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To cite this version:Róger Moya, Alexander Berrocal. Wood colour variation in sapwood and heartwood of young trees of Tectona grandis and its relationship with plantation characteristics, site, and decay resistance. Annals of Forest Science, Springer Verlag/EDP Sciences, 2010, 67 (1), <10.1051/forest/2009088>. Ann. For. Sci. 67 (2010) • With the purpose of understanding the colour variation, different fast-growth plantations were sampled with different growth rates, tree ages, and sites.• Wood colour was measured with a CIELab system, where three variables are estimated: coordinate L * for lightness, coordinate a * defines redness and coordinate b * defines yellowness.• Results showed only a negative correlation between L * and a * . L * and a * were negatively and positively respectively correlated with pith distance in heartwood, but not for b * . No correlations were found between L * and b * in sapwood and plantation characteristics, while a * was positively correlated with age and height of tree and growth rate. In heartwood, tree age and diameter at breast height were correlated with all colour parameters, but tree height and plantation density were correlated with a * and b * . Cluster site had correlation with L * . Multiple correlation analysis showed that the heartwood is increasing darker (L * ) and redder (a * ) when the trees are older and bigger. Correlation coefficient shown that sapwood and heartwood with lighter colour (L * ) is less resistance to fungal attack, but redness colour (a * ) increasing decay resistance. Mots-clés :CIELab / bois tropicaux / Tectona grandis / aubier / bois de coeur / plantations Résumé -Les variations de couleur dans l'aubier et le duramen de jeunes arbres de Tectona grandis, en relation avec les caractéristiques des plantations, du site et de la durabilité.• Il y a une grande variabilité de la couleur du bois de Tectona grandis produit à partir de plantations à croissance rapide et les causes de ces variations sont relativement inconnues.• Pour comprendre l'origine des variations de couleur nous avons échantillonné dans des plantations à croissance rapide qui diffèrent entre elles en termes de vitesse de croissance, d'âge et de site.• La couleur du bois a été mesurée avec le système CIELab qui permet la mesure de trois variables colorimétriques : la luminance L * allant du noir au blanc, a * et b * allant respectivement du vert au rouge et du bleu au jaune.• Les résultats montrent une corrélation négative entre L * et a * . Dans le bois le coeur il y a une corrélation négative entre L * et la distance à la moelle et une corrélation positive entre a * et la distance à la moelle : aucune corrélation n'apparaît pour b * .

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The addition of titanium dioxide nanoparticles (TiO 2 nanoparticles) to a water-based varnish used for finishing tropical woods was studied. Three different concentrations of TiO 2 nanoparticles (0%, 1.0%, and 1.5%) were evaluated. The nanoparticles were characterized by means of the transmission electron microscopy and an X-ray diffractometer. The varnish prepared was evaluated for its viscosity, adhesion of the film to the wood, water absorption, and the effects of natural weathering on the color and quality of the varnish. It was found that viscosity decreases as the concentration of TiO 2 nanoparticles increases, while no variation was found in the thickness of the film. Except for Gmelina arborea and Tectona grandis, the adhesion was not statistically affected. It was found that, in the 9 species tested, incorporation of TiO 2 nanoparticles decreased the values of water absorption. The evaluation of natural weathering showed that the varnish with no added TiO 2 nanoparticles degraded completely after 1 year of weathering exposure, while the modified varnish film endured. Less color change was observed in lumber treated with the varnish containing TiO 2 nanoparticles. The best performance of the varnish in the nine tropical woods used was observed when TiO 2 nanoparticles were added at 1.5% concentration.

Pellets may be produced with different types of agriculture or forestry crops in Costa Rica. This work evaluated the energy, physical, and mechanical properties of pellets fabricated from 12 types of agricultural and forestry crops (Ananas cumosos, Arundo donax, Coffea arabica, Cupressus lusitanica, empty fruit bunch and oil palm mesocarp fiber of the fruit of Elaeis guineensis, Gynerium sagittatum, Pennisetum purpureum, Phyllostachys aurea, Saccharum officinarum, Sorghum bicolor, and Tectona grandis), and similarities among these crops were established by multivariate principal component analysis. High variation was found in the pellet properties. The energy evaluation revealed that C. lusitanica and P. aurea are the crops with the best qualities for fuel use because of their high calorific values (from 16807 kJ/kg and 19919 kJ/kg, respectively) and low ash content (1.03% and 3.39%, respectively). As for physical properties, most crops exhibited values within the range noted by several authors and standards. All 12 pellet crops displayed high durability (from 72.12% to 92.98%) and compression force (from 295.18 N to 691.86 N). Moreover, the evaluation of crop similarities allowed the determination of four group combinations. Within these groups, C. lusitanica, P. aurea, and G. sagittatum had similar energy qualities and the best caloric characteristics.