Calculates Basal Area
silv_stand_basal_area.RdCalculates Basal Area in square meters.
Details
The function uses the next formula:
\(G = \frac{\pi}{40000} \cdot D^2 \cdot \text{ntrees}\)
where G is the basal area in \(m^2\), and D is the diameter in cm. If ntrees
in the number of trees per hectare, then the result will be \(m^2/ha\). It is
recommended to use the squared mean diameter calculated with silv_stand_qmean_diameter().
Note that if ntrees = NULL, the output of the function will be exactly
the same as in silv_tree_basal_area().
Examples
## calculate G for inventory data grouped by plot_id and species
library(dplyr)
inventory_samples |>
mutate(dclass = silv_tree_dclass(diameter)) |>
summarise(
height = mean(height, na.rm = TRUE),
ntrees = n(),
.by = c(plot_id, species, dclass)
) |>
mutate(
ntrees_ha = silv_density_ntrees_ha(ntrees, plot_size = 10),
dg = silv_stand_qmean_diameter(dclass, ntrees_ha),
g = silv_stand_basal_area(dclass, ntrees_ha),
.by = c(plot_id, species)
)
#> # A tibble: 57 × 8
#> plot_id species dclass height ntrees ntrees_ha dg g
#> <int> <int> <dbl> <dbl> <int> <dbl> <dbl> <dbl>
#> 1 7 27 50 18 3 95.5 57.9 0.196
#> 2 7 27 55 17.6 5 159. 57.9 0.238
#> 3 7 27 35 16.5 1 31.8 57.9 0.0962
#> 4 7 27 45 14.6 2 63.7 57.9 0.159
#> 5 7 27 60 19.1 3 95.5 57.9 0.283
#> 6 7 27 25 12.9 1 31.8 57.9 0.0491
#> 7 7 27 120 20.9 1 31.8 57.9 1.13
#> 8 8 83 20 5.10 3 95.5 15.1 0.0314
#> 9 8 83 10 6.10 4 127. 15.1 0.00785
#> 10 8 28 55 15.5 1 31.8 57.6 0.238
#> # ℹ 47 more rows