Shakti Chauhan

Genetic control of very early compression and opposite wood in Pinus radiata and its implications for selection

The long time frame for evaluating selection candidates is a major barrier to the deployment of genetic gain from tree breeding programs. This situation is compounded in wood quality studies by constraints on the number of sampled individuals when trees are older and larger. This paper documents the degree of genetic control and genetic association for wood quality traits in 18-month-old leaning Pinus radiata seedlings. Trees were separately assessed for basic density, green and dry acoustic velocity, and longitudinal and volumetric shrinkage in opposite and compression wood. Heritability estimates were low to moderate for both compression and opposite wood (ranging from 0.15 to 0.38). Estimated genetic correlations were very high in opposite wood, where green velocity displayed the highest correlations with both longitudinal (−0.89) and volumetric (−0.64) shrinkage, closely followed by dry velocity. These correlations were substantially lower for compression wood. The estimated correlations between compression and opposite wood characteristics were high for most traits except for longitudinal shrinkage. We suggest how these results could be used for very early screening for wood stiffness and dimensional stability. We propose that information on early genetic control of wood quality and the methodologies used to elicit it should be integrated in breeding and deployment programs.

Moisture adsorption behaviour of esterified rubber wood (Hevea brasiliensis)

Hevea brasiliensis) esterified with acetic anhydride, maleic anhydride and phthalic anhydride was studied for moisture adsorption behaviour. FTIR spectroscopic technique was used to analyse the chemical changes in the wood through the correspondent reactions. Spectra indicated increasing intensity of the C=O and C-O stretching bands, and reduction in O-H stretching vibrations that reflects formation of less hygroscopic ester bonds with hydroxyl groups of cell wall polymers. Moisture adsorption isotherms show low equilibrium moisture content in esterified wood at all relative humidity values as compared to a control. The adsorption data was analysed by applying Hailwood-Horrobin theory which separated the adsorbed water into hydrated water and dissolved water corresponding to mono-layer and multi-layer adsorption. Curve for Mh and Ms were similar in pattern for esterified wood and control with different magnitude. Low Mh and Ms in esterified wood indicate reduction in moisture adsorption sites. Inaccessible fraction of wood for water vapour was increased by 43%, 32% and 26% in acetic, maleic and phthalic anhydride treated wood, respectively, compared to the control. Acetic anhydride treatment was found most effective in reducing hygroscopicity of wood.Hevea brasiliensis) wurde verestert mit Anhydriden der Maleinsäure, Essigsäure und Phtalsäure. Das Adsorptionsverhalten bei verschiedenen Feuchten wurde mit FTIR-Methoden untersucht, um die entsprechenden chemischen Abläufe zu erfassen. Intensivere C=O, und -C-O- Streckschwingungen sowie reduzierte OH-Schwingungen reflektieren die neu gebildeten, weniger hygroskopischen Esterbindungen. Bei allen modifizierten Proben ergaben sich niedrigere Gleichgewichtsfeuchten. Die Adsorptions-Isothermen wurden mit Hilfe der Hailwood-Horrobin Theorie analysiert, um adsorbiertes (Mh) und gelöstes (Ms) Wasser zu unterscheiden. Der Kurvenverlauf für Mh und Ms für modifiziertes und unbehandeltes Holz war qualitativ ähnlich, und unterschied sich nur quantitativ. Geringe Werte für Mh und Ms zeigen eine Verringerung der möglichen Adsorptionsstellen an. Der nicht zugängliche Anteil des Holzes, bezogen auf Kontrollproben, verringerte sich auf 43% (Acetanhydrid), 32% (Maleinsäureanhydrid) und 26% (Phthalsäureanhydrid). Acetanhydrid erwies sich als das effektivste Mittel, um die Hygroskopizität zu erniedrigen.

Differences in acoustic velocity by resonance and transit- time methods in an anisotropic laminated wood medium

Abstract The influence of inhomogeneity on acoustic velocity measured by a resonance-based WoodSpec acoustic tool and a transit-time-based Fakopp-2D tool was investigated. Four laminated panels with different degrees of inhomogeneity were prepared and acoustic velocities were measured using both tools. Velocities measured by the Fakopp-2D tool were always higher than those measured by the WoodSpec tool in all panels. The difference in the two velocities was found to vary depending on the magnitude of inhomogeneity. It was demonstrated that the velocity measured by the resonance frequency obeys the law of mixtures and is controlled by the volume-weighted average stiffness of the material. In contrast, the velocity measured by the Fakopp-2D tool was the velocity of the pulse that first reached the detector travelling at the dilatational speed.

Relationships between longitudinal growth strain and some wood properties in Eucalyptus nitens

Summary The relationships between longitudinal growth strain and wood properties of Eucalyptus nitens were investigated. Sixty-three 10-y-old trees were selected for this study. Longitudinal growth strain, green density, green moisture content, basic density, radial shrinkage, outerwood and corewood densities, volumetric shrinkage and dynamic modulus of elasticity (MOE) at 12% moisture content and length-weighted fibre length were determined. Amongst all the studied wood properties, only shrinkage-related properties were found to have some association with the mean growth strain in trees. The mean growth strain was moderately but significantly related to the volumetric shrinkage of the outerwood, but not to the shrinkage of the corewood. However, the volumetric shrinkage differential (difference between outerwood and corewood shrinkage) was strongly related to the growth strain (r = 0.70), suggesting that the growth stress gradient might be related to variations in shrinkage properties within the stem. The wood of trees with the lowest growth strains had statistically significantly lower volumetric shrinkage, lower outerwood MOE and less collapse than wood of trees with the highest growth strains. The results suggest that E. nitens trees with low strains could exhibit a lower degree of drying defects such as collapse and checking during processing.

Mechanical and Wear Characterization of GF Reinforced Vinyl Ester Resin Composites with Different Co-Monomers

This article reports the mechanical characterization and sliding wear behavior of glass fiber-reinforced vinyl ester resins of varying acid values, based on epoxy-novalocs in the presence of three different comonomers (styrene, methyl acrylate and butyl acrylate) as reactive diluents. It presents a special account of the optimization of fabrication techniques of glass fiber-reinforced vinyl ester resin composites. It outlines optimum reaction conditions such as temperature, time, monomer type and initiator concentration. The experimental plan consisted of preparation of vinyl ester resin followed by the composite samples. Mechanical characterization was done and a comparison was made between the different samples. It was found that these composites have fairly good tensile and flexural properties. The composites with styrene and butyl acrylate as co-monomers had similar tensile strength which was higher than that of the composite with methyl acrylate. Hardness values of the three composites were almost the same without any significant effect of the comonomer type. Volumetric wear rate was estimated for these samples under various test conditions. A steady wear rate regime after certain amount of sliding was observed all the three cases.

Characterization of mechanically perturbed young stems: can it be used for wood quality screening?

Abstract• IntroductionGenetic testing is the slowest part of a breeding cycle. There is a growing interest in early wood quality screening methodologies. We hypothesized that subjecting 8-month-old radiata pine trees to mechanical perturbance induces reaction wood that permits isolating their likely corewood features.• MethodsFour clones were grown straight, tied at 45° from the vertical, or rocked on a purpose-built frame. Trees were assessed for growth, basic density, compression wood, number of resin canals, and three acoustic stiffness (MoE) measures with an ultrasonic timer.• ResultsThere were no significant differences between stem postures for growth. Both rocked and straight trees developed similar levels of compression wood (between 13% and 17%). Rocked trees had a significantly larger number of resin canals than straight trees. Rocked trees produced the lowest MoE for all acoustic assessments. Clonal rankings for MoE were consistent between standing tree and green stemwood MoE. There were small ranking differences for dry stemwood MoE. Clone F, which expresses low MoE as an adult tree, had consistently the lowest MoE assessments but also the highest basic density.• ConclusionThe observed differences in wood properties between clones make feasible their use for screening purposes at an early age.

Effect of moisture sorption state on transverse dimensional changes in wood

The purpose of the study was to understand the transverse dimensional changes and corresponding anisotropicity in wood during different states of moisture sorption. Oven dried samples of Erythrina variegata, Lannea coromandelica, Gmelina arborea and Albizia chinensis were adsorbed and subsequently desorbed at constant temperature (35°C). Tangential and radial dimensional changes (swelling) were analysed with respect to relative humidity and moisture content during both the states of sorption. Dimensions in tangential direction were found to change at a relatively greater rate than in radial direction at high humidities. It was observed that transverse dimensions were more during desorption compared to adsorption at a given equilibrium moisture content. This confirms presence a second order effect of moisture sorption on dimensional movement. This effect was found to be more prominent in tangential direction compared to radial direction resulting in higher coefficient of anisotropy (αT/αR ratio) during desorption. The magnitude of this phenomenon was found to vary from species to species.ZusammenfassungZiel der Arbeit war es, die transversale Dimensionsänderung und die entsprechenden anisotropen Verhältnisse in Holz während unterschiedlicher Grade der Feuchteaufnahme zu untersuchen. Ofengetrocknete Proben von Erythrina variegata, Lannea coromandelica, Gmelina arborea und Albizia chinensis wurden bei konstanter Temperatur (35°C) einer Sorption und anschließender Desorption unterworfen. Tangentiale und radiale Dimensionsänderungen wurden analysiert im Hinblick auf die relative Feuchte und den Wassergehalt in beiden Zuständen. Bei hohen Feuchten änderten sich die tangentialen Dimensionen schneller als in radialer Richtung. Bei einer gegebenen Gleichgewichtsfeuchte war die transversale Dimensionsänderung stärker während der Desorption als während der Sorption. Dies bestätigt einen Effekt zweiter Ordnung für den Einfluss der Feuchteaufnahme auf die Dimensionsänderung. Dieser Effekt war in tangentialer Richtung vorherrschender im Vergleich zur radialen Richtung, woraus sich ein höherer Grad an Anisotropie (αT/αR-Verhältnis) während der Desorption ergibt. Die Größe dieses Effekts variiert je nach Holzart.

Pontamine fast scarlet 4B: a new fluorescent dye for visualising cell wall organisation in radiata pine tracheids

Using confocal microscopy, tracheid wall organisation was investigated with pontamine fast scarlet 4B (P4B), a cellulose-specific stain that fluoresced red following green excitation. P4B fluorescence was present throughout unlignified walls (cambium, ray cells, resin canals and parenchyma cells) and in two concentric bands around opposite and compression wood tracheids. Scanning electron micrographs demonstrated these bands as the S1 and S3 layers of normal wood, and the S1 and inner S2 layers of compression wood. Fluorescence was also strongly dependent on the polarisation of the excitation light, a phenomenon referred to as bifluorescence. Compared to two other cell wall stains, Congo red and calcofluor white, P4B showed a higher specificity for the S1 and S3 layers and increased bifluorescence. These results suggest that P4B is an ideal tool with which to investigate the orientation of cellulose microfibrils in the S1 and S3 layers of the tracheid wall.

Destructive and non-destructive evaluation of seven hardwoods and analysis of data correlation

Abstract Wood physical and mechanical properties in seven tropical hardwood species viz., Acacia auriculiformis A. Cunn. ex Benth., Artocarpus hirsutus Lamk., Artocarpus heterophyllus Lamk., Swietenia macrophylla King, Xylia dolabriformis Benth., Hevea braziliensis (H.B.K.) M. A.), and Tectona grandis L.f. have been studied by means of destructive and non-destructive techniques (NDT). Mechanical strength properties and specific gravity were evaluated by conventional methods. NDT was carried out by a Pilodyn and Treesonic Microsecond Timer (TMT) to measure a steel pin penetration depth into wood and dynamic MOE, respectively. In focus was the question, whether NDT data are suitable predictors for physical and mechanical properties of the indicated hardwood species. Dynamic MOE obtained by TMT correlated strongly positive with all the strength properties studied, except shearing stress. TMT data also correlated very well to static bending MOE and MOR. A linear relationship was found between Pilodyn steel pin penetration depth and oven dry specific gravity in all the species. Both Pilodyn and TMT proved to be useful predictors of timber properties, and these instruments have a high potential for timber grading.

Measurement of surface growth stress in Eucalyptus nitens Maiden by splitting a log along its axis.

Abstract When a log is sawn along the length, an outward bending or deflection of two half rounds arises from the release of growth stresses in the log. The relationship between this outward bending and the peripheral longitudinal growth strain in logs from a 10-year-old Eucalyptus nitens plantation was investigated. In total, 63 trees were felled and two logs (one bottom and an upper log) were cut from each felled tree. A strong association was observed between the measured longitudinal growth strain and the outward bending produced by splitting the log along its axis. A mathematical model was developed that enables calculation of the relationship between the surface axial growth stress and the opening of the split log. This involves calculation of the lateral deflection of a tapered cantilever beam of semi-circular cross-section under a known bending moment. The relationship between the opening of the slit log and the surface axial stress showed good agreement with the measured data on 126 logs. The model equation is effective in predicting the growth stress from the magnitude of the log distortion. This log sawing or splitting method is quick and reliable for assessing the surface growth stresses in small diameter trees. It could have potential in breeding programs for identifying families or clones for low-growth stresses of superior eucalypts for sawn timber production.