Are soil phenoforms the new normal? Soil classification and soil mapping in the Anthropocene

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• The soil genoform and phenoform concept is reviewed and related to soil security. • In the Anthropocene the soil phenoform concept is increasingly relevant. • Some soil genoforms should be split into several classes. • Soil phenoforms should be described and mapped, with regular updates. The proposed Anthropocene epoch is characterized by intense human intervention on the soil resource. To characterize this, two concepts have been defined. Soil genoforms are the central concepts of mappable soil bodies, including permanently altered soils. These are represented by soil profiles which are the soil “individuals” of soil classification, and are based on relatively permanent soil characteristics. Soil phenoforms are persistent, but reversible, non-cyclical variants of a soil genoform with sufficient physical, chemical or biological differences to substantially affect soil functions, especially regulation and production functions. Soil phenoforms are the result of differential soil management and are directly linked to the soil security concept of soil condition. Map-unit based soil survey and classification has typically identified and mapped soil genoforms, ignoring the diversity of soil phenoforms that may be found within map units, and consequently their differential functioning. This latter is especially important in the evaluation of the soil resource with respect to the Sustainable Development Goals of the UN. Developments in digital soil mapping suggest that it may be feasible to identify and map soil phenoforms in regularly-updated soil survey. This has implications for soil classification: (1) some soil genoforms as presently defined contain more than one stable soil genoform, and so should be split into several genoforms; (2) soil phenoforms should be recognized as dynamic forms within the soil classification system. An open challenge is how to identify and efficiently map soil phenoforms in regularly-updated soil survey.