Thrower et al. (1994) site index models for BC interior species — si

Unified, vectorized implementation of the field-guide formulations in Thrower, Nussbaum, and Di Lucca (1994) for interior British Columbia species.

Usage

si_thrower1994(age, height = NULL, si = NULL, species)

Arguments

age: Numeric vector. Breast-height age (years).
height: Optional numeric vector. Top height (m). If provided, `si` is predicted.
si: Optional numeric vector. Site index (m, base age 50 years at breast height). If provided, `height` is predicted.
species: Character vector of NFI species codes (e.g., `"PINU.CON"`).

Value

A tibble with columns:

height: Predicted top height (m), returned when input `si` is provided.
si: Predicted site index (m), returned when input `height` is provided.

Details

Model scope (species coverage): this implementation includes parameter sets for 11 species: PINU.CON, PICE.GLA, PSEU.MEN, ABIE.LAS, TSUG.HET, THUJ.PLI, PINU.MON, PINU.PON, LARI.OCC, POPU.TRE, BETU.PAP.

Age definition note: `age` is breast-height age (years).

Base-age note: site index in this model family is referenced to height at 50 years breast-height age.

Provide exactly one of `height` or `si`:

If `height` is provided, the function predicts `si`.
If `si` is provided, the function predicts `height`.

References

Thrower, J.S., Nussbaum, A.F., and Di Lucca, C.M. (1994). Site index curves and tables for British Columbia: interior species (2nd ed.). B.C. Ministry of Forests, Land Management Handbook, Field Guide Insert 6.

Examples

# Predict site index from age + height
si_thrower1994(
  age = c(25, 40, 70),
  height = c(8, 16, 24),
  species = c("PINU.CON", "PSEU.MEN", "THUJ.PLI")
)
#> # A tibble: 3 × 1
#>      si
#>   <dbl>
#> 1  13.5
#> 2  18.7
#> 3  19.4

# Predict height from age + site index
si_thrower1994(
  age = c(25, 40, 70),
  si = c(12, 18, 24),
  species = c("PINU.CON", "PSEU.MEN", "THUJ.PLI")
)
#> # A tibble: 3 × 1
#>   height
#>    <dbl>
#> 1   7.05
#> 2  15.3 
#> 3  29.7