Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

The laminated curves (LC) made with steamed veneers make possible to obtain smaller curvature radius (RC) than when this process is not applied. This research shows the behavior of Alnus acuminata, Tectona grandis, Gmelina arborea, Terminalia oblonga and Swietenia macrophylla –all originated from fast growth plantations– in the manufacture of laminated curves with radios of (4, 6, 8, 10, 12 and 14) cm. The results show that it was possible to reach RC of 4 cm in all species except for T. grandis in which it was only possible to reach RC of 6 cm. The steam process increased the moisture content of the veneer in a range from 3,3% to 10,2%. The adhesive makes possible that bondline for RC smaller than 10 cm do not open, while for RC of 12 and 14 cm the bondline tends to get open (1% as maximum) for all the species. Nevertheless, the bondline opening gets stabilized 4 days after it is fabricated. The veneer deliminations occurred mainly in the interval of RC from 4 to 8 cm. The highest delaminations values take place in the T. grandis and T. oblonga. The shear stress values varied from 7,5 MPa to 11,2 MPa in all tested species. The aging test of adhesive did not alter significantly the shear stress, but delaminating due to the failure of the bondline increased in all species.

This research was developed with the objective of evaluating the potential use of residues of the production of sown Pinus spp wood and partial substitutions of Portland cement for high performance metakaolin and residue of calcined ceramic in cement-wood composites. The evaluation of the physical characteristics (specific mass, porosity and water absorption) and mechanics characteristics (compression and traction resistances) of the composites were determined in agreement with the ABNT standards. The was levels of substitution to the Portland cement for 5% to 40% of high performance metakaolin and 5% to 40% of residue of calcined ceramic. In both cases additive chemicals (CaCl2.2H2O) to speed up the cure of the cement were used and super-plasticizer to maintain without altering the rheological characteristics of the composite. The results demonstrated the technical viability to the use of the residue of Pinus spp and the for substitutions of the cement Portland in composites, and the optimized levels, obtained through multivariate statistical analysis, were 10% of high performance metakaolin and  5% of residue of calcined ceramic.

Our planet is facing a strong change induced by human activities, which is usually referred as Global Change. Concern about the socioeconomic consequences of this phenomenon has led to several international commitments for reducing the emissions of greenhouse gasses, which were summarized in the Kyoto Protocol of the United Nations. The Protocol established a number of strategies to mitigate and reduce the atmospheric impacts of CO2 emissions, which led to the creation of the international carbon market. The extensive forested areas of Mexico may position this country in the carbon market as an important provider of environmental services. Therefore, conservation and restoration of Mexican forests can be viewed as a potential business opportunity that would contribute to the economic and social development of the country. However, reaching these goals requires the joint action of different social sectors, including governments, private companies, the scientific community and the general population. This article illustrates how this interaction can be articulated and how it can provide multiple benefits for contributing parties.

The effect of some sources of organic nitrogen such as hydrolyzed casein and the aminoacids L-glutamine and L-Serine were tested in the process of direct secondary somatic embryogenesis, in which somatic embryos of Nothofagus alpina -induced from isolated cotyledons of mature seeds- were used as explants. The highest percentages of direct secondary embryogenesis were obtained in BTM base medium plus MS vitamins, without plant growth regulators, and in this medium plus NAA, BAP and hydrolyzed casein. However, the fresh weight of the proliferated mass was greatest in the presence of an additional source of organic nitrogen. The highest average number of embryos per explant was also produced in the treatment with growth regulators and hydrolyzed casein, although the number was not significantly higher than in the L-Glutamine treatment, in which significantly less callus growth occurred. Alternate use of base medium and NAA, BAP and hydrolyzed casein medium during subculture enabled direct proliferation of the embryogenic culture, which remained stable for over two years and with a low incidence of callus.

Coniferous trees are a vast resource in Durango, Mexico forests and a potential nontimber source of these chemicals, thus, our study for analyzing phenolic content and biological activity in needle extracts from Pinus cooperi (COO), P. durangensis (DUR), P. engelmanii (ENG) and P. teocote ( TEO). Pine needles were dewaxed with hexane and extracted with aqueous acetone and methanol. DUR and ENG extracts showed the higher yields, while acetone TEO and methanol ENG extracts showed the highest catechin equivalent (CE) contents. A partial chromatographic purification on acetone TEO extracts produced five fractions, the third one (F3-TEO) had the highest phenolic content (489,6 CE). In condensed tannins contents, acetone and methanol TEO extracts, as well fraction F3-TEO were the best (24,3, 15.7 and 44,4 mg/g extract, respectively). In DPPH activity, the more effective CE50 were obtained from TEO acetone extract (223,5 ppm) and fractions F3-TEO (145,0 ppm) and F4-TEO (150,8 ppm). In ABTS assay, TEO acetone (27,7%) and methanolic (18,2%) extracts, and fractions F3-TEO (60,1%) and F4-TEO (55,8%) were the best. In LDL assay the highest inhibitory activity was shown by acetone extracts, particularly ENG (99,4%) at 90 ppm. Therefore acetone extracts from TEO and ENG may have utilization as a potential source of bioactive phenolics.

The design methodologies require applying techniques in the phase of generating options, selecting methods to achieve the best of them, and thereby meeting the needs of the various requirements of the project. In the forest industry, the case of engineering glued laminated timber is not immune to these demands. Using the methodology of Integrated Environmental Design (IED) and the Muticriteria Technical Decision (MCTD) method, referred to the stage, it was possible to achieve the successful consolidation of design and conceptual development of a new constructive component of structural quality with technical innovation criteria based on the use of optional materials and new manufacturing processes. First, a total of 53 alternatives to the structural elements were generated with the creative brainstorming technique. Secondly, a selection technique was carried out according to the environmental, socio-economic and technological change, which came to define alternative 7. Using the Expert Choice 2000, it was chosen among the last 7, option number 39. This one met the requirements of the above factors in terms of cost, quality, resistance and Ecodesign principles, such as reduced energy consumption, use of alternative raw materials such as grass, recycling and reuse of raw materials, among others.

Basal area (AB m2/ha) and tree volume (VOL m3/ha) were modeled for even-aged Pinus patula and P. teocote forest stands located in Hidalgo, Mexico. Variables such as tree crown cover (COB), field recorded Leaf Area Index (LAI5 m2/m2), allometric Leaf Area Index (LAIAL m2/m2) ; GIS variables and reflectance data derived from a multispectral SPOT 5  image were used as independent variables. Environmental conditions were characterized by digitizing the INEGI’s chart of climatic effects (scale 1: 250 000) and processing the Digital Elevation Model (MDE) of the study area. A geographic information system (GIS) was set up with variables such as Elevation, Slope’s angle and aspect, Temperature, Precipitation, SPOT derived spectral bands, and two sets of vegetation indices based either on a) the ratio of spectral bands (NDVI and CTVI) or on b) the spectral distance between vegetation and bare soil (PVI and SAVI). Multiple linear regression models were fitted based on field and GIS data. AB was significantly related to LAIAL, Mean Annual Temperature (TMA), ALTITUD and SPOT Band 4 reflectance (P < 0,001, R2 = 0,9662). VOL was significantly related to LAIAL, Mean Annual Temperature (TMA) and ALTITUD (P < 0,001, R2 = 0,8856). 

This paper is the culmination of a wide range of researches carried out at the Laboratorio Nacional de Productos Forestales, Mérida, Venezuela, focused on assessing the potentials of the Pinus caribaea var. hondurensis timber for the production of structural quality glued-laminated beams. Hence, the study allows determining, from the statistical analysis inference, the growth characteristics and fabrication techniques, the possible influences on the mechanical properties of glued laminated beams, especially the finger joints, with respect to the stress at Proportional Limit (ELP), Modulus of Rupture (MOR) and Modulus of elasticity (MOE). From the results, the influence of those defects can be determined in order of importance, which allows to get very concrete conclusions and recommendations to make the glued-laminated beam Venezuelan manufacturers reflect about the continuous improvement of their processes, products and services with the aim of keeping the supply of high quality and reliable structural products.

The seasonal diameter growth of a commercially valuable tree species, Zanthoxylum kellermanii (P. Wilson), was determined. Twenty-two trees were selected in six diameter categories and dendrometric bands were used to take bimonthly growth readings. Other readings related to crown characteristics were also taken: quality (symmetry, vigor, density of foliage) and positions (light incidence). Mean annual growth in diameter fluctuated from 0,86 cm to 1,87 cm within diameter categories; from 0,52 cm to 2,04 cm within crown qualities and from 0,73 cm to 1,70 cm within crown positions. Analyses of variance showed highly significant differences (p≤0,001) among diameter categories, as well as among crown qualities and positions. Tools such as dendrometric bands along with regression models, proved to be useful to determine and project the diameter increment of the species studied.

Reforestation in Mexico is important to recuperate the productivity of deforested and degraded areas and to maintain that of commercial forests. Only 40% of reforested areas have an acceptable level of survival. Characteristics of seedlings out planted, including shoot/root ratio, are essential factors for achieving the desired results of high survival and good growth after transplanting. This study describes the characteristics of mahogany (Swietenia macrophylla King), Spanish cedar (Cedrela odorata L.) and “roble” (Tabebuia rosea (Bertol.) DC when planted at two densities (100 and 50 plants/m2) and in two substrates [soil, and soil + compost (S+C)] in a nursery. The S+C treatment had a significant effect on diameter, height, root biomass and the shoot/root ratio. In soil 76% of seedlings had a shoot/root ratio of 3.0 or less and in S+ C, 21% of seedlings had a ratio less than 3.0. For conifers a ratio of 2/1 is recommended for dry sites and 4/1 for humid sites. For broadleaves the optimum shoot/root ratio is not known. Two months after transplanting in the field more Swietenia produced with the S+C treatment died but less Cedrela and Tabebuia seedlings did. For the three species the seedlings that died were smaller.