Modification of log grading and log segregation strategies for low-quality logs from the East Gippsland FMA of Victoria

摘要

The potential for segregating higher-quality residual logs at sawmills for the production of sawn timber was investigated in low-quality eucalypt logs from mixed-species forests in the East Gippsland Forest Management Area of Victoria, Australia. Studies were conducted on long-length bush logs that were graded in the forest and were below existing minimum specifications for sawlogs (lower quality than A, B, C or D-grade sawlog). Following cross-cutting to sawlog length at the sawmills, 15% of logs (82 logs) were found to meet existing sawlog grades, probably because internal defect visible on the ends of logs was less severe than on the full-length bush logs. Conventional sawing systems and strategies were applied to assess the timber quality from the remaining 85% of the cross-cut logs (449 logs). Multiple regression analysis was used to develop a grading method that could be applied at the sawmill to produce two new residual log grades (Residual grades 1 and 2). After applying the grading method,Residual grade 1 logs were found to have recoveries similar to those of E-grade logs that are currently milled with higher-quality sawlogs. However, a greater percentage of logs could be selected with the new method. While it was found to be ineffectivein low-elevation mixed-species forests where selective logging left a high proportion of large defective trees, the grading method can have broad application across all the other forest types examined. There are four main differences to the existing logcriteria: (i) mean end defect rather than worst-end defect is used as an indicator of log quality; (ii) mean minimum diameter of logs is 25 cm with no small-end restrictions, (iii) the definition of a clear quarter is different; that is, existing rulesallow clear quarters to have a defect or combination of defects that have a width no greater than one third of the surface width of the quarter on which they occur; a clear quarter in the new criteria has no visible defect apart from small epicormics; and (iv) logs with mean diameter >40 cm and end defect <40% are permitted to have four defective quarters.