harden.melanization {aqp} R Documentation

Harden (1982) Melanization

Description

Calculate Melanization component of Profile Development Index after Harden (1982) "A quantitative index of soil development from field descriptions: Examples from a chronosequence in central California". Accepts vectorized inputs for value and reference value to produce vector output. A convenient use case would be to apply this on a profile-specific basis, where the value_ref has a single value, and value is a vector of length equal to the number of horizons within the upper 100 cm.

Usage

harden.melanization(value, value_ref)

Arguments

 value numeric vector containing Munsell values value_ref A numeric vector containingMunsell value(s) for reference material

Details

In Harden (1982), melanization is calculated relative to a reference parent material for all horizons within 100cm of the soil surface. In addition, several other non-color components are normalized relative to a maximum value and summed to obtain the overall Profile Development Index.

Value

A numeric vector reflecting horizon darkening relative to a reference (e.g. parent) material.

Andrew G. Brown

References

Harden, J.W. (1982) A quantitative index of soil development from field descriptions: Examples from a chronosequence in central California. Geoderma. 28(1) 1-28. doi: 10.1016/0016-7061(82)90037-4

Examples

library(aqp)
data("jacobs2000", package="aqp")

# LEFT JOIN hue, value, chroma matrix color columns
horizons(jacobs2000) <- cbind(horizons(jacobs2000)[,c(idname(jacobs2000), hzidname(jacobs2000))],
parseMunsell(jacobs2000\$matrix_color_munsell, convertColors = FALSE))

# calculate a mixed 150-200cm color ~"parent material"

jacobs2000\$c_horizon_color <- profileApply(jacobs2000, function(p) {

# and derive the parent material from the 150-200cm interval
p150_200 <- glom(p, 150, 200, truncate = TRUE)
p150_200\$thickness <- p150_200\$bottom - p150_200\$top

# mix colors
clrs <- na.omit(horizons(p150_200)[,c('matrix_color_munsell','thickness')])
mixMunsell(clrs\$matrix_color_munsell, w = clrs\$thickness)\$munsell

})

# segment profile into 1cm slices (for proper depth weighting)
jacobs2000\$melan <- profileApply(jacobs2000, function(p) {

# sum the melanization index over the 0-100cm interval
p0_100 <- segment(p, 0:100)

ccol <- parseMunsell(p\$c_horizon_color, convertColors = FALSE)

sum(harden.melanization(
value = as.numeric(p0_100\$value),
value_ref = as.numeric(ccol\$value)), na.rm = TRUE)

})

jacobs2000\$melanorder <- order(jacobs2000\$melan)

# Plot in order of increasing Melanization index

plotSPC(jacobs2000, axis.line.offset = -1,
color = "matrix_color",
label = "melan",
plot.order = jacobs2000\$melanorder)

abline(h = c(0,100,150,200), lty = 2)

# Add [estimated] parent material color swatches
lapply(seq_along(jacobs2000\$c_horizon_color), function(i) {
rect(i - 0.15, 250, i + 0.15, 225,
col = parseMunsell(jacobs2000\$c_horizon_color[jacobs2000\$melanorder[i]]))
})

[Package aqp version 1.40 Index]