Landscape complexity and ecosystem processes of an urbanized arid region (Arizona).

摘要

Ecological understanding is limited by two interdisciplinary problems, scaling and linking processes between ecosystems and human societies. Social dynamics extensively influence ecosystem processes and patterns from local to global scales. An understanding of social-ecological linkages requires scaling between processes and patterns having broadly varying extents. Similarly, because there are no regions on the globe that have not been impacted by human activities, a scaling theory extending to a regional extent must incorporate human activities with ecosystem processes. The research presented in this dissertation develops a landscape ecological framework that facilitates the investigation of the linked problems of scaling and social-ecological interactions. This approach highlights the identification of spatial organization as a means to integrate the diverse drivers of ecosystem processes occurring at multiple scales.; This approach was implemented and refined in a series of investigations of the Phoenix, Arizona, USA metropolitan region. First, I examined influences of scale on the behavior of models describing (1) regional urbanization and (2) landscape interactions between two vegetation functional groups and their modification of biogeochemical processes. In both of these models, the scale of analysis had a strong effect on model dynamics and the conclusions drawn from the models. Second, I examined the joint spatial heterogeneity in socio-economic status, vegetation, and surface temperature. Because these data sources were obtained at differing resolutions, scaling theory was applied to analyze the patterns. Using a multivariate model of spatial heterogeneity these patterns showed that within neighborhoods of the Phoenix, AZ metropolitan region, surface temperature decreases by .28°C for every {dollar}10,000 increase in median household income. These changes are primarily due to altered vegetation patterns. These results suggest the luxury effect of increasing ecologic capital with increasing economic capital has a functional effect. Income indirectly modifies both social and ecological processes through micro-climate modification. These changes cascade to regional influences through modification of the resource footprint. Third, I examined the distribution of soil organic matter, nitrogen, and nitrogen stable isotope ratios at two scales, both within individual patches and throughout the entire Phoenix, AZ metropolitan region. Using both data sets I estimate the regional soil storage of organic matter and total nitrogen using three scaling techniques. The relationships between patch and regional heterogeneity were further examined by comparing the scaling relations of the patterns observed at regional and patch scales.; These three components of my dissertation provide the context for a new landscape perspective and examples of its implementation. Together these studies document the strong scale dependencies of ecosystem patterns and processes within the Phoenix, AZ metropolitan region, and show the tight coupling between social and ecological processes within this urbanized arid region.