Mapping soil organic carbon at a terrain unit resolution across South Africa

Abstract

The objective of this paper is to map soil organic carbon content (%) across South Africa in detail and at high spatial resolution. Several existing datasets, namely the Soil Profile Database, the Terrain Unit Database and the Binomial Soil Series Database were used, but had to be enhanced to be able to combine some information to produce detailed soil carbon maps for South Africa at a resolution of terrain units. A distinction was made between soil samples taken under assumed pristine conditions with a natural vegetation cover and those of soils that had been modified by agricultural activities. The results were maps of areas with soil organic carbon content across South Africa at a spatial detail not previously achieved. The methodology did not allow for SOC mapping of stony or rocky soils, so these areas were omitted, but these are likely to be low in SOC. The results show that generally a higher SOC content is found in topsoil horizons than in subsoil horizons, in areas of natural vegetation versus those with agricultural land uses and in the higher rainfall areas compared to drier areas.