Introduction: Metal contamination represents a significant risk to ecosystems; it is therefore necessary to reduce the bioavailability, mobility and toxicity of these elements.
Objective: To isolate a filamentous fungus with the ability to tolerate metals.
Materials and methods: The fungus was isolated from soil with mining activity. The tolerance index and the minimum inhibitory concentration (MIC) of the fungus were determined at 1, 5, 10, 15 and 20 mM of the Cd, Hg, Pb, Ag, Cu, Zn and Cr metal salts.
Results and discussion: The isolated fungus was Aspergillus niger. It had average tolerance indices of 0.89, 1.03, 1.05, 0.94, 0.88, 0.87 and 1.27 at 1 mM of the Cd, Hg, Pb, Ag, Cu, Zn and Cr salts, respectively, after seven days of growth at 28 °C. The MIC of A. niger was found in a range of 5 to 10 mM of the Hg, Cu and Ag salts, and 15 to 20 mM of the Cd salt. The Pb, Zn and Cr salts did not inhibit the growth of the fungus with the highest concentration evaluated; that is, the MIC is greater than 20 mM.
Conclusión: Aspergillus niger has potential for the bioremediation of contaminants since it showed high tolerance to the metal salts.

Introduction: Firewood is the main source of energy for developing countries.
Objective: The relationship between the inhabitants of a cultural landscape and the consumption of firewood, and between the preferences of use and the relative importance of the species were marked.
Materials and methods: A total of 132 semi-structured surveys were conducted in the region of Calakmul, Campeche, Mexico, to analyze the consumption of firewood. The importance value index (IVI) of the species harvested in the region was obtained in nine plots of 500 m2 , divided into three classes of successional age: 7 to 10 years (class one), 11 to 20 years (class two), and over 20 years old (class three).
Results and dicussion: A total of 60 species used as firewood were recorded. There was no correspondence between the preferred species and the first places of the IVI. The species most commonly used as firewood was Haematoxylum campechianum L. The species richness increased (59 to 68) and the number of individuals decreased (2 559 to 921) as the age of the vegetation increased. Firewood collection is a subsistence strategy that focuses on the elderly; traditional practices are at risk in the medium term.
Conclusion: The cultural landscape and the preservation of forest resources should be addressed with strategies of promotion and training on the use of firewood as an energy resource.

Introduction: The seeds of Jatropha curcas L. are used for the elaboration of regional dishes. An easy method of propagation would be useful for producers who market or consume seeds of this species.
Objective: Test a method of vegetative propagation of J. curcas, planted in the field, for human consumption.
Materials and methods: The vegetative propagation was carried out in the spring with 55 cm-stakes, obtained from secondary and tertiary branches from 28 years old trees. The cuttings were planted 3 m away in a loamy clay loam soil with pH of 7.21, and 1.11 % organic matter. The growth was evaluated at 120 days. Total carbohydrates were determined by a colorimetric method, two months before and eight months after field establishment.
Results and discussion: Cuttings of J. curcas secondary branches with exfoliating bark and diameter of 3.6 to 4.0 cm at the base, at the beginning of propagation, achieved greater height, number of branches and greater concentration of total carbohydrates before and after establishment. This vegetative material is recommended for the propagation of J. curcas in the field. The cuttings of tertiary branches with diameters of 1.6 to 1.9 cm had mortality of 17 %, reduced capacity to generate branches and lower concentration of carbohydrates.
Conclusions: The propagation of J. curcas, by cuttings, was successful in the open field; it was not necessary to use a greenhouse, auxins for rooting or polyethylene bags, prior to establishment.

Introduction: Mangroves are ecosystems that provide goods and services for populations that live on the coasts. Therefore, the permanence of these forests must be ensured.
Objectives: To identify the factors that control the distribution and structure of the mangrove vegetation of the lagoon of Mandinga, Veracruz; the degree of dependence of the inhabitants towards the ecosystem; and the sources of habitat disturbance, which prevent natural regeneration.
Materials and methods: A total of 156 random quarter points were identified on 13 transects of variable length to obtain physiognomic values and importance value index of the species, as well as a general physiognomic profile of the community. Through surveys, villagers recognized goods and services and the main threats to the ecosystem.
Results and discussion: Three mangrove species were zoned according to a water-ground gradient: Rhizophora mangle L., Avicennia germinans (L.) L. and Laguncularia racemosa (L.) C. F. Gaertn. Avicennia germinans was the species with the greatest value of importance. Land use change, degradation due to discharge of wastewater and pollution due to hydrocarbons and heavy metals were the main negative factors on mangrove.
Conclusion: The restoration of the Mandinga mangrove should consider the formation of mangrove islands; reforestation based on the microclimatic requirements of each species and geomorphology of the site; and conservation of the surrounding vegetation such as the evergreen forest and coastal dunes.

Introduction: The arbuscular mycorrhizal association is the symbiosis between fungi and the roots of plants, which contributes to maintaining ecosystems in a sustainable manner.
Objectives: To describe the colonization of three arbuscular mycorrhizal fungi (AMF) inoculated in two tree legumes and to determine the morphological type of the symbiotic association.
Materials and methods: The seeds of Pithecellobium dulce (Roxb.) Benth. and Platymiscium diadelphum S. F. Blake were inoculated with three pure strains of AMF: Rhizophagus manihotis (R. H. Howeler, Sieverd. & N. C. Schenck) C. Walker & A. Schüßler, Funneliformis mosseae (T. H. Nicolson & Gerd.) C. Walker & A. Schüßler y Scutellospora heterogama (T. H. Nicolson & Gerd.) C. Walker & F. E. Sanders. At 105 days, the secondary roots were sampled, clarified and stained with acid fuchsin and trypan blue. The fungal structures were observed under an optical microscope and the colonization percentage was determined.
Results and discussion: The colonization of the AMF was greater than 60 %. Thin, transparent and cenocitic hyphae, as well as hylopodia and arbuscules, were observed. In P. dulce, S. heterogama tends to produce more arbuscules. In P. diadelphum, the percentages of colonization and fungal structures of the AMF were similar. The morphological association in the two arboreal species was mainly from the Paris type, with occasional presence of the type Arum.
Conclusion: The inocula of the AMF established high symbiotic association with the legumes studied. The applied techniques evidenced the structures of the AMF inside the root and allowed to identify the morphological association of the symbionts.

Introduction: Fire regimes and climate change affect the regeneration of vegetation, composition and abundance of species.
Objectives: To compare P. hartwegii regeneration and the number of trees with fire scars at different elevations; and determine whether regeneration is related to the density of adult trees and to the density of pine trees with fire evidence.
Materials and methods: P. hartwegii regeneration was studied at the altitudinal ranges 3 050, 3 225 and 3 400 m in the mountain El Potosí located in northeastern Mexico. Adult trees were sampled using the point-centered quarter method and saplings on square plots.
Results and discussion: Density of adult pine trees and seedlings was higher at the low elevations (3 050 and 3 225 m). Density of pine trees with fire scars was similar (P > 0.05) at the three elevations. No correlation was detected between regeneration and number of pine trees with fire scars, but there was a positive correlation between density of seedlings and that of adult pines
Conclusion: Altitude influences regeneration and density of P. hartwegii adult trees. Its regeneration is not related to fire evidence.

Introduction: The characterization of land uses represents one of the essential inputs for the management of natural resources at different scales.
Objective: To develop a methodology to characterize land use in the upper creek basin from the Azul stream (Buenos Aires, Argentina), through the fusion of satellite images with a medium spatial resolution.
Materials and methods: A time-series of 23 images was used from the Normalized Difference Vegetation Index (NDVI) of the MODIS-Terra satellite (product MOD13Q1) for the period May 2015 - May 2016. Landsat 8 images were used to discriminate some categories difficult to classify with NDVI-MODIS. The final cover map was validated regarding verification points independent to the classification process; its accuracy was evaluated by means of the Kappa statistic.
Results and discussion: The NDVI time series allowed to recognize the phenological patterns of the covers and land use of greater representativeness in the region. Seven land cover were discriminated; the agricultural uses represented 81.5 % of the surface, double-crop wheat-soya (soybean in Argentina) system predominated (39.4 %). The overall accuracy of the final map was high (88.9 %, Kappa coefficient = 0.86).
Conclusion: The methodology used has the advantage of being quick and replicable, to characterize the land uses of a given region and to evaluate its potential changes over time.

Introduction: Aerial biomass estimation using the traditional forestry method is laborious, expensive and time consuming. An alternative to solve this problem is the use of remote sensing.
Objective: To evaluate the precision of portable LIDAR technology and photogrammetry (photo-reconstruction) in the generation of point clouds to estimate aerial biomass.
Materials and methods: A total of 26 Quercus L. trees were analyzed from an urban forest in the south of Monterrey, Mexico. Diameter at breast height (DBH), total height and crown diameter were obtained with six methods: 1) traditional forest, 2) portable LIDAR at ground level, 3) normal color photo-reconstruction (PR) at ground level, 4) infrared color PR at ground level, 5) PR of normal color aerial image and 6) PR of infrared aerial image. Aerial biomass was estimated and the precision of each method was evaluated taking as reference the traditional forest method.
Results and discussion: Portable LIDAR offers more accurate information to estimate the aerial biomass (R2 = 0.945), followed by normal color PR at ground level (R2 = 0.824), when compared with that obtained by the traditional forest method. PR of normal color aerial images showed the poorest results (R2 = 0.653), due to the impossibility to measure the DBH. Data collection with sensors was faster (>80 %) with respect to the TFM.
Conclusion: Remote sensing techniques have the potential to obtain forest parameters in large-scale projects.

Introduction: The management of basic sanitation services in Peru is considered a high priority public policy.
Objective: To estimate the economic benefits of an improvement in the provision of basic sanitation services (water, sewage and wastewater treatment) in Puno, Peru.
Materials and methods: The economic benefits were estimated from data obtained in a survey of 392 heads of family. The econometric estimates were made through a choice experiment with multinomial logit and mixed logit models.
Results and discussion: An aggregate marginal willingness to pay of 9.95 PEN (3.32 USD) per month per dwelling was estimated; if the total number of favored households is considered, this amount represents a measure of economic benefit. The wastewater treatment attribute is more valued than the water and sewage provision attributes. With respect to the models used, the mixed logit-dummy codes model presented greater theoretical consistency of the results.
Conclusion: The choice of options for improving basic sanitation services is strongly conditioned by the educational level and monthly income of the users. Any policy aimed at improving basic sanitation services in the city of Puno should focus on solving the issue of wastewater treatment.

Introducción: El sector forestal de México enfrenta problemas de deforestación y de escaso crecimiento productivo. Para activar regiones improductivas, en el estado de Durango se impulsa el establecimiento de plantaciones con Pinus greggii Engelm. ex Parl. var. greggii.
Objetivo: Evaluar el efecto de fertilizantes en el crecimiento, estado nutrimental y supervivencia de brinzales de P. greggii var. greggii.
Materiales y métodos: Se evaluaron cinco fertilizantes de liberación lenta y dos de uso agrícola, en dosis de 7 y 14 g por planta, más un testigo (sin fertilizar).
Resultados y discusión: Después de 12 meses se encontraron diferencias significativas (P < 0.001) en el volumen y en los incrementos de altura y diámetro, debido al efecto de los fertilizantes. En comparación con el testigo, únicamente los fertilizantes de liberación lenta 12-25-12, 09-23-14 y 18-06-12 de N-P-K produjeron incrementos de altura y diámetro, así como volúmenes de madera, significativamente mayores. En cuanto a la concentración foliar, solo el P mostró diferencias significativas entre tratamientos (P = 0.030). El N y P fueron limitantes, pero la aplicación de K favoreció el crecimiento. Con relación a la supervivencia de brinzales, no se encontraron diferencias significativas atribuibles al fertilizante y sus dosis.
Conclusión: La aplicación inicial de fertilizantes de liberación lenta 12-25-12, 09-23-14 y 18-06-12 de N-P-K favorece el crecimiento de los brinzales de P. greggii var. greggii.