Hydropedological importance of calcic diagnostic horizons and andic diagnostic properties

Diagnostic horizons and diagnostic properties have a fundamental importance for soil classification (e.g. WRB, Soil Taxonomy) and also for applications in pedology (e.g. land evaluation). Then soil databases (and soil maps) typically contain information regarding the presence and thickness of diagnostic horizons. Despite these evidences, their importance in relation to hydrological processes remains to some extent unproven. Calcic horizons are subsoil horizons formed after the migration of calcium carbonate (generally) from surface horizons. Its classic explanation is based on the evidence that calcium carbonate in the wet season after solubilised it can migrates, and after drier soil condition it typically deposit over pore walls. This leads to formation and stabilization of new macropores. Andic properties can occur in volcanic and non-volcanic environment in soils having a high content of low order clay minerals and Al-humus complexes, respectively. They induce in turn low bulk density, high specific surface, high water retention and high hydraulic conductivity. We firstly showed the distinctive hydraulic properties, namely soil water retention and hydraulic conductivity of some calcic and andic horizons measured applying the Wind"s method. Then, we show how they deviate from an ""average"" expected behaviour (i.e. from comparison with the estimates applying several PTFs) for both the calcic and andic horizons. We performed a sensitivity analysis applying a physically based model in different upper boundary condition. Specifically, we tested the influence on the hydrological behaviour of (i) thickness and depth for the calcic soils and (ii) thickness and degree of andic properties in andic soils.