Effects of urbanization on landscape pattern and ecosystem function in Phoenix: A multiscale study.

摘要

Cities have become the main habitat for humans and a 'new frontier' in ecology. The main goal of this dissertation was to quantify the spatiotemporal patterns and ecological impacts of urbanization in one of the fastest growing cities in the US---the Phoenix metropolitan region. This quantification was conducted at multiple scales using remotely sensed data. Urban area expansion has resulted in an increasingly fragmented landscape. Spatial and thematic resolutions of data have large effects on interpretability of land-cover dynamics.;While desert vegetation leafing phenology was explained by the 2--5 month accumulated precipitation and negatively correlated with temperature, urban and agricultural vegetation dynamics were essentially unsynchronized with rainfall and correlated positively with temperature. Overall, urban and agricultural development increased the diversity of phenological patterns. Study results support the "inverse texture" hypothesis (vegetation on coarser substrates is more responsive to rainfall) and the "luxury effect" hypothesis (more affluent neighborhoods are greener and more productive in plant biomass). Urbanization in this region tends to weaken the coupling between plant growth and precipitation and increase primary productivity during normal and dry years. During wet years, productivity of natural vegetation can be larger than that of the urban and agricultural areas.;This study also addressed the problem of the urban heat island---a central issue in urban ecology today. Vegetation plays an important role in explaining spatial variation in remotely sensed surface temperature during daytime, but the proportion of pavements was the most significant explanatory variable at nighttime. Daytime temperature was also highly correlated with the neighborhood socio-economic status. While localized surface urban heat islands were consistently detected in all seasons, during daytime the urban area acted as cool islands.;Overall, this research addressed several important issues in understanding urban ecosystems including land-use and land-cover change, urbanization effects on ecosystem properties, landscape phenology, and urban heat islands. In order to address these issues, an integrated research approach was taken to combine methods from landscape ecology, ecosystem ecology, and geography. The findings and techniques developed in this study will be useful for future urban studies in the Phoenix region and beyond.