Implications for Practice
• Urbanization alters soils in dramatic ways, and replacing a soil’s critical ecosystem services requires urban restorationists to employ drastic restorative practice. Urban soils are unique and should not be expected to respond to restoration practices like nonurbanized soils.
• Definitions of baseline and reference conditions are difficult to come up with for urban soils. A more successful approach might include treating the soil formation factors as a conceptual guide and ameliorating urban changes to the state factors.
• Urbanization can mask the influences of predevelopment activities on soils and determine what restoration can achieve. Urban and suburban areas often expand into former agricultural, industrial, or mining areas; land uses that alter plant nutrients, chemicals, and heavy metals; and soil physical properties in unique ways.
• The tale of one or two cities is inadequate. The effects of urbanization on belowground resources can differ among climatic regimes and will differ within cities based on spatial patterns or preurban soil heterogeneity, patterns of urban growth, and land use legacies. Effective restoration will depend on site-specific soils knowledge.
• Creative solutions to urban soil degradation can come from resilience and alternative stable-state perspectives. Short-circuiting indirect urban effects on soils can increase the likelihood of restoration success in cities.
• Restoration in cities involves more than just alteration of site soil conditions; the surrounding urban context must also be managed to ensure restoration success.
Acknowledgments
This article is based on a talk presented at the “Soils in Restoration Ecology Conference” held at DePaul University in December 2006. I would like to thank M. Callaham and L. Heneghan for hosting the conference and for several stimulating discussions on the subject of restoration and soils. I would also like to thank Dr. C. Rhoades, Dr. M. Carreiro, and an anonymous reviewer for their comments that improved the direction and focus of this article.