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Calculate canopy base height metrics from FIA tree data

Source: R/calc_cbh_metrics.R
calc_cbh_metrics.Rd

calc_cbh_metrics() computes canopy base height metrics for FIA tree data based on measurements of uncompacted live crown ratio (UNCRCD) of individual trees >= 5.0 in. (12.7 cm) diameter. Canopy base height represents the lowest height at which canopy fuel, aggregated across multiple tree crowns, can propagate fire vertically (see, e.g., Mast et al. 2026). This function derives individual tree crown base heights from actual tree height and the uncompacted crown ratio, and computes the mean, median, \(20^{th}\) percentile and minimum.

Usage

calc_cbh_metrics(tree_table, plot_id_col = NULL, digits = 1)

Arguments

tree_table

A data frame with tree records for one or more FIA plots. Must have columns ACTUALHT (tree actual height) and UNCRCD (uncompacted live crown ratio as percentage).

plot_id_col

Optional column name in tree_table of a plot unique identifier. If NULL and no column named PLT_CN or plt_cn exists, the input data are assumed to be a single tree list. If PLT_CN or plt_cn exists, it will be used as the plot ID column.

digits

Optional integer indicating the number of digits to keep in the return values (defaults to 1).

Value

Canopy base height metrics aggregated from individual tree crown base heights: "cbh_mean", "cbh_median", "cbh_pct20" and "cbh_min". If the input contains tree data for a single plot without a plot ID column, a named list is returned, otherwise a data frame.

References

Mast, C.N., L. Vallet, M.D. Hurteau, H. Zald, G.M. Jones, G.A. Woolsey, W. Tinkham, C.M. Hoffman, E.J. Francis. 2026. Methods and implications of canopy base height characterization for modeling crown fire potential. Fire Ecology 22(117). doi:10.1186/s42408-026-00567-4 .

See also

calc_ht_metrics(), calc_tcc_metrics()

Examples

system.file("extdata/dfir_plot.csv", package="FIAstemmap") |>
  load_tree_data(columns = NULL) |>
  calc_cbh_metrics()
#> ℹ Fetching tree data
#> ✔ Fetching tree data [9ms]
#> 
#> ℹ 32 tree records returned.
#>            PLT_CN cbh_mean cbh_median cbh_pct20 cbh_min
#> 1 670950967126144     29.1       29.4         9     0.9