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

A potential utilization of oak wood is the production of plywood, but it is necessary to define the more adequate conditions for the heating of wood, for the slicing or peeling of the logs, for the drying of veneer and assembling of the plywood. In this study the optimum parameters for the softening of wood for the production of plywood were determined using two logs of each one of the following species: Quercus candicans, Q. laurina and Q. rugosa. From these logs, flitches were obtained, which were heated in a metallic container through coils with thermic oil to heat water up used as thermoconducting medium for the wood. In each flitch, two thermocouples were embedded to mesure the temperature gradient during the heating. Two of the flitches (Q. candicans and Q. laurina), were tested at 60O C, other two (Q. candicans and Q. rugosa) at 65OC and the last two (Q. laurina and Q. rugosa) at 70O C. In general the veneer of Q. candicans and Q. laurina, was the best in texture, with small checks and uniform in color. The veneer of Q. rugosa showed some variation in color, with dark-brownish spots, apparently due to bacterial attack to the trees, and small holes in the veneer from the outer part of the log, due to large rays dimensions. The temperature between 60 to 75O C is considered adequate to process oak wood. Regarding the heating time used in this study, form 50 to 65 hours, it is suggested to use it as a guideline due to the changes in the practices and equipment between plywood mills. Regarding the porous arrangement in the veneer, it was very uniform in its structure, even though Q. candicans and Q. laurina have circular porous distribution; this characteristic was not reflected in the Acathedral@ configuration, which has a higher demand by the final user of plywood.

Se llevó a cabo un análisis químico para determinar los principales componentes químicos de cinco especies de encinos del estado de Puebla. Las especies estudiadas fueron Quercus affinis, Q. crassifolia, Q. glabrescens, Q. mexicana y Q. laurina. Para cada una se determinaron los contenidos de "-celulosa, lignina, pentosanos, extractivos solubles en etanolbenceno, ceniza, sílice y taninos en una mezcla de madera de albura-duramen. También se determinaron los contenidos de extractivos y sílice en madera de albura y duramen, asimismo el contenido de taninos en la corteza fue determinado. Las cantidades de componentes químicos presentes en la mezcla de madera de albura y duramen de las especies se encuentran en el rango de 54.24 a 56.72% para la "-celulosa, de 19.84 a 22.35% para la lignina, de 18.37 a 21.64% para los pentosanos, de 3.84 a 5.24% para los solubles en etanol-benceno, de 0.87 a 1.38% para la ceniza, de 0.0040 a 0.0096% para el sílice, y de 1.17 a 3.46% para los taninos. Los contenidos de solubles en etanol-benceno y de sílice fueron más altos en la madera de duramen que en la madera de albura de las cinco especies. El contenido de taninos también fue más alto en las cortezas (7.4-10.4%) que en las mezclas de madera de albura-duramen. El análisis de varianza estadístico de los resultados indicaron que los componentes químicos varían significativamente (P < 0.05) entre las especies y el tipo de madera.

In forest ecosystems management it is a primary need to elaborate volume tables and tariffs appropriate for arboreal specimens with economic importance, therefore it turns out to be a fundamental condition in sustainable ecological planning, the establishment of these mensuration systems. The present study is based on the development of a mathematical system to estimate volumes of arboreal species, through the application of an association of mathematical models. The obtained result, after the respective statistical analysis, proves that the use of the volume tariffs for global evaluations within the forest ecosystems represents a tool of great usefulness, by achieving a high precision in considering how valuable the renewable natural resources are.

Some anatomical features of wood, like vessels, fibres and ray dimensions, were studied. Also axial and tangential sound velocity and Young's moduli, axial, radial and tangential were obtanied of three hardwood species from Huayacocotla, Ver. The results show that pore number, fibre cell wall thickness influence directly the axial sound velocity. Rays are structures which are partly responsible for high values of radial velocity and low values of tangential velocity. It is recommended that Prunus brachybotrya and Cleyera sp are used to substitute Acer species employed in box violin construction.

A first dasometric analysis using data from permanent plots was made around the early 70's at El Poleo, in Chihuahua State. The results consist of a set of dasometric equations allowing the estimation of the average behavior along time, of growth, yield and possible survival of the stands represented in the sample. Such equations initially allow us to know the net growth and yield wood of those stands, with the obvious advantage for operative silvicultural management of stands from El Poleo, Madera, Chihuahua.

The ethnic Mayan inherited one of the most outstanding civilizations which have developed in tropical forests. Their autochthonous knowledge regarding the environment continues to serve today as an exemplary case of "forest culture." A historical analysis reveals the conception which these ethnics had regarding their forest resource and how this valorization has changed in the presence of other cultures without brushing aside their autochthonous culture. Presently this culture is restructuring to incorporate contemporary elements of the global market as parte of their inevitable transculturation. The experiences of the government and non-government institutions coincide in their programs and goals with the Mayan's on the Yucatan Peninsula, now surpassing community forestry and are formulating an example of what we can call ethno-silviculture. Education remains as a critical unknown factor which should be attended to enable the continued evolution of the society towards the improvement of the quality of life.

Oakwood (Quercus sp) is a very important forest resource in México, but its use is very reduced. In order to provide options to increase the utilization of oakwood, this paper presents the procedures of fabrication of nine oakwood glue laminated beams, which were tested in bending and the mechanical properties obtained are presented. Two species were collected and sawn to make the gluelaminated beams, for both species their physical and mechanical properties were determined making tests on small clear specimens. Four trees were collected at the Cofre de Perote, three of Quercus laurina and one of Quercus crassifolia.

A system was created to classify Mexican woods in clear (defect free) green condition taking as input a recently created data base. The classification criterion is specific gravity. The mechanical properties considered were: static bending, compression parallel to grain, compression perpendicular to grain, Janka hardness and shear parallel to grain. This system allows to classify woods in five groups: very high, high, medium, low and very low, through a powerlow regression.

It is intended here, to evaluate the efficiency of band saws with the characteristics most commonly used in Costa Rica, as well as treatments recommended for hardwoods (teeth with stelite reinforcements) such as is the case of the species Dialium guinense (Aubl) Sandwith since it is not widely used in Costa Rica in spite of its great abundance because it is considered an extremely hard and abrasive wood. At the same time, the sillica content was determined for this species in two conditions: green logs, near its maximum moisture content and logs with almost six months to be cut. The values of the physical and mechanical properties were also determined in order to disseminate a solution to the problems found in the processing of the wood species with the equipment installed in Costa Rica.

The anatomical characteristics, physical properties, mechanical properties and air-drying speed were determined for the wood of five trees of Quercus sideroxyla Humb. & Bonpl. (red oak) and two of Quercus rugosa Nee (white Oak), collected in three municipalities of the State of Durango. For the macroscopic anatomical study specimens of 12 cm x 7 cm x 1 cm were used and for the microscopic anatomical study, thin slices were cut and used along with fragmented material. Histochemical tests were carried out to determine tannins. The measurable elements were classified based on the average. They included the taxonomic position, morphological characteristics, geographic and altitudinal distribution and common names. The technological characteristics were determined in green and dry conditions, using specimens of various dimensions. The wood of the seven individuals, presented similar characteristics in some cases and different in others between subgenera and differences between individuals of the same subgenus were recorded. The physical characteristics of both species are classified as high to very high; the mechanical properties in both green and dry conditions are classified as hard, stiff and strong in the majority of the cases, with the notable exception of the strength in compression parallel of the two species and shear parallel of Q. rugosa which is moderately strong. The results were compared with data available in the literature for both species, coinciding in many characteristics with the studied in the present work. Based on the results suggested applications are given.