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Calculate tree total and merchantable volume using Nigh (2016) equations (BC)

vol_nigh2016.Rd

Implementation of the British Columbia volume equations developed by Nigh (2016). The model calculates total stem volume and merchantable stem volume as a function of diameter at breast height (DBH) and total tree height.

Usage

vol_nigh2016(DBH, height, species, subregion)

Source

Nigh, G.D. (2016). Total and merchantable volume equations for common tree species in British Columbia: by region and biogeoclimatic zone. Province of British Columbia, Technical Report 106.

Arguments

DBH

Numeric vector of diameter at breast height (cm).

height

Numeric vector of total tree height (m).

species

Character vector of species codes

subregion

Character scalar or vector defining the spatial stratum for the coefficients. Can be "Coast" / "Interior" or a BEC zone code (e.g., "CWH", "ICH", "BWBS"). Must have length 1 or the same length as DBH.

Value

A tibble with volumes (m\(^3\)):

vol_total

Numeric. Total stem volume (m\(^3\)), under bark.

vol_merchantable

Numeric. Merchantable stem volume (m\(^3\)), under bark.

Details

Parameters are stratified either by region ("Coast", "Interior") or by BEC zone (e.g., "CWH", "ICH", "BWBS"), depending on which parameter row is requested via subregion.

Model form (Nigh 2016): $$V = \exp(b_0) \cdot DBH^{b_1} \cdot H^{b_2}$$ where \(V\) is volume (m\(^3\)), \(DBH\) is in cm, and \(H\) is in m.

Merchantable volume in Nigh (2016) is defined as total volume minus stump (0.3 m) and top volume above a 4 cm inside-bark diameter threshold (fixed definition in the original report).

Examples

# Single tree, region coefficients
vol_nigh2016(
  DBH = 35,
  height = 25,
  species = "POPU.TRI",
  subregion = "Interior"
)
#> # A tibble: 1 × 2
#>   vol_total vol_merchantable
#>       <dbl>            <dbl>
#> 1     0.821            0.788

# Multiple trees, vectorized (mixed subregions allowed)
vol_nigh2016(
  DBH = c(22, 30, 45),
  height = c(18, 24, 33),
  species = c("PSEU.MEN", "THUJ.PLI", "POPU.TRI"),
  subregion = c("Coast", "ICH", "Interior")
)
#> # A tibble: 3 × 2
#>   vol_total vol_merchantable
#>       <dbl>            <dbl>
#> 1     0.258            0.244
#> 2     0.661            0.626
#> 3     1.81             1.77