Taxonomic distance between South African diagnostic horizons and the World Reference Base diagnostics

A myriad of soil classifications exist internationally. These usually cater for unique national variations and conditions. These different classification systems, however, hinder international communication. This paper attempted to relate the South African Soil Taxonomic (SAT) soil classification system with the World Reference Base for Soil Resources (WRB) through taxonomic distance classification. A probability matrix of the presence of selected identifiers of the diagnostic elements (properties, horizons, materials) of the South African classification system and the WRB was constructed to determine the taxonomic relationships between them. Euclidean distance calculation on these data enabled numeric expression of the taxonomic similarities and dissimilarities between the South African and WRB diagnostics. Results proved encouraging and some recommendations can be made. For example, a > 20% OC family for the organic O, as well as stagnic and gleyic families for the G horizon is proposed. It is further proposed that the WRB consider recognition of red apedal B, yellow-brown apedal B, and lithocutanic B horizons. Since the compared units are the basic building blocks of the two systems, the results presented here can be useful in the relation of soil classification in the South African Soil Taxonomy to the WRB.