Stem volume models using diameter at breast height (DBH) and height were developed for Pinus densiflora, Pinus koraiensis, and Larix kaempferi. The data were obtained from Gangwon, Gyeonggi, and North Gyeongsang provinces in South Korea, and the sample trees felled were used to provide the parameter estimates of volume equations. The combined-variable function, , was shown to be the best model through the validation of the equation. Also, the model using only DBH, was also evaluated to be applicable in the field. These models revealed higher accuracy when compared with previous studies. Both equations are considered to be easily used in the field.

Tree growth in Korean red pine (Pinus densiflora, hereafter Pd), Korean white pine (Pinus koraiensis, hereafter Pk), and Japanese larch (Larix kaempferi, hereafter Lk) was modeled using Logistic, Korf, Gompertz, Chapman-Richards, and Weibull equations and stem analysis data from sample trees: 38 trees for Pd, 46 trees for Pk, and 45 trees for Lk. The models were fitted to the total increment of tree size variables, diameter at breast height (DBH), height, basal area, and stem volume, as a function of age. After selecting the best-fit growth function, the current annual increment (CAI) and mean annual increment (MAI) were compared for each variable by species. The optimal growth functions were Chapman-Richards for DBH and stem volume, Korf for height, and Gompertz for basal area. The parameter estimates in the final models were all significant (p < 0.01) with best-fit statistics and unbiased residual plots. When plotted with observed values, the growth patterns of each variable were represented properly. The predicted growth curves over age were concave with respect to the Y-axis in DBH and height but lightly convex in basal area, and explicitly convex in stem volume, whereas an asymptote of sigmoid curve in stem volume was not apparent until 100 years. Age with the maximum MAI among variables was arranged similarly to CAI; the age with maximum MAI was earliest for DBH and latest for volume. The maximum growth was achieved earliest in Lk, followed by Pk and Pd. The developed models were able to predict tree size variables and serve as a reference to understand growth characteristics by species.

Appropriate management of stand density is necessary to avoid wasted growing space and overcrowding-induced self-thinning and therefore to optimize profitability. We developed a Gingrich-style stocking chart for Korean red pine (Pinus densiflora), Korean white pine (P. koraiensis), and Japanese larch (Larix kaempferi) in Korea. Datasets for even-aged stands were categorized into two censored datasets via relative density based on species-specific stand density indices to assign adequate plots for tree allometry. Censored plot data for maximum density on full stocking were used to develop A-level stocking based on mean individual tree area. In censored plot data for minimum density on full stocking, individual trees represented open-grown trees, and a crown competition factor of 100 was proposed as B-level stocking. Based on parameters estimated from allometry, stocking diagrams comprising quadratic mean diameter, number of trees, and basal area were correctly expressed. A-level stocking at the same quadratic mean diameter revealed that Korean white pine had the most trees and largest basal area, while Japanese larch had the fewest trees and smallest basal area. In contrast, B-level stocking disclosed that Japanese larch had the most trees and basal area, whereas Korean white pine had the fewest trees and smallest basal area. The stocking diagrams suggest that silvicultural treatments for these species should be species-specific.

The size growth patterns of major coniferous trees species Pinus densiflora (Pd), Pinus koraiensis (Pk), and Larix kaempferi (Lk) in South Korea were found and compared using stem analysis. A dominant or co-dominant tree selected from each of 131 sites (39 sites for Pd, 47 sites for Pk, and 45 sites for Lk) was stemmed and analyzed for the study. Total increment (TI), periodic annual increments (PAI), mean annual increments (MAI), and growth percentage of diameter at breast height (DBH), height, and volume were numerically and statistically compared among the three tree species. As the trees age the total DBH growths of Pk and Lk were similar to each other but higher than that of Pd. A noticeable difference of total height growth was shown among the trees and the total height increment was Lk > Pk > Pd. Like the total height growth, the volume difference was noticeably different among the trees and the growth was Lk > Pk > Pd. Given no difference of DBH between Lk and Pk, the volume difference between the two species was due to height. Unlike DBH and height, MAI and PAI of volume did not meet together.. This inferred that the volume growth was still vigorous to reach the rotation age. Growth percentages of DBH, height, and volume tended to decrease with age and no difference was shown among the tree species. The growth percentage of volume was higher than that of DBH and height, while there was no difference between DBH and height.

The objectives of this study were to develop site index and variable-density yield models for Korean red pine (Pinus densiflora Siebold & Zucc.), Korean white pine (P. koraiensis S. & Z.), and Japanese larch (Larix kaempferi (Lamb.) Carrière) in Korea. The data were collected between 2012 and 2021 from repeatedly measured empirical plots in each target stand in the North Central region of Korea: Gangwon and North Gyeongsang provinces. To develop the site index for each species, a dominant height growth model by species was developed using the Chapman–Richards function. The site index was computed with a base age of 40 years and used as an independent variable to predict the stand volume. To develop the variable-density yield models, three stand density variables, the stand age, and the site index were applied. The stand density variables used were the stand basal area, the number of trees per hectare, and the relative density. All the models were successfully developed with significant parameters and reasonable fit statistics, and the residuals analyzed presented unbiased scatter plots. Yield models with the stand basal area, or the number of trees, can be used to predict the stand volume. The yield model with relative density was flexible to apply across the stand age because the input of the absolute stand density was not required. Model simulation and comparisons with other studies also supported the applicability of the models developed in this study. The models were found to be highly applicable for predicting and simulating these targeted stands, particularly in Korea.