How is it measured?
- Wood density tends to be measured indirectly.
- We use a devise called a Pilodyn gun which fires a blunt pin into the tree at breast height. The distance the pin penetrates the wood in measured off a scale in millimetres. It is possible to measure 2,000 trees/day with this device. Studies have shown a working correlation of the Pilodyn with the more costly (50 trees/day) estimation of wood density using extracted cores (water displacement or X-ray densitometry)
- All trees are measured in the trial including the QCI control.
What does it mean?
- The lower the reading off the Pilodyn; the more dense the timber. The mean performance of all families in test is expressed relative to the QCI control. For example if the QCI mean pin penetration = 15mm and pin penetration of selected family = 17mm, that is a 13% drop of density; 14mm is a 7% increase in density.
- Published data are weighted by genetic repeatability and across-site performance.
- Wood density is poorly correlated with diameter but neutral with stem straightness and branching quality.