Crown characteristics slightly improve lumber mechanical property models for black spruce (Picea mariana(Mill.) BSP)

Most models of modulus of elasticity (MOE) and modulus of rupture (MOR) use classical dendrometric variables and do not use crown characteristics that are known to influence wood formation and properties. The objective of this study was to evaluate the benefit of including crown variables in black spruce MOE and MOR models. Values of MOE and MOR were measured on 99 boards from 21 black spruce trees located in nine stands in the Lac-Saint-Jean region of Quebec (Canada). Site, tree and crown variables (crown surface area, crown length, branch basal area) were measured. Stand age and basal area were found to be positively related to MOE and MOR. Stem DBH and crown length were negatively related to MOE and MOR. When including crown variables, Akaike's Information Criterion was stable while the R2 increased slightly (+ 2.7% for MOE and + 1% for MOR). The small benefit in model performance associated with the inclusion of crown variables in MOE and MOR models suggests that models without crown variables could b...