Wood Properties Characterisation of Thermo-Hydro Mechanical Treated Plantation and Native Tasmanian Timber Species

Thermo-hydro mechanical (THM) treatments and thermo-treatments are used to improve the properties of wood species and enhance their uses without the application of chemicals. This work investigates and compares the effects of THM treatments on three timber species from Tasmania, Australia; plantation fibre-grown shining gum (Eucalyptus nitens H. Deane and Maiden), plantation saw-log radiata pine (Pinus radiata D. Don) and native-grown saw-log timber of the common name Tasmanian oak (which can be any of E. regnans F. Muell, E. obliqua L’Hér and E. delegatensis L’Hér). Thin lamellae were compressed by means of THM treatment from 8 mm to a target final thickness of 5 mm to investigate the suitability for using THM-treated lamellas in engineered wood products. The springback, mass loss, set-recovery after soaking, dimensional changes, mechanical properties, and Brinell hardness were used to evaluate the effects of the treatment on the properties of the species. The results show a marked increase in density for all three species, with the largest increase presented by E. nitens (+53%) and the smallest by Tasmanian oak (+41%). E. nitens displayed improvements both in stiffness and strength, while stiffness decreased in P. radiata samples and strength in Tasmanian oak samples. E. nitens also displayed the largest improvement in hardness (+94%) with respect to untreated samples. P. radiata presented the largest springback whilst having the least mass loss. E. nitens and Tasmanian oak showed similar dimensional changes, whilst P. radiata timber had the largest thickness swelling and set-recovery due to the high water absorption (99%). This study reported the effects of THM treatments in less-known and commercially important timber species, demonstrating that the wood properties of a fibre-grown timber can be improved through the treatments, potentially increasing the utilisation of E. nitens for structural and higher quality timber applications.

Tree species identification via 1H NMR fingerprinting of supercritical carbon dioxide wood extractives

Six tree species were examined using 1H NMR spectroscopy of sap extracted by supercritical CO2. A metabolomic approach was developed to evaluate the sap extracted from sapwood of Norway spruce (Picea abies), Sitka spruce (Picea sitchensis), radiata pine (Pinus radiata), macrocarpa (Cupressus macrocarpa), and two Eucalyptus species—shining gum and mountain ash (Eucalyptus nitens and Eucalyptus regnans. The sap extraction patterns in the different species were visualised using 1H magnetic resonance imaging. In softwoods with distinct annual rings, water was first removed from the latewood bands, and then gradually from the earlywood bands. In the case of the hardwood species an almost random water redistribution, rather than water expulsion, was observed. Analysis of the principal component analysis loading plots showed that the significant differences in the sap between each species were due to the carbohydrate region. Key discriminators were identified as pinitol, sucrose, glucose, and fructose.

Estimation of whole-tree kraft pulp yield of Eucalyptus nitens using near-infrared spectra collected from increment cores

Eucalyptus nitens (Deane and Maiden) Maiden (shining gum) is widely grown for kraft pulp production. Improving the kraft pulp yield of E. nitens increases plantation profitability but traditional assessment is slow and expensive, which hinders improvement. Near-infrared (NIR) spectroscopy provides a rapid and inexpensive method for estimating pulp yield, but studies have been limited to estimating whole-tree pulp yield using whole-tree composite samples obtained destructively. For whole-tree pulp-yield calibrations to be used non-destructively they must be applied to increment cores. In this study we used a Tasmanian E. nitens whole-tree pulp yield calibration to estimate the whole-tree pulp yields of trees from a site not included in the calibration. This was done using NIR spectra from increment cores and whole-tree composite chips. Predictions of whole-tree pulp yield based on increment cores were better than those obtained using whole-tree composite chips. The accuracy of pulp-yield predictions was greatly improved by adding a small number of prediction-set samples to the calibration sets. Calibrations for estimating whole-tree pulp yield were also obtained using NIR spectra from milled cores and whole-tree composite chips. The calibrations had similar statistics, indicating that it is possible to obtain calibrations for estimating whole-tree pulp yield based on increment-core NIR spectra.

Morphological variation within Eucalyptus nitens s. lat. and recognition of a new species, E. denticulata

The complete geographic range of Eucalyptus nitens s. lat. (shining gum) was sampled to determine the pattern of variation in adult and seedling morphology. Analyses of the different data sets indicated the presence of two distinct taxa: one, characterised by denticulate adult leaf margins, is described as E. denticulata sp. nov.; the other, characterised by entire leaf margins, is E. nitens s. str. Many other characters distinguish the two taxa. Mature trees of E. denticulata have leaves with higher oil gland density, longer peduncles, more cup-shaped rather than barrel-shaped fruit, more frequently exserted valves, and rounded and longer flower buds compared with E. nitens s. str. Seedlings of the two species can be distinguished mainly on the basis that those of E. denticulata have longer internodes and leaves which clasp the stem to a lesser extent. The major occurrence of E. denticulata is on the Errinundra Plateau, East Gippsland, with limited occurrences in the Baw Baw Ranges and Central Highlands of Victoria. Eucalyptus nitens s. str. is found in isolated stands in New South Wales and Victoria. The two species are allopatric, with the exception of the Baw Baw Ranges and Central Highlands of Victoria where some stands are mixed. Eucalyptus nitens s. str. is also geographically variable, comprising three distinct geographic races: northern and central New South Wales, southern New South Wales, and the Baw Baw Ranges and Central Highlands of Victoria.