人工林班克松木材材质径向变异规律研究

以人工林班克松的木材解剖性质为研究对象,分析研究其株内木材材质径向变异模式,对其幼龄材和成熟材进行初步界定。结果表明：早材管胞径弦向直径和晚材胞壁率的变化符合PashinⅠ模型,早材胞壁率的变化符合PanshinⅢ模型;回归分析中早材拟合度较晚材好;幼龄材和成熟材的初步界定年限为9-11a。     

人工林马尾松木材性质的变异

本文研究了广西人工林马尾松木材性质的变异及幼龄材与成熟材的差异。结果表明 ,幼龄材与成熟材的分界年龄在 14　 16a ,解剖性质在径向上的变异规律为 :射线比量、树脂道比量、胞壁率、胞腔直径、胞壁厚、管胞长度、管胞宽度和晚材壁腔比是自髓心向外呈递增趋势 ,管胞比量和晚材率为递减趋势 ,早材壁腔比和早材腔径比则近似于一条直线。方差分析结果表明 :树脂道比量、胞壁率、胞壁厚、管胞长度和管胞宽度 ,幼龄材与成熟材差异达显著或极显著水平。 5项木材物理力学性质均为成熟材高于幼龄材 ,且均达差异显著水平。木材性质间的相关分析表明 :木材基本密度与管胞长度、管胞宽度、射线比量、树脂道比量、胞壁率呈显著的正相关关系 ,木材气干密度与抗弯强度、抗弯弹性模量、顺纹抗压强度也呈显著的正相关关系     

油松株内幼龄材与成熟材材性的比较研究

本文就中条山油松株内幼龄材与成熟材材性差异的比较研究,讨论对幼龄期划分的依据。根据木材解剖特征、物理力学性质的径向变异规律,确定其幼龄期为14年。随着树干高度的增加,油松木材幼龄期逐渐缩短、株内幼龄材范围及所占断面上的比例变小。株内幼龄材与成熟材材性差异显著。幼龄材管胞长度短、直径小,胞壁薄,微纤丝角度大,生长轮较宽,晚材率低,浸提物含量高,基本密度较大。幼龄材的力学强度远远小于成熟材。     

基于支持向量机(SVM)的班克松人工林成熟材解剖性质的预测

成熟材含量的高低决定木材性质的优劣,合理界定幼龄材与成熟材的分界点,准确预测成熟材材质有利于木材高效加工利用.为了确定人工林班克松的成熟期和预测成熟材解剖性质,采用支持向量机(SVM)界定幼龄材与成熟材的分界点,在此基础上利用幼龄材解剖性质预测成熟材解剖性质.结果表明:人工林班克松幼龄材与成熟材的分界点在树木生长的第18年;成熟期解剖性质明显优于幼龄期,变化较幼龄期平缓;成熟预测误差低、相关性高;预测曲线能够体现解剖性质整体的变化趋势,但对解剖性质测试集突变点及其之后的变化情况表现不足.     

樟树人工林株间株内材性变异及其材性预测的研究

樟树人工林株内纤维长度径向变异由髓心向外递增，而后趋于稳定；木材基本密度髓心处稍大，由髓心向外先稍递减而后递增，再趋于稳定；纤维长度和基本密度性状与生长轮年龄关系模型可用来预测其性状值。樟树木材幼龄期约为7－9a，株内细幼龄材基本密度较成熟材小1．0％－9．9％，株内幼龄材与成熟材基本密度差异多不显著；其浸提物含量幼龄材与成熟材之间差异不显著。纤维长度株内变异系数大于株间，木材基本密度均值和浸提物含量二性状则是株间变大于株内变异。生长速度对樟树木材纤维长度、基本密度、浸提物含量等性状影响不显著。     

中国主要人工林树种幼龄材与成熟材及人工林与天然林木材性质比较研究

本文对中国１０种人工林和４种天然林的幼龄材与成熟材及４个树种的人工林木材与天然林木材的构造特征、化学性质、物理性质、力学性质的３３项材性指标差异进行了比较研究。结果表明,在幼龄材与成熟材之间,在统计上表现出差异显著性的为幼龄材比成熟材生长轮宽,管胞列数多,管胞短,直径小,微纤丝角大,密度小,径向干缩小,差异干缩大,流体扩散性高,抗弯强度、抗弯弹性模量、顺纹抗压强度、径面顺纹抗剪强度、径面抗劈力和冲击韧性低等１５项,即４６％的测试项目差异显著;表明在木材加工和用作结构材时应将幼龄材和成熟材视作两个性质不同的总体来考虑,在培育结构材时应研究如何缩短幼年期或改善幼年期材性。在人工林与天然林木材之间,采取人工林幼龄材性质与天然林幼龄材性质相比,人工林成熟材性质与天然林成熟材性质相比,结果表明,多数性质在统计上差异不显著,只有人工林木材比天然林木材胞壁率小、顺纹抗压强度低、差异干缩大、流体扩散性高等４项,即只有１２％的很少数测试项目差异显著;表明有可能通过人工培育的方法培育出与天然林木材性质相近的木材。     

黄果厚壳桂纤维特性变异规律研究

以黄果厚壳桂(Cryptocarya concinna)为研究对象,通过测量黄果厚壳桂纤维特性,分析对比各项纤维形态在纵向和径向上的变异规律,初步划分幼龄材和成熟材。结果表明:纤维长度为954.46μm,属于中等长度纤维,纤维宽度、腔径、双壁厚、壁腔比、长宽比分别为19.95μm、10.96μm、8.98μm、0.82、47.87。根据有序聚类分析法确定黄果厚壳桂幼龄材和成熟材的年龄界定为第26年。     

针叶树木材细胞力学及纵向弹性模量的计算--试件纵向弹性模量的预测

依据针叶树木材管胞和射线细胞的结构模型。使用计算机抽样模拟解剖结构参数。以及使用针叶树木材纵向弹性模量计算公式和方法,计算人工林杉木,马尾松幼龄材和成熟材试件纵向弹性模量,计算结果与常温条件下气干试件测定结果十分符合。在试件晚材率和管胞解剖结构参数改变的条件下。计算预测了人工林杉木,马尾松幼龄材和成熟材纵向弹性模量的变化。结果表明：试件纵向弹性模量随晚材率,管胞长度,管胞壁厚度的增加而增加,而试件纵向弹性模量随管胞直径增加而减小。本文提出的纵向弹性模量计算的预测方法,对于运用现代生物技术控制和改变针叶树木材的材质,材性有实际意义。     

刺楸木材幼龄期划分的探讨

以安徽琅琊山天然林内的刺楸木材为材料,在研究其解剖特征和物理力学性质变异的基础上,着重探讨刺楸木材幼龄期。结果发现：根据不同材性指标变异模式划分出的幼龄期不相同,以纤维长度和微纤丝角的径向变异规律划分出的幼龄期为１７年,以基本密度和顺纹抗压强度的径向变异规律划分出的幼龄期为１５年;根据同一材性指标不同高度材性变异模式划分的幼龄期也有差异。其总体趋势为：随着树干高度增加,其幼龄期略微变短。     

刺楸木材幼龄期划分的探讨

以安徽琅琊山天然林内的刺楸木材为材料，在研究其解剖特征和物理力学性质变异物基础上，着重探讨刺楸木材幼龄期。结果发现：根据不同材性指标变异模式划分的幼龄期不相同。，以纤维长度和微纤丝角的径向变异规律划分出的幼龄期为１７年，以基本密度和顺纹抗压强度的径向变异规律划分出的幼龄期为１５年；根据同一材性指标不同高度材性变异模式划分的幼龄期也有差异。其总体趋势为：随着树干高度增加，其幼龄期略为变短。     

Radial variations in the anatomical characteristics and density of the wood of Acacia mangium of five different provenances in Indonesia

The anatomical characteristics and density of wood were examined in 23-year-old Acacia mangium trees that had been planted in Yogyakarta, Indonesia. The seeds had been collected from trees of five different provenances. The distance from the pith of the boundary between juvenile and mature wood was also examined to clarify the maturity of the wood. Lengths of wood fibers near the pith and the distance from the pith of the boundary between juvenile and mature wood differed significantly among provenances. By contrast, other anatomical characteristics of the wood such as fiber wall area, fiber wall thickness, fiber diameter, vessel lumen area, vessel diameter, vessel frequency and wood density did not differ significantly among provenances. Wood density was strongly correlated with the area of fiber walls. Our observations suggest that Sidei and Daintree might be more appropriate provenances among those examined for the Acacia mangium tree-breeding programs in Indonesia that are aimed at improving wood quality, because these provenances are associated with longer initial wood fibers and narrower juvenile areas than the other provenances studied.     

Inter-clonal, intra-clonal, and single tree variations of wood anatomical properties and specific gravity of clonal ramets of Dalbergia sissoo Roxb.

Inter-clonal, intra-clonal and within tree variations in specific gravity and wood anatomical properties of 8-year-old grown ramets of Dalbergia sissoo Roxb. have been investigated. Radial and location-wise intra-clonal variations were non-significant for anatomical properties and specific gravity for all six clones at all three sites. However, inter-clonal variations in wood anatomical properties and specific gravity were significantly different. Inter-clonal variations in anatomical properties and specific gravity were also significant due to sites, which indicated that site-characteristics overshadowed the genetic priority of different clones for wood anatomical properties. Average fiber-characteristics of all clones showed the best performance at Lalkuan, Haldwani (site III), while average specific gravity performed well at Brandis Road, Dehradun (site I) followed by site III (Lalkuan, Haldwani) and site II (Lachchiwala, Dehradun). Within tree variations in anatomical properties like fiber length, fiber diameter, wall thickness, vessel member length and vessel member diameter due to vertical or radial direction and location (pith to periphery) are non-significant. Radial direction, location and height showed no impact on wood element variation. It indicated that there is no impact of juvenile wood, sapwood and heartwood ratio, and reaction wood on wood anatomical properties of 8-year-old ramet of D. sissoo. It further indicated that clone raised ramet of 8-year-old D. sissoo showed the characteristics of mature wood. Within tree variations in specific gravity were significant due to height, which may be related to differential sapwood and heartwood ratio in the vertical direction. Different wood elements viz. fiber length, fiber diameter, wall thickness, vessel member length and vessel member diameter showed significant correlations with each other and with specific gravity.     

Determination of fiber length and juvenile and mature wood zones in Acer velutinum Boiss. trees grown in Iran

In our investigation we studied fiber lengths and the transition age from juvenile to mature wood in Acer velutinum Boiss. For this purpose, samples from three normal maple trees at a Noshahr site in northern Iran were selected. Disks were cut at breast height. Test samples were taken along a radial direction from the pith to the bark, accounting for every ring during a 48-year period. We used the Franklin method to distinguish between fibers of juvenile and mature wood. The results show that the fiber length increased along the radial direction from the pith to the bark. The transition age between juvenile and mature wood was determined at the 14th annual ring from the pith.     

Characterisation of juvenile wood in teak

Juvenile wood properties are studied in a ring-porous tropical hardwood – teak (Tectona grandis L. F), to assess the utilisation potential of short rotation timber. Compared to mature wood, it is characterised by wide rings, short fibres, small diameter, low vessel percentage, high cell wall, wide microfibrillar angle and relatively low or almost similar mechanical properties. While the average modulus of elasticity and modulus of rupture in juvenile wood are 85% and 82% respectively of the mature wood value, the longitudinal compression strength is similar. With relatively small fibrillar angle of 15° and the scope for genetic selection of individual trees, teak juvenile wood has potential for desired dimensional stability. The segmented regression models and visual interpretation of radial patterns of variation in anatomical properties reveal that juvenility in plantation grown teak extends up to 15, 20–25 years depending on the property, growth rate and individual tree and plantation site. The fitted regression models, to explain the age-related variations in juvenile wood properties range from simple, linear to exponential, reciprocal and quadratic equations. Fibre length, microfibrillar angle, vessel diameter/percentage and ring width appear to be the best anatomical indicators of age demarcation between juvenile and mature wood, although maturation age often varies among the properties. The projected figures for proportion of juvenile wood in plantation grown teak at breast height are 80–100% and 25% at ages 20 and 60 years respectively. Received 3 November 1998     

18年生尾巨桉无性系木材纤维形态和基本密度变异研究

对18年生尾巨桉（Eucalyptus urophlla×E．grandis）无性系木材纤维特征与基本密度进行研究,通过测定木材的纤维长度、宽度、壁厚、腔径、木材基本密度,分析结果表明：木材基本密度、纤维长度、纤维长宽比、壁厚、壁腔比在树干径向方向由髓心向外有逐渐增大的规律。纤维长度与基本密度之间呈显著的负相关,纤维宽...     

Characterization of juvenile wood to mature wood transition age in black spruce (Picea mariana (Mill.) B.S.P.) at different stand densities and sampling heights

The radial pattern of both maximum ring density and ring area of 36 black spruce trees were used to determine the transition age from juvenile wood to mature wood. The data were obtained by X-ray densitometry and both segmented linear and polynomial regressions were used to point out the age of the juvenile wood boundary. Three stand densities (1,790, 2,700 and 3,400 stems/ha) and three sampling heights (2.4, 5.1 and 7.8 m) were studied. Although maximum ring density and ring area presented similar radial patterns, they gave two significantly different results of transition ages. The maximum ring density over-estimated the transition age (17.6 years) in contrast to ring area (14 years). The results show that the transition from juvenile wood to mature wood occurred after 12 years at 7.8 m (versus 13.1 years at a height of 5.1 m, and 17.6 years at 2.4 m). Although transition age occurred later in the high stand density group (21 years), the difference was not significant between the three stand density groups. Nevertheless, transition age remains difficult to determine since no standard definition exists. The transition occurs over years, and most probably a transition wood exists between juvenile wood and mature wood. Estimation of the juvenile wood proportion in volume shows that it remains constant along the stem and it increases with stand density.     

Variation in density of Picea sitchensis in relation to within-tree trends in tracheid diameter and wall thickness

The influences of cambial age and ring width on density of Sitkaspruce (Picea sitchensis (Bong.) Carr) were analysed in relationto within-tree trends in tracheid diameter and cell wall thickness.Discs were sampled at breast height from a total of 24 trees,from seven stands at three contrasting sites in Wales, and atbreast height, 30 per cent and 60 per cent total tree heightfrom one of the stands. Across the juvenile wood, ring density decreased with ring numberfrom the pith while radial tracheid diameter increased. Theseoverall trends were considered to be inherent to tree growth,presumably associated with cambial ageing, since they occurredin all trees on all sites. In juvenile wood, density also variedwith site growth rate (as indicated by ring width) at similarcambial age, wider rings being associated with more rapidrateof change in tracheid diameter with ring number and with decreasein tracheid wall thickness. Consequently, on a site having treeswith high growth rate density decreased more rapidly acrossthe juvenile wood, down to a lower minimum value, than on siteswith a slower growth rate. In mature wood, the decrease in densitywith increase in ring width was associated with differencesin both tracheid diameter and wall thickness. Density was slightly(though not significantly) higher at breast height than in comparablerings at 30 per cent total height, associated with significantlythicker tracheid walls at breast height. Changes in radial tracheid diameter (with ring number, or withring width) were associated with greater differences in theearlywood than towards the latewood end of each growth ring,while variations in wall thickness with ring width were associatedwith rate of increase in wall thickness towards the latewoodend. This may account for some previously conflicting reportson influence of silvicultural management on density, for densityis likely to vary with influence of environment on the seasonalcycle of cambial activity. The extent of the juvenile wood as delimited by the inner coreof wide growth rings does not necessarily correspond to theregion of varying tracheid dimensions in Sitka spruce.     

Effects of radial growth rate on selected indices for juvenile and mature wood of the Japanese larch

To examine the differences between juvenile and mature wood, 12 aged sample trees from two areas of Nagano Prefecture were harvested; and the radial development of tracheid length, the ring density, and the relation of the radial growth rate (observed by ring width) with some selected indices of ring structure were investigated. The results proved that the radial variation of tracheid length with ring number can be described by a logarithmic formula, and both plantations reached the demarcation of juvenile and mature wood at age 18. With the segmented regression method, we also analyzed radial variation of mean density and found that the demarcation of juvenile and mature wood was at age 15 for sample trees from Saku and at age 21 for those from Yabuhara. By using the results of estimates from juvenile and mature wood based on ring density, we found that high growth rates resulted when producing lower-density wood during the juvenile period, but these rates did not occur during the mature period. The basic reason for this phenomenon is the variation in patterns of earlywood and latewood in juvenile and mature wood, respectively. This result advised us that when managing plantations of Japanese larch it is necessary to take different measurements at different growth periods.     

Application of the fractometer for crushing strength: juvenile-mature wood demarcation in Taiwania (Taiwania cryptomerioids)

The fractometer is a device that breaks a radial increment core along the fiber for the measurement of crushing strength, which is a direct wood quality indicator for structural lumber. In this study, the crushing strength of Taiwania (Taiwania cryptomerioides Hay) trees using the fractometer was investigated and the data were used to determine the position of demarcation between juvenile and mature wood. Segmented regression and variance component analysis were used to estimate the demarcation position. With increasing cambium age, the core wood improves the crushing strength in the outer wood area. Within-tree variations in wood properties were greater than between-tree variations. In this experiment, the position of demarcation between juvenile and mature wood occurred at an approximate distance of 10.8cm to 13.2cm from the pith at about 18–20 years of cambium age.