% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/diagnostics-materials-wrb.R
\name{histic_horizon}
\alias{histic_horizon}
\title{Histic horizon (WRB 2022)}
\usage{
histic_horizon(
  pedon,
  min_thickness = 10,
  min_oc = 12,
  surface_top_cm = 0,
  cumulative_min_cm = 40,
  cumulative_max_depth_cm = 80
)
}
\arguments{
\item{pedon}{A \code{\link{PedonRecord}}.}

\item{min_thickness}{Minimum thickness (cm) for the contiguous
path (default 10).}

\item{min_oc}{Minimum organic carbon \% (default 12, WRB 2022;
equivalent to \code{>= 20\%} organic matter).}

\item{surface_top_cm}{Maximum top depth (cm) for a layer to be
considered "surface-related" in the contiguous path
(default 0).}

\item{cumulative_min_cm}{Minimum cumulative thickness (cm) for the
cumulative path (default 40).}

\item{cumulative_max_depth_cm}{Depth window (cm) for the cumulative
path (default 80).}
}
\value{
A \code{\link{DiagnosticResult}}.
}
\description{
A surface (or near-surface, after drainage) horizon of organic
material; diagnostic of Histosols. Two alternative qualifying
paths per WRB 2022:
\itemize{
  \item \strong{Contiguous}: a single layer of organic material
        (OC \% >= \code{min_oc}) reaching the surface and at
        least \code{min_thickness} cm thick (default 10 cm).
  \item \strong{Cumulative}: organic material totalling
        \code{cumulative_min_cm} cm (default 40) within the upper
        \code{cumulative_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.
}
\references{
IUSS Working Group WRB (2022), Chapter 3, Histic horizon
  and organic material.
}
