Search

This work focused on the upgrading of non-durable tropical wood species originating from fast-growing plantations of Costa Rica. Modification of such tropical woods with furfuryl alcohol, although ...

Acetylation of softwoods has been largely investigated to increase the dimensional stability and biological resistance of wood. However, the knowledge of this technology has not been applied to tropical hardwood species up to date. The objective of this work was to study the effect of acetylation on nine tropical hardwood species, from forest plantations in Costa Rica, by applying acetic anhydride in three different treatment times (1 h, 2.5 h, 4 h), as well as to evaluate this by Fourier-Transform Infrared Spectroscopy (FTIR). Results showed that weight percentage gain (WPG) of wood varied from 2.2 to 16.8%, withVochysia ferrugineaspecies showing the highest WPG, andGmelina arboreaandTectona grandisspecies exhibiting the lowest WPGs. Tropical woods such asEnterolobium cyclocarpum,Hieronyma alchorneoidesandSamanea samanexhibited statistical differences among treatment times, whereas the rest of the species studied showed no significant differences. In general, the most effective acetylation time was 2.5 h for all the species. The ratio of intensity (RI) from the FTIR spectra was greater at the 1732 cm−1, 1372 cm−1and 1228 cm−1peaks for all tropical species, associated with lignin. A good correlation between the RI of those peaks and WPG was found; the same was also found between all RIs and each other. Meanwhile, RI associated to the hemicelluloses and lignin (1592 cm−1and 1034 cm−1peaks, respectively) showed no correlation with WPG, nor between each other or with the other RIs. Furthermore, it was suggested that RI at 1732 cm−1(associated to acetyl groups C=O) can be considered as a reliable indicator of the degree of acetylation for tropical hardwood species. Finally, it was observed that tropical hardwoods having more suitable anatomical features, like larger vessel diameter, higher ray width and frequency, and lesser deposits such as gums and tyloses in the vessels, resulted in significantly higher WPGs.

Tectona grandis (teak) is an important commercial tree species that is widely used in tropical dendrochronology due to the formation of climate-sensitive annual growth rings. However, young trees growing in plantation conditions exhibit poor ring visibility during the first years of growth, limiting the dendrochronology application. In the present study, we use x-ray densitometry to determine the wood density profile between and within annual rings and at the sapwood-heartwood boundary in trees from fast-growth plantations. The resulting wood density profiles (WDP) can be categorized as uniform, stable growth, unstable growth, and false. The annual ring boundaries were indistinct in trees less than 8 years old. In mature trees, the annual ring boundaries are more defined. In relation to the sapwood-heartwood boundary, the WDP showed a decrease in the wood density; however, this decrease is influenced by the annual ring boundary when the two boundaries coincide. The identification of annual rings in trees growing in fast-growth plantations should be combined with X-ray densitometry and visual identification if wood density data are necessary for deriving other analysis, as climate change, from annual ring.

To elucidate the development of heartwood, bark, sapwood, pith and specific gravity of wood in fast-growing teak (Tectona grandis) plantations in Costa Rica, we sampled three trees in each of 55 plantations and modelled each variable with age, site and different tree heights. Age and stand density of plantations were significant correlated with stem diameter at breast height and total height of the tree. Formation of heartwood was initiated at the age of 4-year-old and increased in direct proportion with age. The age of plantation had a significant relationship with stem diameter at breast height, heartwood percentage, sapwood thickness, sapwood percentage, percentage of bark, pith diameter and percentage, and specify gravity. The model for these tree parameters was model with these parameters as dependent variable and in relation to age as independent variable.

Aim of study: Plantations are threatened by an emerging disease called “Gmelina death disease”. The objective of this study was measured the incidence and severity of this disease and were correlated with the characteristics of the plantations, micro- and macronutrients in the soil and climatic parameters.Area of study: The present study evaluated 16 symptomatic fast-growth plantations of different age in Costa RicaMaterial and methods: Fungi were identified from xylem of infected trees. Incidence and severity was measured and correlated with the characteristics of the plantations, micro- and macronutrients in the soil and climatic parameters. Root condition and the quality (specify gravity, mechanical and decay resistance and chemical compositions), of the wood of symptomatic and asymptomatic trees were compared.Main results: Three fungal species (Chaetomella raphigera, Fusarium solani and Rhizomucor variabilis) were identified from diseased samples. Clay content in the soil profile from 10-20 cm deep explained a significant proportion of the variation in the incidence and severity of the disease, and stand density was related to severity. Although two climatic variables, Holdridge’s potential annual evapotranspiration and Thornthwaite’s potential evapotranspiration, showed a relationship between the incidence in the trees and symptoms of the disease. Infected wood turned black in symptomatic trees. Specify gravity and mechanical resistance of infected wood decreased, whereas its natural durability was unaffected. Changes were observed in the quantities of Mg, Fe, Ca, K and Zn in infected wood.Research highlights: Gmelina plantations established in sites with high stand densities and high contents of clay increase susceptibility to this disease.

La présente étude vise à établir les variations du duramen (pourcentage, diamètre, rayon, volume) rapportées à la hauteur des arbres et à l’épaisseur de l’aubier, ainsi que l’âge de début de formation du duramen et sa hauteur maximale pour les arbres de l’essence Tectona grandis. Les résultats de l’échantillonnage de seize plantations réparties dans différentes zones du Costa Rica, âgées de 2 à 22 ans, montrent que l’aubier est plus épais entre 2 et 10 ans d’âge qu’entre 10 et 22 ans. La formation du duramen commence à la base des arbres âgés de 2 à 3 ans, mais il n’apparaît à hauteur de poitrine qu’à partir de 3 à 4 ans. Le duramen disparaît à une hauteur allant de 0 à 90 % de la hauteur totale selon l’âge de l’arbre. Enfin, des modèles statistiques prédictifs ont été développés pour l’épaisseur de l’aubier et pour le rayon, la hauteur maximale et le pourcentage du duramen, en se basant sur le modèle Y = K0 + K1*(épaisseur de l’aubier) + K2*(hauteur relative de l’échantillonnage) + K3*(diamètre à hauteur de poitrine) + K4*(âge de l’arbre). Ces modèles indiquent des coefficients de détermination de 70 %, 90 %, 95 %, 73 % et 31 %, respectivement.

Artículo científico Trametes versicolor and Pleurotus ostreatus were used for the biopulping from pineapple leaf fiber (PALF). PALF substrate was subjected to T. versicolor for 2 to 6 weeks and to P. ostreatus for 4 to 8 weeks. The yields, holocellulose and lignin contents, and extractives in ethanol-toluene mixture and in sodium hydroxide (NaOH) solution were evaluated. Fourier transform infrared spectroscopy (FTIR) spectra, thermogravimetric analysis (TGA), and color studies by L*a*b* systems were used for sample analysis. The results showed that the pulp yield was 55% to 70% with P. ostreatus and 35% to 50% with T. versicolor. Longer colonization periods increased the amount of holocellulose and decreased the amount of lignin and extractives in ethanol-toluene and NaOH solution. TGA showed an increase in intensity associated with cellulose, and the observed inflexion was attributed to lignin, which showed a tendency to fade. The FTIR spectrum showed high intensity between 3100 cm-1 and 3600 cm-1 (cellulose) and decreased intensity at 1730 cm-1 (lignin). For both fungi, the pulp color produced an increase in L* color parameter and decreased in yellowness, while little variation was observed in redness. The most appropriate colonization period was 5 weeks for P. ostreatus and 4 weeks for T. versicolor.

International audience; Wood colour of Tectona grandis produced from fast-growth plantations is highly variable and the causes of this variation are relatively unknown.* 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.; 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 cœur 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*. Dans l'aubier, on ne trouve aucune corrélation entre L* et b* et les caractéristiques des plantations. Cependant a* est corrélé positivement avec l'âge, la hauteur et la vitesse de croissance des arbres. Dans le bois de cœur, l'âge et le diamètre à 1,3 m des arbres sont corrélés avec les trois coordonnées chromatiques mais la hauteur des arbres et la densité de plantation sont corrélées avec a* et b*. Il y a une corrélation entre le site et L*. On montre que le bois de cœur est d'autant plus sombre et rouge que les arbres sont plus vieux et plus gros. Les corrélations obtenues montrent que les bois d'aubier et de cœur qui sont les plus clairs résistent moins bien aux attaques fongiques et que les bois de tendance plus rougeâtre ont une meilleure résistance aux pourritures.

The color of Tectona grandis wood is an attribute that favors its commercialization, however, wood color from fast-growth plantation trees is clear and lacks uniformity. The aim of this work is to characterize steamed teak wood by means of the Fourier transform infrared spectroscopy (FTIR) and [Formula: see text] color systems. Two moisture conditions (green and 50%) and two grain patterns (flat and quarter) of boards were analyzed through the application of different steaming times (0, 3, 6, 9, 12, 15 and 18[Formula: see text]h). The FTIR results showed that the bands at 1158, 1231, 1373 and 1419[Formula: see text]cm[Formula: see text] did not show any change with steaming, whereas the bands at 1053, 1108, 1453, 1506, 1536, 1558, 1595, 1652, 1683, 1700 and 1733[Formula: see text]cm[Formula: see text] presented a decrease in the intensity with the steaming time. The band at 1318[Formula: see text]cm[Formula: see text] was the only one that increased. Lightness ([Formula: see text]) was the most affected parameter, followed by yellowness ([Formula: see text]), while redness ([Formula: see text]) showed the smallest change. Surface color change ([Formula: see text]) presented the lowest value between 3[Formula: see text]h and 6[Formula: see text]h of steam-drying in the boards with flat grain, whereas for boards with quarter grain, the smallest [Formula: see text] value was obtained after 18[Formula: see text]h of steaming.