The effects of genotype and spacing on Pinus radiata [D. Don] corewood stiffness in an 11-year old experiment

There was a significant (P < 0.01) negative relationship between tree diameter at breast height (DBH) and stiffness, for all genetic populations, which explained 57%, 56% and 14% of the variation in stiffness for the clones, GF27 and GF1, respectively. Although correction for variation in DBH reduced variation in stiffness, residual variation in stiffness between planting densities and genetic population were still significant after the effect of DBH had been removed. These findings highlight the importance of planting density in regulating stiffness, and strongly suggest that effects of planting density and genetic population on stiffness are independent.