Farm Forestry New ZealandUsing NIR to Predict Sawn Timber Quality in E. nitens
By Rosie Sargent, Toby Stovold, Mark Riddell, May 2022.
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Executive summary
An existing NIR model, developed as a screening tool for tree breeding, has been assessed as a possible method for identifying Eucalyptus nitens trees that produce timber that is not susceptible to within-ring checking and collapse. Tangential shrinkage values were predicted for E. nitens discs cut from 28 trees, and these were compared to defect ratings given to the boards cut from each of these trees.
Tangential shrinkage values calculated for inner- and outerwood for each tree were used to predict the defect ratings of either kiln-dried or air-dried boards that had been cut from the same part of each tree. These predictions were very poor at predicting differences in defect ratings between trees, and tended to consistently predict very low defect ratings for air dried boards and very high defect ratings for kiln dried boards, even though both drying techniques showed a wide range of defect ratings between different boards and between trees. Because of these poor predictions it is not recommended that further work be done on predicting the behaviour of individual trees using this NIR model.
Despite not being able to predict defect ratings of individual trees, it was observed that the trees with the highest average tangential shrinkage also contained a high proportion of the trees with high levels of within-ring checking. This suggests that removing trees with high levels of tangential shrinkage from the breeding population could reduce the overall incidence of within-ring checking, without needing to predict the behaviour of individual trees.
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