Biological Rotation Age of Community Teak (Tectona grandis) Plantation Based on the Volume, Biomass, and Price Growth Curve Determined through the Analysis of Its Tree Ring Digitization

Abstract

Teak (Tectona grandis) is a deciduous tree producing a popular, expensive, fancy timber with versatile utilization. The teak population and its habitats in the natural forest have been decreasing consistently; thus, the IUCN Red List classifies it as an endangered species. Teak tree logging from its native natural forest is banned, and commercial teak timber can only be harvested from the plantation. People plant teak on their private lands or in the community forest to meet the increasing demand. This study analyzed the annual tree rings of a teak disk taken from the community plantation and aimed to determine its biological rotation age. Tree ring interpretation provides the increment and growth that are mandatory fundamental components of knowledge in sustainable forest management. It may also decipher the tree’s biography, which contains information about past climate and future predictions responding to climate change. All of the disk’s annual tree rings were digitized, transformed, and then curve-fitted using an elliptical polar form of non-linear regression. The best-fitted curve estimation of every annual tree ring was employed to determine their age-related diameter and basal area, and then allometric equations estimated the above-ground biomass and clear-bole volume. The continuous and discrete formula fit the growth curve well, and this study determined that Chapman-Richards is the best fit among others. The growth curve, current annual increment (CAI), and mean annual increment (MAI) were graphed based on the clear-bole volume, above-ground biomass, and log timber price. The CAI and MAI intersections result in 28, 30, and 86 years of optimum harvesting periods when the growth calculation is based on volume, above-ground biomass, and log timber price, respectively. These results identified that the teak plantation is a sustainable and highly valuable asset to inherit with long-term positive benefits. The sociocultural provision of teak plants as an inheritance gift for the next generation has proven to be economically and ecologically beneficial.