GROWTH COHMJRACTERISTICS AND BIOMASS ACCUMULATIONS OF ACACIA MANGIUM UNDER DIFFERENT MANAGEMENT PRACTICES IN INDONESIA

摘要

Tree biomass accumulations and age-related changes of Acacia mangium plantations were determined using a destructive sampling technique. These data were used to estimate optimum harvesting time. Tree biomass samples were collected in 3-, 5-, 8- and 10-year-old plantations in West Java, and in 2.5-, 5.5-, 8.5- and 10.5-year-old plantations in South Sumatra. About 15 trees were sampled from each stand. Tree growth characteristics were evaluated for both sites. Specific wood density in unthinned plantation was higher than in thinned plantation. Proportion of stem biomass in thinned plantation was constant during thinning period and thereafter slightly increased with age, whereas leaf biomass decreased. In unthinned plantation, proportion of stem biomass increased with age, while leaf biomass drastically decreased when competition occurred in the young stage but became relatively constant thereafter. Allometric equations were developed for each site to estimate root, stem, branch, leaf, aboveground andtotal biomass and stem volume. Using these equations, the stem volume and biomass of each component for each stand age were estimated. A single allometric relationship for all sites was found just for estimation of root biomass and stem volume. Therefore, the use of site-specific equation is recommended. According to the optimum productivity values, longer rotation is available to enhance wood quality and wood utilization for thinned plantation in West Java. A rotation of six and eight years is recommended to maximize biomass accumulation and benefits respectively for unthinned plantation in South Sumatra.