Effect of Thinning on the Chemical Properties of Clonal Teak Trees

Superior teak clones (Jati Plus Perhutani) have been developed by the Perhutani Enterprise, a state-owned company, through a breeding program in various locations. Thinning at the appropriate spacing is one method to enhance the productivity of forest plantations. The purpose of thinning is to reduce stand density, thereby lessening competition. The objective of this research was to examine the impact of thinning and within-tree variation (vertical and radial position) on the chemical properties of clonal teak. The initial spacing of the trees was 3 m × 3 m while the final spacing of 3 m × 15 m. The wood chemical properties were investigated in 20-year-old trees planted in Ngawi, East Java. Results indicated that thinning treatment significantly affected the extractive and cellulose content. The levels of α-cellulose and hexane-soluble extract increased with thinning treatment. However, the amount of hot-water soluble extract from the sapwood obtained from thinned stands was lower than that from non-thinned stands. The vertical direction factor influenced the pH values and cell wall components, whereas the radial direction affected the extractive contents and cell wall components. The amounts of cellulose and lignin decreased, while the hemicellulose content increased from the bottom to the top of the tree. The heartwood exhibited significantly lower values in lignin content and higher values in cellulose and hemicellulose contents compared to the sapwood. These results suggest that thinning may improve the durability and strength properties of teak clones.