Tests whether any horizon meets the cambic horizon criteria. The cambic horizon is a subsurface horizon with evidence of pedological alteration that does not meet the criteria for any stronger diagnostic horizon. It is the diagnostic of Cambisols.
Arguments
- pedon
A
PedonRecord.- min_thickness
Minimum thickness in cm (default 15).
- min_top_cm
Minimum top depth (cm) for a horizon to be considered cambic-eligible (default 5). Anchors the candidate set to subsurface layers. Since v0.9.314 the WRB reading asks it only when it is given.
- engine
v0.9.63+. One of
"soilkey"(hand-coded path, default for back-compat) or"aqp"(canonical NRCS dispatch viaaqp::getCambicBounds). WhenNULL(the new default) the function readsgetOption("soilKey.diagnostic_engine", "soilkey"), so a globaloptions(soilKey.diagnostic_engine = "aqp")flips everycambic()call without modifying call sites. The aqp engine fired 40.6 soilkey 0 v0.9.50 LUCAS WRB benchmark from 0 100cambic_aqp.
Details
v0.2 implementation tests three conditions:
thickness >= 15 cm (
test_minimum_thickness)texture sandy loam or finer (
test_texture_argic)
v0.2 limitations: WRB 2022 also excludes profiles with spodic, calcic, gypsic, plinthic, vertic, and several other diagnostic horizons. Those exclusions, plus the WRB criteria of "evidence of alteration" (color/structure differences from parent material, carbonate removal), are scheduled for v0.3.
v0.9.314
The WRB cambic horizon follows WRB 2022 Ch 3.1.5 (p. 39-40): criterion 4 is read layer by layer, so a layer that forms part of an argic, ferralic, calcic, mollic or other listed horizon (or of a layer with andic properties) is set aside, not the whole profile; the subsurface layers are those below the layer at the mineral soil surface that are not A horizons; the 15 cm are those of the adjoining layers; a layer whose texture or structure is not recorded leaves the result undecided. Criterion 3 is not tested. The USDA keys keep the earlier reading.