The heartwood formation process is little known in fast growing plantation woods. Therefore, the aims of this study were to determine how planting spacing and tree age affect the formation and proportion of heartwood and sapwood, as well as the density of eucalyptus wood. Trees from a eucalyptus clonal plantation (Eucalyptus grandis × E. urophylla hybrid) cultivated in three spacings (3 × 1, 3 × 2 and 3 × 3 m) were sampled at 14, 27, 32, 53, 64 and 76 months of age. Heartwood percentage was quantified with Dimethyl yellow indicator, while the wood density was determined by X-ray densitometry. The heartwood percentage, wood volume, heartwood density and wood density were correlated with the different growth rates. The heartwood formation process started between 32 and 53 months, regardless of spacing. The heartwood proportion doubled with increasing age in the widest spacing and increased about four times in 3 × 1 and 3 × 2 m spacing. The planting spacing influenced the growth rates of the trees, but did not affect the heartwood and sapwood percentage or density. The greatest increase in density values occurred between the first year of growth (14 months) and the beginning of heartwood formation (53 months).

The variable environmental conditions of the Amazon forest can affect the wood properties of the tree species distributed across its diverse phytophysiognomies.Carapa guianensis(Andiroba) occurs in upland and floodplain forests, and the wood and oil of its seeds have multiple uses. The aim of this study was to evaluate the wood properties ofC. guianensistrees in upland and estuarine floodplain forests of the Amazon River. Eight trees were selected, with four being from the upland and four from the floodplain forests. The fiber length, fiber wall thickness, vessel diameter and frequency, microfibril angle, specific gravity and wood shrinkage were evaluated. The juvenile and mature wood zones were determined according to these variables. The fiber length, fiber wall thickness and specific gravity increased, and microfibril angle decreased, in the pith to bark direction. Only the fiber length variable was efficient for delimiting juvenile, transition and mature wood. The fiber length, wall thickness and specific gravity of wood were higher in upland forest trees. However, the environment did not alter the beginning of the formation and proportion ofC. guianensismature wood. This information is important for the log fit in cutting diagrams, aiming toward improving the production, classification and processing of pieces with specific quality indexes in order to direct them to appropriate wood uses.

The Eucalyptus genus is extensively planted in Brazil for industrial use, and with the expansion of forest frontiers and climate changes, studies are needed on how these changes affect wood density (WD). The aim of this study was to evaluate the effect of some climate variables on WD of an Eucalyptus urophylla clone for a 4–5 year period. WD from trees collected in 12 sites were evaluated. Five growth rings were identified using a magnifying glass, X-ray densitometry, and forest inventory. WD was correlated with temperature ( T), precipitation ( P), soil water deficit, ring width, and current annual increment. There was no variation in WD in the first 20 months among sites. From that age on, WD was mainly correlated with T ( r > 0.6). The 1 °C increase in T resulted in a WD reduction of 0.014 g cm⁻¹, and increases of 10 m³ ha⁻¹ in the final volume were related to an increase of 0.004 g cm⁻¹ in WD. Researchers and managers should continue to put efforts into broad experimental networks to assess the effects of climate change on the adaptation and wood quality of Eucalyptus clones. Highlights The influence of climate on E. urophylla wood density was greater after the third year of growth. The mean air temperature was the best correlated climatic variable with E. urophylla wood density. The cross-site climatic gradient was more important in wood density variation of E. urophylla than the variability among the years.

The relationship between grain angle and wood properties has not been focus of researches in wood industry. The aim of this study was to establish grain angle variations in commercialEucalyptuslogs and their effects on physical-mechanical wood properties. Wood maximum angular deviation (MAD) was correlated with density, volumetric shrinkage, compressive strength parallel to grain, flexural strength and stiffness as determined by bending and acoustic methods in wood of sevenEucalyptus grandis × Eucalyptus urophyllaclones at 13 years old. The relationship between MAD at pith-bark and base-top positions and its effect on the physical and mechanical properties were evaluated. Amplitude of MAD values was small for the seven clones, and the mean was 6.2°. The grain deviation decreased by only 8% in base-top direction, and the correlations among MAD and three logs heights were small and negative (r = −0.13). MAD values presented an increasing trend of 33% in pith-bark direction, with a small positive correlation (r = 0.42). Basic density (BD) presented a significant correlation with the MAD (r = 26). There was no significant correlation between the MAD and volumetric shrinkage, mechanical properties and modulus of elasticity dynamic (determined by stress wave timer, ultrasound or transverse vibration).

Environmental conditions can change both the quantity and quality of wood formation. This study aimed to evaluate anatomical and chemical changes in the wood of a Eucalyptus urophylla S.T. Blake clone cultivated in four sites of wide climatic conditions in Brazil. Radial samples were used to evaluate xylem anatomy along the growth cycles. Samples with a quarter of a disk were used to perform chemical analyses of extractives, total lignin (LG), syringyl/guaiacyl (S/G), holocellulose, and elemental analysis of wood. The elements Na, K, Ca, Mg, P, Mn, Fe, Zn, Ni, Cu, Cr, Cd, F, and Cl were also quantified. Correlations using the mean values of the variables per site were higher than those using values per tree growth cycle (years). Mean annual air temperature showed the highest correlations with wood density (r = −0.89) and the anatomical characteristics (vessel area: r = −0.68; fiber wall thickness: r = −0.70; vessel frequency: r = 0.74; and fiber lumen diameter: r = 0.90). Only LG and S/G showed significant correlations with the meteorological variables, with drier sites presenting a higher S/G. The anatomical characteristics change with regionwide climate features, while wood chemical characteristics showed weaker relations with climatic variations.