Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 7 5 2010 10.5194/bg-7-1515-2010 http://www.biogeosciences.net/7/1515/2010/ http://www.biogeosciences.net/7/1515/2010/bg-7-1515-2010.html http://www.biogeosciences.net/7/1515/2010/bg-7-1515-2010.pdf 1515 1541 2010-05-17 Variations in chemical and physical properties of Amazon forest soils in relation to their genesis C. A. Quesada betoquesada@yahoo.com.br J. Lloyd M. Schwarz S. Patiño T. R. Baker C. Czimczik N. M. Fyllas L. Martinelli G. B. Nardoto J. Schmerler A. J. B. Santos M. G. Hodnett R. Herrera F. J. Luizão A. Arneth G. Lloyd N. Dezzeo I. Hilke I. Kuhlmann M. Raessler W. A. Brand H. Geilmann J. O. Moraes Filho F. P. Carvalho R. N. Araujo Filho J. E. Chaves O. F. Cruz Junior T. P. Pimentel R. Paiva Earth and Biosphere Institute, School of Geography, University of Leeds, Leeds, LS2 9JT, UK Max-Planck-Institut fuer Biogeochemie, Jena, Germany Instituto de Investigación de Recursos Biológicos, Alexander von Humboldt, Bogotá, Colombia UMR-ECOFOG, INRA, 97310, Korou, French Guiana, France Centro de Energia Nuclear na Agricultura, Piracicaba, Brazil Institito Nacional de Pesquisas da Amazônia, Manaus, Brazil Centre for Ecology and Hydrology, Wallingford, UK Instituto Venezuelano de Investigaciones Científicas, Caracas, Venezuela now at: Fieldwork Assistance, Postfach 101022, 07710 Jena, Germany now at: Department of Earth System Science, University of California, 2103 Croul Hall, Irvine, CA, 92697-3100, USA now at: Geography and Ecosystem Analysis, Lund University, Lund, Sweden deceased on 29 June 2006 Soil samples were collected in six South American countries in a total of 71 different 1 ha forest plots across the Amazon Basin as part of the RAINFOR project. They were analysed for total and exchangeable cations, C, N, pH with various P fractions also determined. Physical properties were also examined and an index of soil physical quality proposed. A diverse range of soils was found. For the western areas near the Andean cordillera and the southern and northern fringes, soils tend to be distributed among the lower pedogenetic levels, while the central and eastern areas of Amazonia have more intensely weathered soils. This gives rise to a large variation of soil chemical and physical properties across the Basin, with soil properties varying predictably along a gradient of pedogenic development. Nutrient pools generally increased slightly in concentration from the youngest to the intermediate aged soils after which a gradual decline was observed with the lowest values found in the most weathered soils. 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