Nigh and Courtin (1998) site index model for red alder (BC coast)
Source:R/si_nighcourtin1998.R
si_nighcourtin1998.RdImplementation of the Nigh and Courtin (1998) anamorphic
height-age/site-index equations for red alder (ALNU.RUB) in
coastal British Columbia.
Arguments
- age
Numeric vector. Breast-height age (years).
- height
Optional numeric vector. Dominant height (m). If provided, `si` is predicted.
- si
Optional numeric vector. Site index SI25 (m at breast-height age 25). If provided, `height` is predicted.
- si50
Logical scalar. Default `FALSE`. If `TRUE`, interpret input `si` (when provided) as SI50 and return predicted `si` (when `height` is provided) as SI50 using: $$SI50 = -0.4063 + 1.313 \times SI25$$ and its inverse.
Value
A tibble with columns:
- height
Predicted dominant height (m), returned when input `si` is provided.
- si
Predicted site index SI25 (m), returned when input `height` is provided.
Details
Species coverage: ALNU.RUB.
Age definition note: `age` is breast-height age (years).
Base-age note: site index in this model is SI25 (m at breast-height age 25 years), not SI50.
Provide exactly one of `height` or `si`:
If `height` is provided, the function predicts `si`.
If `si` is provided, the function predicts `height`.
Both directions are explicit closed forms from the source publication.
References
Nigh, G. D., & Courtin, P. J. (1998). Height models for Red Alder (Alnus rubra Bong.) in British Columbia. New Forests, 16, 59-70.
Examples
# Predict site index SI25 from age + height
si_nighcourtin1998(
age = c(10, 25, 40),
height = c(8, 18, 24)
)
#> # A tibble: 3 × 1
#> si
#> <dbl>
#> 1 14.1
#> 2 18.0
#> 3 19.8
# Predict height from age + site index SI25
si_nighcourtin1998(
age = c(10, 25, 40),
si = c(14, 18, 22)
)
#> # A tibble: 3 × 1
#> height
#> <dbl>
#> 1 7.93
#> 2 18.0
#> 3 26.6
# Use SI50 instead of SI25
si_nighcourtin1998(
age = c(10, 25, 40),
si = c(18, 23, 28),
si50 = TRUE
)
#> # A tibble: 3 × 1
#> height
#> <dbl>
#> 1 7.94
#> 2 17.8
#> 3 26.2