Spatial variation of wood density, stiffness and microfibril angle along Eucalyptus trunks grown under contrasting growth conditions

Key message Sloped terrains tend to produce trees with higher radial variation in wood density while at high wind speeds, the wood tends to present higher stiffness and lower MFA in Eucalyptus. Few studies have investigated the influence of environmental conditions on the within-tree variation in Eucalyptus wood traits. The genotype and environment effects and their interactions influence the wood properties. Their evaluations are crucial to estimate the genotype values and to select with efficiency. Thus, the aim of this study was to better understand the effect of ground slope and wind speed on the spatial variation of basic density ( ρ ), stiffness (MOE) and microfibril angle (MFA) of Eucalyptus wood. Wood discs cut along the trunk were sampled from one-hundred fifty 6-year-old Eucalyptus grandis × E. urophylla hybrids growing in three contrasting growing conditions influenced by ground slope and wind regime. Near infrared (NIR) calibrations previously developed for ρ , MOE and MFA were used to predict in our discs. 2-D plots presenting the spatial variation of predicted wood traits were compared. The higher the ground slope, the greater the magnitude of radial variation in ρ , principally in the medium zone of the trunk. The spatial variation of wood stiffness seems to be sensitive to two environmental conditions. The MFA radial decreases were more pronounced where the wind speed was higher. At the base and top of the trees, however, there was no significant effect of growing conditions on the radial variation of the wood properties considered here.