Direct and Indirect Effects of Urbanization On Soil Ecological Processes: Implications for Restoration.

Urban landscapes cover less than 5% of Earth’s land surface but are home to more than 50% of the world’s population and affect airsheds that extend tens to hundreds of kilometers past their borders.  As a part of the Central Arizona–Phoenix Long-Term Ecological Research project (CAP LTER), our research group combines manipulative experiments with city gradients to explore the multiple, co-occurring effects of human activity on soil functioning.  Urbanization homogenizes soil biogeochemical cycling temporally and spatially at the plant-interplant scale, most clearly observed within managed landscapes.  However, human activity increases heterogeneity at larger, neighborhood scales between yards, likely due to differences in management practices between households.  Protected desert remnants within urban open space parks resemble both residential landscapes and outlying desert ecosystems in their biogeochemistry.   These patterns suggest that native landscapes within the city are being domesticated by exposure to the urban environment.  As ‘ambassadors’, urban soils should be managed to maximize and sustain the suite of abiotic and ecological functions that provide ecosystem services to urban dwellers.