Description of what it is and means
- Researchers are discovering that the stiffness of trees is most important in determining how timber grades at the sawmill.
- Microfibril angle is well correlated with wood stiffness.
- Acoustic Velocity is a non-destructive indirect assessment of microfibril angle.
Sound travels between two probes knocked into the tree via the microfibrils in the wood. If they are straight (good, stiff timber) the sound travels very fast; if they are at an angle (bad, less stiff timber) the sound travels slower. The units of measure are km/sec.- Stiffness can be derived from the formula: Acoustic velocity² x wood density = Modulus of Elasticity
- Due to cost of assessment restrictions we tend to only measure families we are interested in for other reasons, and of course the QCI control which is standard yard-stick.
What does it mean
- All data are presented relative to the QCI control. Due to the squaring effect of the AV figure in the formula, a modest increase in AV translates into a significant improvement in wood stiffness. For example, QCI = 4.0 km/sec and the selected family is 4.2 km/sec (5% improvement in AV), the selected family is thought to be 10% stiffer.
- The Conifer Breeding Co-operative is working to increase the AV database.