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Human-induced vegetation dynamics and avian responses in a rapidly expanding desert metropolis

Walker, Jason Scott

Titre : Human-induced vegetation dynamics and avian responses in a rapidly expanding desert metropolis

Auteur : Walker, Jason Scott

Université de soutenance : ARIZONA STATE UNIVERSITY

Grade : Doctor of Philosophy (PhD) 2008

Burgeoning population growth alongside a vastness of inexpensive land in the American Desert Southwest has generated a culture of extraordinary urban expansion. In this dissertation, I analyzed how humans modify vegetation within the Phoenix metropolitan area (Arizona, Untied States of America), and how these alterations affected avian abundance and distributional patterns across the region. The research presented combines theories, methods, and data from the ecological and social sciences. Plant species diversity patterns in the desert ecosystem result from abiotic sorting, but not in urban sites. Species richness per plot was found to be higher for desert sites ; however, the estimated species pool in the urban ecosystem was higher than in the desert resulting from the enhanced importation of exotic species through the nursery trade. A remote sensing classification scheme to extract woody vegetation cover from high-resolution aerial photography was developed and tested generating an urban forest map of the region. This urban forest map was analyzed with sociological census data to study the interplay among economics and patterns of residential development and their effects on canopy cover. Results showed higher canopy cover for older neighborhoods, indicating a detectable temporal lag of urban forest development. Also, more affluent neighborhoods tended to have higher canopy cover, independent of age, even though they are more densely constructed. Lastly, it was found that urbanization in a desert ecosystem affects avian communities at two distinct scales. At the regional level, land use configuration affected the distribution of native and exotic species. While exotic species were found to be isolated to the city ; native species actively utilized the entire region, even occurring at higher densities in the city than in some areas of the desert. This approach was also used to compare distributional patterns of foraging guilds of birds. At a local scale, the abundance of native species, exotic species and how the foraging guilds of birds responded to vegetation cover measured at varying spatial scales were examined. Bird guilds responded to vegetation at different scales, depending on their association with vegetation.

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Page publiée le 28 octobre 2013, mise à jour le 5 décembre 2018