Wood properties of young Douglas-fir in Southern Italy: results over a 12-year post-thinning period

This paper describes the study of a 31-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stand located in Southern Italy, which was thinned 19 years after planting. The aim of the study is to evaluate the influence of three thinning treatments (unthinned, selective, and geometrical) performed twelve years later on wood density (WD), moisture content, shrinkage, ring width (RW), latewood proportion (LW%), modulus of elasticity, compression (CS), and bending strength (BS). The WD was higher in the unthinned stand. LW% and BS were lowest in the selective thinning and in the geometrical thinning, respectively. No significant differences were found in other variables. In addition, the thinning processes mostly affected the medium tree class more than the dominant and suppressed ones. Regression analysis established a correlation between mechanical characteristics and WD, RW and LW%. Mechanical strength is strongly correlated with WD than other variables. The stepwise model showed that WD and RW are most closely related to the behavior of CS, whereas only WD explained variation in BS. Stand density reduction may improve the development of stands without greatly affecting wood quality.