A surface (or near-surface, after drainage) horizon of organic material; diagnostic of Histosols. Two alternative qualifying paths per WRB 2022:
Contiguous: a single layer of organic material (OC % >=
min_oc) reaching the surface and at leastmin_thicknesscm thick (default 10 cm).Cumulative: organic material totalling
cumulative_min_cmcm (default 40) within the uppercumulative_max_depth_cm(default 80). Relevant for folic / mossy Histosols on slopes.
Either path qualifies. The "after drainage" qualifier (recently drained organic soils) is treated as implicit since the same OC and thickness criteria apply.
Usage
histic_horizon(
pedon,
min_thickness = 10,
min_oc = 12,
surface_top_cm = 0,
cumulative_min_cm = 40,
cumulative_max_depth_cm = 80
)Arguments
- pedon
A
PedonRecord.- min_thickness
Minimum thickness (cm) for the contiguous path (default 10).
- min_oc
Minimum organic carbon % (default 12, WRB 2022; equivalent to
>= 20%organic matter).- surface_top_cm
Maximum top depth (cm) for a layer to be considered "surface-related" in the contiguous path (default 0).
- cumulative_min_cm
Minimum cumulative thickness (cm) for the cumulative path (default 40).
- cumulative_max_depth_cm
Depth window (cm) for the cumulative path (default 80).