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Landscape pattern and process of an urban ecosystem: an integrated field inventory approach.
HOPE, DIANE1, GRIES, CORINNA1, ZHU, WEIXING2, CARROLL, STEVEN1, STABLER, LINDA1, REDMAN, CHARLES1, GRIMM, NANCY1, KINZIG, ANN1, 1 2
ABSTRACT- Incorporating the integral role of humans in landscape pattern and process poses uniques challenges in cities. We used an extensive field survey and integrated inventory to sample an entire urban ecosystem (6387 sq. km), consisting of the urbanized, suburbanized and agricultural areas of metropolitan Phoenix and the surrounding desert. The inventory was conducted in spring 2000 at 204 sample plots (30m x 30m) located randomly using a tessellation-stratified dual-density sampling design. Objectives were a) to characterize patches in terms of key biotic, physical, chemical and socio-economic variables and b) to examine relationships between land use, plant diversity, soil nutrient status and socio-economic indices along an indirect urban gradient. As predicted urbanization markedly increased plant diversity with three times the number of genera in urban versus undeveloped desert patches. We also hypothesized that urbanization would result in an urban to desert gradient in soil chemistry and that land use would explain much of the variation in soil nutrient pools. While inorganic soil nitrogen content was significantly higher in urban and agricultural patches compared with undeveloped desert (mean nitrate-N content of 45.4, 86.7 & 6.6 mg/kg respectively), patch type alone was not an adequate predictor either of soil nitrogen or organic matter content. This study constitutes a novel approach to quantifying ecological and social characteristics of extremely heterogeneous landscapes and will be repeated every 5 years as part of CAP LTER's monitoring program.
KEY WORDS: urban, inventory, patch, gradient