TIMBER VOLUME GROWTH MODELS FOR Pinus kesiya Royle ex Gordon PLANTATIONS IN DUC TRONG AREA, LAM DONG PROVINCE

Abstract

The establishment and selection of an appropriate growth function are of great importance in silviculture, as they allow for accurate description of growth dynamics, yield prediction, and support for decision-making in forest plantation management. The study presented the estimation and prediction results of timber volume growth for Pinus kesiya Royle ex Gordon plantations in the period from 5 to 30 years old in Duc Trong area of Lam Dong Province using different growth functions. Data were collected from 18 sample plots, with a size of 1000 m². The research results indicated that: (1) if using 4 functions, Gompertz (1825), Korf (1929), Chapman - Richards (1959), and Kumaraswamy (1980), to describe the growth process of timber volume of P. kesiya plantations in the period from 5 to 30 years of age, the results obtained are different. (2) Different data processing methods lead to different reports on the growth characteristics of timber volume growth of P. kesiya plantations. (3) To obtain consistent results, this study proposes to use only the Korf function to describe the growth process of timber volume of the P. kesiya plantations in the period from 5 to 30 years of age. According to the Korf function, the maximum annual growth rate (ZM_Max) and the maximum annual average growth rate (DM_Max) of the P. kesiya plantations in the period from age level 5 to 30 years are 21.1 and 15.4 m³/ha/year, respectively. The ages at which ZM_Max and DM_Max are reached are 17 and 35 years, respectively. Therefore, age 17 was the time when the timber volume of the P. kesiya plantations changed from the rapid growth stage to the slow growth stage. The age at which the quantity of the P. kesiya plantations matures is 35 years. The results of this study provide a scientific basis for selecting a model to analyze the growth process of P. kesiya plantations from the young to middle - aged stages.