Tests whether any near-surface horizon meets the mollic horizon criteria. The mollic horizon is the diagnostic surface horizon of Chernozems, Phaeozems, Kastanozems, and several other RSGs; it indicates a thick, dark, base-rich, organic-matter-enriched topsoil formed under steppe or comparable vegetation.
Arguments
- pedon
A
PedonRecord.- min_thickness
Minimum thickness in cm (default 20).
- min_oc
Minimum SOC % (default 0.6).
- min_bs
Minimum base saturation % (default 50).
- surface_top_cm
Maximum top depth (cm) for a horizon to be considered "surface-related" (default 5). v0.1 uses this as a proxy for the WRB rule that mollic must form continuously from the soil surface (after mixing of upper 20 cm if required).
Details
Since v0.9.314 the criteria are read as WRB 2022 Ch 2.1 (p. 23) sets them for a horizon of several subhorizons: every criterion except the thickness in every layer, unless the text says otherwise. Criteria 1 (structure; structure not recorded does not block it), 2 (>= 0.6% SOC) and 3 (colour, items a-c; a plough layer takes the colour of the subhorizon below it) are read in each layer, and the horizon is the run of such layers from the mineral soil surface. Criterion 5, the base saturation, is the weighted average over the run (by pH where it is not recorded, Annex 2 Table 9.2), and criterion 6 its thickness: >= 20 cm (6b), or since v0.9.315 >= 10 cm directly over continuous rock, technic hard material or a cryic, petrocalcic, petroduric, petrogypsic or petroplinthic horizon (6a, p. 53; the umbric horizon names cryic, petroduric and petroplinthic, p. 70). A moist value with no dry value recorded reads the dry value as the moist value + 1; a layer with no colour recorded at all and >= 1.5% SOC is read as dark (Hugo, 2026-10-29). A dry colour alone leaves criterion 3 undecided unless its value is above 5. The colour subtest records where each layer's reading came from.