Predict individual tree crown width using species-specific equations

calc_crwidth() predicts tree crown width using species-specific regression equations from the literature.

Usage

calc_crwidth(tree_list, digits = 1)

Arguments

tree_list: A data frame containing tree records. Must have columns SPCD (FIA integer species code), STATUSCD (FIA integer tree status code, 1 = live) and DIA (FIA tree diameter in inches).
digits: Optional integer indicating the number of digits to keep in the return values (defaults to 1).

Value

A numeric vector of length nrow(tree_list) with predicted crown width in feet for live trees. NA is returned for trees with STATUSCD != 1.

Details

Crown width is predicted from tree diameter using coefficients provided in the lookup table cw_coef (see ?cw_coef) The method also incorporates adjustment factors used to derive crown width estimates for FIA "saplings", i.e., trees less than 5.0 in. (12.7 cm) diameter but greater than or equal to 1.0 in. (2.54 cm) diameter. Details are described in the documentation for the lookup table cw_sapling_adj.

Large diameter trees in the temperate rain forests of the Pacific Northwest region can far exceed the range of diameters in the broadly applicable datasets that have been used to develop crown width prediction equations (Bechtold 2003, 2004). To avoid extrapolation beyond the range of the model fitting data in those cases, calc_crwidth() makes use of the "old growth" equation presented by Gill et al. (2000) to estimate crown width for nine tree species when their diameter is greater than 50 in. (127 cm).

References

Bechtold, W.A. 2003. Crown-diameter prediction models for 87 species of stand-grown trees in the eastern United States. Southern Journal of Applied Forestry, 27(4): 269-278.

Bechtold, W.A. 2004. Largest-crown-width prediction models for 53 species in the western United States. Western Journal of Applied Forestry, 19(4): 245-251.

Gill, S.J., G.S. Biging, E.C. Murphy. 2000. Modeling conifer tree crown radius and estimating canopy cover. Forest Ecology and Management, 126(3): 405-416.

Examples

calc_crwidth(plantation)
#>  [1] 11.9 13.0 10.8 15.8 13.7 10.8 10.2  9.7 15.3 13.9 12.2 11.9 13.0  9.7 14.2
#> [16] 14.7 12.2 10.8 12.5 13.0 10.7 15.1  9.9 12.8 11.9 13.0 10.3 13.9 11.7 14.6
#> [31] 11.0 13.9 11.8 12.4 12.1 14.4 10.8  9.9 14.3 11.8 11.1 14.3 13.7 11.3 13.7
#> [46] 15.5 10.7 11.5 10.2 14.6 14.6 13.9 11.3 13.0 11.4 10.3 14.3 11.0 14.0 13.3
#> [61] 12.9 13.5 11.9 11.5 10.0 12.9  7.8 13.9 11.1 10.8 12.6 14.7 12.9 11.7 12.5
#> [76]  9.7 14.6 11.3 10.6 11.0 11.9 14.2 11.4 12.2 12.6 10.6 13.0 12.9 11.5  9.5
#> [91]  8.6