As part of the Global Urban Soil Ecology and Education Network and to test the urban ecosystem convergence hypothesis, we report on soil pH, organic carbon (OC), total nitrogen (TN), phosphorus (P), and potassium (K) measured in four soil habitat types (turfgrass, ruderal, remnant, and reference) in five metropolitan areas (Baltimore, Budapest, Helsinki, Lahti, Potchefstroom) across four biomes. We expected the urban soil characteristics to “converge” in comparison to the reference soils. Moreover, we expected cities in biomes with more limiting climatic conditions, or where local factors strongly affect soil characteristics, would exhibit the greatest variance across soil types within and among cities. In addition, soil characteristics related to biogenic factors (OC, TN) would vary the most because of differences in climate and human efforts to overcome limiting environmental conditions. The comparison of soils among and within the five cities suggests that anthropogenic, and to a lesser degree native, factors interact in the development of soils in urban landscapes. In particular, characteristics affected by anthropogenic processes and closely associated with biogenic processes (OC, TN) converged, while characteristics closely associated with parent material (K, P) did not converge, but rather diverged, across all soil habitat types. These results partially supported the urban ecosystem convergence hypothesis in that a convergence occurred for soil characteristics affected by climatic conditions. However, the divergence of K and P was unexpected and warrants adjusting the hypothesis to account for variations in anthropogenic effects (e.g., management) that may occur within soil habitat types impacted by humans.
1U.S. Department of Agriculture Forest Service, Research & Development, Washington, DC.
2U.S. Department of Agriculture Forest Service, c/o Baltimore Ecosystem Study, Baltimore, MD.
3Institute for Soil Sciences and Agricultural Chemistry, Centre for Agricultural Research, Hungarian Academy of Sciences, Budapest, Hungary.
4Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD.
5Department of Environmental Sciences, University of Helsinki, Lahti, Finland.
6Unit of Environmental Sciences and Management, North-West University, Potchefstroom, South Africa.
7Department of Ecology, Faculty of Veterinary Science, Szent István University, Budapest, Hungary.
8Environmental Science and Technology, University of Maryland, College Park, MD.
Address for correspondence: Richard V. Pouyat, U.S. Department of Agriculture Forest Service, Research & Development, 1400 Independence Ave SW, Washington, DC 20250. E-mail: firstname.lastname@example.org
Financial Disclosures/Conflicts of Interest: The idea for GLUSEEN was made possible by a Fulbright Specialist grant to R. Pouyat at the University of Helsinki. The GLUSEEN network is supported by a supplemental grant to NSF-ACI 1244820. Soil analyses were supported by the FEKUT grant (SZIE-AOTK-KK-UK 12007) of the Hungarian Ministry of Human Resources (E.H.). The use of trade, firm, or corporation names in this publication is for the information and convenience of the reader. Such use does not constitute an official endorsement or approval by the U.S. Department of Agriculture or the Forest Service of any product or service to the exclusion of others that may be suitable.
Received April 29, 2015.
Accepted for publication September 9, 2015.