Search

Short-rotation crop (SRC) systems with woody species have been planted in Costa Rica. However, information about different tree species and spacing is limited. The objective of the present study was to examine biomass production and the physical, energy, and chemical properties of feedstock of four tropical tree species (Cordia alliodora, Dipteryx panamensis, Gmelina arborea, and Tectona grandis) in 34-month-old plants planted at four spacings (0.5x1.0 m, 1.0x1.0 m, 1.0x2.0 m, and 2.0x2.0 m). The highest mortality rate (50%) was found in G. arborea; however, diameter, height, basal area, and biomass production in G. arborea plantations were higher than T. grandis, C. alliodora, and D. panamensis. Spacing effects on diameter, height, basal area, and biomass production were observed in 10-month-olds. Wide spacing presented the highest values in diameter and height, but the highest biomass production was found in the narrow spacing. Also, biomass distribution was different in D. panamensis in relation to other species. Specify gravity, density, and moisture content of biomass showed high variation between species and spacing, but the energy and chemical properties of biomass showed few differences. These results suggest that these four species were uniform in terms of their energy and chemical properties, regardless of the spacing used. Finally, three species (G. arborea, C. alliodora, and T. grandis) presented important potential for use in SRC systems. G. arborea was the species with the highest production but a high mortality rate.

Densification is one method used to modify low-density woods to make them achieve the hardness required for flooring application. The purpose of this study was to investigate the effect of thermo-mechanical densification with pre-heating in wood of Alnus acuminata, Vochysia ferruginea and Vochysia guatemalensis from, seeking to stabilize and reduce spring-back of the densified wood and evaluate its performance in flooring applications. The results showed that the wood of the three species turned dark. This is because brightness diminished and yellowness and redness increased. Weight loss due to pre-heating was statistically higher in V. ferruginea and V. guatemalensis. The final density and spring-back were statistically similar in the three species. The percentage of densification of A. acuminata and V. guatemalensis were statistically higher than for V. ferruginea and the degree of compression was statistically higher in V. guatemalensis. As for flooring evaluation, the percentage of densification, temperature and time of pre-heating affected the behavior of densified wood flooring. The low percentage of densification and high weight loss in the pre-heating stage caused greater values of wear, wear index, residual deformation, residual indentation for the falling ball indentation test, and more damages in the surface indentation test in wood of V. ferruginea.

This study evaluated the effect of thermo-treatment (THT) at 4 temperatures on the density, shrinking, mass loss, moisture absorption, color, durability in terms of resistance to decay, flexural strength, tensile adhesion of glue line and the infrared spectrum of the wood of Tectona grandis and Gmelina arborea. Sapwood, heartwood and radial and tangential grain patterns were studied. The results showed that the THT temperature decreases the density, the percentage of moisture absorption, the modulus of elasticity and modulus of rupture in the flexure test and the tensile adhesion of glue line. The percentage of shrinking and durability presented irregular behavior relative to the THT temperature. The percentage of mass loss increased with increasing THT temperature in both species. The total color change (∆E*) of thermo-treated wood (THTwood) also increased with increasing THT temperature. Sapwood of T. grandis and G. arborea, having clearer shades, showed a more noticeable color change compared to hardwood; however, no significant differences were obtained between some of the THT temperatures.DOI: http://dx.doi.org/10.5755/j01.ms.24.1.17545

The main objective of this research was to evaluate the use of unmanned aerial vehicles (UAVs) in estimating the aboveground biomass and carbon, and the dasometric characteristics at three different spacings (2.5 m × 1.0 m, 2.5 m × 2.0 m and 2.5 m × 3.0 m) in a silvopastoral system (SPS) for the biomass production of Tectona grandis. A total of 90 trees were sampled, 63 of which were used to perform a dasometric evaluation (vertical and horizontal) in a spacing test in an SPS, and the rest to evaluate the use of UAVs in estimating the aboveground biomass in the spacing test. The results showed significant differences in average diameter at breast height (dbh) between spacings, and in aboveground biomass per tree. The amount of aboveground biomass and carbon per hectare increases at smaller spacings, but the differences were not statistically significant. A logarithmic model was prepared to estimate the dbh based on the crown diameter from the data collected taken in the field, since estimating this variable by means of UAVs is difficult. Significant differences were found in the aboveground biomass estimated using the field data compared to UAV data. The estimation of the crown diameter of the selected trees, hindered by the canopy closure in the SPS, was not adequate, which could influence the amount of aboveground biomass estimated using UAV data.

La torrefacción y peletización se han estudiado en la generación de calor a partir de residuos lignocelulósicos, para incrementar las propiedades energéticas del material. El objetivo del presente trabajo fue torrefaccionar aserrín de Gmelina arborea y Dipteryx panamensis a 200 °C en tres tiempos: 0, 15 y 20 minutos. Con las biomasas obtenidas se fabricaron pellets de 6 mm de diámetro y se evaluaron sus propiedades físicas, el poder calórico, la densidad y la propiedad mecánica de resistencia a la compresión. Ambas especies presentaron características físicas similares con respecto al diámetro (0.50 mm), longitud (21.50 mm) y porcentaje de absorción de agua (6.00 %). El poder calórico aumentó de 9,749 kJ·kg-1 en la biomasa sin torrefaccionar a 18,126 kJ·kg-1 en la biomasa torrefaccionada. Los pellets de D. panamesis presentaron mayor densidad y resistencia a la compresión que los de G. arborea. Con base en los resultados, la resistencia a la compresión del pellet disminuye cuando el tiempo de torrefacción aumenta. Existe correlación positiva entre la densidad de los pellets y la resistencia a la compresión. La especie D. panamensis presenta mejor comportamiento a la torrefacción y peletización que la madera de G. arborea.

Shade-trees with energy use in coffee plantations are an important alternative to increase profitability in groforestry systems. The aim of this study was to investigate gross calorific value (GCV) of 15 shade-tree species in coffee plantations in Costa Rica. The relationships between specific gravity and extractives content on GCV was evaluated. The results revealed that GCV varied from 15.9 to 21.9 MJ kg-1 for sapwood, and from 15.3 to 21.9 MJ kg-1 for heartwood. No consistency was observed regarding to relation of type of wood (sapwood or heartwood) and GCV. The highest GCV value was found in Pinus caribaea for sapwood and heartwood. However Cupressus lusitanica, presented high GCV in sapwood too. The lowest values were found in Schizolobium parahyba in sapwood and Zygia longifolia and Eucalyptus globulus in heartwood. Carbon content (C) and carbon/nitrogen ratio (C/N ratio) and extractives in sodium hydroxide and dichloromethane were correlated with GCV in sapwood and heartwood. Meanwhile extractives in hot water were correlated in heartwood, and nitrogen content (N) and extractives in cool water were too correlated in sapwood.

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 Rica Material 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.

Physical and mechanical properties were evaluated on cross-laminated panels (plywood) fabricated with three plantation species (Cordia alliodora, Gmelina arborea and Vochysia ferruginea) from tropical climates in Costa Rica. The panels were glued with urea-formaldehyde resin modified with nanoclay at four concentrations (0.75, 1.00, 1.50 and 2.00 per cent) and unmodified resin. It was determined that addition of nanoclay to urea-formaldehyde adhesive positively decreased moisture absorption and swelling of the plywood panel with statistical significance. However, nano-modification did not have a significant effect on the density and specific weight of plywood. Nano-modification of urea-formaldehyde resin with nanoclay at 0.75 per cent improved the Module of rupture and Modulus of elasticity in flexure parallel to surface in the three species, also increasing mechanical resistance to strains in parallel tension, shear and compression. By means of electronic microscopy, it was evidenced that the nano-modified adhesive became diffused at the inside of the cellular structure of wood in a better way, allowing for the generation of a transition zone that increased the mechanical properties at the macro level. According to the properties evaluated, it was determined that 0.75 per cent is the optimal percentage to use of nanoclay on urea-formaldehyde resin.

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.

Coffee bean (Coffea arabica) processing generates high amount of residues that are sources of environmental pollution. Therefore, an appropriate solution is needed. The objective of this study was to determine the potential of coffee pulp to produce briquettes and pellets. The study included pulp drying (using air, solar and hot air methods); the production of briquettes and pellets; the evaluation of their energy, physical and mechanical properties; and the evaluation of pellet quality using X-ray densitometry. The results showed that the pulp presented an initial moisture content of 90%, resulting in drying times of 699, 308 and 55 hours for air, solar and hot air drying, respectively, and the calorific values of the pellets and briquettes were 12,501 kJ kg-1 and 11,591 kJ kg-1, respectively. The ash content was 8.68% for the briquettes and 6.74% for the pellets. The density of the briquettes was 1,110 kg m-3, compared with 1,300 kg m-3 for the pellets. The apparent densities were 1,000 kg m-3 and 600 kg m-3 for the briquettes and pellets, respectively, and the water absorptions by the briquettes were 7.90% and 8.10% by the pellets. The maximum horizontal compression effort was 26.86 kg cm-2, measured in the pellets, compared with 4.52 kg cm-2 in the briquettes. The maximum horizontal load was 93.24 kg, measured in the briquettes, compared with 33.50 kg in the pellets. The value of the pellet durability test was 75.54%. X-ray densitometry showed that the pellet was uniform and a few cracks were observed on the pellet surface.

El objetivo principal de este trabajo fue determinar los rendimientos en aprovechamiento e industrialización de dos plantaciones de Gmelina arborea de 15 años de edad sin manejo, en dos grados de pendientes: 30 y 60 %. Los árboles presentaban un diámetro promedio a la altura del pecho (DAP) de 31.23 cm y una altura total de 14.87 m. Se obtuvieron en promedio tres trozas por árbol. Del volumen total en pie, únicamente el 22 % es aprovechable como producto final para la venta en mercado. El desperdicio en la plantación fue de 42.57 %; al trocear el árbol se desperdicia el 14.43 %; al producir el semi-bloque en el aserrío primario se desperdicia el 26.27 % y al obtener las tablas comerciales se desperdicia el 22.10 %. El rendimiento de la troza fue de 53.22 % en madera aserrada en semi-semi-bloque y de 45.88 % en madera aserrada en tablas.

The main objective of this study was to evaluate three methodological approaches for the drying (air drying, solar drying, and hot-air drying) of three lignocelluloses residues in Costa Rica, namely the empty fruit bunches of oil palm (EFB), pineapple plant leaves (PL) with different treatments on this leaf, and sawdust from Gmelina arborea (GAD). The initial moisture content (MCi), the drying times, and the variation of moisture content (MC) with time were determined. A mathematical model of the relation between MC and drying time was also established. The results showed that the MCi was the highest in PL (over 79%), followed by EFB (over 47%), and GAD (lower than 47%). Drying times were higher for air drying, followed by solar drying, and finally hot-air drying. PL showed the longest drying times, followed by GAD and EFB. However, it can be reduced by shortening strands, application of grooves in the cuticle, or crushing the leaf. The MC variation model revealed that the function was Y = ax3 + bx2 + cx + d for all three drying techniques, and the weather conditions where the drying was tested. This model presents high coefficients of determination (over 0.97) and low percentage of errors (1.85-4.73%).

Persian ironwood (Parrotia persica) is native species from Iran and covers 10,54% of the commercial volume. Its wood structure and its chemical composition are affected by growth conditions. The aim of the study was to assess the variation of mineral content (Ni, Fe, Cu, Zn, Pb, Cd), wood density and chemical properties (cellulose, lignin, ash and extractive) of ironwood in relation to altitude above sea level (100, 500 and 700 meter) and pith distance within stem (near to pith and bark and middle point). In addition was investigate the relationship between mineral content with oven-dried density and chemical properties. Results showed that Cd, Cu, Fe, Ni and Zn content (except Pb concentration) increased by increasing of altitude and decreased along radial position within stem from the pith to the bark. Lignin, ash and extractive content increased by increasing altitudes from 100 to 700 meter while cellulose decreased. Radial position had not significant impact on the chemical properties. There are significant relationships between mineral content–chemical properties and between mineral content-wood density (except Cu - density). Forward stepwise regression showed that ash and lignin content had important role on the variation of all of mineral content except on Cd.

The purpose of the biomass torrefaction and pelletizing processes is to increase its energy properties, be environmentally friendly, decrease shipping costs, and make handling easier. The objective of the present work is to evaluate the density, internal density variation by X-ray densitometry, moisture content, water absorption, and compression force of torrefied biomass pellets of five wood species (Cupressus lusitanica, Dipterix panamensis, Gmelina arborea, Tectona grandis, and Vochysia ferruginea) under three torrefaction temperature conditions (light, middle, and severe) and three torrefaction times (8, 10, and 12 min). The results showed that the bulk density of the pellets was 0.90–1.30 g/cm3. The density variation of the pellets was higher with torrefaction at 250 °C. The moisture content decreased with increasing torrefaction temperature from 3% to 1%. Water absorption was lower in the pellets torrefied at 250 °C. The compression force was lower in the pellets torrefied at 250 °C with approximate loads of 700 N. Based on the above results, it was concluded that pellets made with biomass torrefied at 200 °C have better energy properties and evaluated properties. According to these results, pellets fabricated with the torrefied biomass of tropical species can be used in stove, gas, and hydrogen production because the pellet presents adequate characteristics.

Resumen En la búsqueda de elementos estructurales versátiles y eficientes se genera el interés de construir vigas laminadas con plywood de melina (Gmelina arborea) y alas de bambú (Guada angustifolia) laminado encolado, para utilizarlas principalmente en vivienda. En este estudio se analizaron vigas de sección I con alas de bambú laminado encolado y alma de plywood de melina con un peralte de 18,5 cm de altura. Las vigas fueron ensayadas en tamaño natural en flexión estática y cortante. Los resultados mostraron que el módulo de ruptura en flexión promedio de 39,45 MPa y el módulo de elasticidad promedio 17,05 GPa. En la prueba en cortante se encontró que el esfuerzo en la línea de cola fue de 5,95 MPa y en el esfuerzo laminar fue de 6,45 MPa. En relación con los esfuerzos de diseño se determinó que esfuerzo a flexión es de 94,28 kg/cm2 y a cortante de 47,2 kg/cm2. Finalmente, al derivar las tablas de longitud permisibles para usar las vigas en usos de entrepisos o techo, se encontró que estas longitudes pueden variar de 2,6 m a 3,7 m en el caso de entrepisos y de 5 a 7 metros en techos. Abstract The search for efficient and versatile structural elements, leads the interest to fabricate I-joist (6.5 cm × 18.5 cm × 600 cm (width × depth x length) with glue bamboo (Guada angustifolia) in the flanges and Gmelina arborea 12-mm structural plywood in the web. The results showed a modulus of rupture (MOR) of 39. 45 MPa and a modulus of elasticity (MOE) of 17.05 GPa. Shearing in glue line was 5.95 MPa and in laminated strength of 6.45 MPa. Structural design values averaged 9.43 MPa in the bending test and 4.72 MPa in the shear stress according to Costa Rican structural standards. Both resistance value (flexure and shear) was considered satisfactory for structural proposes and I-joist fabricated with bamboo and G. arborea plywood can be compared with “C” structural grade Andean classification group. The use of this I-joist was also shown in roofing and flooring systems. And this beam produce optimum allowable span for the market, from 2 to 7 m in span for roofing systems and from 5 to 7 m for roofing application.

The effect of three levels thinning intensity in Gmelina arborea plantation on tree diameter, heartwood (diameter and percentage), wood density and drying defects (twist, crook, bow and check) was studied. Wood used for this study was obtained from eight-year-old plantations with thinning intensity of 60, 70 and 80% of initial density. Nine trees were selected from each trial. Results showed that tree diameter and wood density were similar in thinning intensity of 70 and 80%, but tree diameter from the plantation with 60% of thinning intensity was lower than plantation of 70 and 80%. Wood density of trees from 60% thinning intensity plantation was higher than 70 and 80%. Heartwood diameter and its percentage were the highest in 80% of thinning intensity. But not difference was found between 60 and 70% in heartwood (diameter and percentage). Finally, drying defects were not affected significantly by thinning intensity.

ABSTRACT Research and implementation of energy crops using short-rotation woody species (SRWC) are increasing in Latin America, especially for biomass production and use in bioenergy. For this purpose, one of the main factors to consider is species assessment. Therefore, the objective of the present study was to evaluate the growth characteristics, the production and distribution of biomass, and the chemical, physical, and energetic properties of the biomass of three-year-old Dipteryx panamensis plantations in SRWC in three different spacings (1.0x2.0 m, 1.0x0.5 m and 1.0x1.0 m) and establish the best spacing condition for this tropical species. The results showed that the production of biomass varies between 1.1 and 42.36 t.ha-1, and that 33-44% of the production are concentrated in the leaves. At three years, the SRWC presented 50% mortality, with a diameter of 4.8 cm at 30 cm-height from the ground, with total tree heights ranging from 5.17 to 6.98 meters. The evaluation of the biomass showed a calorific value between 18.9 and 19.4 MJ/kg, less than 1.81% of ash content and 86% of volatile content. As for the effect of the spacing, the green density of the wood and the moisture content increased with increasing spacing, while spacings of 1.0x1.0 m and 1.0x0.5 m showed the best behaviour regarding annual biomass production.

Dendrocalamus asper (Schult. & Schult.f.) Backer and Guadua angustifolia Kunth are cultivated in Costa Rica for their commercial benefits, and their application in different constructions projects. G. angustifolia has two varieties: the Caribe and the South varieties. Existing knowledge of the variation in culm properties of these two varieties and the differences between the two species is limited. The main objective of this study was to evaluate the physical and mechanical properties of G. angustifolia varieties and D. asper planted at various heights at the same site in the Atlantic Region of Costa Rica. Some properties exhibited statistical differences between species, but almost no properties of the two varieties of G. angustifolia differed significantly. D. asper exhibited the highest levels of moisture content, specific gravity, density, parameters of flexion test, tension stress, diameter, area and frequency of bundles specifically from base to 25% of height, although beyond this height, no significant differences were observed between species. Regarding the two varieties of G. angustifolia, external and internal diameters, wall thickness culm, moisture content, specific gravity, density, parameters of flexion test, tension stress, diameter, area, and frequency of bundles showed no statistical differences. These results indicate that the differences observed in the two varieties of G. angustifolia may be attributable to the adaptation of the species to distinct soil and climate conditions for growth. When the two varieties were planted at the same site, no differences were observed.

Costa Rica produces a considerable, important quantity of wood residues. This waste can be pyrolyzed to produce charcoals as main products that can be effectively used as an energy source or to immobilize carbon for soil treatment. However, there is a lack of information about the pyrogenic carbonaceous materials (PCMs), such as charcoal or biochar, obtained at different pyrolysis temperatures. Hence, this study aimed to evaluate the quality of PCMs (physical, mechanical, ultimate analysis, and FTIR analysis) and charcoal characteristics (energetic properties and thermogravimetric analysis—TGA) and biochar characteristics (conductivity, pH, initial contact angle, and wetting rates) for four tropical wood residues produced in five temperatures (300 °C, 350 °C, 400 °C, 450 °C, and 500 °C). In general, pyrolysis temperature between 450 °C and 500 °C produced charcoals with lower values of density, moisture content, compression strength, volatiles, H and O content, and higher values of C and ash contents, conductivity, pH, initial contact angle, and wetting rates. FTIR and TGA analyses show that celluloses and lignin are pyrolyzed at these temperatures, so these temperatures are recommended. The range of 300–350 °C is not recommended, as these parameters were inverse. Multivariate analysis shows that (i) PCMs obtained at lower temperatures (300–350 °C) from Dipteryx panamensis, Hieronyma alchorneoides, and Tectona grandis belong to a cluster with poorer properties, indicating that these temperatures are not adequate for pyrolysis of these species; (ii) all the PCMs obtained from Gmelina arborea were grouped into one cluster, suggesting different PCM quality; and (iii) the PCMs produced from D. panamensis, H. alchorneoides, and T. grandis at 400–500 °C were grouped into another cluster with better properties, suggesting this pyrolysis temperature range as the best for these species.

Dipteryx panamensis and Hieronyma alchorneoides are two species of high specific gravity used in reforestation programs in Costa Rica, but they lack products with structural value for commercialization. In order to introduce the wood of these two species in the market, the objective was established to study the behavior of solid timber beams and glued laminated timber beams of two cross sections (2 cm × 10 cm and 2 cm × 15 cm) and establish the design values in bending test. The results showed that the bending design values (fb) ranged from 2 to 26 MPa in glued laminated timber beams, while in solid timber beams, fb ranged from 6 to 15 MPa. In the shear design values (fv), the variation was from 0.29 to 0.67 MPa in glue laminated timber beams and from 1.80 to 2.58 MPa in solid timber beams. It was also found that the D. panamensis beams showed higher values than H. alchornoides beams. Finally, it was established that glued laminated timber beams showed better performance in bending parameters and higher design values, resulting in wider span values, than solid timber beams when used in floor and roof construction.

Pineapple leaf fibers (PALF) were biopulped using Trametes versicolor, and the resulting biopulp was bleached with xylanase-enzymatic treatments. The biopulping was extensively described using determinations of fiber morphology, color, chemical composition, extractive content, and thermal stability using the structural characteristics determined by XRD and paper properties. The results showed that the chemical and enzymatic treatments shortened the fiber, almost to 50%, and the Kappa index decreased from 27 to 13. Cellulose and holocellulose contents increased from 65% to 74% and from 86% to 91%, respectively, but extractives, lignin (from 12% to 4%), pentosans (from 25% to 14%) and the crystallinity decreased from 58% to 67% in both chemical bleaching and further xylanase-enzymatic processing. Xylanase-enzymatic processing allowed us to obtain whiter (increased lightness color and decreased redness and yellowness tonality) and heavier paper, even though it presented decreased mechanical properties (decreased stress resistance, rupture length, tear resistance and index longitudinal tearing). The xylanase-enzymatic treatment with the best pulping and paper properties is when the biopulp is treated with a xylanase enzyme concentration of 0.04% (w/w).

Abstract 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%, with Vochysia ferruginea species showing the highest WPG, and Gmelina arborea and Tectona grandis species exhibiting the lowest WPGs. Tropical woods such as Enterolobium cyclocarpum, Hieronyma alchorneoides and Samanea saman exhibited 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−1 and 1228 cm−1 peaks 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−1 and 1034 cm−1 peaks, 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.

Biochar from agroforestry biomass residues is an alternative source of fertilizers for improving the soil fertility. In Costa Rica, Cedrela odorata is planted in pure plantations and agroforestry systems and different types of substrates are used in the nursery to enhance the growth and performance of the young saplings. The main objective of the present study was to evaluate the growth (in height, diameter, biomass) and distribution of carbon (C), hydrogen (H), and nitrogen (N) for C. odorata plants in a nursery with different application rates of biochar produced from Tectona grandis wood residues. The results showed that the above-measured variables were statistically affected by different application rates of the biochar. The stem diameter, total height, number of leaves, and height increment were statistically significantly higher in the substrate with an application rate of 25–50 tons/ha, in contrast to the 0 and 75 tons/ha application rates, which were statistically the lowest. As for the levels of C, H, and N, there were differences, with the highest values of N and C being in the leaves and stem with the 50 tons/ha application rate and the highest values of H for the 75 tons/ha application rate. The above results showed that applying biochar obtained from T. grandis residues improved soil conditions, resulting in better growth of C. odorata saplings with an application rate of 25 and 50 tons/ha.

Abstract   Gmelina arborea is one of the most important species for plantation in tropical areas. However, high variability in final moisture content (MCf) is a problem in the drying process. This study sought to determine the variability in MCf in relation to distance from the pith (DP), and anatomic elements. Boards of 1.2 cm in thickness obtained from bark to the pith from 15-year-old plantation trees were dried in a pilot kiln. Anatomical characteristics, initial moisture content (MCi), and specific gravity (SG) were also determined. Pearson correlation matrix was conducted between MCf and the other variables. DP, fiber length, and ray width were correlated negatively with MCf, while fiber diameter was positively correlated. Other studied anatomical properties showed no statistical correlations. Other wood properties such as SG and MCi showed some influence on MCf. DP can be considered as a good practical predictor for MCf in G. arborea because some wood properties are related to MCf. However, other wood characteristics that are not related with DP also influence MCf, such as the presence of sapwood, MCi variation between and within trees, fiber diameter, and ray width. These results suggest that MCf variation in G. arborea is difficult to determine. [ABSTRACT FROM AUTHOR]

La gasificación es un proceso termoquímico en el que materias primas orgánicas se convierten en gases que contienen H2 y CO (gas de síntesis), los cuales pueden utilizarse para obtener productos como electricidad, combustibles y otras sustancias químicas. El proceso se encuentra influenciado por características propias del sistema donde se desarrolla la conversión térmica, las condiciones de operación y las materias primas empleadas. Se simuló un proceso de gasificación de biomasas enriquecidas con hidrocarburos en el que los gases generados son aprovechados para generación eléctrica, con tal de evaluar el uso de dichas materias primas. Se empleó un modelo de gasificación no estequiométrico, la ecuación de estado de Peng-Robinson, así como reacciones de gasificación conocidas. Se consideró un gasificador de corriente descendente trabajando con 22 kg/h de alimentación de mezcla 3:1 biomasa:hidrocarburos, 20 kg/h de aire (agente gasificante), 1 atm de presión absoluta y temperatura de gasificación de 900-1000°C. Los gases generados se componen de 27,44 % H2; 39,79 % CO; 5,73 % CH4; 0,1 % CO2 y 27,01 % N2. La potencia neta del gasificador es 27,82 kW y el consumo de la mezcla 3:1 biomasa:hidrocarburos 0,79 kg/kWh. La adición de hidrocarburos a biomasa mejora las características del gas de síntesis obtenido y disminuye los requerimientos de materia prima para el funcionamiento del gasificador. La mezcla 3:1 biomasa:hidrocarburos es adecuada para el desempeño del proceso, permitiendo aprovechar residuos que de otra manera tendrían que ser dispuestos y tratados, generando beneficios energéticos, ambientales y económicos.

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.

• The wood formation appears to be more affected by growth site than rainfall reduction. • Our findings indicated that there was a difference in performance as to growth and hydraulic adjustments between eucalyptus species. • E. urophylla (A1) was productive clone with respect to volume and radial growth under water restriction. • The xylem of E. grandi s × E. camaldulensis (C3) had greater hydraulic adjustments compared to E. urophylla. The increase in global temperature results in changes in rainfall patterns and can cause structural and functional changes in trees. Each plant is forced to face hydraulic safety limits and adopt a behavior to regulate its water status. The objective of this work was to evaluate the changes in the hydraulic architecture of the xylem of commercial eucalyptus clones in order to distinguish the hydraulic adjustments in a wide gradient of water availability. Eucalyptus urophylla (A1) and E. grandis × E. camaldulensis (C3) clones at six years old at 4 sites in Brazil distributed in a rainfall gradient and in two water conditions were analyzed: control (100% of total local rainfall) and rainfall reduction (RR). Xylem traits were evaluated at annual intervals and averaged over the entire growth period of the seven trees sampled at each site and water condition. The sites influenced the clones, with the greatest effect being the rainfall reduction treatment in C3 on the vessel wall diameter, area and thickness, double wall thickness, conduction area, vessel composition index, theoretical and potential hydraulic conductivities, vessel implosion resistance and vulnerability. The rainfall reduction provided an increase of 12% in vessel density, 8% in the double vessel wall, and 27% in theoretical hydraulic conductivity in the drought-tolerant C3 clone. The vessel wall thickness in the A1 clone was more responsive with a 3% increase in rainfall reduction, with an effect on double-wall thickness and vessel implosion resistance. Other hydraulic adjustment strategies were observed, such as the highest occurrence of tylose and a tradeoff between vessel diameter and frequency for the C3 clone. The greater variation in wood density was explained by variations in the lumen area of the xylem vessels and by vessel implosion resistance. [ABSTRACT FROM AUTHOR]

Studies related to biomass production, with a focus on energy uses for short-rotation woody crops (SRWCs), are limited in Latin America. The research that is available relates to a variety of tested SRWC species (50 species), however, the most important species are Populus, Salix, Eucalyptus, Acacia, and Gmelina arborea. In the existing studies, stocking densities varied from 1111 to 20,000 trees per hectare, with square or rectangular spacing. One important advantage of SRWC systems in this region, compared to most regions worldwide, is the predictability of biomass yields due to the tropical climate conditions of the majority of the Latin American countries. Rotations of three and four years can be projected to produce total biomass yields of 30⁻50 tons/ha, with increments of 10⁻20 tons/ha/yr. Fertilization is performed in SRWC with the aim of preventing soil degradation and maintaining further production. In regards to possible uses of biofuel generated from SRWC in Latin America, an inconvenience is that there are neither well-established harvesting systems nor conventional pre-treatments to process the biomass. Processes that are available in the region that use biomass from SRWC for energy production are gasification and pellet production. Other potential biofuel processes, such as torrefaction and biochemical conversion, are limited in this area.

A total of 45 native Costa Rican tree species are threatened or in danger of extinction, but the Convention on International Trade Endangered Species (CITES) includes only eight of these in its Appendices. However, the identification of other species based on their wood anatomy is limited. The present study objective was to describe and to compare wood anatomy and fluorescence activity in some endangered or threatened species of Costa Rica. A total of 45 (22 endangered and 23 threatened with extinction) wood samples of these species, from the xylaria of the Instituto Tecnológico de Costa Rica and the Forest Products Laboratory in Madison, Wisconsin, were examined. Surface fluorescence was positive in eight species, water extract fluorescence was positive in six species and ethanol extract fluorescence was positive in 24 species. Almost all species were diffuse porous except for occasional (Cedrela odorata, C. fissilis, Cordia gerascanthus) or regular (C. salvadorensis and C. tonduzii) semi-ring porosity. A dendritic vessel arrangement was found in Sideroxylon capari, and pores were solitary in Guaiacum sanctum and Vantanea barbourii. Vessel element length was shortest in Guaiacum sanctum and longest in Humiriastrum guianensis, Minquartia guianensis and Vantanea barbourii. Finally, anatomical information and fluorescence activity were utilized to construct an identification key of species, in which fluorescence is a feature used in identification.

En los procesos de transformación y aserrío de la madera se generan residuos que pueden usarse como fuentes de materia prima para la producción de pellets. El objetivo de este trabajo fue evaluar la eficiencia, la calidad por imágenes de rayos X y las propiedades energéticas, físicas y mecánicas de pellets fabricados con residuos obtenidos del procesamiento de trozas de Cupressus lusitanica y Tectona grandis. Los resultados indicaron un porcentaje de eficiencia bajo para ambas especies forestales, con 25% para C. lusitanica y 20% para T. grandis. En la evaluación de calidad, los pellets de C. lusitanica se caracterizaron por poseer zonas de mayor claridad y pocas fisuras de corto tamaño en su superficie, mientras que en los de T. grandis se presenta un mayor número de zonas de mayor claridad, además de mostrar fisuras de mayor profundidad y largo. En relación con las propiedades evaluadas, se encontró que los pellets de T. grandis tienen una menor densidad aparente, menor PC, menor resistencia a la compresión y menor uniformidad en la densidad de su superficie y un porcentaje de cenizas, CH y durabilidad mecánica mayor, al compararlos con los de C. lusitanica.

In Costa Rica, there has been a growing interest to use pineapple fiber from plant, for which current processes need to be improved or new processes need to be developed, with emphasis on drying methods. This work presents the design and evaluation of the behavior of a prototype portable solar dryer in four sites of Costa Rica. The design describes the main parts of the dryer, as well as how they were constructed. The behavior was evaluated according to temperature and relative humidity inside e outside the chamber, and the influence of direct and indirect solar radiation. In order to achieve improved dryer efficiency, a dehumidifier was used to control relative humidity, and a heating system was implemented during the hours of low temperature, low solar radiation and high relative humidity. Based on drying time, final moisture content of fibers of pineapple leaves from plant, and the varying hours when fibers were put to dry, the evaluation of the dryer revealed that the best fiber-drying interval is from 6h00 to 14h00, and after that, it is convenient to inject hot air and use a dehumidifier in the dryer in order to increase its efficiency.Na Costa Rica, o interesse pelo uso da fibra proveniente da folha de abacaxizeiro. Tem almentado e essa atividade precisa de melhoramento ou implementação de novos processos para alcançar maior eficiência, principalmente na secagem da fibra. O presente trabalho apresenta o design e comportamento de uma protótipo portátil de secadora solar em 4 sites geográficos da Costa Rica. Estão descritas as principais partes do secador, bem como a metodologia de construção. O comportamento foi avaliado de acordo com a temperatura e umidade relativa interna e externa da câmara e a influencia da radiação direta e indireta. Com a finalidade de melhorar a eficiência da secadora, foi usado um desumidificador para controlar a umidade relativa e ainda um sistema de aquecimento durante as horas de baixa temperatura e baixa radiação solar e nos períodos de alta umidade relativa. Foram avaliados o tempo de secagem, o teor de umidade final das fibras e a variação das horas que as fibras são colocadas no secador. O intervalo do dia onde apresenta as melhores condições para secagem é de 6h até 14h. Após essa hora, é conveniente acrescentar ar quente e/ou desumidificador dentro do secador para aumentar sua eficiência.

The heterogeneity of color distribution between sapwood and heartwood limits the market for wood from fast-growth plantations of tropical species. Wood color is associated with wood extractives contents. This study presents the relationship between wood color parameters measured by the CIELab color system and total amount of extractives and phenolic-type extractives in ethanol-toluene and hot water extracts of wood from two fast-growth plantation species. The results demonstrated that the difference in sapwood and hardwood color in Vochysia guatemalensis and Acacia mangium is caused by lower concentrations of extractives in sapwood of both species. Additionally, variations in total extractive and phenolic content have different effects on the color parameters (L*, a* and b*) of both species studied. In Vochysia guatemalensis wood, parameter L* decreases as total extractive and phenolic content increases; however, parameter a* increases as the content of extractives and phenols increases. In Acacia mangium, the amount of phenols showed no relationship with the color parameters. The ethanol-toluene total extractive content, however, shows a relationship with several color parameters. An increase in the content of total extractives in water and ethanol-toluene increases parameter a*, but decreases parameter L*.

La madera de Vochysia guatemalensis Donn Sm. actualmente se obtiene de plantaciones forestales en diversas regiones de Costa Rica. La alta variabilidad en el contenido de humedad final (CHf) y la alta incidencia de defectos presentes en el proceso de secado constituyen la principal problemática de esta madera. Se investigaron las causas de estos problemas, al tomar en cuenta factores como el clima o procedencia de la madera, el patrón de corte aplicado en el aserrío, el tipo de programa de secado utilizado, la posición radial de la tabla en la troza (distancia de la médula) y la presencia de albura o duramen. Se concluyó que las causas principales de esta variación y del desarrollo de estos defectos son: la alta variabilidad en el contenido de humedad inicial de la madera, la procedencia y los programas de secado inapropiados. Así mismo, se proponen una serie de recomendaciones a considerar antes de iniciar el secado para de esta manera lograr una mejor calidad de madera en cuanto al CHf y la presencia de defectos.

Estudou-se o efeito das propriedades físicas e químicas do solo em algumas propriedades da madeira de Tectona grandis oriundas de plantações entre 7 e 15 anos de idade, localizadas nas regiões Norte e Noroeste da Costa Rica, as quais apresentam dois tipos de clima (tropical seco e tropical úmido) e com grande variedade de fertilidade de solo. As análises do solo consistiram no estudo de suas propriedades físicas (porcentagem de argila, limo e areia, densidade aparente, porcentagem de retenção de água e de água útil, retenção 15 Bar e 0,33 Bar) e propriedades químicas (pH, acidez e conteúdo de Ca, Mg, K, P, Zn, Cu, Fe e Mn). As contrações tangenciais e radiais foram as propriedades da madeira mais correlacionadas com as características do solo, seguidas da porcentagem de cerne, medula e casca e teor de umidade na condição verde. A propriedade de menor correlação foi a densidade básica, enquanto a contração volumétrica não foi correlacionada com nenhuma propriedade do solo. Os coeficientes de correlação foram altamente significativos (a = 0,05), embora baixos valores (

We evaluated the thermogravimetric and devolatilization rates of hemicellulose and cellulose, and the calorimetric behavior of the torrefied biomass, of five tropical woody species (Cupressus lusitanica, Dipteryx panamensis, Gmelina arborea, Tectona grandis and Vochysia ferruginea), at three temperatures (TT) and three torrefaction times (tT) using a thermogravimetric analyzer. Through a multivariate analysis of principal components (MAPC), the most appropriate torrefaction conditions for the different types of woody biomass were identified. The thermogravimetric analysis-derivative thermogravimetry (TGA-DTG) analysis showed that a higher percentage of the hemicellulose component of the biomass degrades, followed by cellulose, so that the hemicellulose energy of activation (Ea) was less than that of cellulose. With an increase in TT and tT, the Ea for hemicellulose decreased but increased for cellulose. The calorimetric analyses showed that hemicellulose is the least stable component in the torrefied biomass under severe torrefaction conditions, and cellulose is more thermally stable in torrefied biomass. From the MAPC results, the best torrefaction conditions for calorimetric analyses were at 200 and 225 °C after 8, 10, and 12 min, for light and middle torrefaction, respectively, for the five woody species.

Cedrela odorata y Carapa guianensis son maderas utilizadas para la elaboración de muebles, puertas e inmobiliario de casas en Costa Rica. Así mismo, dos tipos de acabados (tipo nitrocelulosa y de poliuretano) son muy utilizados en estas maderas. No obstante, los cambios en los parámetros del color (CIE L∗a∗b∗) por el intemperismo es poco conocido para estas especies y estos acabados. Al evaluar estos acabados ante el intemperismo se encontró que el acabado con poliuretano y nitrocelulasa producen cambios en la coloración de la madera apreciables en los primeros 40-60 días de exposición a la intemperie y este cambio del color fue diferente en cada acabado. Además, los resultados mostraron que en C. guianensis los cambios medido por ∆E∗ de color fueron inferiores a los obtenidos en la C. odorata en los dos acabados con el tiempo y que estos a su vez son inferiores si no se aplica ningún tipo de acabado. Finalmente fue encontrado que las relaciones de los parámetros de color (L∗, a∗, c∗) y la relación entre los mismo parámetros (L∗-a∗, L∗-b∗ y a∗-b∗) son alterados ante la intemperie por la aplicación de los acabados.Carapa guianensis and Cedrela odorata wood are used for furniture and doors manufacturing in Costa Rica. Similarly, two kind wood coatings (nitrocellulose and polyurethane) are widely used in these manufactures. However, the effects of degradation in the components of color (CIE L∗ a∗ b∗) of these coatings by the weathering is little known for these wood species and these coatings. It was evaluated these coatings under weathering and it was found that surface painted with polyurethane and nitrocellulose produced significant change in wood color during the first 40-60 days of weathering and the intensity of color change was different in two coatings. The results showed that color changes in Carapa guianensis wood were lower measured by ∆E∗ than Cedrela odorata wood in two coating of surface treatments. Finally, it was found that there are relationships among wood color parameters (L∗, a∗, c∗) with weathering time and the relationship between color parameters (L∗- a∗, L∗- b∗ and a∗- b∗) are altered by the coatings.

Vochysia guatemalensis has been planted over large tropical areas to obtain lumber products. However, compared with naturally-grown material variations in wood color have been noted. In the current research, trees from two 8-year-old fast-grown plantations were sampled from different climatic conditions in order to identify the causes of color variation. The study evaluated the heartwood presence, grain pattern, distance from pith, height within the tree, and effect of drying schedules. The wood color was measured by CIEL*a*b* systems.Wood color of Vochysia guatemalensis is a combination of different tonalities of lightness (L*), redness (a*), and yellowness (b*), however, the lightness and yellowness components were the dominant tones. The color of heartwood and sapwood were different before and after drying. A negative relationship was found between a* and L*, and a* and b* in the undried state, but no relationship was found between L* and b*. The L* index is only correlated with heartwood presence in undried wood. In dried wood, only a relationship between a* and L* is maintained, while other color parameters were affected by climate, drying schedule and heartwood presence, the L* parameter being the most affected. The dried wood displays a lighter surface than the wood before drying. The variations in the dried wood suggest that it is useful to establish dried lots of lumber according to the drying schedule, source and presence of sapwood and heartwood.La especie Vochysia guatemalensis ha sido plantada sobre largas áreas en regiones tropicales. Así mismo, han sido observadas grandes variaciones del color de su madera. En la investigación fueron muestreadas plantaciones de 8 años de edad en diferentes condiciones de clima con el fin de establecer las causes de variación de la madera. Fueron evaluadas la presencia de duramen, el patrón de aserrío, la distancia de la medula y el programa de secado. El color fue medido por el sistema CIELab. Fue encontrado que la madera de V. guatemalensis presenta una combinación de tonalidades de claros (L*), rojos (a*) y amarrillos (b*), siendo los colores claros y amarrillos los tonos dominantes. El color del duramen y la albura fueron diferentes antes y después del secado. Una negativa correlación entre a* y L*, y a* y b* fue encontrada, pero ninguna correlación fue observada entre L* y b*. El índice L* fue el único parámetro correlacionado con el duramen en madera verde. En la madera seca, solamente se mantuvo la relación a* y L*, mientras que los parámetros del color fueron afectados por el clima, programa de secado y duramen, siendo L* el más afectado. La madera seca presentó una superficie más clara que la madera antes del secado. Las variaciones en madera seca sugieren la conveniencia de establecer lotes de secado de acuerdo al programa de secado aplicado, procedencia y presencia de albura y duramen.

The tree Gmelina arborea has been widely introduced in Costa Rica for commercial purposes. This new conditions for melina cause variations on anatomy in secondary xylem of the trees growing in plantations. The objective of the present research was to determine the variation in the anatomy of xylem caused by the ecological conduction variation. Dimensions of fiber, axial parenchyma percentage of cross sections, parameters of vessels and the ray were measured. The results showed that some anatomical characteristics remained stable despite variations of ecological conditions, especially radial parenchyma and anatomical features which were less affected by the altitude. On the other hand, the vessels, axial parenchyma and fiber were less stable because they were affected significantly by the longitude, latitude, altitude and precipitation. Latitude significantly affected vessel percentage, length and diameter of the fiber and lumen. Longitude affected vessel percentage and fiber diameter. Altitude had a significant correlation with the amount of cells at ray height. Annual average precipitation affected vessel percentage and diameter, not only of the fiber, but also of the lumen. These results suggest that the new growth conditions of G. arborea trees in Costa Rica have produced an anatomic adaptation. Rev. Biol. Trop. 56 (2): 689-704. Epub 2008 June 30.Gmelina arborea ha sido introducida y ampliamente sembrada en Costa Rica en plantaciones de rápido crecimiento. Estas nuevas condiciones ecológicas provocan variación en la anatomía del xilema de estos árboles. El presente trabajo tuvo como objetivo determinar la variación en la anatomía del xilema debido a la variación de la latitud, longitud, altitud y precipitación. Se evaluaron las dimensiones de las fibras, el porcentaje de área ocupada por el parénquima y los parámetros de los vasos y los radios. Algunas características anatómicas se mantuvieron estables con las variaciones de las condiciones ecológicas evaluadas, especialmente el parénquima radial. La altitud es la condición ecológica con menor afecto en la anatomía de la madera. Los vasos, el parénquima axial y las fibras fueron menos estables debido a que fueron afectados significativamente por la longitud, latitud, altitud y precipitación. La latitud afectó significativamente el porcentaje de vasos, porcentaje de radios, largo y diámetro de la fibra y diámetro del lumen; la longitud afectó el porcentaje de vasos y el diámetro de la fibra; la altitud únicamente mostró relación significativa con la cantidad de células en la altura de los radios. La precipitación media anual mostró efectos sobre el porcentaje de poros y el diámetro de la fibra y el lumen. Dichos resultados sugieren que las condiciones de crecimiento en Costa Rica para G. arborea son indicadores de un posible genotipo del árbol.

Este trabajo presenta los efectos de la fertilización de la pradera en árboles de Pinus radiata en la resistencia mecánica a la flexión estática. Los árboles muestreados provenían de 2 ensayos silvopastorales de 16 años de edad con igual cantidad y frecuencia de podas y raleos, pero con la diferencia que en uno de ellos, la pradera se fertilizó y en el otro no se aplicó el fertilizante. En el ensayo fertilizado fue realizada esta actividad en 3 diferentes edades de árboles (3, 6 y 11 años). En cada uno de los rodales se evaluaron los diferentes estratos: dominantes, intermedios y suprimidos, seleccionando 3 árboles al azar de cada clase, dando como resultado 9 árboles por cada ensayo. De cada árbol se obtuvo una troza entre la base del árbol y el diámetro a la altura del pecho (DAP). Los resultados mostraron que la fertilización de la pradera produce una disminución del módulo de elasticidad, del módulo de ruptura y del esfuerzo en el límite de proporcionalidad en la madera de Pinus radiata. La disminución para estos parámetros se encuentra dentro de un rango de 8% a 16%. Por otro lado, en los diferentes estratos del rodal se estableció que los árboles suprimidos son menos afectados por la fertilización, mientras que los árboles intermedios y dominantes en las diferentes edades de fertilización presentaron una disminución de los parámetros de resistencia a la flexión, específicamente el módulo de ruptura, el módulo de elasticidad y el esfuerzo en el límite de proporcionalidadThis study presents the effects of pasture fertilization on static bending of Pinus radiata. Sampled trees came from two silvopastoril trials of 16 years of age, presenting same amount and frequency of thinning and pruning interventions. One trial was fertilized; the other received no fertilization to the prairie. The first trail was fertilized at ages of 3, 6 and 11 years. On each stand three different strata were evaluated: dominant, intermediate, and suppressed trees. selecting 3 individuals randomly on each class. One stern log from the base to the DBH was cut from each tree. Results show that fertilization reduces the module of elasticity, the module of rupture and the stress proportional limit of Pinus radiata wood in the next three years after fertilization. The reductions on these parameters varied between 8 and 16%. Suppressed trees were less affected by fertilization, while intermediate and dominant trees presented a clear reduction in bending resistance, module of rupture, module of elasticity, and stress proportional limit

Vochysia guatemalensis has been planted over large tropical areas to obtain lumber products. However, compared with naturally-grown material variations in wood color have been noted. In the current research, trees from two 8-year-old fast-grown plantations were sampled from different climatic conditions in order to identify the causes of color variation. The study evaluated the heartwood presence, grain pattern, distance from pith, height within the tree, and effect of drying schedules. The wood color was measured by CIEL*a*b* systems. Wood color of Vochysia guatemalensis is a combination of different tonalities of lightness (L*), redness (a*), and yellowness (b*), however, the lightness and yellowness components were the dominant tones. The color of heartwood and sapwood were different before and after drying. A negative relationship was found between a* and L*, and a* and b* in the undried state, but no relationship was found between L* and b*. The L* index is only correlated with heartwood presence in undried wood. In dried wood, only a relationship between a* and L* is maintained, while other color parameters were affected by climate, drying schedule and heartwood presence, the L* parameter being the most affected. The dried wood displays a lighter surface than the wood before drying. The variations in the dried wood suggest that it is useful to establish dried lots of lumber according to the drying schedule, source and presence of sapwood and heartwood. La especie Vochysia guatemalensis ha sido plantada sobre largas áreas en regiones tropicales. Así mismo, han sido observadas grandes variaciones del color de su madera. En la investigación fueron muestreadas plantaciones de 8 años de edad en diferentes condiciones de clima con el fin de establecer las causes de variación de la madera. Fueron evaluadas la presencia de duramen, el patrón de aserrío, la distancia de la medula y el programa de secado. El color fue medido por el sistema CIELab. Fue encontrado que la madera de V. guatemalensis presenta una combinación de tonalidades de claros (L*), rojos (a*) y amarrillos (b*), siendo los colores claros y amarrillos los tonos dominantes. El color del duramen y la albura fueron diferentes antes y después del secado. Una negativa correlación entre a* y L*, y a* y b* fue encontrada, pero ninguna correlación fue observada entre L* y b* . El índice L* fue el único parámetro correlacionado con el duramen en madera verde. En la madera seca, solamente se mantuvo la relación a* y L*, mientras que los parámetros del color fueron afectados por el clima, programa de secado y duramen, siendo L* el más afectado. La madera seca presentó una superficie más clara que la madera antes del secado. Las variaciones en madera seca sugieren la conveniencia de establecer lotes de secado de acuerdo al programa de secado aplicado, procedencia y presencia de albura y duramen.

Cedrela odorata y Carapa guianensis son maderas utilizadas para la elaboración de muebles, puertas e inmobiliario de casas en Costa Rica. Así mismo, dos tipos de acabados (tipo nitrocelulosa y de poliuretano) son muy utilizados en estas maderas. No obstante, los cambios en los parámetros del color (CIE L*a*b*) por el intemperismo es poco conocido para estas especies y estos acabados. Al evaluar estos acabados ante el intemperismo se encontró que el acabado con poliuretano y nitrocelulasa producen cambios en la coloración de la madera apreciables en los primeros 40-60 días de exposición a la interperie y este cambio del color fue diferente en cada acabado. Ademas, los resultados mostraron que en C. guianensis los cambios medido por ΔE* de color fueron inferiores a los obtenidos en la C. odorata en los dos acabados con el tiempo y que estos a su vez son inferiores si no se aplica ningún tipo de acabado. Finalmente fue encontrado que las relaciones de los parámetros de color (L*, a*, c*) y la relación entre los mismo parámetros (L*-a*, L*-b* y a*-b*) son alterados ante la intemperie por la aplicación de los acabados. Abstract Carapa guianensis and Cedrela odorata wood are used for furniture and doors manufacturing in Costa Rica. Similarly, two kind wood coatings (nitrocellulose and polyurethane) are widely used in these manufactures. However, the effects of degradation in the components of color (CIE L* a* b*) of these coatings by the weathering is little known for these wood species and these coatings. It was evaluated these coatings under weathering and it was found that surface painted with polyurethane and nitrocellulose produced significant change in wood color during the first 40-60 days of weathering and the intensity of color change was different in two coatings. The results showed that color changes in Carapa guianensis wood were lower measured by ΔE* than Cedrela odorata wood in two coating of surface treatments. Finally, it was found that there are relationships among wood color parameters (L*, a*, c*) with weathering time and the relationship between color parameters (L*- a*, L*- b* and a*- b*) are altered by the coatings.

En años recientes, el mercado de la madera en Costa Rica ha sido abastecido por especies de plantaciones forestales de rápido crecimiento. No obstante, aún se presentan vacíos en el diseño y comercialización de productos de alto desarrollo tecnológico. Con el propósito de introducir las maderas de plantación en el mercado, se estableció como objetivo determinar los esfuerzos de diseño (esfuerzo en flexión, cortante y la rigidez a flexión) de vigas tipo I construidas con madera de Gmelina arborea, utilizando madera sólida en las zapatas y plywood de 12 mm en el alma. Se desarrollaron tres tipos de perfiles (24, 16 y 10 cm de alto) y dos tipos de calidades (A y B). Los resultados mostraron que los esfuerzos de diseño variaron de 60 a 147 kg/cm2 en el esfuerzo en flexión y de 42 a 92 kg/ cm2 en el esfuerzo en cortante. Las vigas de 10 cm y de calidad A presentaron los esfuerzos más altos en flexión y cortante, seguidos por las vigas de 24 cm y 16 cm. Con respecto a la rigidez a flexión, las vigas perfil 24 son las que poseen el valor más alto, con 302787437,1 kg-cm2; seguidas de los perfiles 16 y 10. Al demostrar el uso de las vigas en entrepisos, se observó que las vigas de calidad A son las que producen las longitudes óptimas para el mercado. Para techos, la clasificación por calidad de las vigas no produce efectos en la longitud permisible.

Acacia mangium, es actualmente, una de las especies más utilizadas en plantaciones comerciales en Costa Rica. Sin embargo, los usos de su madera han sido restringidos debido a que presenta algunos problemas durante el proceso de secado artificial, entre los que destaca la alta variabilidad del contenido de humedad final, la alta incidencia de defectos y la presencia de bolsas de humedad. Se han investigado las causas de esta variación y del desarrollo de estos defectos y se ha encontrado que los principales factores que influyen son: la alta variabilidad en el contenido de humedad inicial de la madera, la procedencia de la materia prima, la altura, la posición radial de la tabla al extraerla del árbol y el uso de programas de secado inadecuados para la especie. Asímismo se dan una serie de recomendaciones a considerar antes de iniciar el secado artificial con el fin de lograr una mejor calidad de madera en cuanto a la variabilidad del secado y la presencia de defectos.

Las primeras experencias llevadasa cabo en CostaRica con la reforestación con especies nativas se dieron en la Estación Biológica La Selva por parte de la Organización de los Estudios Tropicales (OET) a partir del año de 1985 en la zona de Sarapiquí, provincia de Heredia. Por parte de la mencionada organización se han establecido ensayos con especies tales como Dipteryx panamensis, Vochysia ferruginea, Vochysia guatemalensis, entre otros grupos de especies de gran interés para el país.