A conceptual model for physical and chemical soil profile evolution

A simplified soil model is presented for evolution of the mineral soil profile. The model provides a compromise between highly empirical models and highly mechanistic/geochemical models, and represents some of the main features of observed profiles, with features that can be identified with ‘A’, ‘B’ and ‘C’ horizons. The model is responsive to a range of global environments, which can be represented through climate and parent material parameters. In many cases there is an almost single-valued relationship between surface weathering and soil depth, allowing further simplification of the model, and allowing it to be included within a parsimonious landform evolution models. A key parameter and assumption of the model is the degree of weathering below which no further solution occurs, which limits the maximum extent of soil development. This is speculatively linked to CO₂ turnover rates and the degree of aridity.