Loss of Sawn Recovery Associated with Growth Stress and Potential Indicators of Sawlog Quality-A Case Study with Eucalyptus globulus Labill.
A study was carried out to assess the loss of sawn recovery due to log end splits and spring in slabs and to evaluate the potential of various wood property measurements as sawlog quality indicators. Thirty dominant or co-dominant, straight trees were selected from a 32-years-old thinned plantation of Eucalyptus globulus Labill. Longitudinal growth strain at the tree surface at breast height was estimated. One full-diameter increment core of 12mm diameter was removed from each tree at breast height and one strip specimen prepared from each core. Microdensity, microfibril angle (MFA), Youngs modulus (E<,L>), and cellulose crystallite width of the strip specimens were determined using SilviScan-2 technology. The severity of end splits in the butt logs was quantified using split indices. The butt logs were quarter-sawn following a pre-determined sawing pattern. The curved-edge off-cuts were collected and their total volume for each butt log was estimated. The end sprits in the dried sawn boards were measured and die volume of the boards containing the splits calculated. The estimated reduction in sawn recovery due to removing the curved edges in the slabs was found to be equivalent to 6％ of the log volume. The estimated reduction in recovery due to end-docking log-end splits was found to be equivalent to 1％ of the log volume, or approximately 4％ of the dried board volume. These would translate into a large annual loss for sawmills. The mean longitudinal displacement, indicating growth stress, was found to be a moderately successful indicator of the severity of log end splits. However, it had no direct relationship with the volume of end docking, nor with the volume of the curved-edge off- cuts. The radial variation of MFA appeared to be the most useful indicator of spring in dried boards. The radial variation of Youngs modulus appeared to be more useful than other wood properties in predicting distortion in green slabs (i.e. flitch and slab movement during sawing). Microdensity and cellulose crystallite width, either as tree means or as descriptors of their radial variation, showed no significant relationship with log-end split indices, spring in dried boards, the volume of curved-edge off-cuts, and the volume of end docking.
J L Yang
Ensis-Wood Quality, ensis-the joint forces of CSIRO and Forest Research, Private Bag 10, Clayton South, Victoria 3168, Australia
国际会议
The International Conference on Plantation Eucalyptus(桉树国际会议)
广东湛江
英文
92-102
2005-12-01（万方平台首次上网日期，不代表论文的发表时间）