Longitudinal Residual Strain of Eucalyptus Clone in Location Subject to Action of Winds

ABSTRACT During development and growth of trees, mechanical stresses are generated in order to keep it balanced and upright in response to various environmental factors. These efforts are known as growth stresses and can vary in distribution and intensity across different species of the genus Eucalyptus. Thus, the objective was to evaluate the longitudinal residual strains (LRS) and its correlations with tree growth features, physical and mechanical properties of the Eucalyptus urophylla × Eucalyptus grandis hybrid clones. Trees were 30 and 35 months old, located in forest plantations of Vale do Rio Doce, Minas Gerais, in areas subject to wind action, with damping effect and even the breaking of these trees. The LRS measured with extensometer was on average 0.086mm and when associated with other characteristics of the wood, the correlations were not significant. The growth characteristics of trees, basic density, modulus of elasticity (MOE) and modulus of rupture (MOR), and absorbed work were not enough to explain the LRS behavior.

摘要：在树木的发育与生长过程中，为维持自身平衡并保持直立姿态以应对各类环境胁迫，会产生机械应力。这类应力被称为生长应力，其分布特征与强度水平会因桉属（Eucalyptus）不同物种产生差异。因此本研究以尾叶桉（Eucalyptus urophylla）×巨桉（Eucalyptus grandis）杂交无性系为研究对象，旨在评估其纵向残余应变（Longitudinal Residual Strain，LRS），并分析该应变与树木生长特征、木材物理及力学性能的相关性。试验所用树木树龄为30个月与35个月，种植于巴西米纳斯吉拉斯州Vale do Rio Doce的人工林地块，该区域易受风力侵袭，虽存在一定防风缓冲效应，但仍会发生树木倒伏甚至折断的情况。通过引伸计测得的纵向残余应变平均值为0.086mm；将该应变与其他木材特性进行关联分析后，未发现显著相关性。树木生长特征、基本密度、弹性模量（Modulus of Elasticity，MOE）、断裂模量（Modulus of Rupture，MOR）以及吸收功均无法充分解释纵向残余应变的变化规律。