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

In pine forests with an historical fire regime of frequent low severity surface fires, under extreme weather conditions or a consequence of fire suppression, the severity of fires may increase. Response of vegetation to severe fire events was studied in a chronosequence of 8 years, 28 years and 60 years in a forest dominated by Pinus douglasiana in Mexico. Tree density (> 2.5 cm diameter) reached values of 1095 stems ha-1 ± 609 stems ha-1 and a basal area of 10.0 m2 ha-1 ± 2.2 m2 ha-1 in the 8 years stands; 28 years after stand-replacement fires, basal area (44.6 m2 ha-1 ± 3.0 m2 ha-1) was close to that of 60-year-old stands (49.0 m2 ha-1 ± 6.4 m2 ha-1). Pines showed the highest importance value across the chronosequence; with post-fire time, a formation of a sub-canopy of shade-tolerant broad-leaved species and an increase in species richness and diversity was observed. Long periods without fire increased surface fuel loading (66.0 Mg ha-1 ± 5.5 Mg ha-1 for 28 years and 61.5 Mg ha-1 ± 4.6 Mg ha-1 for 60 years-old stands) and changed fire behavior (spread velocity increased from 1.3 m s-1 to 4.1 m s- 1 and flame length from 0.7 m to 1.7 m between the 8 years stands and 28 years - 60 years stands combined). Results suggest that the fire suppression policy in pine forests should be evaluated considering the balance between biological conservation goals and mitigation of high severity fire danger.

Mangroves have been considered as an important carbon storage, and in general, exceeding the carbon content of terrestrial forests. Even when mangrove aerial carbon sequestration has been studied in several regions of Mexico, the information at the Pacific coast is lacking. The aim of this work was to characterize the structure of riverine mangroves in order to determine height, coverage, DBH and to estimate the complexity and importance value indexes, as well to relate it with the carbon storage, in 32 circular sampling units (400 m2) at La Encrucijada Reserve, Chiapas. The carbon content was quantified according allometric equations for Neotropical mangrove species, with high structural development and we used a biomass to carbon conversion factor of 0.48. The influence of the interstitial sediment parameters (pH, salinity, temperature) on the stored carbon was determined using an analysis of variance and covariance. Mangrove density was 2103 ind ha-1, the tree mean height was 12 m; basal area, 18.7 m2 ha-1; coverage, 9.9 m2 and DAP, 8.4 cm. A complexity index of 40.1 was recorded; the order of importance of the species was Rhizophora mangle / Avicennia germinans / Laguncularia racemosa. The carbon store was 87.0 Mg ha-1. Structural parameters showed a high correlation (R = 1.00, 0.94 and 0.84) with the mangrove biomass. In function of this structure, this ecosystem was classified as a successional stage of intermediate community with a high structural complexity.

Forest management decisions are addressed using dynamic growth and yield equations, which predict the future forest dynamic as a function of stand-level attributes and providing information for decision-making in sustainable development. They are more widely used as practical tools in forestry and can be desirable for plantation management-planning. Teak (Tectona grandis L. f.) is an important commercial species in plantations from Mexico, although there is a lack of scientific knowledge as regards the management or modeling tools to support functional forest management decision making. In this study an explicit growth and yield system (G&YS) was developed for plantation of Teak in Campeche, Mexico. The G&YS was integrated for algebraic difference dynamic equations and they were fitted to pairs of dasometric variables of stem-mapped re-measurements plots. The G&YS components were selected according to the goodness-of-fit system, also the graphical analysis between actual and fitted values was used. Both analyses considered the statistic accuracy and biologically realistic predictions. The mortality function was associated with the initial planting density and also it was sensitive to the site index. The selected growth systems for the basal area and volume per hectare were based on Schumacher equation. For a site index of 18 m at a reference age equal to 7.5 years and forest rotation equal to 19-year, the global estimated yield was of 152.75 m3 ha−1, while for densities of 1,250 trees per hectare and 816 trees per hectare, the yields were 136.86 m3 ha−1 and 113.12 m3 ha−1, respectively. The G&YS generated allows estimating the total volume with bark per hectare under the specific local conditions of establishment, silvicultural management and site quality of the teak plantations analyzed.

The work in the sawmill industry is physically demanding because it is performed under unhealthy body postures that generate musculoskeletal injuries and its study requires risk assessment tools to identify the most serious. In the sawmills of El Salto, Durango, Mexico, the level of risk of the work positions in people is unknown; therefore, the objective of this study was to perform a postural analysis in 15 workplaces. From 7.5 hours of video that considered effective work in the workplace, 900 still images were obtained at 30-second intervals to analyze them using the OWAS method. The global index of postural risk was estimated and contingency tables and association tests between categorical variables of chi square were elaborated. The results showed a frequency of postures of 48% with risk levels 2, 3 and 4, indicating actions for postural correction for risks 2 and 3 as well as immediate modifications for the 4. The global risk index was established at 166 points cataloged as minimum. By workplace, the workers in the manual logs handling and manual stacking and carriage of lumber are the most susceptible to present injuries with global risk indexes above 200 points. By body area, 43% of the positions of the back and 40% of the legs are in a level risk 2 considered as not harmful, and 100% of the positions of the arms resulted with a level risk 1 not requiring any modification.

This research had the objective to know the emotional perception of designers about the five most sold commercial woods in Chile, to establish conclusions referred to perceived quality. The study seeks to assess comparative and hierarchical preferential valuations among species and learn about relevant visual characteristics of wood with influence in user satisfaction. Usually, the eligibility criteria for aesthetic applications is focused on the designer, assigning him/her the task of making decisions to devise spatial configurations designed to meet end users requirements, who are making use of these facilities. Through this study, the designer acquires new useful information to assess emotions the living space could cause in future occupants, based on the use of wood species. The methodological foundation focuses on kansei engineering application, a discipline responsible of establishing relationships between the emotions that a given stimulus generates in human beings, in this case, the presence of wood. The study was carried out on an intentional non-probabilistic sample of experts from the design area, using survey with quantifiable options and structured questions according to semantic axes. As result, the answers obtained were referred to wood valuations and a data collection method that can be extrapolated to studies related to other types of commercial wood was generated. The specific conclusion is that dark, knotless woods are better valued emotionally by users.

By estimating forest biomass, it is possible to determine the amount of forest resources existing in a given territory, however, this is an expensive and time-consuming process. Therefore, the objective of the present study was to model the aerial tree biomass of a forest ecosystem located in the south central region of the state of San Luis Potosí. To define this process, we compared deterministic methods (weighted reverse distance) and stochastic methods (kriging and cokriging), with which the forest biomass was determined based on field and spectral data. Field data corresponded to 50 conglomerates of the National Forest Inventory, from which the biomass was calculated by using allometric equations. The spectral data (traditional NDVI -red and infrared bands of electromagnetic spectrum) were derived from a Landsat 5TM image of the year 2009. With the results of calculation of biomass and NDVI, semivariograms and cross variograms were tested with spherical, exponential and gaussian models to analyze which will result in the best fit. Subsequently, the exponential model derived from the cokriging technique was selected, based on which a square root value of the RMSE mean squared error of 32.01 Mg ha-1 was obtained. Finally, based on the selected model, a map was generated of the aerial biomass distribution, in which results that range from the 0.85 Mg ha-1 to 157 Mg ha-1 are presented.

In the state of Chiapas, Mexico, Pinus oocarpa Schiede ex Schlechtendal is one favorite species for the establishment of forest plantations and ecological restoration. However, the variation of important variables such as wood density is unknown. The objective of this study was to know the sources of the phenotypic variation of the basic wood density, the patterns of axial and radial variation, and predictive models to estimate the mean wood density (DPM) of Pinus oocarpa in seed production stands in Chiapas, Mexico. Wood samples was obtained at a 1.30 m, 0.30 m, 1.30 m, 40% and 60% height from trees from each population. The density of the wood was determined with an empirical method. The variation was determined by an analysis of variance and components variance. The variation attributable to the seed production stands was low (10.70%). The highest variation was detected between and within trees with 39.30% of the total variation. The pattern of axial variation was descending, presenting higher density in the lower part of the stem. The radial variation for this species indicates an increase in the density of the wood from the pit to the bark. The model DPM = 0.107 + (0.714 * den0.30) is the simplest and has a value of R2adj of 0.927 to determine the mean density of the tree. The correlation indexes in Corazón del Valle suggest the possibility of selecting and producing P. oocarpa genotypes of fast growth, and at the same time obtaining a higher density in the produced wood.

Here, we studied the composition, structure and functioning of the woody vegetation of a 1000-ha area of the Central Argentine Chaco. First, we identified, through Landsat satellite image processing, three different vegetation classes: two forest types and a savanna. Each class was field surveyed to analyze the composition and structure of the woody plant community. Functioning was assessed through the enhanced vegetation index – a proxy of productivity – obtained from the MODIS sensor. The forest classes showed no differences in composition but some differences in structural attributes, particularly in the density of the dominant tree species in the area, Aspidosperma quebracho-blanco. As expected, the savanna showed less density and basal area of woody plants, with a relative high proportion of tree species seedlings and heliophilous shrubs. The forest class with less density of A. quebracho-blanco presented higher productivity. This could be related to a higher ability of the shrub layer to intercept radiation because shrubs are under an open canopy, as has been noted for early successional stages. Additionally, we found that annual mean productivity for the three classes showed a negative trend in the period 2000-2014. Our results provide valuable information since there are no studies addressing relationships between structural and functional attributes at local level in the Chaco Region.

The implicit prediction is an important tool to know the type of products that can be obtained from the forest in a given time, and thus to plan the sustainable forest management. In the Sierra Norte de Oaxaca, Mexico, there are even-aged stands of Pinus patula, a fast-growing timber species with economic and ecological value. The aim of this study was to estimate the growth and yield timber of this species with the diameter distribution models approach. The database consisted of 132 diameter distributions from 66 permanent sampling plots of 400 m2, located in Ixtlán de Juárez, Oaxaca, Mexico. Stand diameter distribution was estimated through Weibull function with parameters prediction and percentile prediction approaches. Also, minimum diameter and quadratic mean diameter projection models were fitted to recover the parameters and to estimate the diameter structure of stands on the future. The best system was the prediction of parameters because of this had the smaller bias in the prediction of the total volume with respect to an explicit projection system designed for the species. Therefore, it is recommended to use this implicit prediction system to plan the management of even-aged stands of P. patula.

Pests represent a negative effect on forests and are often underestimated by man. Pests outbreaks contribute directly or indirectly to the economy and the environment. One of the main problems in the forest ecosystems is the pine defoliating pests, known as "sawfly". The aim of this research was to characterize extracts from different parts (leaf, stem and root) of Datura stramonium to evaluate their toxic properties and potential use as an organic insecticide on larvae of Neodiprion autumnalis. The repellency and mortality of the sawfly in Pinus leiophylla, treated with hydroalcoholic extracts, was evaluated in the laboratory at 0 h, 3 h, 6 h, 12 h and 24 h. To do the characterization, the extraction of alkaloids was carried out. Extracts were analyzed by gas chromatography coupled to mass spectrometry that allowed identification of the main tropane alkaloids. Statistical analyzes were performed comparing means by the Tukey test at 5% of probability, and differences were found between treatments performed for each plant extract and applied doses (10 mg/L, 30 mg/L y 50 mg/L) with respect to the control. Results showed mortality percentages of 7% to 30%, depending on the dose and the time of exposure to the larvae. The plant structure presenting the best results was the root, followed by the leaves and the stem. These extracts could be a fundamental part of an integrated pest management.