Development of a model describing modulus of elasticity across environmental and stand density gradients in plantation-grown Pinus radiata within New Zealand

Abstract

Modulus of elasticity (E) is an important property in plantation grown softwoods that describes resistance of timber to deformation under load and is a key criterion in machine stress grading. This paper presents an accurate (R2 = 0.96) site-level model of E for radiata pine ( Pinus radiata D. Don) that is applicable across a wide range of tree ages and broad environmental gradients and sensitive to a wide variation in stand density. In the final model, E increased sigmoidally with age and increased linearly with both stem slenderness (height/diameter at 1.4 m) and mean minimum autumn air temperature. For a given age, the model shows stem slenderness to be the main determinant of environmental variation in E, with variation in E ranging approximately 10 GPa across the range in slenderness. Given the simple formulation, this model could be readily used by managers to gain greater understanding of how they can manipulate stands to achieve desired end-use products and maximize crop value. Further research should extend the developed framework so that it can be used to account for intratree, intertree, and clonal variation in E.