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

The watershed of the Pilón River is important for its water capture for commercial agriculture and for the conservation of the biological diversity of Nuevo Leon state. However, the magnitude of the forest and shrub fragmentation has not been determined, and the remaining fragments of higher conservation priority have not been identified. This study evaluates the vegetation fragmentation, using the fragment size and the relation between the perimeter and the fragment area (P/A) as indicators of size and shape, as well as the distance to the nearest neighbor and the intersection index and juxtaposition as connectivity indicators. These indicators were calculated in maps generated through satellite images Landsat of 1974 and 2000 interpretation (classification supervised and stratified). The results show statistically significant changes in the size and shape of fragments as well as in connectivity for all plant communities evaluated. The communities more affected by fragmentation in their size and shape were Abies and Oak forests, as well as the huizachal (Acacia scrub), piedmont scrub and pine forest. In its connectivity, fragmentation was more severe for Tamaulipan thorn scrub, piedmont scrub and desert scrub as well as huizachales. The fragments with higher priority conservation were determined considering their functions as buffer zones and as vegetation for slope stabilization, through the criteria application in a geographical information system. The conservation of 347 fragments for buffer zone and 210 fragments for slopes stabilization is recommended.

In order to assess the feasibility of creating a water market in the Tapalpa, Jalisco, Mexico watershed, the SWAT model was fitted to obtain the watershed water balance. The model was calibrated in one of the five subwatersheds included in the Tapalpa watershed with a good fit (R2 = 0,85). All five forestry subwatersheds had good hydrologic behavior, allowing high infiltration water rates, which later on emerges as surface runoff with low sediment yields. The subwatersheds with high percentage of agriculture and grasslands yield more surface runoff as well as more sediment yields. The evapotranspiration from the forestry subwatersheds were higher than agricultural subwatersheds. The water supply from the Tapalpa watershed is 42’963,900 m3 per year on average.

The Nevado de Toluca was declared a National Park, recognizing its importance as a site for aquifer recharge, as well as the value of its natural resources. Today, however, it is the scene of a rapid depredation both human caused and natural. The mistletoe is one of the most important plant parasites group of heterophytes because they cause serious harm on other plants, which has become a problem recently because of the infestation levels of the parasite. In this study data were obtained that permit to know the spatial distribution of this parasite and maps its density in the study area; they can be used for software platforms already in place that have been tested extensively. The results of this study will permit management programs of this parasite that are broked up by reliable information, presumably leading to pretend adequate control of this problem.

Mexican sawn wood is facing a lack of competitiveness with respect to imported wood. Over the period 1993-1995 average national production was able to supply 80% of the national consumption whereas by the period 2001-2003 only was capable of supplying 24%. In order to determine the factors that could revert this tendency, a non linear programming model was used. Results indicate that if there were subsidies a 30% reduction in production costs would decrease imported wood in about 1 ,1%, which means 50,139 m3 of sawn wood, and it would increase the national production in 2,1%. A 20 % reduction in transportation cost would lead to a rise in the national sawn wood production of 3,8%, this is 90 500 m3 in terms of sawn wood; consequently, imported sawn wood would decrease in 2 ,2%, which means 102 034 m3 of sawn wood. If a 6% tariff above the international price were to be implemented, the national production would increase in about 5,6%, this means 132 355 m3 of sawn wood. This tariff will help to decrease imported wood in about 9,5%, this is 306 923 m3 of sawn wood with respect to those of the 2001-2003 period. 

The anatomical, physical and mechanical characteristics of 24 Quercus species of the Lobatae section (red oaks) and of the Quercus section (white oaks) collected in several states of the Mexican Republic are presented. The sample consisted of one to five specimens per species growing in pineoak forests. For the macroscopic anatomical study 12 x 7 x 1 cm specimens were used and slides with views of the different planes as well as the dissociated material were made for the microscopic study. For the physical and mechanical studies, specimens of different sizes were made, according to ASTM standards. All the material was prepared in the different planes: transverse, tangential and radial. Descriptive statistics were calculated for each variable measured and the different properties were classified into categories according to their mean values. Tests were made with small clear green specimens. Based on bibliography, information on other characteristics is included. According to the results obtained, end uses for the woods are suggested.

In this paper an alternative method to evaluate the geometric properties of the cross section of bamboo culms is presented, which are necessary to obtain the mechanical properties of this material subjected to bending tests. The standard test methods recommend calculating the second moment of area for a cross section of bamboo culms with the average diameter of the specimen, measuring two cross sections near of load points. But the section irregularities of culms yield errors of up to 10%. In this paper a procedure is presented to make a numerical integration using Computer Aided Design ( CAD) software. Basically the procedure proposes to obtain a scanned image of the cross sectional area and then to digitalize it for use with the CAD software and carry out the numerical integration to get the moment of inertia. Using this method the errors are reduced to around 0 ,011%. Another possible source of error is analyzed when the MOE is calculated using the deflection values measured at mid-span, instead of the maximum value which occurs outside of this point.

The kiln-drying of lumber is a very important stage into wood-based products processing. During drying process, some defects are produced due to the variable moisture and heat distribution inside of material. In order to optimize the kiln-drying of lumber is important to take into account the transport phenomena controlling the heat and mass transfer in the solid. Due to its physical properties, the hardwoods are a very important raw material, since its hardness, colour, dimensional stability and high resistance to weathering give them a very important commercial value. At the last years, the drying process modelling has been an effective tool to optimize such operations; these models associates energy, mass and momentum balances, which can be expressed as differential equations that are numerically solved to obtain particularly solution for each problem. In this work, the heat and mass transfer mechanisms presents in kiln-drying of lumber are explained, heat and mass transport equations are written, and finally moisture and temperature profiles for European Oakwood Quercus pedoncula during kiln-drying are presented.

The diversity of arboreal species and the forest structure composition of Pinus patula Schl et Cham under different silvicultural conditions, in Ixtlán of Juárez, Oaxaca, Mexico was evaluated and compared. The information was registered only for trees over 7,5 cm of diameter breast height ( dbh ). The diversity was estimated through the Shannon Index (H’), the structural composition was defined through three characteristics, mingling species, spatial distribution and size differentiation, through the indices, Mingling by Godow (Mi), Contagion (Wi) and Dominance (Ui), respectively. The analysis was carried out comparing four silvicultural conditions called, pole stage, young stem, medium stem and old stem. The comparative results showed that greater diversity was presented in the medium stem and old stem forest. The major mingling degree was presented in the old stem condition. The tree distribution, in the four environments, presented a random distribution pattern and the dominance of Pinus patula is increasing while the condition develops.

The Sierra Fría in Aguascalientes is part of the Sierra Madre Occidental Physiographic Province. The predominant vegetation types in the area are pine (P i n u s spp.), oak (Q u e r c u s s p p . ) , juniper (J u n i p e r u s spp.) and mixed forests that have been modified due to wood extraction, fire and heavy grazing. In order to estimate the degree of deterioration or recuperation of these forests a multitemporal study was done from the comparative analyses of airphotos of the area for 1956, 1970 and 1993, that were digitized and georeferenced. Changes in the areas occupied by different types of forest were compared the degree of site fragmentation of each vegetation type, using functions from the geographical information systems. Photographic mosaics for each date were generated, processed and analyzed. The area occupied by each of the forest types in the three dates was compared and an increase was found for Juniper forest, for pine forests and for oak forests from 1956 to 1993. At the same time, oaks increased in number of sites, as will as pine and juniper. Due to these results it was considered that the changes in area and fragmentation degree were not significant which indicates that the rate of use of these resources is about equal to the rate of recuperation. Nonetheless, notable changes were observed in the cover degree or micro fragmentation within sites of each vegetation type, with a tendency to increase.

The macroscopic and microscopic anatomical description of the wood of five fruit species of the Rosaceae family is described. Species of Crataegus mexicana Moc & Sessé ex DC. (Hawthorn), Pyrus communis L. (Pear), Pyrus malus L. (Apple) Maloideae subfamily, Prunus armeniaca L. (Peach) and Prunus domestica L. (Plum) Prunoideae subfamily were collected. The state of Puebla, Municipality of San Felipe Teotlalcingo was the collection site. One tree by species was recollected. The macroscopic study was made in wood samples of 15 x 7 x 1 cm and the microscopic study this was made by using slides of dissociated material and cuts from a cube. Samples of wood and slides showed the three typical planes of wood, namely, transverse cross section, tangential and radial. A univariate statistic analysis was performed to the quantitative elements, which were classified according to their average. The five wood species showed similar macroscopic and microscopic characteristics between subfamily, although there were differences between species of the same subfamily, these were stronger between both subfamilies. The purpose of the study was to suggest possible end uses for the wood of fruits trees, since generally speaking this is not used once the trees are no longer productive.