Declining natural forests in Indonesia has forced communities to search for alternative sources of wood. In order to meet the demand, wood is taken from fast-growing species grown in community forests. The species have short cutting cycle and contain a large proportion of juvenile woods. This article discusses the characteristics and demarcation point of juvenility in sengon (Falcataria moluccana) and jabon (Anthocephalus cadamba) at two different ages (5 and 6 years old) based on density, fibre length, rnicrofibril angle and modulus of rupture. Segmented modelling approach was used to estimate juvenile and mature transition and the SAS non-linear procedure was applied to identify the juvenile to mature transition ring. To determine juvenile and mature transition ring for sengon and jabon, three trees of each species and age were sampled from a community forest. in Sukabumi, Bogor, Indonesia. Discs of 2 cm thick were collected to determine density, modulus of rupture (MOR), fibre length and microfibril angle. Density was measured along the radial from pith to bark by X-ray densitometry. Fibre length and microfibril angle were measured on isolated segmented rings of 1-cm width from pith to bark. Results showed that fibre length and microfibril angle were better anatomical indicators of demarcation point between juvenile and mature wood than density and MOR. The segmented regression models for radial patterns of variation in fibre length and rnicrofibril angle revealed that juvenility in sengon and jabon extended up to 6 years old. (Résumé d'auteur)
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