Growth stresses and strains in Acacia mangium

The growth stresses and other properties of timber from plantation trees of Acacia mangium affected by the high growth rate were investigated in order to clarify the relationship between growth stresses and growth rate on tropical fast-growing species. Twenty-four stands with various ages (4 to 10 yr.) and diameters (8.8 to 30.5 cm) from one section of Perum Perhutani manmade forest area in West Java, Indonesia were selected. The growth stresses of A. mangium were higher compared to those from species of temperate zones. From the radial vectors 4 to 15 cm the longitudinal released strains were almost constant with average values ranging from -0.04 to -0.10 percent. Higher negative values were located in the tension wood regions. The growth rate did not affect either the magnitude or the radial distribution of growth stresses inside the stem (residual stresses). There was no significant relationship between growth rate and specific gravity. However, a clear correlation was found between the released strains and the microfibril angle (MFA). The smaller the MFA (below 8 degrees), the higher the absolute values of the released strains. In order to obtain stands of A. mangium with lower growth stress levels, it is important to avoid the formation of tension wood.

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