Abstract:

The study of height-diameter model is a basic research in forest growth and yield modeling. 1 139 individual trees in Wangqing Forest Bureau, Jilin Province were used in this study to develop the generalized height-diameter models. PROC NLIN in SAS was used to develop ten generalized height-diameter models, and PROC GLM was used to estimate the error of each models. The function with the highest R², lowest RMSE, and relatively fewer parameters was chosen as the optimal generalized height-diameter model. We found that the function (9)H=1.3+a₁ H^{^}₀ a₂ (1-exp(-a₃ SPH^{^}a₄ D))^{^}a₅ （where H is height, D is diameter, H₀ is dominant height, SPH is number of individuals in the stand, a₁, a₂, a₃, a₄ and a₅ are parameters specific to species）, which was based on Richards function, could calibrate the relationship between height and diameter best for the main coniferous tree species fir, spruce, and korean pine. In addition, we compared the accuracy between the optimal generalized height-diameter model and the optimal local height-diameter model. Results indicated that, with including stand variables, the optimal generalized height-diameter model is more accurate.

Key words: natural forest, generalized height-diameter model, fir, spruce, korean pine