Modelling the influence of environment on juvenile modulus of elasticity in Pinus radiata grown in Chile

- Measurements of modulus of elasticity (E) were taken from Pinus radiata in Chile.
- Models were developed that accounted for site and tree level variance in E.
- The final site model accounted for 43% of the variance in the data.
- Random effects were included in the site model to extend this to the tree level.
- Key variables in the models were stem slenderness and minimum May air temperature.

Measurements of modulus of elasticity (E) were taken from Pinus radiata D. Don growing at 88 sites that encompass the range of environmental conditions over which forest plantations have been established in Chile. Using this dataset the objectives of this research were to (i) identify the key determinants of E across sites and (ii) develop a robust tree level model to predict E across the environmental range over which P. radiata is grown in Chile.Variance components analysis showed variation between sites to account for almost twofold more variation in E than variation within sites. Across the studied region, mean site values of E varied widely ranging fourfold from 3.41 to 14.1 GPa, with a mean of 8.52 GPa. The mean within site variation at each site was 4.50 GPa, ranging from 1.50 to 14.6 GPa.Of the climatic and stand level variables used in analyses stem slenderness, S, (tree height/diameter at breast height) exhibited the strongest correlation with E accounting for 43% of the variance in the property. The final model of E at the site level included S and minimum air temperature during May, both of which were positively related to E. This model was extended to the tree level through inclusion of a term that accounted for the random intercept between S and E. This model accounted for 75% of the variation in the data and exhibited little apparent bias.