Generates a root density depth function for soil layers

Generates a root density depth function for soil layers

make_rootden(
  soilnodes,
  maxrootdepth = min(soilnodes),
  method = "betamodel",
  beta = 0.97,
  rootdat = NULL
)

Arguments

soilnodes

Vector of soil layer depth limits (including the top and the bottom of the profile) for which the relative root distribution will be calculated (m, negative downwards).

maxrootdepth

The maximum rooting depth (m, negative downwards) below which relative root length density will be set to zero (not applying when method = 'table').

method

Method name for the root depth distribution. Possible values are 'betamodel', 'table', 'linear', 'constant'. See details.

beta

Parameter of the root distribution function.

rootdat

data.frame with a given root depth density distribution. Columns are depth limits ('upper' and 'lower' in m, negative downwards) and relative root densities of fine or absorbing roots ('rootden') per unit stonefree volume. Only used when method = 'table'.

Value

Vector of relative root length densities for the soil layers framed by soilnodes. Length is one less than length(soilnodes).

Details

method = 'betamodel' calculates the relative root length densities of the soil layers from the cumulative proportion of roots derived by the model after Gale & Grigal (1987). method = 'table' distributes the relative root densities provided by rootdat to the soil layers, under preservation of total root mass. method = 'linear' returns linearly decreasing root densities with a value of 1 at the top of the soil profile to 0 at maxrootdepth. method = 'constant' returns a uniform root distribution with a relative root length density of 1 for all soil layers above 'maxrootdepth'.

References

Gale, M.R. & Grigal D.F. (1987): "Vertical root distributions of northern tree species in relation to successional status." Canadian Journal of Forest Research, 17:829-834

Examples

depths <- c(max(slb1_soil$upper), slb1_soil$lower)
roots_beta <- make_rootden(soilnodes = depths,
                              maxrootdepth = -1,4,
                              beta = 0.97,
                              method = "betamodel")

rootden_table <- data.frame(
  upper = c(0.03,0,-0.02, -0.15, -0.35, -0.5, -0.65,-0.9,-1.1,-1.3),
  lower = c(0,-0.02, -0.15, -0.35, -0.5, -0.65,-0.9,-1.1,-1.3,-1.6),
  rootden = c(10,15, 35, 15, 7.5, 4, 12, 2, 2, 0))

roots_table <- make_rootden(soilnodes = depths,
                               method = "table",
                               rootdat = rootden_table)

roots_linear <- make_rootden(soilnodes = depths,
                                maxrootdepth = -1.4,
                                method = 'linear')

roots_constant <- make_rootden(soilnodes = depths,
                                  maxrootdepth = -1.4,
                                  method = 'const')

plot(roots_constant, slb1_soil$lower +runif(n=length(slb1_soil$lower), -0.02,0.02),
     type = 's', lwd = 1.5,ylab = "soil depth [m]",xlab = "relative root density",
     xlim = c(0,1), col = "red")

lines(roots_linear, slb1_soil$lower,
      type = 's', col = "blue", lwd = 1.5)

lines(roots_beta*10, slb1_soil$lower, type = 's', col = "brown", lwd = 1.5)

lines(roots_table/100, slb1_soil$lower,
      type = 's', col = "green", lwd = 1.5)


legend("bottomright", c("'betamodel'","'table'","'linear'", "'constant'"),seg.len = 1.5,
       pch = NULL, lwd =1.5, col = c("brown", "green", "blue", "red"), bty = "n")