Removing Soil Moisture Regime from Higher Levels in Soil Taxonomy.

Soil moisture regime is used as criteria to classify soils at the order, suborder, great group, and subgroups categories in Soil Taxonomy. One change to Soil Taxonomy currently in debate is to consistently apply soil moisture regime classes by moving it from the higher levels into the family level. One advantage of this would be that both soil climate taxonomic components (temperature and moisture) are in the same level. This makes sense since both soil temperature and soil moisture are rarely measured for classification purposes and are inferred from climatic data and accessed through maps. Inceptisols, Alfisols, Andisols, Vertisols, Mollisols, Oxisols, and Ultisols all have udic, xeric, and ustic moisture regimes at the suborder level. By moving these to the family level other important soil properties can be applied higher in the hierarchy. For example, for Inceptisols new classes would be Durepts, Fragepts, Humepts, and Calcepts to recognize soils with duripans, fragipans, umbric/mollic horizons, and calcic horizons, respectively. The current number of great group and subgroup taxa under the Xerept, Ustept, and Udept suborders is 201. By moving soil moisture regime to the family level one proposed fundamental change would reduce this number to only 117 taxa at the great group and subgroup level without losing any of the classification detail in the currently defined taxa in Soil Taxonomy. We will also discuss questions such as: What are the disadvantages to making these changes? What should be done with “aquic” suborders since these are not really climate related?