ECOPHYSIOLOGICAL AND SOCIAL FUNCTIONS OF URBAN FOREST PATCHES
Sonti, Nancy Falxa
Sullivan, Joseph H
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Urban trees provide many ecosystem services to cities: alleviating the urban heat island effect, absorbing stormwater runoff, and contributing to residents’ social and psychological well-being. The production of these benefits is influenced by tree growth and physiological function within the urban ecosystem, and also by the social-ecological context in which urban forest patches exist. This dissertation investigates the ecophysiological and social functions of urban forest patches of the eastern United States using a multidisciplinary approach that combines diverse empirical methods across varied timescales and geographies. Using data collected from urban and reference forest patch sites, this dissertation begins by addressing the following questions: How does native tree growth and physiology vary between urban and reference forest patches? Are there differences in ecophysiological responses by tree species and by city within the eastern United States? Air temperature and soil data from each field site are analyzed alongside tree ring and leaf-level physiological data. Next, results from a controlled growth chamber experiment are presented to examine how Baltimore’s urban vs. reference forest soils and air temperature interact to affect seed germination and seedling growth of white oak (Quercus alba), a dominant species in the region. Finally, the social functions of forest patches are investigated using qualitative data from semi-structured interviews conducted with Baltimore residents. Overall, urban forest patches were found to support robust growth and physiological function of white oak (Quercus alba L.) and red maple (Acer rubrum L.) trees, with differences by species and site type (urban vs. reference), and over time. In particular, urban soils appear to support greater biomass and photosynthesis rates than reference soils. Regardless of the favorable ecophysiological conditions of urban forest patches, community awareness and engagement with these sites will be critical to their continued protection and management. Qualitative interview data revealed local residents’ strongly ambivalent attitudes towards urban wilderness, with only limited differences by homeownership and property management regime. In sum, dissertation documents important ecophysiological and social functions of urban forest patches, with implications for the continued provision of benefits to urban and rural communities.