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

Tropical forests contain approximately 40% of the carbon accumulated in terrestrial biomass. However, the loss and degradation of forests worldwide liberates this carbon and contributes 11% of total global emissions. Forest degradation is an increasing source of carbon emissions, contributing 25% in tropical forest environments; and selective logging is among the principal causes.  The central objective of this study was to evaluate biomass impacts and committed carbon emissions from selective logging in two forestry communities (ejidos with common forest use and rights) in the southern Yucatan Peninsula, Mexico. We compared emissions performance from logging operations in both ejidos, one of them certified as sustainably managed by the Forest Stewardship Council (FSC). The species of roundwood extracted as well as the number of impacted trees from harvesting were recorded and the type of collateral damage from felling, skidding, and transport of timber was quantified. Biomass of harvested timber and impacted vegetation was estimated to calculate carbon emissions using allometric equations. Results indicated that selective logging generated 1.2 Mg m-3 1.5 Mg m-3 of total carbon emissions in the Caobas and 20 de Noviembre ejidos, with 5% and 12% corresponding to collateral damage during felling, respectively.  Overall lower committed emissions and collateral damage from felling and skidding were present in Caobas, the FSC certified ejido. We discuss how forest certification, through implementation of reduced impact logging (RIL) practices can significantly reduce carbon emissions from selective logging in the region.

In recent years in southeastern Mexico, forest plantations of Pinus caribaea have been established, whose purpose is resin extraction and wood production. Both variables have been positively correlated with morphological characteristics such as the shaft shape. Generally, two expressions are used for the description of the stem profile: form factor and taper. In this sense, the objective of the present study was to build a set equations to estimate the stem taper and merchantable volume of three progenies of tropical pines established in a forest plantation in Las Choapas, Veracruz, as well as assess their differences in the stem profile through the approach of dummy variables. Through the model of the linear combined variable and the use of dummy variables, the effect of the provenances on the form factor was analyzed, finding that the hybrid between Pinus caribaea and Pinus elliotti presents a geometry close to the paraboloid. For taper modelling the Demaerschalk model presented the best performance among the tested structures. The mathematical integration of the Demaerschalk model produces a merchantable volume equation that was simultaneously fitted with the taper expression to generate a compatible taper-volume system. The results indicate that the hybrid is superior in the geometry of the bole and in merchantable volume compared to the other two provenances of Pinus caribaea.

Remote sensors in combination with information derived from forest inventories estimate variables of interest with precision and low cost. The objective was to estimate the basal area (AB), timber volume (VTA) and aboveground biomass (B) in different forest ecosystems using Landsat ETM information and National Forest and Soil Inventory (INFyS) in Quintana Roo, Mexico. A correlation matrix was generated between INFyS data and spectral information, and later, a multiple linear regression model. With the selected equations, spatial distribution maps of AB (m2 ha-1), VTA (m3 ha-1)and B (Mg ha-1)were generated. The total inventory was estimated using three approaches: i) Reason Estimators (ERaz), ii) Regression Estimators (EReg), and iii) Estimators of Random Simple Sampling. The first two approaches correspond to the alternative inventory using remote sensors and the third corresponds to the traditional inventory. The correlation coefficient was greater than the normalized difference index with 0.35, 0.39 and 0.39 for AB, VTA and B. The regression models had adjusted determination coefficients of 0.28, 0.32 and 0.32 to estimate AB, VTA and B, respectively. The three estimators are statistically different and show that the EReg is the most conservative and with precision in AB, VTA and B of 2.73%, 2.92% and 2.71%, respectively, in addition to confidence intervals of smaller amplitude than the MSA and ERaz. By updating the inventory using remote sensors, the process of evaluating forest resources and their planning is improved.

We studied species the composition and structure in two sites of the subdeciduous tropical forest in Hobomó, Campeche, Mexico. We analyzed 10 plots of 10 m2 × 10 m2 (1000 m2), in each site, where all individuals with a diameter ≥ 1 cm were measured. Vegetation structure was characterized using the importance values of the species, and species diversity was estimated with the Shannon-Wiener (H’) Index. A total of 79 species, representing 67 genera and 30 families, was recorded. The most diverse families were Fabaceae and Rubiaceae at the two sites. The most diverse genus was Diospyros, followed by Coccoloba and Guettarda. The diversity of woody species in the study sites were 3.68 and 3.59 in site one and site two, respectively, while their corresponding evenness values (according to Pielou’s index) were 0.88 and 0.87, respectively. The mean densities of the woody species encountered in the sites one and two were 6610 ind/ha and 8670 ind/ha, respectively. The three species with the greatest density were Malpighia glabra, Guettarda combsii and Lonchocarpus xuul in site one, and Machaonia lindeniana, Coccoloba cozumelensis and Malpighia glabra in site two. The highest values of importance value index were Bursera simaruba, Lonchocarpus xuul, Guettarda combsii, Platymisium yucatanum and Malpighia glabra in site one and   Lysiloma latisiliquum, Bursera simaruba, Vitex gaumeri, Lonchocarpus xuul y Machaonia lindeniana in site two. These species are the most important in the structure and physiognomy of the community. We can conclude that the richness of the tree species of the two sites studied its similar (site 1with 63 spp. and site two with 62 spp.). The scarcity or abundance of the species is related to human activity (wood extraction), which affects the structure and floristic composition.

Wood is comparatively more conservative than other parts of trees, such as leaves, which present greater phenotypic plasticity. We studied the effect of seed origin on annual increment, physical-mechanical properties and anatomical characteristics of Balfourodendron riedelianum wood in a homogeneous plantation (Luiz Antônio Experimental Station (LAES)) from three natural provenances (Gália and Bauru in São Paulo State and Alvorada do Sul in Paraná State, Brazil). Because genotypic information is a determinant of wood formation, trees were expected to develop wood structure based on their provenances. Our results demostrate that variations in volume, properties and wood anatomy were influenced by provenance. Alvorada do Sul trees showed lower growth in volume and higher strength and homogeneity, compared to Gália and Bauru. Typical radial pattern was not observed for most characteristics, except modulus of elasticity and fiber length in Gália and compression parallel to the grain in Bauru that increased towards the bark. Based on the latter characteristc, B. riedelianum wood in a homogeneous planting has class C40 mechanical strength, as indicated for use in medium-sized structures, light civil construction and the manufacture of furniture.

Fire is a natural phenomenon and indispensable within the biogeochemical cycles of soils, especially those that sustain a forest vegetation as in the case of Andosols. Nevertheless, little is known about the temperatures that are reached in the soils in forest fires, and their immediate effect on their edaphic properties. In April 2017, field trips were conducted in San Pablo Ixayoc, Texcoco, State of Mexico, two days after the start of the forest fire. Composite and unaltered soil samples in the first 5 cm of soil were collected for the analysis of their edaphic and micro-morphological properties. The estimation of the temperature was made through a thermal experiment and mineralogical analysis. Based on the destruction, formation and dominance mainly of the oxides, ferromagnesian and pseudo-sands, the temperatures reached in the forest fires can be grouped in: < 250 °C for superficial and crown fires in Quercus sp. and Pinus sp., and 250 °C - 500 °C in fallen trees and tree roots that continued to be incinerated. The MO, pH, CIC, P, K+ and Na+ and texture show direct and indirect tendencies according to the type of ashes and temperature and not with the severity and type of vegetation. Surface and crown fires immediately modified Andosols' properties and improved their quality, while, at those points where higher temperatures were reached, the soil is affected but there is less impact because fires occur in specific and small areas.

The spatial structure reflects the pattern of arrangement of trees on the ground and is a basic element to understand the dynamics of forest ecosystems. The objective of the present investigation was to evaluate the bivariate structural characteristics of five different associations of Pinus durangensis forests, identifying the similarities and differences in the bivariate distribution of uniformity of angles, dominance and mingling. The data comes from five quadrate sites with an area of 2500 m2, each established in different forests of P. durangensis in the Sierra Madre Occidental. For each site, the average height, average diameter and crown coverage were determined, as well as the species mingling index, angle uniformity and dominance indexes. The indices were combined two to two to obtain three bivariate distributions. The pure forest of P. durangensis presented individuals with higher height, while the largest diameter was found in the association with P. teocote. The mingling index (Mi) indicates that only in the pure forest there is a low species mingling. The uniformity angle index (Wi) shows that trees generally present a random distribution. The values of dominance (Ui) show that in all the sites there are all the social classes represented in an equitable way. The indexes and their combinations adequately describe the spatial distribution of the trees and their relationship with their closest neighbors. The information obtained from the combination of the structural variables contribute to improve the understanding of the spatial structure of the forest, and in addition to contributing to the regulation of cutting intensity and ensuring sustainable management.

This work was carried out with the objective of evaluating, technically and economically, timber extraction in plantations of Pinus caribaea var. caribaea of Macurije forest company located in the province of Pinar del Río, Cuba. For this, time and movement studies were carried out using "productivity" and "unit cost" of wood extraction as evaluation criteria. The skidders and oxen performance evaluation, in different harvest systems and slope classes, was performed through univariate and multivariate (cost and/or productivity) factorial experiments (3 × 3 × 2), following a randomized block design (B1 = 21 years and B2 = 32 years), with the factors "machinery" and "slope" with three and "harvest systems" with two levels. The feasibility and usefulness of the multivariate approach in the evaluation of timber extraction were evidenced; timber extraction is more viable with the tree length harvest systems in stands of 32 years. The interaction machinery-slope had a significant influence on the variation of the whole cost-productivity. The John Deere 548E skidder, for presenting lower unit cost and higher productivity than the J-80A, is recommended for semi-mechanized timber extraction. The most viable is the yoke of oxen because of its greater profitability. However, due to its low productivity, it can only be used in combination with other machines or during periods of decelerated production. Its exclusive use is impracticable since it would imply significantly increasing its quantity to compensate for its low productivity.

The global energy model is based on fossil fuels, which has been replaced by environmental and economic considerations, giving way to biomass and dendroenegetic plantations. In Chile, non-conventional renewable energies (NCRE) have been gaining space, and the nation has focused efforts on species with good energy potential. Thus, this study aims to evaluate the physical-chemical potential, energy and thermal profiles of two species (Paulownia elongata x fortunei and Miscanthus x giganteus) for energy use in three contrasting sites of Chile. The analyses were mostly performed under DIN Standards. The results for Paulownia showed differences between the sites, obtaining the best results in the Vergel site with a percentage of lignin of 34,84%, ashes of 1,16%, volatile material of 81.70%, carbon of 47.02% and a liquid energy density (EL) of 2.16 GJ m-3. For Miscanthus, the best results were also recorded in the Vergel, with a percentage of lignin of 30.60%, ashes of 2.84%, volatile material of 82.26% and carbon of 45.97% and a DEL of 1, 67 GJ m-3, highlighting that the best results of the Vergel site are for density D1. With respect to the thermal profile (TGA-DTG), Paulownia presented mass loss greater than Miscanthus and had ignition at a lower temperature of 197.76 °C and 209.66 °C respectively. Therefore, the highest percentage of waste was presented by Miscanthus with 5.63%. Accordingly, both species have desirable characteristics for their energetic use.

Eucalyptus tereticornis is an important species used in reforestation programs in Colombia. Information on the dynamics and development of the E. tereticornis stands is required to improve management planning. This study compares nine basal area growth models, evaluating their goodness of fit and prediction, and describes their linkage to a thinning response model for E. tereticornis plantations. The evaluated models showed a good fit to the data, the R2adj ranged between 0.90 - 0.92 and 0.69 - 0.86 for the basal area projection and prediction models, respectively. The root of the mean square error (RMSE) ranged between 1.080 m2 ha-1 - 1.343 m2 ha-1 for basal area projection models and 1.671 m2 ha-1 - 2.206 m2 ha-1 for basal area prediction models. The selected basal area model for unthinned stands depends on the age, stand density, and dominant height. For the thinned stands, the basal area was predicted using a competition index that depends on the age and the dominant height of the stand. The competition index had an R2adj = 0.87, and a standard error of estimate of 0.031%. The system of equations presented a slight tendency to overestimate with a mean error of -0.14 m2 ha-1 and a RMSE of 0.696 m2 ha-1. This way, the developed models have the potential to be applied to unthinned and thinned stands with different ages, productivity, and planting densities. The developed models provide new tools to support forest management and research of the species growing in plantations.