| 摘要: |
| 【目的】研究20个不同赤桉家系及其不同部位物理力学性质的差异，为赤桉材性选育及木材的合理利用提供参考。【方法】以采自广东湛江南方国家级林木种苗示范基地大田区的20个45月生赤桉家系为研究对象，分别于树干梢部、中部、底部取木材试样，按照国家标准测量木材基本密度、气干（径向、弦向、体积）干缩率、全干（径向、弦向、体积）干缩率、抗弯强度、抗弯弹性模量、顺纹抗剪强度、顺纹抗压强度等11个指标，并计算气干和全干差异干缩值（弦向干缩率/径向干缩率），运用SPSS、Excel、DPS等软件对数据进行统计和分析，并采用隶属函数法综合比较20个赤桉家系木材的材性优劣状况。【结果】20个赤桉家系木材的基本密度为0.344~0.558 g/cm3，木材基本密度在家系间以及家系与部位交互间差异性极显著，不同家系立木部位间差异不显著。赤桉气干差异干缩值、全干差异干缩值分别为1.60和1.51；不同家系间气干干缩率（径向、弦向、体积）及全干干缩率（径向、弦向、体积）差异极显著；不同部位间气干体积干缩率和全干体积干缩率差异不显著，而全干（径向、弦向）和气干（径向、弦向）干缩率差异均极显著。赤桉不同家系间抗弯强度（26.79~103.11 MPa）、抗弯弹性模量（3 987~10 498 MPa）、顺纹抗剪强度（11.31~39.32 MPa）、顺纹抗压强度（32.46~59.33 MPa）差异极显著；不同部位间除抗弯弹性模量差异极显著外，其余性状差异均不显著；赤桉不同家系间4个力学性质的变异系数范围为12.05%~20.25%。幼龄期赤桉木材4个力学性质间两两相关性极显著。利用隶属函数法对20个赤桉家系进行综合材性评价，隶属值均值排名前5位的家系依次为2007、20016、20021、10014、10079，其木材材性较优，其中10079、20016、2007生长情况较好，可作为赤桉用材林定向培育。【结论】45月生的赤桉木材属轻材，容易开裂，树干底部的差异干缩值比中部、梢部大，即底部木材更容易开裂和变形。 |
| 关键词: 赤桉 幼龄材 木材物理性质 木材力学性质 |
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| 基金项目:国家自然科学基金面上项目“桉树抗风特性及其主要影响因子研究”(31570615);“十三五”国家重点研发计划项目“桉树、云南松（思茅松）、华山松丰产增效技术集成与示范”（2017YFD0601202） |
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| Physical and mechanical properties of Eucalyptus camaldulensis juvenile wood |
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SHANG Xiuhua,ZHANG Peijian,LUO Jianzhong,et al
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| Abstract: |
| 【Objective】To provide reference for the selection and rational utilization of Eucalyptus.camaldulensis wood,the physical and mechanical properties of E.camaldulensis from 20 families were compared.【Method】The 45-month-old E.camaldulensis from 20 families were collected from the South China Experimental Nursery in Zhanjiang,Guangdong.Wood samples were taken at the top,middle and bottom of trunk.Comparative analyses were carried out with SPSS Statistics,Excel and DPS Statistics on wood basic density,air-dried shrinkage ratio (radial,tangential and volume),over-dried shrinkage ratio (radial,tangential and volume),static bending, modulus of elasticity of bending,shear strength,compression strength,and calculate dry shrinkage value (dry shrinkage/radial dry shrinkage) of air dried and total dry.The wood properties of the 20 families were then comprehensively evaluated by subordinate function method.【Result】The basic density of 20 E.camaldulensis wood was 0.344-0.558 g/cm3.The difference of wood density between families and between family and part was very significant,while the difference between different parts was not significant.The differences between air-dry and absolute-dry shrinkage were 1.60 and 1.51.Volume air dried shrinkage and volume over dried shrinkage ratio of different parts were not significant,but their air dried (tangential and radial) and over dried (radial and tangential) shrinkage were significant.The dry shrinkage value of trunk base was higher than that of the middle and top parts,more prone to cracking and deformation. The differences of mechanical properties of static bending (26.79-103.11 MPa),modulus of elasticity of bending (3 987-10 498 MPa),shear strength (11.31-39.32 MPa) and compression strength parallel to grain (32.46-59.33 MPa) between different families were very significant.Modulus of elasticity of bending between different parts was also very significant,while other indexes were not significant.The coefficient of variation of mechanical properties between different families was 12.05%-20.25%.The correlation between mechanical properties of Eucalyptus camaldulensis juvenile wood was very significant.Using subordinate function of 20 families for comprehensive evaluation,the top five families were 2007,20016,20021,10014 and 10079.The 10079,20016 and 2007 families had better growth than others and can be selected for directional cultivation for timber.【Conclusion】The wood density of 45-month-old E.camaldulensis was light,which was easy to crack,and the bottom of trunk was more likely to crack than the middle and top parts. |
| Key words: Eucalyptus camaldulensis juvenile wood physical properties mechanical properties |
