The radial variation of fiber length increment (due to intrusive growth) and its relation with internal and external (climatic) factors were investigated for Acacia mangium trees collected in Indonesia and Malaysia. Wood fiber length and fiber length increment were approximated with respect to the distance from the pith (x) by a logarithmic function and vessel element length by a linear function. The results were y = 0.14 . ln(x) + 0.48, y = 0.0005 . x + 0.20, and y = 0.13 . ln(x) + 0.31, respectively. The radial variation of fiber length was related to the growth rate rather than the age of the cambium. The results of the cross-correlation function between wood fiber length increment and climatic factors showed that fiber lengths responded to changes in precipitation with a time lag of between zero to four months.
We investigated the feasibility of using several fast-growing tropical or subtropical hardwood species for timber production by measuring key wood qualities in relationship to the high rates of lateral growth. The trees tested were sampled from even-aged plantations of Acacia mangium, A. auriculiformis, hybrid Acacia(A.mangium × A. auriculiformis), Eucalyptus grandis, E. globulus, and Paraserianthes falcataria (Solomon and Java origin) that had already reached commercial harvesting age. The released strain of the surface growth stress (RS), xylem density (XD), microfibril angle (MFA), and fiber length (FL) were measured at the outermost part of the xylem at breast height in each tree. Results were then compared to the lateral growth rate (radius/age) at breast height, which provides a relative indicator of the amount of tree growth per year. Our findings indicated that RS was constant, regardless of lateral growth rate in each species. Similar results were observed for XD, MFA, and FL, with a few exceptions, suggesting that high growth rates do not intrinsically affect the wood properties of fast-growing tropical or subtropical species that have reached harvesting age. However, special attention must be paid to patterns of xylem maturation when developing plantations of such species.
The objective of this study was to evaluate physical and mechanical properties of medium density fibreboard (MDF) panels made from kenaf core as function of fibre geometry and refining conditions. Raw material was prepared by using pressure levels of 3, 5 and 7 bar at two heating times, namely 3 and 5 min. The length and width of the fibres were determined employing image analyser. Experimental samples with a target density of 700 kg m−3 were produced with 12% of urea formaldehyde as a binder. Physical properties such as swelling in thickness (TS) and water absorption (WA) of the panels in addition to their mechanical properties including modulus of rupture (MOR), modulus of elasticity (MOE) and internal bonding (IB) were evaluated based on MS 1787:2005. Based on the test results, low digestion pressure produced longer fibre length and panels made from these fibres had higher TS with MOR and MOE than those of the others panels. However, the IB properties of samples were low. Panels made from shorter fibre resulted in contradict properties found above. The ideal properties of the samples were found for the panels made having fibre length of 0.81 mm and aspect ratio of 23.4. Such sample had 14.
SUMMARYSix plantation grown Kelempayan trees [Neolamarckia cadamba (Roxb.) Bosser, syn. Anthocephalus chinensis (Lamk.) A. Rich. ex Walp., Rubia ceae] were sampled along their radii and at five different height levels to evaluate variations of wood anatomical properties. Analysis of variance indicates that between tree differences in all anatomical properties meas ured were significant. Vessel proportion increases while ray proportion decreases with height, while both fibre diameter and fibre lumen diame ter decrease with height. No significant trend was found for fibre length vertically. Cell wall substance and vessel and ray proportion increase from pith to bark. while fibre proportion decreases. Fibre length and fibre wall thickness increase from pith to bark. while fibre diameter and fibre lumen diameter first increase and then decrease. Within-tree variations . are more consistent radially than vertically.
A study on the tissue proportions and fibre dimensions of plantation-grown Acacia mangium was carried out. Ten selected trees from two age groups (4- and 8-year-old) were obtained from plantation forests in Selangor. Disks were taken from four sampling heights. Acacia mangium wood is diffuse-porous with mostly solitary vessels. The rays are uniseriate. The average percentage of fibres, vessels and rays of 4-year-old and 8-year-old samples are 85.8%, 9.1%, 5.2% and 84.8%, 9.8%, 5.3%, respectively. Acacia is a shortfibred tropical species. The average fibre length, fibre diameter, fibre lumen diameter and fibre wall thickness are 934, 24, 17 and 3.3 µm for 4-year-old samples and 1017,20, 12 and 4.3 µm for 8-year-old sampies, respectively. The sampies near the pith have the shortest fibres and the length increases toward the bark. Fibre length also tends to decrease with height. The vessel percentage decreases with increasing height.
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