Calculate Structural Diversity (B2)

Computes forest structural diversity using Shannon diversity index applied to canopy strata and age class distributions.

Usage

indicator_biodiversity_structure(
  units,
  layers = NULL,
  strata_field = "strata",
  age_class_field = "age_class",
  species_field = NULL,
  method = "shannon",
  weights = c(strata = 0.4, age = 0.3, species = 0.3),
  use_height_cv = FALSE
)

Arguments

units

An sf object with forest parcels.

layers

A nemeton_layers object. Used as fallback for structural diversity estimation via LiDAR MNH or NDVI when strata/age fields are missing.

strata_field

Character. Column name containing canopy strata classes (e.g., "Emergent", "Dominant", "Intermediate", "Suppressed").

age_class_field

Character. Column name containing age classes (e.g., "young", "mature", "old", "ancient").

species_field

Character. Optional column name containing species names. If NULL, species diversity is not included in calculation. Default NULL.

method

Character. Diversity calculation method. Currently only "shannon" is supported.

weights

Named numeric vector. Weights for strata, age, and species components. Default c(strata = 0.4, age = 0.3, species = 0.3).

use_height_cv

Logical. If TRUE and strata_field is NULL, use coefficient of variation of height as proxy for vertical diversity. Default FALSE.

Value

The input sf object with added column:

• B2: Structural diversity index (0-100). Higher = more diverse.

Details

**Formula**: B2 = w1 × H_strata_norm + w2 × H_age_norm

Where H is Shannon diversity index, normalized to 0-100 scale.

**Interpretation**: Multi-layered, multi-age stands score high (>75). Monocultures or even-aged stands score low (<25).

See also

Other biodiversity-indicators: indicator_biodiversity_connectivity(), indicator_biodiversity_protection()

Examples

if (FALSE) { # \dontrun{
library(nemeton)

data(massif_demo_units)
units <- massif_demo_units

# Add structure attributes (normally from BD Forêt)
units$strata <- sample(c("Emergent", "Dominant", "Intermediate"),
  nrow(units),
  replace = TRUE
)
units$age_class <- sample(c("Young", "Mature", "Old"),
  nrow(units),
  replace = TRUE
)

result <- indicator_biodiversity_structure(
  units,
  strata_field = "strata",
  age_class_field = "age_class",
  species_field = "species"
)

hist(result$B2, main = "Structural Diversity Distribution")
} # }