Calculates the Stand Density Index — silv_density

The Stand Density Index (SDI) is relationship between the average tree size and density of trees per hectare.

Usage

silv_density_sdi(ntrees, dg, classify = FALSE, max_sdi = NULL)

Arguments

ntrees: Numeric vector with number of trees of the diameter class per hectare. If ntrees = NULL, the function will assume that each diameter corresponds to only one tree
dg: Numeric vector of quadratic mean diameters
classify: whether to classify the values using USDA thresholds
max_sdi: used when classify = TRUE. The maximum SDi, which depends on the species, stand type, and site

Value

A numeric vector

Details

The SDI has different interpretation depending on the species, location, and also the management type (even-aged, uneven-aged...). The value of maximum SDI must be determined from the literature and used carefully. The option classify = TRUE will use this value to classify the SDI in low density (<24%), moderate density (24-35%), high density (34-55%), and extremely high density (>55%).

Examples

## calculate SDI for a Pinus sulvestris stand (max 990)
silv_density_sdi(ntrees = 800, dg = 23.4, max_sdi = 990)
#> [1] 70.84156

## check base classification (other can be used)
silv_density_sdi(ntrees = 800, dg = 23.4, classify = TRUE, max_sdi = 990)
#> [1] "Extremely high density"