【作者】 刘晓丽；

【导师】 姜笑梅；

【作者基本信息】 中国林业科学研究院 ， 木材科学与技术， 2005， 博士

【摘要】 本文以我国南方大面积种植的人工林尾巨桉（Eucalyptus urophylla ×E. grandis）为研究对象,对其生长应变和主要木材性质进行了详尽的研究,揭示了生长应变与木材性质的相互关系以及正常木高生长应变的形成机理。研究结果对森林定向培育和木材加工利用具有重要的理论意义和实际应用价值。本研究采用应变片法测定了活立木的表面轴向生长应变,比较了该方法与法国轴向生长应变仪法之间的差异;研究了伐倒木表面轴向生长应变与木材物理力学性质间的关系;揭示了残余应变的径向分布规律及其与木材性质的关系,提出了根据残余应变径向分布曲线和树木直径划分幼龄材和成熟材的新思路;应用透射电子显微镜、可见光显微分光光度计、扫描电子显微镜结合X 射线能谱分析（SEM-EDXA）等先进设备,特别是结合木质素溴化等细胞和组织化学分析方法,得到了木质化过程中细胞壁各微区上的木质素含量的分布规律,探讨了正常木高生长应变产生与木质化过程的相互关系,提出了高生长应变正常木存在“欠木质化”现象的新观点。本文的主要研究结果如下: 1. 用应变片法测试尾巨桉活立木胸高处表面轴向生长应变,测试过程一般需要3min左右;表面轴向生长应变一般分布在651×10^-6-1100×10^-6 之间。单因素方差分析表明,尾巨桉表面轴向生长应变在两家系间、南北向间、株内不同高度间差异不显著,胸高处表面轴向生长应变可以作为评估整株树生长应力水平的一个参考指标。2.法国轴向生长应变仪的结果要大于应变片法的结果,不共点测试时前者是后者的1.3 倍,共点测试时前者是后者的2.0 倍。3. 沿树高增加方向,尾巨桉木材径向、轴向、弦向和体积干缩率的变化趋势相似,基本密度变化甚小,抗弯强度没有明显的变化规律,抗弯弹性模量呈现出明显的增大趋势。单因素方差分析表明,轴向、弦向、体积干缩率、基本密度和抗弯强度在不同高度间没有显著差异,而径向干缩率和抗弯弹性模量差异显著。表面轴向生长应变只与轴向干缩率具有显著相关性。4. 尾巨桉原木内部轴向残余应变径向分布沿髓心的对称性较好,靠近树皮的位置为最大的拉应变,向髓心方向,拉应变在绝对值上呈下降趋势至某个半径处达到零值,随后转变为压应变,向髓心处呈现明显的增加趋势。尾巨桉内部轴向残余应变径向分布的回归方程为:y = -21.075x² + 4.5297x + 890.75（相关系数0.87）,在0.01 水平下极显著相关;拉应变向压应变转变的树干半径为0.681R。尾巨桉内部轴向残余应变在不同高度上的径向分布模式相似,相关性随着树干高度的增加而降低。5. 尾巨桉木材的解剖性质(纤维长度、宽度、壁厚、纤维的长宽比、微纤丝角、更多还原

【Abstract】 In this research, growth strain and main wood properties of Eucalyptus urophylla ×E. grandis plantation widely planted in south China were investigated, the relationship between growth strain and wood properties and high growth strain formation mechanism of normal wood were obtained. The results were provided with important theoretic and realistic values for forest oriented cultivation and wood processing utilizing. The paper adopted Strain Guage Method for the first time in China to measure surface longitudinal growth strain （SLGS） of standing trees, and the differences between Strain Guage Method and CIRAD-Foret method was compared. It and discussed The relationship between SLGS and wood physical and mechanical properties of fallen wood and between radial distribution of internal longitudinal residual strain （ILRS） and wood properties was analyzed, a new approach for classifying juvenile wood and mature wood was brought forward, according to radial distribution of ILRS and tree diameter. Using advanced transmission electronic microscope, visible light micro-spectrophotometer and scanning electron microscope and energy dispersive X-ray analysis（SEM-EDXA）, especially using cell and histo-chemical method （lignin bromazition etc.）, lignin distribution regulation in different micro-morphological regions of cell wall was opened out during lignification process.The relationship between high growth strain formation and lignification process was discussed, a new viewpoint that there was“deficient lignification ”phenomenon in wood fiber cell wall of high growth strain normal wood was brought forward. The results were as the followings, 1. It took about three minutes using Strain Gauge Method to test SLGS at 1.3m height for standing trees. The value of SLGS was between 651×10^-6 and 1100×10^-6. Single factor variation analysis showed, there was no significant difference between two families, south and north and among different heights in tree; consequently, SLGS at 1.3m height should be as a reference criterion to evaluate the level of growth stress of the whole tree. 2. CIRAD-Foret Method and Strain Gauge Method were used to measure SLGS for fallen woods at the same point and at two points. The values obtained from the CIRAD-Foret method were bigger than those from strain gauge method. The former was 1.3 time as high as the latter for the measurement at two points, and it was 2.0 times as high as the latter for the measurement at the same point. 3. Along tree height increasing,there was similar changing tendency of volume shrinkage, longitudinal shrinkage, tangential shrinkage and radial shrinkage; Basic density showed little change while MOR displayed no obvious changing regulation and MOE increased obviously with tree height increasing. Single factor variation analysis showed, there was no distinct difference in volume, longitudinal and tangential shrinkage, basic density and MOR, while there was very significant difference in radial shrinkage and MOE at different heights. SLGR and longitudinal shrinkage was tightly related despite of single tree and different height. 4. The radial distribution of ILRS was symmetrical across the diameter.The largest tensile strain was near the bark, to the pith direction, tensile strain absolute value declined and turned zero at certain radius, after that tensile strain changed into compressive strain which presented obvious increasing tendency to the pith direction. The regression equation of radial distribution of ILRS was y = -21.075x2 + 4.5297x + 890.75, significantly correlated at 0.01level （correlation coefficient was 0.87）. Tree radius of crossover point from tensile strain to compressive strain was 0.618R. Radial distribution pattern of ILRS at different heights was similar, but the correlation coefficient decreased with tree height increasing. 5. There was different changing tendency for wood anatomical properties（fiber length, fiber width, fiber wall thickness, ratio of length to width, microfibril angle, ratio of different tissue, cell wall percentage etc.）, wood physical property（basic density） and wood chemical properties（alpha-cellulose content, Klason lignin content, hollocellulose content and degree of crystallinity） from the pith to bark. Single factor variation analysis showed, there were great differences among 5 radial positions in fiber length, fiber width, fiber wall thickness, distributing frequency of vessel, T-diameter of vessel element, alpha-cellulose content, hollocellulose content and basic density. However, there were no significant differences in microfibril angle, ratio of length to width, ratio of wall to lumen, ratio of lumen to diameter, ratio of different tissue, cell wall percentage, degree of crystallinity among 5 radial positions. There was positive correlation between tensile residual strain and fiber length, fiber width, T-diameter of vessel element and hollocellulose content, and between compressive residual strain and fiber wall thickness and distributing frequency of vessel. There was great positivecorrelation between tensile residual strain and alpha-cellulose content. 6. Radial distribution Changing gradient of ILRS was greatly affected by tree diameter, the curve of the smaller tree was much steeper. For Eucalyptus urophylla ×E. grandis in this study, when tree diameter was larger than 19.9cm, effect of diameter on radial distribution of ILRS became weak.It indicated that tree grow enters mature period while tree diameter reaches 19.9cm.So a new approach for classify juvenile wood and mature wood was brought forward, according to radial distribution of ILRS and tree diameter. 7. There was no significant difference between high growth strain material and low growth strain material for lignin deposition. After the appearance of S1 layer, lignin deposited with a style of patches firstly at the middle lamellae of cell corner. Accompanying with S2 layer deposition, lignification extended from corner to the rest regions of middle lamellae and secondary cell wall at the same time, and lignin content at cell corner increased sharply. After S3 layer appeared, lignin with irregular patches deposited on the entire secondary cell wall. 8. The results of histo-chemical dyeing showed, Syringyl（S） lignin and Guaiacyl（G） lignin were main component in micro-morphological regions of wood fiber cell wall for high growth strain and low growth strain material during lignification process. S lignin and G lignin content increased firstly and then leveled off. With lignification process, S lignin content was higher than G lignin content. S lignin and G lignin content decreased with growth strain increasing, at the same time, the difference of S lignin content among micro-morphological regions of wood fiber cell wall became smaller, but the difference of G lignin content became bigger. 9. The results of lignin bromazation method showed, lignin content in micro-morphological regions of wood fiber cell wall increased firstly and then leveled off during lignification process. Lignin content in sequence was cell corner, compound middle lamellae, S1, S2, S3.With growth strain increasing, lignin content decreased, lignification rate was slowed down and lignification process was delayed. Thereout, a new viewpoint that there was“deficient lignification”phenomenon in wood fiber cell wall of high growth strain normal wood was brought forward. This phenomenon was intrinsic response for trees adapting and counteracting outside circumstance changes.更多还原