La aplicación de silvicultura intensiva en el manejo forestal sustentable requiere de herramientas cuantitativas eficientes para estimar de manera adecuada los patrones de crecimiento de los árboles y rodales. El desarrollo de modelos matemáticos con bases científicas representa un insumo vital para realizar proyecciones de crecimiento y rendimiento de especies forestales comerciales a través del tiempo. El objetivo de este estudio fue ajustar ecuaciones dinámicas de diferencia algebraica (ADA) y diferencia algebraica generalizada (GADA) para crecimiento en altura dominante e índice de sitio en Pinus patula Schiede ex Schltdl. & Cham. que crece en rodales coetáneos de Ixtlán de Juárez, Oaxaca. Los datos usados provinieron de 66 sitios permanentes de muestreo establecidos en 2015 y remedidos en 2016 y 2017. Las ecuaciones se ajustaron mediante el método iterativo anidado, que es una técnica invariante de la edad base. Los indicadores estadísticos de bondad de ajuste, los análisis gráficos y la capacidad predictiva de los modelos sugieren que la mejor ecuación para modelar el crecimiento en altura dominante es la formulación GADA derivada del modelo de Bertalanffy-Richards. La altura dominante promedio a la edad base de 40 años fue de 29 m. El modelo tipo GADA propuesto permitirá estimar adecuadamente la productividad de los rodales de P. patula. Los enfoques empleados para modelar el crecimiento en altura dominante demuestran ser metodologías eficientes para generar herramientas biométricas de apoyo en la toma de decisiones del manejo forestal para predecir la producción actual y futura.
Background and aims – The hypothesis of ecological niche conservatism postulates that closely related species share ecologically similar environments; that is, they tend to maintain the characteristics of their fundamental niche over time. The objective of this study is to evaluate the similarity and equivalence of the ecological niches among species of the genus Zaluzania (Asteraceae), characteristic of the Mexican arid and semi-arid regions, to infer their potential niche conservatism. Methods – Based on critically reviewed herbarium occurrence data, potential distribution models for eight species of Zaluzania were generated using the Maxent algorithm. The overlap between potential distribution areas was then evaluated using equivalence and ecological niche parameters implemented in the ENMTools software; for this we quantified the degree of overlap and similarity between the niches using the equivalence (D) and similarity (I) parameters.Key results – The resulting models show that species display areas of high suitability along the Mexican dry regions, as well as overlapping heterogeneous values. All models showed high AUC (Area Under the Curve) values (> 0.8). The D and I values between each pair of species showed low values of overlap.Conclusions – Each species of the genus shows a fundamental niche distinct from their sister species. The genus thus offers an example of niche divergence among species, with each one adapting to different environmental pressures. Our results do not support the hypothesis of niche conservatism in the genus, suggesting that the species evolved in divergent environments.
The potential use of forest species as fuels depends on their energy quality. However, in rural communities in developing countries, fuelwood is still an energy source without any technical study evaluating its energetic characteristics. Therefore, this study aimed to analyze the energetic characteristics of 22 forest species from four communities in the state of Oaxaca, Mexico. The basic wood density, proximal analysis, and high heating value were evaluated. As a result of the analysis, the fuel number (FN) is proposed as a measure of the energy quality of biomass fuels in the form of firewood. FN considers the basic wood density, the fixed carbon, and the high heating value of each species. Wood basic density ranged from 0.472 g·cm-1 for Pinus pseudostrobus to 0.814 g·cm-3 for Dodonaea viscosa, fixed carbon ranged from 4.74% to 21.27% for Liquidambar styraciflua and Quercus rugosa, respectively, and high heating value from 18.33 MJ·kg-1 to 22.07 MJ·kg-1 for Liquidambar styraciflua and Pinus leiophylla, respectively. Classifying wood according to FN, in decreasing order, Quercus rugosa stands out as the best wood (66.97%), followed by Liquidambar styraciflua (39.52%). Regarding the fuel value index, the nine pine species showed the highest values (27.32 to 77.76). The FN provides a measure of the quality of biomass fuels in the form of firewood, and can be evaluated by easily measured variables.
The wood chemical composition was determined for five tree species that cohabitate in the forest of Ixtlán de Juárez (Oaxaca, Mexico). These species were Alnus acuminata, Arbutus xalapensis, Myrsine juergensenii, Persea longipes, and Prunus serotina. The chemical composition was then correlated with the higher heating value of the wood. The chemical components determined were total extractives, ash, lignin, and holocellulose (alpha cellulose and hemicelluloses). The extractives were separated using Soxhlet equipment, and the ash obtained was analyzed via atomic absorption spectrometry. On average, the species presented 8.26 to 19.64% of total extractives, 0.56 to 1.50% of ash, 23.1 to 37.2% of lignin, 74.0 to 79.5% of holocellulose, 56.3 to 66.3% of α-cellulose, and 12.3 to 21.0% of hemicelluloses. In the ash, higher percentages of calcium, potassium, and magnesium were detected. The amount of chemical components was different between species (p ≤ 0.05). The higher heating value showed a positive correlation with the extractives content (r = 0.582), while with the ash content it was negative (-0.575). The high proportions of polysaccharides predict good performance of these species in pulp production, and the calorific value indicates that they have the potential for use as fuel.
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