Gilles Chaix

Robustness of models based on near infrared spectra to predict the basic density in Eucalyptus urophylla wood

Scientific contributions have shown good results by using near infrared (NIR) spectroscopy as a rapid and reliable tool for characterising lignocellulosic materials. Many reports have evaluated the predictive power and the robustness of the NIR models by means of methods known to validate them. However, in most of these investigations, the samples were divided systematically into two non-independent groups: one group was used to build and the other to validate the NIR models. This approach does not adequately simulate a real situation in which the properties of unknown samples should be predicted by established NIR models. Hence, the aim of this paper was to evaluate the robustness of models based on NIR spectroscopy to predict wood basic density in Eucalyptus urophylla using two totally independent sample sets. Wood density and NIR spectra were measured in diffuse reflectance mode on transversal, radial and tangential surfaces of wood samples in two data sets. We used one data set to build partial least squares regression (PLS-R) models and another to validate them and vice versa. The predictive models developed from the radial surface NIR spectra proved satisfactory with r2 p varying from 0.79 to 0.85 and RPD ranging from 2.3 to 2.7, while the spectra measured on tangential and transversal wood surfaces generated less robust regression models. Our results showed that it is possible to assess wood density in unknown samples by established PLS-R models from solid wood samples preferably using radial surfaces.

Estimation of physical and mechanical properties of agro-based particleboards by near infrared spectroscopy

Partial least square regression (PLS-R) calibrations based on near infrared (NIR) spectroscopic data were developed in order to predict mechanical and physical properties of agro-based particleboards. The panels were manufactured using Eucalyptus and Pinus wood particles and sugar cane bagasse. The following panel properties were evaluated according to standard methods: modulus of elasticity (MOE), modulus of rupture (MOR), internal bonding (IB) strength, water absorption (WA24H), and thickness swelling (TS24H) after 24 hours of immersion. NIR spectra information was measured on samples cut from each particleboard and correlated with their physical and mechanical properties by PLS-R to build predictive NIR models. The NIR models for IB, WA24H and TS24H presented satisfactory coefficient of determination (0.73; 0.72 and 0.75, respectively.) The key role of resins (adhesives), cellulose, and lignin for NIRS calibrations of mechanical and physical properties of the particleboards is shown. These models can be useful to quickly verify such properties in unknown agro-based particleboards.ZusammenfassungPartial Least Square Regression (PLS-R)xa0Kalibrierungen auf der Grundlage von nahinfrarot- (NIR)-spektroskopischen Daten wurden zur Bestimmung der mechanischen und physikalischen Eigenschaften von agro-basierten Spanplatten entwickelt. Die Platten wurden aus Eukalyptus- und Kiefernholz- und Bagassespänen hergestellt. Die folgenden Eigenschaften wurden mittels Standardprüfverfahren beurteilt: Elastizitätsmodul (MOE), Biegefestigkeit (MOR), Querzugfestigkeit (IB), Wasseraufnahme (WA24H) und Dickenquellung (TS24H) nach 24-stündiger Wasserlagerung. NIR-Spektren wurden an Proben aus jeder Spanplatte gemessen und mit den mittels PLS-R bestimmten physikalischen und mechanischen Eigenschaften korreliert, um daraus NIR-Modelle zu entwickeln. Die NIR-Modelle für IB, WA24H und TS24H ergaben zufrieden stellende Bestimmtheitsmaße (0,73, 0,72 bzw. 0,75). Aufgezeigt wurde die Schlüsselrolle der Harze, Zellulose und Lignin für die NIRS-Kalibrierung der mechanischen und physikalischen Eigenschaften von Spanplatten. Diese Modelle können sich zur schnellen Überprüfung dieser Eigenschaften von agro-basierten Spanplatten als nützlich erweisen.

Predicting Microfibril Angle in Eucalyptus Wood from Different Wood Faces and Surface Qualities Using near Infrared Spectra

The microfibril angle (MFA) of crystalline cellulose in the wood cell wall along the stem axis has major effects on stiffness and longitudinal shrinkage of wood and is of key importance to timber quality. The aims of this study were: (1) to develop partial least square (PLS) regression models for microfibril angle (measured on tangential sections by X-ray diffraction) based on NIR spectra measured on tangential and on radial surfaces; (2) to develop PLS regression models for MFA based on radial NIR spectra collected from wood surfaces of different quality; and (3) to verify the reliability of these PLS-R models by external validations. T values were recorded by X-ray diffraction on tangential sections while NIR spectra were taken on tangential and radial wood surfaces. PLS-R calibrations for MFA based on tangential NIR spectra were better (r2p = 0.72) than those using radial NIR spectra (r2p = 0.64). The key role of the chemical components and the effect of surface quality of wood on NIR spectroscopy calibrations are discussed. Considering the differences between experimental conditions, these findings showed the potential of the NIR-based models for predicting MFA in Eucalyptus wood, even using spectra taken from different wood faces and surface qualities.

Genetic variation of wood chemical traits and association with underlying genes in Eucalyptus urophylla

We developed a quantitative and association genetic study with Eucalyptus urophylla using a progeny trial. Based on a sample of 831 trees distributed in 84 half-sib families whose wood was phenotyped by near-infrared spectroscopy, the results showed that traits related to lignin, cellulose, and wood extractives presented significant additive genetic variability with moderate to high narrow sense heritability (h2u2009=u20090.28 to 0.93). Genetic correlations varied with high standard error and showed low to moderate values. Using three cellulose synthase genes (EuCesA1, EuCesA2, and EuCesA3) and three candidate genes involved in the lignin pathway (EuC4H1, EuC4H2, and EuCAD2), an association study was performed for each of the gene action models (co-dominant, recessive, and dominant) using two methods. Firstly, single-marker association tests were done and 539 tests (49 single nucleotide polymorphisms (SNPs)u2009×u200911 traits) were analyzed. After Bonferroni correction with a significance level of Pu2009=u20090.00102, only four SNPs presented significant association with syringyl and syringyl-to-guaiacyl ratio with an adjusted coefficient of determination varying between 2.6 and 4.4xa0%. Secondly, a model selection method, the backward approach, was implemented. Similar SNPs were detected by both the backward selection and the individual marker approaches. However, the latter detected new associations with other traits, genes, and SNPs and improved the quality of the model as shown by the BIC criteria and the higher adjusted determination coefficient (1.5 to 8.3xa0%). Our results reveal that cellulose genes can be associated with lignin traits (syringyl-to-guaiacyl ratio) and stress the possible pleiotropic effect of some genes.

Relationships between biochemical attributes (non-structural carbohydrates and phenolics) and natural durability against fungi in dry teak wood (Tectona grandis L. f.)

Abstract• IntroductionNon-structural carbohydrates and phenolic compounds are implicated in the natural durability of wood. In order to find the chemical traits of natural durability in teak wood, the radial distribution of phenolics compounds and non-structural carbohydrates were studied in trees ranked by contrasting natural durability class against Antrodia sp.• MethodsNon-structural carbohydrates were analyzed by spectrophotometry after enzymatic assays and phenolics compounds using HPLC.• ResultsHigh concentrations of starch, sucrose, glucose, and fructose were found in the sapwood, whereas only trace amounts were found in the heartwood. In the sapwood, low concentrations of H1 (a hydroxycinnamic acid derivative) were specifically detected. Tectoquinone was also detected in the sapwood but its content increased dramatically in the heartwood. 2-(Hydroxymethyl)anthraquinone and P1, an unidentified compound, were only detected in the heartwood and at high concentrations (>3xa0mg equivalent 5-methoxyflavonexa0g−1 dry weight. Lower concentrations of 1,4-naphthoquinone, anthraquinone-2-carboxylic acid, and lapachol were also only detected in the heartwood. H1 and tectoquinone present in the sapwood could be considered as phenolic precursors of the synthesis of heartwood toxic phenolics in the heartwood.• ConclusionCorrelations between natural durability and chemical composition of heartwood (quinone derivatives, P1, and non-structural carbohydrates) suggest that P1, 2-(hydroxymethyl)anthraquinone and tectoquinone could be natural durability traits. Heartwood extractives, mainly quinone derivatives, were formed from non-structural carbohydrates which were weakly correlated to natural durability.

Resonance and near infrared spectroscopy for evaluating dynamic wood properties

Dynamic longitudinal (L) and transversal (T) tests based on wood resonance were performed on Eucalyptus specimens measuring 410 mm × 25 mm × 25 mm to obtain the dynamic elastic modulus (EL and ET), the first resonance frequency (f1L), the loss tangent (tan δT) and the specific modulus (E′L and E′T). Such dynamic traits and the air-dry density of wood were correlated by partial least squares (PLS) regressions to the near infrared (NIR) spectra measured in the central position of the longitudinal–radial surfaces. The statistics of the validation models for E, E′ and f1L ranged from 0.72 to 0.81 while the calibrations for loss tangent presented lower r2v (0.38), but promising RPD (ratio of performance to deviation) values (1.88). The key role of chemical wood components in the NIR-based calibrations for dynamic properties of wood is discussed. The association of the NIR spectroscopy and resonance techniques appears to be a rapid, low-cost and precise way to evaluate the visco-elastic properties of woods.

Genetic variation of growth and tree quality traits among 42 diverse genetic origins of Tectona grandis planted under humid tropical conditions in Sabah, East Malaysia

Forty-two different genetic origins of teak (Tectona grandis) comprising 26 open-pollinated families from a clonal seed orchard (CSO) were planted in a replicated trial under 2,500xa0mm of annual rainfall and no distinct dry season, in 1997, in Sabah, East Malaysia. The trees were measured or scored for various traits at 13, 35, 49, 61, 72, 85, 96, and 106xa0months after planting. Mortality rate, height (H), diameter at breast height (DBH), volume (V), and fork height (FH) varied strongly among populations and origins. The best population means after 106xa0months for growth H (21.1xa0m), DBH (21.1xa0cm), and V (278xa0dm3) were for the CSO families. Narrow sense heritabilities for the CSO families increased gradually with age but remained lower after 106xa0months for DBH (h2u2009=u20090.24) and V (h2u2009=u20090.34) than for H (h2u2009=u20090.51) and FH (h2u2009=u20090.56). Overall, the CSO families were also straighter, less forked, and grew more vertically than the native provenance and seed-derived sources. Such differences did not exist for flowering ability, and at 106xa0months, the great majority of the trees of the various origins had not yet entered the flowering stage. Overall, at 106xa0months, the phenotypic correlations between the various quantitative and qualitative traits were weak, except between straightness and bending with values higher than 0.50. These findings confirm the usefulness of CSO for teak improvement and demonstrate the beneficial influence of wet tropical conditions on traits of major economical importance for this species.

Provenance effect on the ring structure of teak (Tectona grandis L.f.) wood by X-ray microdensitometry

Abstract• ContextTeak (Tectona grandis L.f.) is a tropical timber which is appreciated worldwide and has been planted into many regions of the tropics. It is essential to obtain information about provenance variation of basic wood properties in order to preserve the wood quality of end-products derived from future plantations. Figuring is one of the wood characteristics valued for panelling and furniture and it is an important parameter to evaluate the quality of teak wood. The ring structure affects within-ring and between-ring colour variation and, therefore, the figure of wood and the related aesthetical aspects.• MethodsBy means of microdensity profiles, we constructed a segmented linear model that depicts the anatomical structure of the rings. It effectively distinguished ring porous and diffuse porous rings, leading to the development of an efficient ring porosity index, further used to study the provenance variation of the ring structure.• ResultsA significant provenance effect was detected for both wood density variables and ring anatomical structure. Although no correlation was detected between the ring structure and the precipitation level at the provenance origin, the two provenances from very wet climates were distinguished by low values of ring porosity index (diffuse porous ring).• ConclusionThe progenies in our study, collected from origins with various climates, planted in a new climate, seem to maintain to some extent the wood characteristics typical of their mother trees, suggesting that these ring characteristics may be inherited.

Rapid prediction of shrinkage and fibre saturation point on teak (Tectona grandis) wood based on near-infrared spectroscopy

Abstract• Dimensional stability, along with the natural durability and colour of the wood, is one of the most important characteristics of teak used as timber. However, it is very time-consuming to take measurements of this kind. For the purposes of selection for the production of improved varieties, the number of samples to be measured rapidly exceeds the capacity of a traditional laboratory.• Near-infrared spectroscopy, based on a set of reference data, is a tool enabling many of the chemical properties of wood to be predicted and the number of laboratory measurements to be reduced exponentially. The issue here is a question of checking the effectiveness of NIRS tool to build models and predict the shrinkage and fibre saturation point of teak wood from Togo.• The results show the possible use of NIRS to measure the dimensional stability of teak wood and that it is appropriate to choose the type of wood and type of surface to be measured by NIRS. The best prediction models for radial and tangential shrinkage and fibre saturation point give R2 values of 0.72, 0.83 and 0.87 respectively with ratios of performance deviation of 1.8, 2.4 and 2.8.• Consequently, after verification on other sets of teak samples, which may or may not be included in the prediction model, NIRS can be used to predict shrinkage and fibre saturation point values accurately for a large number of samples, making it possible to include these characteristics in the selection criteria for classifying wood and high throughput phenotyping.Résumé• La stabilité dimensionnelle avec la durabilité naturelle et la couleur du bois, est l’une des plus importantes caractéristiques pour le teck utilisé en bois d’œuvre. Néanmoins, les mesures de ce caractère sont longues et coûteuses en temps. Pour les besoins de la sélection pour la production de variétés améliorées, le nombre d’échantillons à mesurer devient vite supérieur aux capacités d’un laboratoire traditionnel.• La spectroscopie proche infrarouge, sur la base d’un jeu de données de références, est un outil qui permet de prédire de nombreuses propriétés chimiques du bois et de réduire le nombre de mesures de laboratoire de façon exponentielle. La question ici est de vérifier l’efficacité de l’outil NIRS pour construire des modèles et prédire les retraits et le point de saturation des fibres du bois de teck provenant de plantations du Togo.• Les résultats démontrent la possible utilisation de la SPIR pour mesurer la stabilité dimensionnelle du bois de teck et qu’il a y lieu de choisir le type de bois et le type de face que l’on mesure par SPIR. Les modèles de prédiction pour les retraits radial et tangentiel et le point de saturation des fibres montrent des R2 de 0,72, 0,83, 0,87 respectivement avec des rapports d’efficacité de 1,8, 2,4 et 2,8.• En conséquence, et après vérification sur d’autres jeux d’échantillons de teck, qu’il conviendra ou non d’intégrer dans le modèle de prédiction, la SPIR permet de prédire des valeurs de retrait et de PSF avec efficacité pour un grand nombre d’échantillons rendant possible l’intégration de ces caractères dans les critères de sélection pour le classement des bois et pour le phénotypage à grande échelle.

Age trends of microfibril angle inheritance and their genetic and environmental correlations with growth, density and chemical properties in Eucalyptus urophylla S.T. Blake wood

Abstract• ContextThe genetic and environmental control of microfibril angle (MFA) and its genetic correlations with other wood and growth traits are still not well established in Eucalyptus sp.• AimsTo determine the narrow-sense heritability estimates (h2) of MFA, wood density (D), Klason lignin (KL) content, syringyl to guaiacyl (S/G) ratio and growth traits, their variation from pith to cambium and their genetic correlations.• MethodsHeritability and correlations were assessed in 340 control-pollinated progenies of 14-year-Eucalyptus urophylla S.T. Blake using near infrared spectroscopic models.• ResultsModerate to high heritability were found for MFA (h2u2009=u20090.43), D (h2u2009=u20090.61), S/G (h2u2009=u20090.71) and LK (h2u2009=u20090.76). The genetic control of D and MFA and the genetic and residual correlation between chemical and growth traits varied with age. The genetic correlation Cu2009×u2009D was always strongly negative (ru2009<u2009−0.80) while the correlation Du2009×u2009MFA remained constant and positive in the juvenile wood (ru2009=u20090.7), before disappearing in the mature wood. These results could be explained by gene pleiotropic effect, low microfibril angle compensating for low wood density and fast growth or by linkage disequilibrium induced by sampling. Variations in MFA and KL in the mature wood were also genetically controlled.• ConclusionsThese findings provide the opportunity for developing breeding strategies for pulpwood, fuelwood and sawntimber production in Eucalyptus sp.