Preharvest Veneer Quality Evaluation of Douglas-fir Stands Using Time-of-Flight Acoustic Technique

Abstract

Acoustic technology has been successfully used as a nondestructive technique for assessing mechanical properties of various wood products and species as well as in tree selection and breeding based on stiffness. In an ongoing endeavor to optimize merchandizing and enhance timber value recovery, seven second-growth Douglas-fir stands of similar age classes in western Oregon were sampled, totaling 1400 trees and more than 3000 logs. The objectives of this research were to 1) investigate the spatial variability of time-of-flight (TOF) acoustic velocities in standing Douglas-fir trees; 2) develop relationships between average Director ST300® (ST300) TOF acoustic velocities of standing Douglas-fir trees and actual veneer produced; and 3) determine the influence of diameter at breast height (DBH) on TOF sound speeds. Spatial location of the stands in terms of their latitude, longitude, or altitude had no predictive capability regarding their veneer quality. Standing tree TOF acoustic velocity and the actual G1/G2 veneer produced using a stress-wave grade sorter had no significant correlation. Significant differences were found among the three different ST300 tools used along the duration of the study as well as between the two opposite side measurements within trees. DBH correlated poorly with both acoustic velocity and G1/G2 veneer recovery

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