Soil color indicates carbon and wetlands: developing a color-proxy for soil organic carbon and wetland boundaries on sandy coastal plains in South Africa

  • M. L. Pretorius
  • C. W. Van Huyssteen
  • L. R. Brown


A relationship between soil organic carbon and soil color is acknowledged—albeit not a direct one. Since heightened carbon contents can be an indicator of wetlands, a quantifiable relationship between color and carbon might assist in determining wetland boundaries by rapid, field-based appraisal. The overarching aim of this initial study was to determine the potential of top soil color to indicate soil organic carbon, and by extension wetland boundaries, on a sandy coastal plain in South Africa. Data were collected from four wetland types in northern KwaZulu-Natal in South Africa. Soil samples were taken to a depth of 300 mm in three transects in each wetland type and analyzed for soil organic carbon. The matrix color was described using a Munsell soil color chart. Various color indices were correlated with soil organic carbon. The relationship between color and carbon were further elucidated using segmented quantile regression. This showed that potentially maximal carbon contents will occur at values of low color indices, and predictably minimal carbon contents will occur at values of low or high color indices. Threshold values can thus be used to make deductions such as “when the sum of dry and wet Value and Chroma values is 9 or more, carbon content will be 4.79% and less.” These threshold values can then be used to differentiate between wetland and non-wetland sites with a 70 to 100% certainty. This study successfully developed a quantifiable correlation between color and carbon and showed that wetland boundaries can be determined based thereon.


Soil color Soil organic carbon Wetland delineation Segmented quantile regression Maputaland coastal plain Hydric soil 



The author would like to acknowledge the following people and institutions: Prof. Jutta Zeitz and Niko Roßkopf from the Humbolt Universität zu Berlin, Dr. George van Zijl and Prof. Pieter le Roux from the University of the Free State, and Dr. Althea Grundling from the Agricultural Research Institution in South Africa. The South African National Research Foundation, Deutscher Akademischer Austauschdienst (German Academic Exchange Service) and the Inkaba yeAfrica program (Publication no. 188) are thanked for their funding.


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Copyright information

© Springer International Publishing AG 2017

Authors and Affiliations

  1. 1.Applied Behavioural and Ecological Ecosystems Research Unit (ABEERU)University of South AfricaPretoriaSouth Africa
  2. 2.Soil- and Crop- and Climate SciencesUniversity of the Free StateBloemfonteinSouth Africa

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