Proposed changes to the soil family taxon within the Canadian System of Soil Classification

Abstract

The soil family was developed in the 1960s as the fourth level of taxa within the hierarchical structure of the Canadian System of Soil Classification. The original aim of the soil family category was to provide a framework for checking and establishing limits for soil series while providing a link between the series and the subgroup level. Its intended use was to define and group numerous soil series based on soil characteristics important for the purpose of applying appropriate management practices. In the current Canadian System of Soil Classification, taxa at the family level represent subdivisions of the subgroups. Classification of mineral soils at the family level is based on properties of the parent materials which include particle size; soil mineralogy; reaction (soil pH); calcareousness; depth to bedrock and permafrost; as well as climactic factors: soil temperature and soil moisture regimes. The soil family particle-size classes were originally intended as a compromise between both agronomic and engineering influences; however, the resulting product has limited functionality because of differences in definitions between engineering and agronomic grain sizes and non-alignment with soil textural classes. Consequently, classification and use of the family taxon have largely been ignored. Some adjustments to the family taxon for mineral soils and terric layers in organic soils are proposed including realignment of classes in the current family particle-size triangle to follow the divisions of the soil textural classes. Minor adjustments to mineralogy classes and depth to bedrock are also proposed.