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Regression coefficients for predicting tree crown width

Source: R/data.R
cw_coef.Rd

A curated set of linear regression coefficients for predicting crown width from stem diameter of tree species in the conterminous US.

Usage

cw_coef

Format

cw_coef

A data frame with 430 rows and 8 columns:

symbol

character, USDA PLANTS Database species symbol

SPCD

integer, FIA tree species code or -1

common_name

character, FIA tree species common name

surrogate

character, Common name of surrogate species if applicable

b0

numeric, Regression b0 coefficient

b1

numeric, Regression b1 coefficient

b2

numeric, Regression b2 coefficient

reference

character, Literature source of the species coefficients (see References)

Source

Toney et al. 2009. A stem-map model for predicting tree canopy cover of Forest Inventory and Analysis (FIA) plots. https://research.fs.usda.gov/treesearch/33381.

Details

The regression equation is of the general form:

CW = b0 + b1 * DIA + b2 * DIA^2

where CW is the predicted tree crown diameter in feet, DIA is FIA stem diameter in inches, and b0, b1, b2 are the regression coefficients. The quadratic term b2 was not included in the regression models for some species, and has been assigned 0 in that case for purposes of this lookup table.

In cases that species-specific equations were not available in the literature, surrogate species were assigned based on subjectively similar tree physiognomy.

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, Vol. 27, No. 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, Vol. 19, No. 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, 405-416.

Examples

# Abies grandis
cw_coef[cw_coef$SPCD == 17, ]
#>   symbol SPCD common_name surrogate   b0   b1    b2       reference
#> 3   ABGR   17   grand fir      <NA> 5.75 1.11 -0.01 Bechtold (2004)