ABSTRACT
While urban ecological studies began during the fifteenth century, with the identification of species diversity in cities such as London and Paris, systematic studies of urban soils are much more recent, largely undertaken since 1945 (Sukopp 2008). For a long time, substrates in cities were regarded by pedologists as heterogeneous and too young to develop into soil systems and therefore were not subjects of scientific interest, Spirn (1984) regarding them as one of the most misunderstood and least studied aspects of the urban environment. Some of the first systematic studies of soils in large cities attempted to identify the unique conditions of urban soils (Craul 1985; Craul and Klein 1980; Patterson 1976). Many focused on trace element concentrations and fluxes in urban street dust and urban soils (Purves 1966, 1972; Purves and Mackenzie 1969). Emphasis was often given to the engineering aspect of soils and the accompanying challenges for urban development (Gray 1972). Urban soil studies multiplied with the growing interest in urban ecology. Gilbert (1989) devoted an entire chapter to soils in his comprehensive study of the impact of cities on various environmental resources. By the 1990s, books devoted to urban soils appeared (see for example, Brown et al. 2000; Bullock and Gregory 1991; Craul 1992). Recommendations for mapping soils in cities were published and by 1998 an International Working Group on “Soils of urban, industrial, traffic and mining areas” was founded (Sukopp 2008). Since 2000 ecosystem studies have paid more attention to ecosystem services and the relationship between these services and human well-being (Millennium Ecosystem Assessment 2005; Daily 1997). Interest in urban soils has increased with the notion that these systems provide a number of different and important ecological services, even in cities. Palm et al. (2007) argue that soils underpin the production of food, feed, fiber and fuels and play a central role in determining the quality of our environment (including provisioning, regulatory, cultural, and supporting ecosystem services). In urban landscapes, soil services include regulating the retention and supply of nutrients and adsorption and storage of water, and provisioning growth media and substrate for soil fauna and flora. Urban soils are the foundation for ecological processes such as biogeochemical cycling, distribution of plant communities and provide purification services by intercepting contaminants such as pesticides and other toxics generated through human activities (Effland and Pouyat 1997).
