No abstract

Realized genetic gains brought by the firstgeneration tree improvement of Acacia mangium were evaluated by analyzing the 1-year growth performance of growth (height, dbh) and form (stem straightness, multi-stem) traits using data collected from three secondgeneration orchards: groups B, C, and D. Each orchard was composed of improved families derived from openpollinated seed of plus trees selected from the firstgeneration seed orchards and newly added unimproved families collected from the same geographic region. The number of improved families and that of the unimproved in each orchard were 31 and 23 for group B, 28 and 39 for group C, and 24 and 30 for group D. Gains were calculated as percentage increase of improved families over unimproved ones. Improved families performed better than unimproved ones in 11 out of 12 comparison cases: four traits each in the three orchards. Averages of the realized genetic gain across the three seedling seed orchards were 3.1%, 5.2%, 4.3%, and 0.5% for height, dbh, stem straightness, and multi-stem, respectively. Except for multi-stem, the performances of improved families were significantly better than those of unimproved families in all the three orchards for dbh and in two out of three orchards for height and stem straightness.

Increases in stand volume with some currently introduced provenances of Acacia mangium: Papua New Guinea (PNG) and Far North Queensland (FNQ), were projected based on their superiorities in 3-year height growth in seedling seed orchards using the growth model developed for unthinned plantation for pulp and paper production in South Sumatra, Indonesia. The height growth of these provenances was better than that of the local selections from Subanjeriji by 10%-15% at 3 years old and these percentage superiorities would be expected to remain at around 9%-14% until the 8-year rotation. This amount of increase would result in a 7%-10% increase in basal area and hence it would produce a 17%-26% increase in stand volume at rotation age when compared with the Subanjeriji seed source that was being widely used for the plantation establishment of A. mangium in Indonesia.

No abstract

Following the results of the comprehensive tree improvement programs for Acacia mangium, it is necessary to estimate the real amount of genetic improvement and to develop an improved seed deployment strategy. This study was aimed to verify realized genetic gain on stand volume productivity attained by the firstgeneration Seedling Seed Orchards (SSO) of A. mangium and to identify the magnitude of seed sources x site interaction as a basis for improved seed deployment. Seeds from five SSOs were tested together with seeds from seed stand in genetic gain trials which were established in South Kalimantan and Central Java. Realized gains were calculated from the percentage improvement of respective SSOs compared with seed stand at two and four years of age. Seed source x site interaction was investigated through analysis across the two sites. Results of the study showed that trees derived from the five SSOs produced better stand volume than those from seed stand. At four years of age, stand volume of the best SSO reached around 127 m 3 /ha in South Kalimantan and 84 m 3 /ha in Central Java. Realized genetic gain were around 66% at two years and 59% at four years in South Kalimantan, and around 136% at two years and 81% at four years in Central Java. Seed source x site interaction was not significantly different indicating superiority of improved seed were consistent across the two sites with the average realized gain ranging from 18% to 79% and 24% to 62% at two and four years, respectively. The best three SSOs were SSO-1 located in Pleihari-South Kalimantan, SSO-2 in Pendopo-South Sumatra and SSO-5 in Wonogiri-Central Java, all of which originated from Papua New Guinea provenances. Improved seed from the orchards could be used at plantation sites without any significant change of the order in their superiority for stand volume productivity.