Drivers of spatial variation in plant diversity across the Central Arizona-Phoenix ecosystem.

Society and Natural Resources. 19(2):101-116

Hope, D., C. Gries, D. Casagrande, C. L. Redman, N. B. Grimm, and C. Martin (2006)

abstract

We examined how human management of the Phoenix urban landscape has altered the spatial patterns in plant diversity from the native Sonoran desert vegetation that these human-created landscapes have replaced. Combining data from the US Census with a probability-based field inventory of vegetation and other variables, using spatial and multivariate statistical models, we demonstrate that plant diversity across the region is significantly influenced by human actions. Spatial variations in plant diversity among sites were best explained by current and former land use, income, housing age, and elevation. Perennial plant genera showed similar diversity between desert and urban sites on an average per plot basis, but variations in the suite of plant genera among sites was much greater for the irrigated urban landscape, enhanced by a varied palette of imported exotic plants. We highlight the ‘luxury effect’ of income, whereby urban plant diversity is highest at sites in wealthier neighborhoods, as well as the importance of techno-cultural controls such as the advent of air conditioning and drip irrigation. We conclude that the natural, spatially autocorrelated patterning of plant diversity in the desert is replaced by a variable suite of site-specific human factors and legacy effects, which give rise to strong spatial discontinuities in the city. These patterns require an integration of ecology and social science in order to be fully understood.