Edinburgh Napier University

  This paper is concerned with the extent to which portable stress-wave-based instruments can be used to segregate Sitka spruce trees and logs; in particular the relationship between acoustic velocity and the properties of sawn timber. Measurements were made at 64 sites which were selected to span a range of conditions. At each site a portable stress wave timer (IML Hammer) was used to estimate the dynamic modulus of elasticity (Ed) on a sample of ten standing trees. Differences between sites accounted for 36 percent of the total variation in Ed, while differences between trees within a site and sides of the tree account for 55 and 9 percent of the variation respectively. Trees were felled from a representative sub-sample of 12 sites and the Ed of logs estimated using the HM-200 resonance instrument. At an individual tree level, a strong relationship was observed between measurements made on standing trees and those made on the butt log. The mean bending stiffness (Es) of timber cut from an individual site was strongly related to the mean stress wave velocity of both trees and logs from that site showing that it is possible to directly manipulate the characteristic stiffness of a population of sawn timber by segregating logs based on stress-wave velocity values. Taken together, these results demonstrate how non-destructive measurements made on standing trees and logs can assist the forest products industry to improve timber properties and that such approaches work for Sitka spruce grown under UK conditions. The average Ed of logs at a site was also found to be negatively associated with the average live crown ratio of trees at the site offering the possibility of partial sorting, even without acoustic tools.