Radial variation in modulus of elasticity, microfibril angle and wood density of veneer logs from plantation-grown Eucalyptus nitens

Abstract

& Key message Radial variation of wood properties affects product recovery from veneer logs. In Eucalyptus nitens, the radial variation in wood density, microfibril angle and modulus of elasticity was described using non-linear models. The timing of radial change was trait-dependent, and the age at which thresholds for structural products were reached differed between sites. & Context Eucalyptus nitens is widely planted in cool temperate regions of the world. While mainly grown for pulpwood, rotarypeeled veneer is becoming important. Threshold levels of wood stiffness are required for using this veneer for structural purposes. Stiffness is determined by wood density and microfibril angle, which improve with tree age. The nature of this radial variation affects the recovery of suitable veneer and profitability of the plantation resource. & Aims We model the radial variation of these veneer-critical wood properties and determine whether it varies with growing conditions. & Methods We used logs from three 20-22-year-old Tasmanian plantations. Radial variations in wood density, microfibril angle and modulus of elasticity (measuring stiffness) were assessed using SilviScan. Eight linear and non-linear models were examined using cambial age as the independent variable. & Results The increases in wood density and modulus of elasticity with age were modelled by sigmoidal functions and the decrease in microfibril angle modelled by an asymptotic function. The timing of radial change was trait-dependent, and the mean ages at which thresholds for structural products were reached between sites. & Conclusion Radial variation varied among sites and will likely impact the recovery of structural grade veneer from plantations.

Genetic variation of microfibril angle and its relationship with solid wood and pulpwood traits in two progeny trials of Eucalyptus nitens in Tasmania

“…higher KPY) and has lower MFA than normal wood (Bailleres et al 1995). Similarly, the age-related radial changes in wood properties involve MFA decreasing (Vega et al 2020) and KPY increasing (Downes et al 1997) in the outerwood of E. nitens. Genetic variation in either susceptibility to growth stresses or the pattern of radial change may thus induce synchronous genetic-based changes in KPY and MFA.…”

“…These means of the area-weighted average values of microfibril angle were approximately 20% lower than the means based on the simple average MFA for the wood strips taken from each tree (not reported). This difference is expected as MFA ss declines radially toward the cambium in E. nitens (Vega et al 2020), and the area weighted estimates give ) and its standard error in parenthesis, and additive genetic coefficient of variation ( ĈV a ) followed by their significance. DBH, diameter at breast height; MFA ss , area-weighted microfibril angle; MOE ss , area-weighted modulus of elasticity; AWV, acoustic wave velocity; DENS, Wood basic density; KPY, kraft pulp yield; CHECK, internal wood checking; STR, straightness; BRS, branch size; MOE B , static modulus of elasticity measured from boards.…”

“…It is the populations from the central ranges in Victoria which form the basis of most Australian breeding programs , and within this region the populations have been grouped into three races (Hamilton et al 2011;INFOR 2001). In this species, MFA declines radially across the stem in an asymptotic manner and stabilizes at angles of between 6.4 and 8.2°dependent on site (Vega et al 2020). At the ring level, E. nitens MFA is decreased by water stress (Wimmer et al 2002) and temporarily increased by earlyage tree thinning (Medhurst et al 2012).…”

“…Triassic sandstone soils also have poor moisture retention capacity compared with Tertiary basalt, thus the Southport trial is likely to have experienced greater water limitation than Tarraleah (Blackburn et al 2014). As dry conditions have been shown to reduce MFA by proportionally reducing the amount of earlywood within each ring (Wimmer et al 2002), it is possible that this, in combination with slower growth (Medhurst et al 2012) and lower productivity (Vega et al 2020), could explain the lower MFA observed at Southport.…”

Radial variation of wood anatomical and chemical properties in eight poplar clones

“…In particular, the FL and VL exhibited a significant increase trend from the pith to the outer layer (Jiang and Jiang 2008;Luo et al 2015;Longui et al 2017). In contrast, MFA gradually decreased and subsequently remained relatively constant (Jiang et al 2003;Vega et al 2020). The transition between juvenile and mature wood was recorded D r a f t about 12 years in clone "Zhonglin Sanbei-1" (Bao and Jiang 1998).…”