Allometric equations to assess biomass, carbon and nitrogen content of black pine and red pine trees in southern Korea

A total of 74 Japanese black pine (Pinus thunbergii Parl.) and red pine (P. densiflora S. et Z.) trees were destructively sampled in southern Korea, which is severely affected by pine wilt disease (PWD). Species-specific allometric equations were developed to estimate the biomass, carbon (C) and nitrogen (N) content of the tree components (i.e., stem wood, stem bark, branches, needles and roots) based on the diameter at breast height (DBH) and stem diameter at 20 cm aboveground (D-20). The C concentrations of the various tree components were not correlated with DBH (P > 0.05), except for the C concentration in the stem bark (r = -0.29, P < 0.05) of the black pine and the branches (r = 0.40, P < 0.05) of the red pine. However, the N concentrations in the stem wood (r = -0.53, P < 0.05), stem bark (r = -0.37, P < 0.05) and branches (r = -0.40, P < 0.05) of the black pine were negatively correlated with DBH. The mean C concentrations of the tree components were not significantly different between the black pine and red pine, except for the stem bark, whereas the mean N concentrations were significantly lower in the black pine than in the red pine, except for the stem bark. The allometric equations developed for the biomass, C and N content for all the tree components were significant (P < 0.05). The adjusted coefficient of determination (adj. R-2) of the DBH allometric equations ranged from 0.66 to 0.97, while the coefficients for the D-20 equations were between 0.66 and 0.95. Black pines consistently exhibited more biomass, C and N content in the tree components compared with the red pines with similar DBH or D-20. These results suggest that the accuracy of estimates for biomass, C and N stocks in black pine and red pine forests could be improved by specific allometric equations for PWD-disturbed forests.