Spiral and Interlocking Grain in Eucalyptus Dunnii

Spiral grain in 181 trees from a 9-year-old plantation-grown Eucalyptus dunnii was normally distributed with mean 0.33 degrees (to the left) and standard deviation 1.7 degrees, and was affected by family and by crown asymmetry. Interlocking grain was common, exhibiting a mean amplitude of 3.4 degrees (standard deviation 1.5 degrees) and a mean wavelength of 39 mm (standard deviation 12 mm). The relatively large amplitude of interlocking grain means that most trees will have spiral grain that alternates between left and right during each year. The wavelength of interlocking grain is influenced by tree size, but amplitude of interlocking is under genetic control. Both spiral grain and the amplitude of any interlocking were heritable (h2 = 0.99 and 0.63 respectively)

Wood stiffness and strength as selection traits for sawn timber in Acacia auriculiformis

Acacia auriculiformis A. Cunn. ex Benth. is an important planting tree species, but little attention has been paid to its wood properties, such as shrinkage, stiffness, strength, and basic density, which are important for use in structural and appearance-grade timber applications. Here we report the genetic variation in static bending stiffness and strength of wood in a 5½-year-old clone trial in southern Vietnam and the genotypic correlations among these traits and tree diameter, wood shrinkage, and basic density. There was significant variation in stiffness and strength among 40 randomly selected clones. Clonal repeatability (H2) was high for stiffness and moderate for strength. There was no consistent pattern of difference between heartwood and sapwood for the estimates of H2 for stiffness and strength, whereas the estimates of H2 were lower for heartwood density than for sapwood density. Diameter showed a significant negative genotypic correlation with stiffness but a nonsignificant correlation with strength. Genotypic correlations between density and stiffness, and density and strength, were positive, but only the latter was significant. Stiffness and strength were not significantly correlated with wood shrinkage. There is potential to simultaneously improve tree growth, wood basic density, and the mechanical properties of juvenile wood of this species. </jats:p

Relationships between early assessments of stem and branch properties and sawn timber traits in a Pinus sylvestris

A sample of 162 trees was harvested from a 36-year-old Scots pine (Pinus sylvestris L.) progeny trial to evaluate correlations between early measurements of branch diameter, and other stem and branch traits, with sawn timber traits, and hence their potential utility for predicting wood quality. The sample trees were assigned to three genetic groups of small, medium and large branch diameter, based on parental breeding values. Bottom logs were cut and sawn, and several important traits for the visual quality of the boards were assessed. Phenotypic correlations were then estimated between these traits and measurements of the height, diameter, branch diameter, branch angle, stem crookedness, number of branches and grain angle under bark of the corresponding trees when they were 16 and 36 years old. The diameter of the coarsest knot in the board was correlated with the branch diameter at the age of 16 years (0.50), and there were significant differences in this trait among the genetic branch diameter groups. In addition, the board twist was correlated with the grain angle under bark at the age of 36 years (0.54). Thus, the field assessments of branch diameter and grain angle under bark show relevance for the visual quality of centrally sawn small timber.</p

Genetic analysis of fiber dimensions and their correlation with stem diameter and solid-wood properties in Norway spruce

Adverse genetic correlations between growth traits and solid-wood, as well as fiber traits are a concern in conifer breeding programs. To evaluate the impact of selection for growth and solid-wood properties on fiber dimensions, we investigated the inheritance and efficiency of early selection for different wood-fiber traits and their correlations with stem diameter, wood density, modulus of elasticity (MOE), and microfibril angle (MFA) in Norway spruce (Picea abies L). The study was based on two large open-pollinated progeny trials established in southern Sweden in 1990 with material from 524 families comprising 5618 trees. Two increment cores were sampled from each tree. Radial variations from pith to bark were determined for rings 3â\u80\u9315 with SilviScan for fiber widths in the radial (RFW) and tangential (TFW) direction, fiber wall thickness (FWT), and fiber coarseness (FC). Fiber length (FL) was determined for rings 8â\u80\u9311. Heritabilities based on rings 8â\u80\u9311 using joint-site data were moderate to high (0.24â\u80\u930.51) for all fiber-dimension traits. Heritabilities based on stem cross-sectional averages varied from 0.34 to 0.48 and reached a plateau at rings 6â\u80\u939. The â\u80\u9cage-ageâ\u80\u9d genetic correlations for RFW, TFW, FWT, and FC cross-sectional averages at a particular age with cross-sectional averages at ring 15 reached 0.9 at rings 4â\u80\u937. Our results indicated a moderate to high positive genetic correlation for density and MOE with FC and FWT, moderate and negative with RFW, and low with TFW and FL. Comparison of several selection scenarios indicated that the highest profitability is reached when diameter and MOE are considered jointly, in which case, the effect on any fiber dimension is negligible. Early selection was highly efficient from ring 5 for RFW and from rings 8â\u80\u9310 for TFW, FWT, and FC