Trend of within-plot selection practiced in two seedling seed orchards ofAcacia mangium in Indonesia

A trend of within-plot selection was examined by applying a retrospective selection index to the results of the selection in two seedling seed orchards ofA. mangium at South Kalimantan in Indonesia. The orchards were established in randomized complete block design with ten replications of four tree row plots. Within-plot selections were conducted twice with around 50% of selection intensity in those orchards: at 22 months and at 51 months after planting, then the results were analyzed with the data on volume, stem form and bole length measured before each selection. Bole length was found to be the highest priority trait throughout the two stages of selection in both orchards. Growth expressed by volume was also an important criterion at the first within-plot selection, while the priority was not obvious at the second selection. Expected gains by within-plot selection were generally small, although predicted gains were positive on all of the three traits at each stage of selection. The seedling seed orchards analyzed in this study were established under a technical cooperation project between JICA (Japan International Cooperation Agency) and Ministry of Forestry in Indonesia in collaboration with Inhutani 3.