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Summary The lianas in the family Sapindaceae are known for their unique secondary growth which differs from climbing species in other plant families in terms of their cambial variants. The present study deals with the stem anatomy of self-supporting and lianescent habit, development of phloem wedges, the ontogeny of cambial variants and structure of the secondary xylem in the stems of Serjania mexicana (L.) Willd. Thick stems (15–20 mm) were characterized by the presence of distinct phloem wedges and tangentially wide neo-formed cambial cylinders. As the stem diameter increases, there is a proportional increase in the number of phloem wedges and neo-formed vascular cylinders. The parenchymatous (pericyclic) cells external to phloem wedges that are located on the inner margin of the pericyclic fibres undergo dedifferentiation, become meristematic and form small segments of cambial cylinders. These cambia extend tangentially into wide and large segments of neoformations. Structurally, the secondary xylem and phloem of the neo-formed vascular cylinders remain similar to the derivatives produced by the regular vascular cambium. The secondary xylem is composed of vessels (wide and narrow), fibres, axial and ray parenchyma cells. The occurrence of perforated ray cells is a common feature in both regular and variant xylem.

Paulownia tomentosa is utilized in Costa Rica and other countries for wood production and as feedstock for biomass, though the variation of wood properties for this species is scarcely known. In this work, the specific wood properties of a 5-year-old plantation in Costa Rica were studied. The results showed that bark and pith percentage and wood specific gravity (SG) increased with tree trunk height, while the proportion of heartwood, green wood density and green wood moisture content decreased. The average wood SG was 0.26 and tended to increase from pith to bark. Low wood SG values are related to low mechanical properties, with the advantage that wood shrinkage is low as well, which gives this wood species the potential to be utilized for reforestation purposes in Costa Rica. The gross calorific value of this species was 17809 kJ/kg, which, together with its cellulose and extractives contents, recommend P. tomentosa as a biomass source for energy production.

The present work aims at determining the behaviour relative to load applied and displacement and the design values of Howe trusses 7.2 m long fabricated with timber from Gmelina arborea, Tectona grandis and Cupressus lusitanica, using metal plates. The static flexural strength of the trusses was tested by applying the load to three different points, determining the load and the displacement at the central point of the truss, and then these values were used in the SAP2000 program, to define the design values. The results showed design loads at 5.00 kN, 6.34 kN and 5.52 kN and displacements at 1.53 cm, 1.27 cm and 1.71 cm, for trusses fabricated with G. arborea, T. grandis and C. lusitanica timber, respectively. As for the design tables, the values of maximum load diminished with increase in support spans (with 5 m, 6 m, 7 m and 8 m simulated support spans). The load ranged between 59.05 and 186.21 kg/m for G. arborea, 91.38 to 286.39 kg/m for T. grandis and 57.45 to 183.35 kg/m for C. lusitanica. Although truss manufacturing with the three species is viable, T. grandis showed the highest potential.

Alnus acuminata, Vochysia ferruginea, and Vochysia guatemalensis are three low-density wood species used for reforestation in Costa Rica. The goal of this work was to study a thermo-hydro-mechanical densification process and test the characteristics of densified wood of these species. Twelve densifying treatments based on temperature, compression time, and use/no use of steam were tested. The variables of the densification process and the properties of the densified wood were determined. The results showed that the densification percentage was over 80% for wood of A. acuminata and over 70% for wood of V. ferruginea and V. guatemalensis. In the three species, the densification process was influenced by initial density. The influence of temperature during the densification process affected the heating rate and color change. An increase in the modulus of elasticity and modulus of rupture in static bending and in the hardness of the densified wood relative to the normal wood was observed, as well as a clear positive correlation of the properties with final density and maximum load, the latter being highly correlated with initial density. This showed that initial density was significant in the densification process and affects wood properties.

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.

HighlightsArundo donax, Pennisetum purpureum, and P. purpureum × P. glaucum planted at 103 plants ha-1 were studied.Biomass production and energy characteristics were evaluated at 12, 18, 24, and 30 months.The production of dry biomass varied between 2.52 and 39.25 Mg ha-1.The biomass quality and production of Arundo donax were different from those of Pennisetum ssp.Abstract.The high global demand for fossil fuels has led to the search for alternative sources of renewable energy, such as the production of biomass from short-rotation crops (SRC). This study evaluated three grass species (, , and × ) in SRC systems planted at 103 plants ha-1 in humid tropical conditions in Costa Rica, considering biomass production, moisture content, and energy and chemical properties at four harvest ages (12, 18, 24, and 30 months). The results showed that the height of all species varied between 0.9 and 3.5 m at the different harvests, while the production of dry biomass varied between 2.52 and 39.25 Mg ha-1. As for their chemical properties, the ash content varied between 5.9% and 10.2%, volatile matter varied between 73.3% and 81.9%, and net calorific value varied between 15.86 and 18.94 MJ kg-1. In the three species, the production of biomass was greater at the 12-month and 18-month harvests; at later harvests, biomass production began to decrease, leading to increased moisture and ash contents, lower volatile matter, and lower calorific value. The biomass quality and production of were different from those of . Keywords: Bioenergy, Energetic potential, Forage, Pastures, Short-rotation plantations, Tropical species.

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.

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.

The first attempts to establish energy crops in the tropical regi­on using short rotation species are premised on the utilization of clones for wood production. Therefore, the present study is aimed at examining the growth aspects (survival, diameter and tree height), leaf architecture (leaf area index [LAI], number and angle of the branches and sylleptic branches), biomass production, as well as biomass flow at the age of 24 months of two clones of Gmelina arborea in short rotation crops within three spacings (1.0x1.0 m, 0.75x0.75 m and 1.0x0.5 m). The results showed an increment with age, as the diameter increa­sed from 3.00 cm at six months to 8.0 cm at 24 months, where­as the total height increased from 2.00 m at six months to 10.00 m at 24 months. Clone survival varied from 20 to 60 %, whereas the LAI, branch angle and sylleptic branches increased with age. The differences between clones appeared after 12 months. Biomass production was similar between clones, from 6 ton/ha at six months to 67 ton/ha at 24 months, with clone 2 showing greater biomass flow than clone 1. On the basis of biomass pro­duction results and the development of diameter as well as height, clone 1 is recommended for spacing 1.0x1.0 m and clo­ne 2 for spacings 0.75x0.75 m and 1.0x0.5 m.

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.

Micro- and nanofibrillated cellulose (MNFC) was extracted from pineapple stems by acid hydrolysis, then characterized and tested in two concentrations (0.5 and 1.0 wt%) in polyvinyl acetate (PVAc) and urea-formaldehyde (UF) adhesives. The modified adhesives were used to glue three tropical wood species (Vochysia ferruginea, Cordia alliodora, and Gmelina arborea), and their corresponding bond strength resistance was determined. MNFC and the correspondent adhesives were characterized by TGA, FTIR, SEM, TEM, AFM, and viscosity determination. The TGA analysis of MNFC showed three decomposition reactions. The SEM, TEM, and AFM evaluations demonstrated the presence of micro- and nanosized dimensions of particles after the acid hydrolysis of pineapple stems. Adding 1 wt% MNFC to PVAc and UF adhesives increased their thermal stability in similar manner. Viscosity diminished in both modified adhesives with MNFC; however, this reduction did not affect the adhesion properties in the tropical wood tested. MNFC added to PVAc and UF adhesives improved shear strength (SS) of the glue line in the three tropical species tested. The highest SS increase was obtained when adding 0.5 wt% MNFC to PVAc in V. ferruginea, and 1 wt% MNFC concentration in the case of C. alliodora and G. arborea. In the case of UF adhesives, the application of 1 wt% MNFC produced significant differences in SS for the three tropical species studied.

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.

The present work studies the morphological, physical, mechanical and chemical properties, decay resistance, preservation and workability of Cedrela odorata wood from trees growing in agroforestry systems with Theobroma cacao at four ages (4-, 5-, 6- and 7-years-old) in Costa Rica. It was found that the morphological properties (heartwood, pith and bark), together with the physical properties (specific gravity, green density, shrinkage and green moisture content) presented few differences at the four ages. The wood from 4-years-old trees was the only exception, showing less resistance in compression, flexion and lateral hardness. The content of lignin, carbon, and extractives in hot water were not affected among the different ages, contrary to the rest of chemical properties. In relation to decay resistance in accelerated tests with the fungus Trametes versicolor, the wood is classified as highly resistant, while with the fungus Lencites acuta it is classified as moderately resistant. As concerns properties related to industrialization, it was found that the wood can be preserved through vacuum-pressure methods obtaining similar results as those from other plantation timbers. As for workability tests, the wood from the 4-years-old trees show acceptable to very poor performance, differing from trees from the other ages.

Torrefaction can increase the energy yield of biomass for better utilization in bioenergy, but chemical changes occur during the pretreatment process. Wood residues of Cupressus lusitanica, Dipteryx panamensis, Gmelina arborea, Tectona grandis, and Vochysia ferruginea were torrefied for three different time periods (8, 10, and 12 min) and three different temperatures (200, 225, and 250 °C). The mass loss, net calorific value, ash, volatiles, lignin, cellulose, extractives, and infrared spectra were evaluated. The results showed that the mass loss in torrefied biomass varied between 10% and 70%, ash content varied between 0.19 and 7.00%, and volatiles content varied between 63 and 85%. Net calorific value values varied between 17 and 23 MJ/kg, increasing with the increased torrefaction temperature. Cellulose varied between 49.85 and 67.57%. Lignin varied between 27.33 and 41.09%. The extractives varied between 3.70 and 16.86%. The change in the ratio of intensity (RI) for the bands identified using FTIR analyses showed that large changes occurred in hemicellulose components. The multivariate analysis showed that lignin, ash, extractives in hot water, volatiles, and mass loss were the variables that contributed most. The analysis of all these variables showed that torrefaction at 250 °C for 12 min presented the greatest biomass degradation. Torrefaction at 200 °C and 225 °C for 8, 10, and 12 min was optimal for thermal treatment of the biomass of these woody species.

Tree diameter and height, yield and chemical and energy properties increment throughout two different ages (1- and 2-year-old) were evaluated in Gmelina arborea trees growing in short rotation woody crops at three sites and three spacings (0.5 × 1.0, 1.0 × 1.0 and 2.0 × 1.0 m). The results showed great variation in parameters evaluated in relation to site, whereas for spacing the results were regular. Diameter, height and biomass yield increased in 2-year-old trees at all sites and spacings. The higher increments were observed in the 0.5 × 1.0 m spacing at sites 2 and 3. Biomass distribution in the different parts of 2-year-old trees showed increased biomass in the trunk and branches, and reduced biomass in leaves. The study of biomass properties showed increments in the specific gravity and reductions in the moisture content (MC) of trunk and branches, but MC of bark was regular. The increment in specific gravity and volatile contents was highest in the 0.5 × 1.0 m spacing, while MC of trunk, branches and bark, heat calorific value and ash content decreased. Carbon and nitrogen contents were irregular throughout spacing and sites. It was determined that at 2 years of age, Sites 1 and 2 presented normal behavior of Gmelina arborea in SRWC conditions, and in the Site 3 the changes produced improved the quality of biomass for energy purposes.

Tectona grandis is the second most important species for reforestation in Costa Rica, and any improvement in its industrialization process is important, especially the drying process. Lumber obtained from a plantation of 12-year-old T. grandis trees was used to evaluate three drying schedules that include integrated steaming processes to determine the combined effect of the steam-drying system on the dried lumber. The variations in the moisture content (MC) and drying rate (DR) with drying time (DT) both before and after the steaming process were modeled mathematically for boards that have a flat and quarter grain pattern. For both types of boards that were dried with and without steaming, a relationship between MC and DT was observed. There was inflexion at 40%, and two mathematical models were computed. Additionally, the relationship between DR and DT for boards with flat and quarter grain patterns was not affected by the steaming process, and an inflection point was observed at 30 h (40% MC for...

Woody biomasses from five fast-growth plantations of Costa Rica were evaluated in relation to thermal degradation characteristics and devolatilisation rate (Drate) using thermogravimetric analysis (TGA). The relationship between TGA parameters and Drate with content of cellulose, lignin and extractives were established. The results indicate that during degradation, the five woody biomass types (Cupressus lusitanica, Dipterix panamensis, Gmelina arborea, Tectona grandis and Vochysia ferruginea) show different temperatures and residual mass, as well as different Drate of the polymers conforming them, indicating that each biomass type has unique pyrolysis characteristics. The difference in these parameters is influenced by extractives content, and a little effect is presented due to lignin content, cellulose content and ash composition. A greater amount of extractives decreases the degradation temperatures of the different biomass components, although the residual mass was scarcely affected and if so, a positive correlation was presented. Extractives also affected the Drate more significantly than cellulose, lignin and macro- or micro-nutrients contents. Moreover, the Drate of cellulose was more affected by the extractives content than was Drate of hemicellulose, indicating a higher degree of association of extractives with cellulose than hemicellulose. In this concern, the higher the amount of extractives, the lower the Drate of cellulose.

Mortality, diameter at 30 cm over ground level, height, biomass production, and carbon capture (CC) for different tree components (trunk, bark, branches, and leaves) in two locations in Costa Rica, during their first three years and with three plantation spacings (1.0 &times, 0.5 m, 1.0 &times, 1.0 m, and 1.0 &times, 2.0 m) were obtained for Gmelina arborea Roxb. trees growing in short rotation coppice systems (SRC). In addition, regression models were developed to predict biomass production and CC using location, age, spacing, and their interactions. Biomass production was measured by weight of trees without considering dendrometric variables. Results showed that mortality was lower than 15% for one location, with probable high fertility, and almost 85% for the other location. Diameter and height of trees increased with plantation age in both locations. The highest biomass production and CC were observed in the spacings of 1.0 &times, 0.5 m2 and 1.0 &times, 1.0 m2, with 20 Mg/ha/year and 8 Mg/ha/year, respectively. The models to predict biomass production in trunk with bark, branches, leaves, total biomass without leaves, and CC in trunk, branch, and total biomass were developed using this equation: Y = &beta, 1 + &beta, 2 (location &times, age) + &beta, 3 (age) + &beta, 4 (spacing). The R2 values varied from 0.66 to 0.84, with error from 0.88 to 10.75 and indicators of goodness of fit from 60 to 83%.

In countries like Costa Rica, there is an interest in developing wooden trusses in a versatile and light way. However, there is a key aspect in the behavior of truss connections in this product. Therefore, the present study determines the structural behavior of the truss connections and the displacement, the resistance, the stiffness values and the failure mode of truss connections made with Gmelina arborea and Tectona grandis timber for angles of 0° and 90°; and three types of truss connectors (metal plates, screws and nails), subject to tension and compression loads. The results showed that metal plates show the highest load values with respect to the nails and screws in both species. Likewise, in the design and critical displacement stress, metal plates surpass the nails and screws in both species; and in the two angles. From these stress values, we proposed a model for the prediction of the stiffness for the truss connections of the intermediate angles (30°, 45° and 60°) and the test showed that the prediction was low, the bias was 3%.

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.

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 torrefaccion y peletizacion se han estudiado en la generacion de calor a partir de residuos lignocelulosicos, para incrementar las propiedades energeticas del material. El objetivo del presente trabajo fue torrefaccionar aserrin 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 diametro y se evaluaron sus propiedades fisicas, el poder calorico, la densidad y la propiedad mecanica de resistencia a la compresion. Ambas especies presentaron caracteristicas fisicas similares con respecto al diametro (0.50 mm), longitud (21.50 mm) y porcentaje de absorcion de agua (6.00 %). El poder calorico aumento 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 compresion que los de G. arborea . Con base en los resultados, la resistencia a la compresion del pellet disminuye cuando el tiempo de torrefaccion aumenta. Existe correlacion positiva entre la densidad de los pellets y la resistencia a la compresion. La especie D. panamensis presenta mejor comportamiento a la torrefaccion y peletizacion que la madera de G. arborea .

Modifications to a pellet manufacturing process must be made based on the characteristics of raw material used. The purpose of this work was to determine the alternations required to a wood pellet manufacturing process and the quality of the pellets produced using this process from five energy crops. Quality measurements include: the caloric value, the loss of moisture content in each production stage, the efficiency index of particle-pellet, ash content and quality as defined using the quantity of cracks and the transversal density and longitudinal density determined using X-ray radiography. The crops analyzed were rhizomatous plants, with caloric values ranging between 17.1 and 20.3 MJ kg −1 . This work determined that it was possible to produce pellets with Gynerium sagittatum and Phyllostachys aurea using the same production process for wood; however, Arundo donax and Pennisetum purpureum needed pre-air-drying and the Sorghum bicolor required mechanical dewatering before drying. A. donax , P. purpureum and G. sagittatum provided the highest efficiency index. When evaluating the pellet quality P. aurea and G. sagittatum hard a large quantity of cracks, unlike A. donax , P. purpureum and S. bicolor . The transversal and longitudinal pellet density varied from 1129 to 1294 kg m −3 . The highest values of bulk density were obtained in A. donax and P. purpureum , followed by G. sagittatum and P. aurea , and the lowest bulk density was obtained in S. bicolor . Althogh out, some species produced cracks and high ash content, this work demonstrated that it is possible to produce pellets with moderate quality.

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.

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

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.

The object of this research is to develop a model for the calibration of prefabricated timber wall frames (PTWFs) with dimension of 244 by 244 cm (width by height) respectively made of Gmelina arborea Roxb. and Hieronyma alchorneoides Allemão wood and two types of fastener (nails and screws). The PTWFs were submitted to a lateral load test and the vertical and horizontal displacement, maximum load (Pm), strength, stiffness values and mode of failure were determined. Results showed a greater failure percentage in the joint between the central stud and the top and bottom plates for both species and both fastener types used. PTWFs made of H. alchorneoides timber using screws showed greatervalues than PTWFs made of G. arborea for load at the proportionality limit and maximum load. Finally, computational model showed that the highest calibration percentage was achieved in the vertical orientation in PTWFs made using nails in both species. Meanwhile, PTWFs using screws showed calibration percentages of 58.0 and 43.5 %. The highest calibration percentage of 89.9 % was recorded in G. arborea PTWFs joined with nails, whereas the lowest calibration percentage of 69.4 % was recorded in H. alchorneoides PTWFs joined with screws., Cilj istraživanja bio je razviti model za kalibraciju montažnih drvenih zidnih okvira (PTWF) dimenzija 244 × 244 cm (širina × visina) izrađenih od drva Gmelina arborea Roxb. i Hieronyma alchorneoides Allemão te uz upotrebu dviju vrsta vezivnih elemenata (čavala i vijaka). PTWF-ovi su podvrgnuti testu bočnog opterećenja te su utvrđeni vertikalni i horizontalni pomak, maksimalno opterećenje (Pm), čvrstoća, krutost i način oštećenja. Rezultati su pokazali najveći postotak oštećenja u spoju između središnjeg nosača i gornjega odnosno donjeg okvira za PTWF-ove od obiju vrsta drva i spojenih obama tipovima vezivnih elemenata. PTWF-ovi izrađeni od drva H. alchorneoides i spojeni vijcima imali su veće vrijednosti opterećenja na granici proporcionalnosti i maksimalnog opterećenja od PTWF-ova proizvedenih od drva G. arborea. Konačno, računalni je model pokazao da je najveći postotak kalibracije postignut u vertikalnom smjeru u PTWF-ova izrađenih od obiju vrsta drva i spojenih čavlima. Istodobno, PTWF-ovi spojeni vijcima pokazali su postotke kalibracije 58,0 i 43,5 %. Najveći postotak kalibracije bio je 89,9 %, a zabilježen je u PTWF-u od drva G. arborea i spojenom čavlima, dok je najniži postotak kalibracije ustanovljen u PTWF-u od drva H. alchorneoides spojenom vijcima, a iznosio je 69,4 %.

Bent trees have been observed during the early years in juvenile plantations (less than 5 years-old) of Tectona grandis in Costa Rica. The relationship between bending and the morphological characteristics of the trees was explored. An evaluation of bent trees was conducted in six juvenile plantations (8, 17, 27, 28, 31, and 54 months old) of Tectona grandis. Site 1 with 8-month-old plantations did not display any relationship with any tree morphological variable (diameter, height, and crown weight of tree), whereas for the sites 2, 3, and 4 with 17-, 27-, and 28-month-old plantations, respectively, all the tree morphological variables were statistically correlated with the bent trees. A multiple regression analysis showed that the most influential variables were height to crown base, crown weight, diameter, and total height of the tree. An evaluation of the bending risk factor (RF) was correlated with the height to crown base, crown weight, and form factor. The modulus of elasticity and chemical compositions of bent trees differed from those of straight trees. The causes of tree bending are complex, involving, among other factors, the morphology of the trees, plantation conditions, and other factors specific to the xylem, such as the specific gravity, modulus of elasticity, and presence of calcium and magnesium in the wood.

Bent trees have been observed during the early years in juvenile plantations (less than 5 years-old) of Tectona grandis in Costa Rica. The relationship between bending and the morphological characteristics of the trees was explored. An evaluation of bent trees was conducted in six juvenile plantations (8, 17, 27, 28, 31, and 54 months old) of Tectona grandis. Site 1 with 8-month-old plantations did not display any relationship with any tree morphological variable (diameter, height, and crown weight of tree), whereas for the sites 2, 3, and 4 with 17-, 27-, and 28-month-old plantations, respectively, all the tree morphological variables were statistically correlated with the bent trees. A multiple regression analysis showed that the most influential variables were height to crown base, crown weight, diameter, and total height of the tree. An evaluation of the bending risk factor (RF) was correlated with the height to crown base, crown weight, and form factor. The modulus of elasticity and chemical compositions of bent trees differed from those of straight trees. The causes of tree bending are complex, involving, among other factors, the morphology of the trees, plantation conditions, and other factors specific to the xylem, such as the specific gravity, modulus of elasticity, and presence of calcium and magnesium in the wood.

Anatomía del tallo y desarrollo del floema interxilar en Strychnos bredemeyeri (Loganiaceae) En Strychnos bredemeyeri, pequeñas porciones de cambium dejan temporalmente de producir xilema secundario y produce más floema centrífugamente. Un nuevo segmento del cambium se diferencia en la parte exterior de este floema formado, entonces estos se unen al cilindro regular para formar un anillo. Esta repetida actividad da como resultado la inclusión de islas de floema dentro del xilema secundario, llamado floema interxilar. Luego aparecen nuevos elementos del floema asociado al cambium y a las islas de floema que aplastan los elementos no conductores de islas de floema. Junto al floema interxilar, el floema intraxilar está formado por la adición desde las células marginales de la médula. Posteriormente, pequeños arcos del cambium interno se inician en el borde interno del protoxilema en tallos gruesos. Abstract: In Strychnos bredemeyeri small segments of the cambium cease to produce secondary xylem temporarily and produce more phloem centrifugally. A new segment of the cambium differentiates outside to this phloem, which unite with the regular cylinder to form a complete ring by leaving the cambium segment in the furrow. Such repeated activity of cambium results in inclusion of phloem islands within the secondary xylem, called interxylary phloem. New phloem elements added by the cambium associated with phloem islands crush the non-conducting sieve elements in older phloem islands. Beside interxylary phloem, intraxylary phloem is added from the marginal pith cells. Subsequently, small arcs of the internal cambium initiate on the inner margin of the protoxylem in thick stems.

Lignocellulosic wastes resulting from agricultural activities as well as Tetra Pak residues from urban centres can cause significant levels of pollution. A possible action to minimize this problem is to use them in the production of particleboards. The purpose of this study was to evaluate the physical, mechanical, and hydration properties of particleboards manufactured with the mixture of woody biomass (Cupressus lusitanica, Gmelina arborea, and Tectona grandis) and either agricultural wastes [pineapple leaves (Ananas comosus) and palm residues (Elaeis guineensis)] or Tetra Pak residues (TP). The results show that the particleboards prepared with TP and woody biomass can reduce the swelling and water absorption in up to 40% and 50% compared with particleboards without TP. Also, these particleboards had increased flexure resistance and shear stress (up to 100%) compared with those without TP. On the contrary, particleboards prepared with pineapple leaves in combination with woody biomass showed the lowest mechanical properties, particularly for tensile strength, hardness, glue-line shear, and nail and screw evaluation. Los desechos lignocelulósicos resultantes de las actividades agrícolas, así como los residuos de Tetra Pak de los centros urbanos pueden causar niveles significativos de contaminación. Una posible acción para minimizar este problema es usarlos en la producción de tableros de partículas. El propósito de este estudio fue evaluar las propiedades físicas, mecánicas y de hidratación de tableros de partículas fabricados con la mezcla de biomasa leñosa (Cupressus lusitanica, Gmelina arborea y Tectona grandis) y residuos agrícolas [hojas de piña (Ananas comosus) y residuos de palma (Elaeis guineensis)] o residuos de Tetra Pak (TP). Los resultados muestran que los tableros de partículas preparados con TP y biomasa leñosa pueden reducir la hinchazón y la absorción de agua hasta en un 40% y 50% en comparación con los tableros de partículas sin TP. Además, estos tableros de partículas tenían una mayor resistencia a la flexión y al esfuerzo cortante (hasta 100%) en comparación con aquellos sin TP. Por el contrario, los tableros de partículas preparados con hojas de piña en combinación con biomasa leñosa mostraron las propiedades mecánicas más bajas, particularmente para la resistencia a la tracción, la dureza, el corte de la línea de pegamento y la evaluación de clavos y tornillos. Universidad Nacional, Costa Rica Escuela de Química

Teak (Tectona grandis L. f) has been introduced to reforestation programs in many tropical countries for timber production. The use of teak plantations has changed the supply from large-diameter logs to small-diameter logs featuring a higher proportion of juvenile wood and more knots. Generally, the teak from fast-growth plantation is harvested after 15–30 years of growth, with logs ranging from 12 to 30 cm in diameter. The goal of this work was to review the factors that influence the heartwood formation, variation, quality, color, and durability in teak and to understand which factors should be controlled in fast-growth plantations. Important factors in the heartwood properties of teak trees from fast-growth plantations are as follows: the tree age, longitudinal variation, geographic location, environmental conditions, and silvicultural activities. These factors influence heartwood extractive content, color variation, and durability.

Tectona grandis and Gmelina arborea are common in commercial reforestation in the tropics. However, color variations, moisture content, and drying defects are also present in dried lumber. Moisture content variations, drying defects, and color changes were evaluated in the present work for three drying methods (kiln, solar, and air drying) during three seasons (dry, rainy, and transition season) in Costa Rica. According to the results, kiln drying had the fastest drying times, regardless of the season. On the other hand, air drying had slower drying time and higher final moisture content. With regard to defects, kiln drying produced the highest number and magnitude of defects in both species, whereas air drying showed the lowest quantity and severity of defects. No variations due to the drying methods or the season were observed in check and split, though solar drying presented intermediate values in all drying defects. The seasons of the year did not present any effect on drying defects. Finally, T. gran...

Tectona grandis (teak) plantations are being produced with trees from genetic improvement programs, including clonal selection. However, limited information about inheritance of wood properties is available. For studying genetic parameters of T. grandis wood properties and stem diameter two 10-yr-old trials were studied involving nominally 2 sites × 20 clones × 3 replicates × 1 ramet. Clonal variation was observed in: heartwood (HWP), pith (PP) and bark (BP) percentages; green moisture content (IMC) and density (GD); tangential (TS), radial (RS) and volumetric (VS) shrinkage and ratio tangential/radial: shrinkage (ratio T/R); L*a*b* color parameters; and stiffness and specify gravity (SG). Some wood properties evidenced strong across-sites genotypic control. The higher broad-sense heritability estimates (over 0.36) were for PP, IMC, SG, TS, VS and L*, a*, and b* color coordinates and stiffness. Low and non-significant values were estimated for HWP, BP, GD, RS, ratio T/R and decay resistance of sapwood and heartwood to Trametes versicolor and Pycnoporus sanguineus. However, HWP showed marked clone x site interaction. Phenotypic and tentatively estimated genotypic correlations indicate that selecting faster-growing clones will improve some important wood properties, such as increasing HWP, and decreasing PP and BP, without affecting other wood properties. Selecting clones for denser wood, as expected, improved stiffness, should decrease IMC and affect negatively b* (yellow/blue) color. Clone selection with lower L* values could increase redness (a*) of wood.

Residues from fast-growth plantations in the tropics have recently become important for energy production. However there is not yet enough information on their combustion and thermal degradation characteristics. The present study aims to determine the behavior of the different parameters of thermogravimetric analysis (TGA) for 10 species of reforestation. The relationship between TGA parameters with chemical and extractives was established too. Also it is identified the different parts of the combustion process at different moisture contents for these species. The results indicate that Bombacopsis quinata, Vochysia guatemalensis and Gmelina arborea are species with the highest thermal stability and they presents combustion stages poorly defined, making them less suitable for a combustion process. By contrast, Tectona grandis, Sweitenia macrophylla and Cupressus lusitanica have a lower thermal stability, but a combustion process with well-defined stages, which makes them more suitable species in combustion processes. Acacia mangium, Terminalia amazonia, Alnus acuminata and Terminalia oblonga showed combustion parameters easily identifiable and moderate thermal stability, considering as acceptable combustion properties. Extractives and chemical compositions presented little influence on the process of combustion and thermal stability of wood. However, moisture content was the greatest influence on the process of combustion and thermal stability.

To prevent the photodegradation process, a wide range of coatings have been developed. This study evaluated wood color change (ΔE*) and the surface quality index (SQI) generated by ASTM D-660 standards in wood protected with polyurethane and varnish finishes of three tropical species (Acacia mangium, Cedrela odorata and Tectona grandis) in two weathering conditions (natural and accelerated condition). In addition, a model was developed to predict ΔE* and SQI in natural weathering based on ΔE* and SQI from accelerated weathering. The results showed that the application of these finishes generated variations in the color parameters of wood before being exposed to the elements. Additionally, it was found that finishes generated increases in ΔE*, especially the varnish type finish, and decreasing of SQI. Finally, models were found to predict color changes or surface quality in natural weathering based on color changes or surface quality in accelerated weathering. The model algorithm was expressed by ΔE* or SQI measured (X) and time exposure (t) in accelerated weathering by equation . With these models, it is possible to predict the equivalence of exposure times in natural weathering in tropical conditions for different kinds of finishes in three tropical species. © 2013 Wiley Periodicals, Inc. Col Res Appl, 39, 519–529, 2014

Lignocellulosic residues resulting from agricultural activities and urban centers cause pollution. A possible solution to this problem is to combine these residues with woody plants to produce particleboards. The purpose of this study was to evaluate decay resistance, coating and burning properties and the change of color caused by accelerated weathering of particleboards manufactured with a combination of 3 woody species used for commercial reforestation in tropical areas (Cupressus lusitanica, Gmelina arborea and Tectona grandis), pineapple (Ananas comosus) leaves from the crown and the plant (PL), empty fruit bunch of Elaeis guineensis (EBF) and tetra pak packages (TP). According to the results, the mixtures of T. grandis and EFB were classified as moderately resistant and other mixtures (woody species and PL or TP) were classified as slightly resistant. The finish performance test determined that the mixtures with TP presented the best performance, followed by the mixtures with oil palm components and the mixtures composed of pineapple leaves. Regarding lacquer consumption, no differences were found between the mixtures. The combustion test determined that particleboards with TP and EFB showed the highest resistance to combustion, while pineapple presented the lowest resistances to combustion. In the accelerated weathering exposure test, the mixtures of the three species with TP showed the best performance in accelerated weathering. Contrariwise, the mixtures with pineapple leaves showed the lowest resistance to accelerated weathering. Oil palm particleboards presented lower resistance to weathering than TP, though higher than pineapple leaves’ resistance.

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.

The addition of titanium dioxide nanoparticles (TiO2 nanoparticles) to a water-based varnish used for finishing tropical woods was studied. Three different concentrations of TiO2 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 TiO2 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 TiO2 nanoparticles decreased the values of water absorption. The evaluation of natural weathering showed that the varnish with no added TiO2 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 TiO2 nanoparticles. The best performance of the varnish in the nine tropical woods used was observed when TiO2 nanoparticles were added at 1.5% concentration.

En Costa Rica, el concreto, el acero y los plásticos son los materiales más utilizados para construcción. Mientras que por otro lado la utilización de madera de plantaciones forestales se ha incrementado en los últimos años. Ante tal situación en el presente estudio, fueron determinadas las propiedades físicas y mecánicas de tableros terciados manufacturados con chapas de Gmelina arborea, Tectona grandis y Acacia mangium provenientes de plantaciones forestales para usos estructurales. Se analizaron tres tableros (plywood) de cada una de las especies, se realizó una caracterización general y se midieron sus principales propiedades físicas y mecánicas. Los resultados mostraron que los tableros producidos con árboles de T. grandis en general presentan propiedades físicas y de resistencia superiores a las de G. arborea y A. mangium. De acuerdo con las normas del Voluntary Products Standart PS 1-95 y PS 1-09 de los Estados Unidos, es posible producir tableros estructurales de grado 3 con G. arborea, y grado 2 estructural con T. grandis y A. mangium, los cuales pueden ser usados en la fabricación de elementos estructurales.

• Context Teak’s wood color is considered an important attribute in the marketing phase and it has been influenced by environmental setting, stand conditions and management, plant genetic source, and age. However, there is a lack of understanding about how the environmental factors might affect the teak’s wood color planted in short-rotation forest plantations.

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*.

Acacia mangium is an important plantation species cultivated in Costa Rica and other tropical countries worldwide. However, wood uses have been limited due to drying-related problems such as high initial moisture content (MCi) and high variability in final moisture content (MCf). The objective of this study was to investigate the causes of these problems. Climatic conditions where trees grow, tree height, grain pattern, drying schedules, distance from pith, and sapwood or heartwood presence were considered. Results showed an average MCi of 127% ranging from 58 to 186%. MCi variation was influenced by climatic conditions, tree height, and grain pattern. Average MCf was 19%, ranging from 9 to 52%. Lack of MCf uniformity after drying is influenced by tree height, drying schedule, and the interaction of both factors. Wet pockets were also found to develop during drying. Lumber from trees growing in humid tropical climates subjected to a low relative humidity drying schedule as well as rift-sawn or double rift...

Commercial Tectona grandis plantations using clones have attracted considerable interest for lumber production in tropical regions where small areas are frequent. However, studies on wood properties are limited. Therefore, the purpose of this study is to group clones with similar wood color characteristics using the CIELab system, and mechanical resistance by dynamic stiffness (Ed) in order to obtain different types of clones for different climate and edaphic conditions. It was found that lightness (L*), yellowness (b*), redness (a*), and Ed are similar to those found for other plantation trees. These wood characteristics are significantly influenced by clone and site. Variance due to clone and site went from 31 to 53% and from 2.95 to 24.22%, respectively. Another source of variance was distance from pith, with the exception of parameter b*, which was not affected. Finally, clones were grouped (using multivariate analysis) according to color and mechanical resistance. This analysis established 4 groups by color and 5 groups by Ed. Clone clustering will allow us to choose or use clones with similar wood properties according to site and environmental conditions increasing area production and wood quality uniformity.