Challenges of Soil Taxonomy and WRB in classifying soils: some examples from Iranian soils

Abstract The two most widely used soil classifications are the Soil Taxonomy (ST) and the World Reference Base for Soil Resources (WRB). The purpose of this paper is to clarify the differences and the similarities between ST and WRB in their current state, with some examples for representative soils in arid and semi-arid regions of Iran. Four representative pedons were classified and soil units from WRB were compared to those obtained by using ST at the family level. WRB could show the status of soils polluted by heavy metals through the Toxic qualifier and its subqualifiers. On the other hand, ST could indicate the status of shallow soils in our studied soils but it was not able to show gleyic conditions and the existence of a salic horizon because of the differences in its criteria compared to those of WRB. Special effort should be made to quantify various anthropogenic activities in upcoming editions of both classification systems.