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

With commercial aperture, Mexican forest products have faced difficulties for accessing international markets and maintaining their participation in internal markets; exports have decreased and imports increased, with a consequent increase in trade-balance deficit. The sawn timber industry, the most important because of the volume that processes, as for the number of existent industrial plants, has been the most affected one. In the last six years, the lumber imports have increased significantly. This implies greater commercial dependence of this product, supplying great part of the lumber apparent national consumption with imports coming from Chile, the United States, Brazil and Canada. To reverse this tendency, it is urgent to implement a series of public policies aimed at strengthening this industry in the medium and short terms. Otherwise negative effects are sure to show, such as greater pressure on natural forests, partial or total closing of sawmills, unemployment increase, and loss of an important source of revenue for the owners of the forest resource.

Wooden structural elements that support permanent loads bear mechanical strains. This indicates the viscoelastic nature of this material. In order to guarantee the structure’s reliability it is necessary to predict the elastic and viscous response of wood in service. The objective of this research is to show the viscoelastic nature of wood, which in turn is manifested by the difference between the Static and Dynamic Modulus of Elasticity values of a standard sample of Prosopis sp. wood. Non-destructive tests were carried out by following two procedures: transverse flexural vibration and static bending. Results showed that the Static Modulus of Elasticity (MOE) is a good predictor of the Dynamic Modulus of Elasticity (Ed) and viceversa. In addition, the high coefficient of correlation found between these parameters denotes that if the value of MOE of Prosopis sp. wood increases, the value of its Ed increases proportionally. The dynamic tests were reliable, fast and the parameters measured were more repetitive in contrast with the Static tests. This research was a case study. As a consequence of this study, the methodology for studying other wood species with different specimen’s geometry is possible.

To evaluate the effect of the production and consumption of pine lumber related to variations in prices, the elasticities for supply and demand were calculated in a 23 year period (1980-2003), and fitted to a system of simultaneous equations for supply, demand, price transmission and identity. The results indicate that pine saw wood production is inelastic (0,0748) to the variations in prices and the factors that affect the supply are the used capacity and the installed capacity in forest industries, the minimum wage and the real interest rate. The demand is also inelastic (-0,1743) to the changes in prices in the short and long term, and the factors that affect the lumber consumption, based upon their elasticities, are the delayed consumption and available real income.

The microbiological effect of the secondary metabolites developed as mechanism of passive defense, in the wood of the species Puy (Tabebuia serratifolia (Vahl.) Nicholson), Zapatero (Peltogyne porphyrocardia Griseb.), Algarrobo (Hymenaea courbaril L.) and Cartan (Centrolubium paraense Tul. var. orinocense Benth) was evaluated under laboratory conditions, against two common microorganisms that cause deterioration on the wood G. traveum and T. versicolor. Antifungal assay was carried out using the agar dilution method with superficial inoculation. Solvents, like acetone, ethanol and water, of different polarity were evaluated for the recovery of the extractives. Malt extract agar was used in the antifungal assay at concentration of 0,05%, 0,1% and 0,2% (v/v). The growth inhibition was used as a measure to evaluate the effectiveness of the natural chemical product. Results of the preliminary evaluation demonstrated that all the evaluated extracts present biological activity associated with the microorganisms test. The antifungal activity of the soluble extract in water, sustains that it is the most tolerant for the microorganisms that deteriorate wood. This may be attributed to the presence of organic materials called heartwood´s sugar. The acetonic and ethanolic extracts showed to have the capacity to extract the higher quantity of active biologically compound of the heartwood of the species, producing higher growth inhibition of the microorganisms used in the study.

This work was carried out to evaluate the effect of two silvicultural treatments on the composition and structure of forest ecosystems in the “Sierra de la Candela” (Mountain range) near Tepehuanes, Durango. The analysis was done comparing two experimental plots managed under different silvicultural practices, the first with thinning and the second using selective logging. Several neighborhood-based indices were used via the so-called “structural group of five trees” sampling method. The results obtained in the study show that the tree species mixture and diversity is greater in the plot where the selective logging was applied, compared to that treated by thinning. Both plots present a clumped spatial tree distribution. On the other hand, the size differentiation results were not significantly different in relation to the dimensional tree structure of the studied plots.

Free radicals scavengers of ethanolic and aqueous extracts from Pinus ayacahuite, Pinus cooperi, Pinus durangensis, Pinus leiophylla and Pinus teocote bark were evaluated, using the diphenylpicrylhydrazyl (DPPH) radical assay, to extract concentrations of (250, 500, 750, 1000 and 1250) mg L-1. The scavengers were compared with butilhydroxitolueno (BHT) and butilhydroxianisol (BHA) . Ethanolic extracts had higher activity than the aqueous one, specially P. leiophylla and P. durangensis, with scavengers at500 mg L-1 of (90,4 ± 0,98) % and (83,0 ± 1,41) %, similar to BHA (83,6 ± 0,20) % and higher than BHT (50,3 ± 0,72) %. Other than P. cooperi all extracts showed scavengers higher to 90,0 % at 1250 mg L-1. The concentration for scavengers 50,0 % of radical (CE50)  was evaluated. The antimicrobial activity of the extracts was evaluated using agar dilution method against Staphylococcus aureus, Enterococcus sp., Escherichia coli and Pseudomonas aeruginosa to concentrations of (0,625, 2,5, 5,0, 10,0 and 20,0) mg/mL. The minimal inhibitory concentration (MIC)  was reported. Ethanolic extracts had higher activity than the aqueous one. S. aureus was the most inhibited (MIC 0,625 mg/mL), Enterococcus sp. moderaty inhibited (MIC 2,5 mg/mL), E. coli do not had a good inhibition (MIC 10,0 to 20,0) mg/mL. P. aeruginosa only was efficiently inhibited by P. cooperi (2,5 mg/mL) ethanolic extract.

Chips of avocado wood (Persea americana Mill.) were pulped by means of conventional Soda and Kraft pulping processes. The pulps were bleached with an elemental-chlorine-free sequence OD1-Eop-D2, pre-setting reaction conditions for the first chlorine dioxide stage (D1) . The results show that during the chemical pulping process, avocado wood is easier to cook than other hardwoods such as eucalyptus. The avocado pulp also showed a very good bleachability, reaching brightness levels of up to 92% ISO compared to 84% for eucalyptus after the ECF bleaching sequence. The avocado Kraft pulps required more chemical input in the bleaching sequence than the Soda pulps. On the other hand, the physico-mechanical properties of the pulp were not notably reduced by the bleaching process, the Kraft pulp being stronger than the soda pulp. Strength properties of avocado are similar to those of eucalyptus; therefore this raw material constitutes a worthwhile choice for cellulosic fiber supply.

The purpose of this work was to compare the population structure and some demographic parameters of Juniperus flaccida between two populations in order to contribute for a better understanding of the management practices, as well as the use and conservation of this species. Two permanent plots of1ha each one were settled down under different perturbation conditions to compare both, the population structures and demographic parameters of Juniperus flaccida. Perturbation conditions were: for plot P1, with selective wood extraction and presence of cattle grazing, and for plot P2 with neither selective wood extraction nor cattle grazing but natural disturbances. In each plot all individuals of J. flaccida were marked, numbered and measured in their height, diameter to breast height (dbh) and survival, growth and fecundity were estimated on an annual basis in both plots. Population density and sex ratio (males:females) were estimated for each plot, and based on height and dbh individual parameters each population was structured in 8 size categories. The densities of the categories of both population sizes showed differences statistically significant between them. The sex ratio did not present significant differences from a theoretical 1:1 ratio in the population with selective wood extraction and cattle grazing. On the other hand, there were significant differences in the population without wood extraction. The frequencies of mortality by size categories showed significant differences into populations. The absolute rate growth of mature individuals and their fecundities were higher in the plot with wood extraction and cattle grazing. The differences in both population structures and demographic parameters of the population were associated with the perturbation conditions.

This paper analyzed some socio-economic conditions of forest-dependent, non-forest dependent, and policy-sensitive municipalities in the state of Durango, Mexico. Knowledge of the socioeconomic relationships among variables that determine the main characteristics of a geographic area is important for planners and decision makers in both public and private sectors. For example, assigning monetary resources for socio-economic development or business expansion requires recognition of the territory boundaries in which the projects are embedded. The study used 51 variables to assess the socio-economic conditions, including poverty and migration indexes, and its influence on current forest conditions. Durango’s forests are characterized by pine, oak, and other conifer associations. Yearly, the forest production hits 1,8 million m3r and generates around USD $120 million. While this figures position the state as the first forest producer, it ranks seventh among the Mexican states with the highest rate of illegal immigration, primarily to the USA, and sixteenth with the highest poverty index. The study recommends diversify the use of natural resources and prioritize those policy-sensitive counties when planning and assigning monetary resources.

Despite the severe problems of deforestation that suffer the forests in México, there are only a few detailed studies to identify, in a very precise manner, the dynamics of disturbance or recovery of such ecosystems. In the present work, a detailed methodology to analyze the land cover change in the Nevado de Toluca National Park is presented. With the aid of Geografical Information Systems and the production of two land cover maps of the national park for two different years (1972 and 2000), it was possible to obtain a map of changes. The transition observed in this map was then re-classified with a loss or gain criteria and, with this, it was possible to obtain a final map of forest disturbance-recovery. The national park presented a deforestation rate of 8,4%, with a land cover change of more than 2 000 hectares along the period.