from Baltimore, MD, and the Balti- more Ecosystem Study (BES) to address these two questions. (Society and Natural Resources 2006. 19(2):117–136) RIPARIAN WOODY PLANT DIVERSITY AND FOREST STRUCTURE ALONG AN URBAN-RURAL GRADIENT Michele L. Burton, Lisa J. Samuelson, and Shufen Pan Changes in riparian woody plant assemblages are anticipated in the southeastern United States due to increases in urban- ization rates. Because riparian forests serve important roles in maintaining water quality and biodiversity, understanding how they respond to urbanization is crucial. The objective of this study was to examine forest structure and woody veg- etation diversity indices of riparian communities in response to an urbanization gradient in West Georgia, USA. Measures of forest structure and diversity were compared to measures of urbanization and land cover. Although Liquidambar sty- racifluaand Quercus nigrawere dominant species in the forest stand and regeneration layer for all riparian communities, the invasive, non-native shrub Ligustrum sinense was the most dominant species observed in the regeneration layer for ur- ban, developing, and agriculture communities. The propor- tion of non-native species in the forest stand and regeneration layer decreased and Shannon diversity of the regeneration layer increased with increasing distance from the urban cen- ter. Shifts in diversity indicate that anthropogenic disturbance may subdue the ability of diverse communities to resist non- native plant invasions. (Urban Ecosystems 2005. 8(1):93– 106) THE EFFECT OF URBAN LEAF AREA ON SUMMERTIME URBAN SURFACE KINETIC TEMPERATURES: A TERRE HAUTE CASE STUDY Perry J. Hardin and Ryan R. Jensen The urban heat island effect (UHIE) has been documented in many temperate region cities. One cause of the UHIE is the replacement of green spaces with impervious materials as urbanization commences and the city builds up and fills in. During the summer, elevated urban temperatures result in increased electricity usage, higher pollution levels, and greater resident discomfort. Through evapotranspiration and the interception of solar radiation, increasing urban tree canopy cover can help mitigate the UHIE. While this is uni- versally accepted, the exact statistical relationship between urban leaf area (as measured by leaf area index, LAI) and urban temperatures has not been extensively studied. In a case study conducted in urban/suburban Terre Haute, Indiana, USA, simple linear regression was employed to quantify the relationship between in situ ceptometer LAI measurements and surface kinetic temperatures (SKTs) measured using ther- mal satellite imagery acquired at 1100 local time. For the 143 sample sites located in the study area, LAI accounted for 62% of the variation in surface temperature. For every unit in- crease in LAI, surface temperature decreased by 1.2°C. (Ur- ban Forestry & Urban Greening 2007. 6(2):63–72) ©2007 International Society of Arboriculture
September 2007
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