Models of Utah Juniper and Two-Needle Pinyon Biomass for One Site in Southwest Utah

Abstract

Twenty-three Utah juniper (Juniperus osteosperma) trees and 20 two-needle pinyon pine (Pinus edulis) trees in southwest Utah were selected, and whole-tree green weights were obtained. In addition, trees were measured for diameter at groundline (dgl), dbh, crown length and width, and total height. These data were used to model aboveground biomass for both species. The coefficient of determination (R2), standard error of the estimate, mean percent standard error, and percent bias were calculated for each model. For both species, the best model for estimating aboveground biomass included dgl, crown width, and total height as predictors. With these predictors, the model for Utah juniper had R2 = 0.97, whereas the model for pinyon pine had R2 = 0.98. Both dgl and dbh alone were also very good predictors of aboveground biomass and had R2 values for Utah juniper of 0.94 and 0.95, respectively. For pinyon pine, using dgl and dbh as predictors, R2 values were 0.98 and 0.97, respectively. Site-specific models outperformed published biomass equations.