New Developments in WRB: From Pedon to Map and From Individual Classification to Automated Classification.

The international soil classification system “World Reference Base for Soil Resources / WRB” has two recent developments to present.

Originally designed for the classification of pedons, WRB can now also be used to construct legends for maps with a scale of 1 : 250 000 and smaller. For classification purposes, WRB has only two hierarchical levels, and on the lower level all qualifiers are equal. For mapping, the qualifiers were redistributed into main map unit qualifiers (ranked) and optional map unit qualifiers (non-hierarchical). This introduces on the one hand the hierarchy which is necessary for making maps at different scales and conserves on the other hand the big advantage of WRB as a flexible classification system with a loose hierarchy.

Most soil descriptions available in databases are made according to national soil survey manuals. The big task to classify the described soils according to WRB requires an automated soil classification. The German Federal Institute for Geosciences and Natural Resources is developing a tool which gives a full WRB classification on the basis of field and laboratory data collected according to the German rules of soil survey. This tool can serve as a proxy for automated classification using other national soil databases. A major problem is encountered: Different classification systems usually require different parameters to be surveyed. From the WRB point of view this means that some data are missing which would be needed to identify diagnostic horizons, soil groups and qualifiers, and therefore the classification remains tentative. More important for the future of soil classification is what we learn about the principles of writing a definition in soil classification. Most definitions in WRB can be transformed into algorithms in a satisfying way. But for some definitions this is almost impossible. These definitions should be rewritten in a more logical way.