Fast growing Eucalyptus logs for engineered wood products: variation in end-splitting and dynamic MOE

Commercially grown Eucalyptus plantation trees are mostly used for low value applications such as pulp, board, and energy products. The broad aim of the research described in this paper was to assess and develop the use of fast-growing Eucalyptus species in South Africa for use in high value engineered wood products. As a first step the variation in the most important wood and processing properties was established for two species (E. grandis and E. nitens) and a hybrid (E. saligna x urophylla) commonly used in commercial forestry in South Africa. Standing tree dynamic modulus of elasticity, log splitting and log dynamic modulus of elasticity (MOEdyn) were determined as a function of species, site, and log height position. Log and board end-splitting is arguably the defect having the largest value impact for Eucalyptus species processed into sawn timber. Log end-splitting was assessed using a visual splitting score which included length, opening width and position of splits in a log. The stiffness of timber is an important mechanical property affecting the grade and value of engineered wood products and was assessed firstly on standing trees using the Fakopp Treesonic device, and then on the logs using Fibre-gen’s Director HM200 device through evaluation of the acoustic wave speed (AWS) and subsequently MOEdyn. Linear mixed effects models were developed to examine the effects of species, site, and log height position on the MOEdyn of logs. All three factors played a role, to some extent, in the measured properties of logs. The research showed that an understanding of the variation of end-splitting and MOEdyn of Eucalyptus logs is important to select the best resource for engineered wood products and also to help improve processing decisions for each log resource.