Land use change is one of the most complex problems observed as part of the urban expansion process. It generates different consequences such as the Urban Heat Island (UHI) development. With the objective of identifying the presence of UHI in Tuxtla Gutierrez, Chiapas, MM5 meteorological model was implemented to simulate the meteorological conditions for April 30th to May 6th, 2017. Considering the atmospheric conditions over the study area, the UHI was represented at different times of May 3rd, 2017. The results show the formation of the UHI over the city at different hours during the day. The UHI intensity varies from 0.5 to 2.5 degrees C but, it could be higher than 5 degrees C. The UHI affects mainly the center of the city as a consequence of factors such as soil properties, heat fluxes, and the geomorphological characteristics of the study area. Furthermore, considering the actual growth of the city, land use change was simulated. In some cases, the results show a bigger area and a higher intensity of the UHI phenomenon. Therefore, the presence of the UHI in the city is showed and the importance of the protection and conservation of green areas is indicated, which points out that UHI studies should be considered as part of territory planning for urban development.

Dust emissions from unpaved roads are one of the main pollutants affecting air quality around the world. As part of initial air quality studies in Tuxtla Gutiérrez (TGZ), Chiapas, Mexico, urban aeolian emission events from unpaved roads and simple meteorological inputs were measured in February 2014 at two different sites located within the city to characterize emissions for representative road conditions and to produce Industrial Source Complex (ISC3) model inputs. Emissions of particulate matter of aerodynamic diameter less than 10 µm (PM₁₀) were determined for eight wind erosion events. PM₁₀ concentrations were measured downwind from sites using a Minivol sampler during February and March 2014. Three high PM₁₀ concentration scenarios, associated with unstable conditions generated by cold fronts (CF) were selected to simulate dust plume dispersion to identify impacted areas. Results show that unpaved roads represent a potential source of dust that affect air quality of urban regions; in this study generating emissions ≥ 1.92 × 10⁻³ g·m⁻²·s⁻¹ when winds ≥6 m·s⁻¹ were present. Air pollution events that exceed the Mexico national standard for 24-h average PM₁₀ concentration (≥75 µg·m⁻³) were observed, impacting different areas in the city, representing a risk to human health. This demonstrates the influence of CF over southern Mexico, generating high PM₁₀ concentrations in urban regions.

This research has identified the landscapes in the state of Chiapas (Mexico) with the best natural conditions by using the theoretical-methodological principles of complex physical geography. To achieve this goal, the biodiversity was assessed by calculating the number of vascular plant species for each landscape unit and correlated with the results of previous research regarding landscape diversity and the anthropization of vegetation cover. The results indicate that the highest levels of biodiversity correspond to the predominant and recurring landscapes. These geographical relationships indicate the influence of the geomorphological component on the distribution of biodiversity, which was quantitatively validated via two statistical correlations. It is found that the complexes of summits, hillslopes, and gullies in mountain landscapes of tectonic-karstic, tectonic-accumulative, and tectonic-intrusive origin, in temperate, semiwarm humid to subhumid, warm humid, and warm subhumid climates located in the physicogeographical regions of the Lacandona Mountains, the Southern Mountains of Chiapas, and the Western Mountains of Chiapas, all have the best preserved geographical landscapes. In recent years, however, geocomplexes have been impacted by society, which is particularly evident in the Northern Mountains of the Chiapas region. The results of this research are an important contribution to land-use planning processes, because they make it possible to objectively establish environmental policies in Chiapas. For instance, this research provides the geographic basis for modifying or promoting new natural protected areas.

El objetivo del trabajo fue cuantificar las emisiones de gases de efecto invernadero (GEI) y otros contaminantes generados por el consumo de leña y carbón en la preparación de pollos asados en Tuxtla Gutiérrez (TGZ), Chiapas, mediante la aplicación de factores de emisión (FE). Se hizo una categorización de los establecimientos en función a su producción y la infraestructura utilizada para la actividad para determinar el combustible consumido anualmente. Los gases con emisiones más altas fueron el dióxido de carbono (CO₂, 5 312.12 t año^-1) y el monóxido de carbono (CO, 290.13 t año^-1); mientras que las partículas con diámetros aerodinámicos menores a 10 μm (PM₁₀) fueron las más abundantes (27.23 t año^-1). Los resultados muestran la relevancia del consumo de leña y carbón en la preparación de pollos asados como fuente de contaminación del aire que se suma a la problemática ambiental de la ciudad.

Background. Forest litterfall is a fundamental process of ecosystem nutrient cycling, also, it is a source of energy for the development and propagation of wildfire. Understanding the temporal dynamics of litter production and storage is critical for sustainable management and conservation of forest ecosystems. Objective. To quantify the monthly production and storage of forest litter in an elevation gradient. Methodology. We selected forest sites at three elevations: 670, 775, and 1010 masl, corresponding to pine, oak, and tropical lowland forest ecosystems in Nambiyugua hill, Chiapas, Mexico. Sixteen sampling sites with a radius of 11.28 m were established for tree measurements, and 48 litter traps of 0.50 m2 were installed to collect monthly litterfall for a year. To sample ground litter eight 30 by 30 cm2 quadrats were used in each site. The fallen woody material was measured with the planar intersection method. Litter samples were oven-dried at 60 °C for 72 h and separated into leaves and other plant parts. One-way ANOVA was used to test the significant differences between forests. Results. The highest total loads of litter and fallen woody material were obtained in the pine forests of upper elevation with 29.01 t ha-1. The highest litter production was obtained in January and April, with a mean of 1.34 ± 0.19 and 0.74 ± 0.13 t ha-1 respectively in pine forests. In the oak forest, the highest production occurred in March, with 1.08 ± 0.25 t ha-1; while the lowland forest reached the highest production in January with 0.85 ± 0.26 t ha-1, with a decreasing trend in June. Implications. Understanding the seasonal variability in litter production and forest fuel loads is crucial for forest productivity, carbon sequestration, and wildfire prevention Conclusions. The production of forest fuels was different among the ecosystems representing the elevation gradients. The highest monthly production of litter was registered during the January-May period for the pine and oak ecosystems but in November - January in tropical lowland forests.