Total and labile carbon and nitrogen in anthropogenic and native soils of New York City

Abstract

Urban soils are key components of urban ecosystems and can contribute to the solution for many ecological and environmental problems such as stormwater runoff, pollution mitigation, and urban food production. Urbanization processes often result in highly disturbed and spatially variable urban soils. Besides heterogeneity, one of the unique and intriguing aspects of urban soil is the nature and properties of organic carbon, with a significant percentage being anthropogenic carbon such as black carbon, which is less biologically active than natural organic matter. We sampled 13 soil profiles covering a wide range of soil conditions, including both anthropogenic and native soils, across New York City. At each site from each horizon, soil samples were collected for laboratory determination of total carbon and nitrogen, black carbon, microbial biomass carbon and nitrogen, and pools of readily mineralizable carbon and nitrogen. We hypothesized that the carbon present in urban soil profiles derived from human-altered and human-transported (HAHT) parent materials has a lower capacity to support microbial biomass and a limited nitrogen supplying ability compared to the carbon found in urban soils derived from native parent materials. We found that total carbon and nitrogen were as high, or even higher in soils derived from HAHT parent materials than in native soil profiles, but that labile pools were lower in the HAHT soils. Assessment of the quality of organic carbon, which is strongly affected by HAHT materials, is important for understanding the ability of urban soils to support a wide range of ecological and environmental functions.