Umbric horizon (WRB 2022) — umbric

Tests for the umbric horizon – a thick, dark, organic-rich surface horizon like mollic, but with low base saturation (< 50%). Diagnostic of Umbrisols.

Usage

umbric_horizon(
  pedon,
  min_thickness = 20,
  min_oc = 0.6,
  max_bs = 50,
  surface_top_cm = 5
)

Arguments

pedon: A PedonRecord.
min_thickness: Minimum thickness (cm; default 20).
min_oc: Minimum SOC % (default 0.6).
max_bs: Maximum base saturation % (default 50; profile must be BELOW this).
surface_top_cm: Maximum top_cm for surface-related layers (default 5).

Value

A DiagnosticResult.

Details

Implementation reuses every mollic sub-test except the BS test, which is inverted via test_bs_below.

References

IUSS Working Group WRB (2022), Chapter 3, Umbric horizon.