SOIL PROPERTY PROFILES IN URBANIZED LANDSCAPES AND THEIR CONVERGENCE ACROSS CITIES

Urbanization processes and urban land management can result in dramatic changes to soils. The consequences of these activities for fluxes of matter, energy, and information through a landscape are strongly dependent on how they affect soil properties, especially organic matter content, mineral particle size, and reactivity level. In an 11-city assessment of soil profiles to 1.5 m depth, we found major shifts in urban soil profiles of carbon and particle size relative to pre-urban reference soils. Urban soil profiles had lower carbon content in surface soils but similar levels in subsurface soils. For particle size, urban soils broadly had smaller mean particle size (i.e., finer texture) at all depths.

We also tested for and found evidence of convergence in the profiles of urban soil properties across cities. Convergence was evaluated as the level of profile anisotropy. For both carbon and particle size, urbanization increased profile anisotropy where it occurred on soils with low anisotropy, and decreased profile anisotropy where it occurred on soils with high anisotropy. Thus, we found evidence of convergence in urban soils towards a common intermediate level of profile anisotropy. These soil-based changes in ecosystem structure with urbanization suggest likely shifts in ecosystem functioning and services, such as stormwater management.