Development of a generic model describing modulus of elasticity of Pinus radiata in Chile and New Zealand

Abstract

Using three national datasets collected across Chile and New Zealand we developed a model of Modulus of Elasticity (E) for Pinus radiata D. Don to ascertain whether predictions can be generalised across countries. Data used within the model covered a wide range in E (3.1–19.0 GPa) and tree age (6–25 years). The temperature range of 8.2–15.9 °C and rainfall range of 636–3276 mm covered the variation present within plantations in both countries. A range of models were tested that varied in complexity with the simplest including only the tree dimensions (diameter (DBH), height (H) and stem slenderness (S)), to tree dimensions and stand age, and finally, for the most complex models, all of these variables as well as climatic data and stand density. Modelling approaches included general linear models, and for the models with more variables, elastic net, partial least squares and sparse partial least squares.Analyses show S to be a more precise predictor of E than either H or DBH. The most precise model of E, which had R2 of 0.82 and RMSE of 1.57 GPa, included stand age, S, air temperature and rainfall as significant predictors. This model was constructed using a linear modelling approach and predictions using more sophisticated methods were not significantly more precise. Predictions were applicable across both Chile and New Zealand as evidenced by the lack of bias, with respect to country level datasets, in the final model.