EUCALYPTUS NITENS FOR SOLID-WOOD PRODUCTS. 1: INDIVIDUAL-TREE VARIATION IN QUALITY AND RECOVERY OF APPEARANCE-GRADE LUMBER AND VENEER

A New Zealand stand of Eucalyptus nitens (Deane & Maiden) Maiden was pruned up to height 8 m and grown for 15 years at low stocking to 57 cm diameter at breast height. This stand provided 15 trees, preselected for a range of wood density. Lumber and veneer were cut from the 5-m butt logs, veneer was peeled from the second logs from height 7 to 13 m, and each tree was evaluated for production of appearance-grade lumber and rotary-peeled veneer. Butt-log quality was good as pruning had effectively restricted the knotty core, and there was little decay from branches in either butt logs or veneer billets. Longitudinal growth stresses varied widely among trees, resulting in log end-splitting and sawlog flitch movement during sawing (spring), which led to crook in sawn timber, substantially reducing timber conversion in some trees. Collapse and internal checking were prevalent in air-dried lumber, and numbers of checks varied widely among trees. Face-checking was found in boards from all trees after kiln-drying and reconditioning, and even those with very few face checks had internal checks. Veneer thickness varied unacceptably, caused probably by incorrect knife- and pressure-bar settings. Veneer splitting also varied among trees, and was worse in butt-log than in second-log veneers. Unsatisfactory pre-heating of billets before peeling may have exacerbated splitting. Knots severely downgraded structural plywood veneer grades, <8 % of sheets from the second logs being acceptable compared with 87 % of sheets from the pruned butt logs. Stiffness of veneer sheets was successfully measured using a sonic device (Pundit™) to sort veneers for manufacture of laminated veneer lumber