GS {leafR}

Gini-Simpson index of foliage structural diversity

Description

Calculates the Gini-Simpson (GS) index metric (i.e. complement of Simpson diversity (1 - \gamma) from abundances considered as per-voxel relative LAD values.

Usage

GS(lad_profile, evenness = FALSE, LAD.threshold = -1)

Arguments

lad_profile

a data.frame including values of relative LAD at height intervals, output of the lad.profile function (use relative = TRUE)

evenness

boolean, defines whether GS should be based on Simpson's diversity or evenness (Hill 1973). The default FALSE calculates Simpson's diversity (\gamma); the alternative TRUE was recommended by Valbuena et al. (2012), and it divides by the number of voxels with LAD values above the threshold, following Smith and Wilson (1996).

LAD.threshold

numerical (0,1), defines the minimum value of LAD for considering the relative leaf abundance of a voxel in GS calculation. Defaults to the inverse of the total number of voxels.

Value

A numeric containing the Fini-Simpson index calculated from the Leaf Area Density profile

References

Hill M. O. (1973) Diversity and evenness: a unifying notation and its consequences. Ecology. 54: 427–432. doi: 10.2307/1934352

Smith B., and Wilson J.B. (1996). A consumer's guide to evenness indices. Oikos 76: 70–82. doi: 10.2307/3545749

Valbuena R., Packalen P., Martín-Fernández S., Maltamo M. (2012) Diversity and equitability ordering profiles applied to the study of forest structure. Forest Ecology and Management 276: 185–195. doi: 10.1016/j.foreco.2012.03.036

Examples

# Get the example laz file
normlas.file = system.file("extdata", "lidar_example.laz", package="leafR")

# Calculate LAD from voxelization
VOXELS_LAD = lad.voxels(normlas.file,
                        grain.size = 2)

# Calculate the LAD profile
lad_profile = lad.profile(VOXELS_LAD, relative = TRUE)

GS(lad_profile, evenness = FALSE)
GS(lad_profile, evenness = TRUE)