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

In order to study if mechanical elements are involved in conduction, relationships between wood anatomical variables and functional relations were analyzed. For this purpose canonical correlation analysis was performed. Vessel area, diameter and length were selected as the dependant set to represent xylem conductivity, and fiber diameter, length and wall thickness as well as fiber percentage as the independent set, associated to mechanical elements, assuming that they are involved in conduction too. Results showed that both sets of variables were highly correlated showing the association between conduction and mechanical systems. Aspidosperma quebracho-blanco has specialized xylem to avoid water stress. Solitary vessels provide efficient water conduction, while tracheids and fiber-tracheids provide a subsidiary system responsible also of water movement. In this species xylem works as an interconnected network in which conductive and resistance systems are interrelated.

The Las Joyas Field Station (LJFS) in the Sierra de Manantlán is characterized by a long history of anthropogenic disturbance. In 1988 a fence was established that delimited Las Joyas, excluding any anthropogenic disturbance. The fence divides different areas of cloud, pine and oak forests; consequently some forest areas have been under the pressure of cattle grazing and others not. The study was carried out in these forest with two replicates, where 180 plots of 2 x 2 m were randomly: 90 plots where established outside of the LJFS and the rest inside. In these plots, tree regeneration was recorded (specie, density and tree height), and 38 species from 33 families and 35 genus were recorded. The number of juvenile trees was significantly different in the cattle excluded sites and the cattle grazing sites (in all the cases, χ2 >7.5 y p <0.001). Floristic composition was also different. Inga hintonii and Alnus jorullensis are species that were not found in those sites with cattle grazing, suggesting that such species might be extinct with cattle grazing activities. Xylosma flexuosum and Pinus douglasiana showed significant importance values in the cattle excluded sites on cloud forest and pine-oak forest, respectively. In pine forest, Pinus douglasiana and Prunus serotina showed the highest importance values in both cattle excluded sites and cattle sites. It is concluded that cattle grazing is influencing a change on the species composition and is also declining the number of juvenile trees per hectare in the three types of vegetation studied.

A greenhouse study on sixteenmonth-old seedlings of Pinus greggii was carried out to determine whether geographic variation exists in relation to soil acidity. The study included five openpollinated families from each of twelve populations. Significant differences were found both among and within populations for seedling emergence, leaf color and total height. A pattern was detected in relation to geographic location. Northern populations as a group showed different treatment effects than the southern populations. This result agrees with information recently published in the description of a new variety of the species. Seedling height and leaf color were found to be under genetic control which may be useful for early selection of families within superior provenances.

This research study focused on strategic planning for sustainable community forestry in Chihuahua State, Mexico. The research involved two forest ejidos in the Sierra Tarahumara: Basihuare and Cusarare from Guachochi Municipality.  The objectives were: 1) assess the current forest resource management in both communities, 2) conduct a Search Conference (SC) (participative strategic planning methodology) for forest-based community development to achieve a greater awareness of development needs, positive perceptions and attitude change and to design a strategic action plan for a future community, and 3) assess the attitudinal and perceptual impact of the SC (strategic planning intervention) of local people toward community development. The results showed that: 1) ethnographic interviews were a valuable complement to and cross-check on the participatory approaches to obtaining views from the community members about their community forest resource management, and 2) the SC achieved a greater awareness of development needs and created more positive attitudes and perceptions about community development in Basihuare more than Cusárare who did not receive the intervention (SC). Additionally, the SC helped the Basihuare community to design its own strategic action plan for future development. The community not only developed its own strategic action plan, but also, because of the participative and democratic process they used, they became a planning community. Finally, the results suggest that the study could serve like a model for the application of the open system theory for the development of sustainable forestry communities in the Sierra Tarahumara and in other places more to regional, national, and international level. 

Some of the drying problems of tropical species in conventional kilns are associated with the diversity of their technological properties, with the difficulty of gathering adequate volumes of the same species to apply them a drying schedule according to the wood characteristics, and with the high cost of the process that determines the profitable capacity of the kilns and limits its utilization to dry small volumes of lumber. An alternative to overcome these limitations is  to  integrate  groups of similar species in volumes according to the capacity of the kilns, to be able to apply them the same drying schedule. This study was performed with the goal of integrating groups of tropical wood species that could be dried with the same schedule in order to make feasible the drying process in conventional kilns. For this study, the sawn lumber of 33 tropical species was used, which was integrated in two groups according to their specific gravity, 16 species with specific gravity of 0.30 to 0.60, and 17 with 0.60 to 0.90. A drying schedule was formulated for each group, that was evaluated in a conventional kiln, analyzing the deffects of each board  before and after the drying process (checks, twist, cup, bow and crook). In general, the two schedules applied to the two groups of species were adequate since no significant defects  due to the drying process were observed. In the group of species with specific gravity below 0.60, 10 of them  dried faster than the other 6, which suggest the possibility of subgrouping them to optimize the used of the dry kilns applying them a faster schedule. With the schedule for the species with specific gravity higher than 0.60, 7 of them dried at aproximately half of the time (10 - 14 days) than the other 10, which suggests the possibility of subgrouping them to optimize the use of dry kilns. If it is not possible to regroup the species within each category  to achieve a uniform process, it is suggested to integrate the lumber with similar moisture content and dimensions in each one of the two groups analized in this study.

An analysis considering the effect of harvest volume estimated through the Mexican Method of Forest Regulation (MMFR) on the sustainability of forest is presented. The analysis postulates that growth projection of a forest population must follow a logistic behavior, instead of an exponential behavior as assumed by the MMFR. When growth projection follows a logistic behavior, then harvest regulation is possible in the long run and it is easy to identify criteria to evaluate sustained yield and the sustainability of the residual forest in the short run. In addition, it is possible to identify economically optimal harvest volumes. On the other hand, the assumption of exponential growth does not allow neither harvest regulation nor sustainability criteria identification. In addition it is not possible to estimate an economically optimal harvest volume. Results show that the assumption of exponential growth from the MMFR must be modified and the management of residual forest structures must be emphasized in order to achieve sustainability on the Mexican forests managed under an irregular system.

The content of holocellulose, alfacellulose, lignin, ash, and extractives in cold water, hot water and ethanol-benzene was determined in sapwood and heartwood of Casuarina equisetifolia L. according to ASTM standards. The heartwood of casuarina wood has a greater alfa-cellulose, ash and extractives content than does its sapwood. The contents of lignin and holocellulose are similar in both samples.Fibrous material was prepared by the rapid method with a mixture of nitric acid, acetic acid, lactic acid and glycerine in equal parts. The fibers in this material were measured with a microscope and with the obtained data the indices for stiffness, flexibility, Peteri coefficient and Runkel ratio were calculated. The fibers of casuarina wood have a thick wall cell and according to the pulp index quality they are classified as regular for paper, wuith a IV quality grade.

The relationships between economy and environment are analized within the context of sustainable development in the forest sector of México. The central argument is that the premises of both are not necessarily in opposition and that a harmonious development can be achieved, provided that a series of principles are upheld, and in particular, the opinion of all of the society is taken into consideration in the governmental plans. From an ecological point of view, some points in relation with the effects of the industrial production on the global warming are discussed and some ways of mitigating it are mentioned. The challenges that the forest sector faces in México are detailed, along with the impact of the forest industry in the national development. The propositions of a State Forest Development Plan are mentioned, arguing that this sort of plan could be a model for other States. As a conclusion, a positive outlook for the forest industry is foreseen, on the condition that the principles of sustainable development are put into practice with the support of the society as a whole.

A dasometric analysis using data from permanent plots established during the early 70's at San Juan Tetla Forest Experimental Camp, Puebla State, was made. The results included a set of dasometric equations which allow us to estimate the average behavior through time, of growth, yield and probable 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 the operative silvicultural management of stands of Pinus montezumae Lamb., Chiautzingo, Puebla, México.

A description is made of the situation of oak wood use in México. The most recent statistics of standing forest volume and wood production are included. Reference is made of the distribution of this resource in the country. The subjects treated in this work are: utilization of oak wood (including cellulose, sawn wood, fuel, crossties, poles, piles, round wood, veneer and plywood), and the influence of the technological characteristics on its use. The exploitation of oakwood is discussed in the context of the international market.It is concluded that the conservation of oak forests is an urgent task to preserve the ecological equilibrium of its growing areas.