Función ahusamiento-volumen comercial de Abies religiosa (Kunth) Schltdl. & Cham. en varias regiones de México

The taper-volume relationship is an essential tool for planning silvicultural management in forests with the final aim of promoting the distribution of products. The objective of this study is the generation of a compatible model that allows an accurate estimation of the taper-volume of Abies religiosa in several regions of Mexico. A data set of 2608 values was considered for the analysis of the information; the model was simultaneously adjusted by seemingly unrelated regression (SUR) for the estimation of compatible parameters. The model generated coefficients of determination with fit levels higher than 97 %, roots mean square less than 0.40, biases lower than 0.11, with certainty to model each forest region, which are complemented with their respective Akaike information criteria (AIC). In most cases, the shape factor of the species went from neiloid to paraboloid. This information will be useful for timber forest inventories.La relación ahusamiento-volumen es indispensable para la planeación del manejo silvícola en los bosques con la finalidad de favorecer la distribución de los productos. Por esta razón, el objetivo del presente estudio fue generar un modelo compatible que permitiera estimar de forma precisa el volumen-ahusamiento de Abies religiosa en varias regiones de México. Se utilizaron 2608 datos en el análisis de la información y el modelo se ajustó simultáneamente mediante la regresión aparentemente no relacionada (RAN) para la estimación de parámetros compatibles. El modelo generó coeficientes de determinación ajustados superiores al 97 %, raíces del medio cuadrático menores al 0.40, sesgos menores a 0.11, con certeza para modelar cada región forestal; datos que fueron complementados con sus respectivos criterios de información Akaike (AIC). En la mayoría de casos el factor de forma de la especie fue neiloide a paraboloide, información que será de utilidad para la elaboración de inventarios forestales

Estimación de volumen de Abies religiosa (Kunth) Schltdl. & Cham. en diferentes entidades federativas de México

Diameter and height are crucial parameters in forest inventories to determine the volume that is stored in the forest. The objective of this research was to generate an equation for eight federative entities that allows an accurate estimate of the timber volume of Abies religiosa in the center and south of the country. Around 2,747 trees were used to adjust equations of total tree roll volume, branch volume and total tree volume (vrta, vramas and vta). The following criteria were set for the selection of the best model; adjusted coefficient of determination, bias, mean error; as well as the graphical and numerical analysis of the residuals. Due to the lack of information on the branches, for Tlaxcala and Veracruz states only the total tree roll volume was obtained. The goodness of fit generated by the equations is reliable, since it explains more than 93% to the dependent variable, the errors are less than 0.47 m. These expressions are useful tools that can be applied by forestry technicians in different stands in the study area.Las variables diámetro y altura son factores indispensables en inventarios forestales para determinar el volumen que se almacena en el bosque. El objetivo de esta investigación fue generar una ecuación para ocho entidades federativas que permita estimar de forma precisa el volumen maderable de Abies religiosa en el centro y sur del país. Se utilizaron 2747 datos para ajustar ecuaciones de volumen rollo total árbol, volumen de ramas y volumen total árbol (vrta, vramas y vta). Para la selección del mejor modelo se fijaron los siguientes criterios: coeficiente de determinación ajustada, sesgo, error medio; así como el análisis gráfico y numérico de los residuales. Debido a la falta de información de las ramas para las entidades de Tlaxcala y Veracruz solo se obtuvo el volumen rollo total árbol. La bondad de ajuste generada por las ecuaciones es confiable, ya que explican más del 93 % a la variable dependiente, los errores son menores a 0.47 m. Estas expresiones son una herramienta útil que podrá ser aplicada por los técnicos forestales en distintos rodales en la zona de estudio

Evaluación de modelos de diversidad-abundancia del estrato arbóreo en un bosque de niebla

Los modelos de diversidad-abundancia pueden emplearse para detectar impactos o perturbaciones en ecosistemas forestales que han sido aprovechados. Se compararon cuatro modelos en cuanto a la distribución-abundancia de especies arbóreas en dos parcelas de observación con diferente historial de manejo en el bosque mesófilo de montaña “El Cielo”, Tamaulipas, México. Se probaron dos esquemas de muestreo para evaluar su eficiencia en colectar la información requerida para el ajuste de estos modelos. Los resultados sugieren que las parcelas de observación se encuentran en un estadio sucesional entre las etapas pioneras y tardías, donde dominan las especies con abundancia intermedia. El esquema de muestreo en transectos resultó ser más adecuado para colectar el tipo de información requerida para el ajuste de los modelos. La parcela que fue previamente sometida a cortas selectivas se encuentra en una etapa de sucesión más temprana que aquella sin intervención, ya que en esta última la abundancia relativa de especies se ajustó al modelo normal logarítmico, mientras que los datos de la primera no se ajustaron. Contrario a estudios en los que no se recomienda el uso de modelos de abundancia de especies para detectar impactos o perturbaciones en ecosistemas forestales después de haber sido intervenidos, esta investigación indica que dichas ecuaciones son herramientas útiles para evaluar y cuantificar tales cambios

Modelos de volumen específicos y regionales para 12 especies forestales en el estado de Durango, México

Introduction: Estimating the volume of individual trees is an important aspect in dendrometry and in the conducting of forest inventories. Objective: Significant differences were evaluated in additive equation systems for estimating the total volume of individual trees in nine species of the genus Pinus (P. cooperi, P.durangensis, P. arizonica, P. leiophylla, P. teocote, P. engelmannii, P. lumholtzii, P.strobiformisand P. herrerae), and three of the genus Quercus (Q. sideroxyla, Q. durifoliaand Q. rugosa), and among regional forest management units (UMAFOR) when dealing with the same species. Materials and methods: To evaluate whether equation systems are different among tree species of the same genus and among the UMAFORs for the same species, two complementary statistical analyzes were used based on the fitting of a reduced and a full equation system: the F test of nonlinear extra sum of squares method, and the parameter significance analysis. Results and discussion: For most of the species studied, equation systems are significantly different. The need to use regional models in 10 of the 12 tree species, except for P. strobiformis and Q. rugosa, is also reported. Conclusion: The use of a state model for P. strobiformis and Q. rugosa is recommended.Introducción: La estimación del volumen de árboles individuales es un aspecto relevante en la dendrometría y en la realización de inventarios forestales. Objetivo: Se evaluaron diferencias significativas en sistemas de ecuaciones aditivas para la estimación de volumen total de árboles individuales en nueve especies de Pinus (P. cooperi, P. durangensis, P. arizonica, P. leiophylla, P. teocote, P. engelmannii, P. lumholtzii, P. strobiformis y P. herrerae), y tres de Quercus (Q. sideroxyla, Q. durifolia y Q. rugosa), y entre unidades de manejo forestal regional (UMAFOR) cuando se trata de una misma especie. Materiales y métodos: Para evaluar si el sistema de ecuaciones difiere entre especies de un mismo género y entre las UMAFOR para una misma especie, se utilizaron dos análisis estadísticos complementarios basados en el ajuste de un sistema reducido y un sistema completo de ecuaciones: la prueba F asociada al método de la suma adicional de cuadrados no lineales y el análisis de significancia de los parámetros. Resultados y discusión: Para la mayoría de las especies estudiadas, los sistemas de ecuaciones son significativamente diferentes. Se reporta la necesidad de utilizar modelos regionales en 10 de las 12 especies, exceptuando a P. strobiformis y Q. rugosa. Conclusiones: Se recomienda el empleo de un modelo estatal para P. strobiformis y Q. rugosa.We thank the Program Fomento a la Organización Social,Planeación y Desarrollo Regional Forestal (PROFOS) of CONAFOR for funding the collection of the data used in this studyS

Allometric Equations for Estimating Biomass and Carbon Stocks in the Temperate Forests of North-Western Mexico

This paper presents new equations for estimating above-ground biomass (AGB) and biomass components of seventeen forest species in the temperate forests of northwestern Mexico. A data set corresponding to 1336 destructively sampled oak and pine trees was used to fit the models. The generalized method of moments was used to simultaneously fit systems of equations for biomass components and AGB, to ensure additivity. In addition, the carbon content of each tree component was calculated by the dry combustion method, in a TOC analyser. The results of cross-validation indicated that the fitted equations accounted for on average 91%, 82%, 83% and 76% of the observed variance in stem wood and stem bark, branch and foliage biomass, respectively, whereas the total AGB equations explained on average 93% of the total observed variance in AGB. The inclusion of total height (h) or diameter at breast height2 × total height (d2h) as a predictor in the d-only based equations systems slightly improved estimates for stem wood, stem bark and total above-ground biomass, and greatly improved the estimates produced by the branch and foliage biomass equations. The predictive power of the proposed equations is higher than that of existing models for the study area. The fitted equations were used to estimate stand level AGB stocks from data on growing stock in 429 permanent sampling plots. Three machine-learning techniques were used to model the estimated stand level AGB and carbon contents; the selected models were used to map the AGB and carbon distributions in the study area, for which mean values of respectively 129.84 Mg ha−1 and 63.80 Mg ha−1 were obtained.This study was financially supported by the Mexican National Council for Science and Technology (CONACyT) and by the State of Durango Government (Project FOMIX- DGO-2011-C01-165681)S

Assessment of Pellets from Three Forest Species: From Raw Material to End Use

This study aimed to evaluate and compare the relationship between chemical properties, energy efficiency, and emissions of wood and pellets from madroño Arbutus xalapensis Kunth, tázcate Juniperus deppeana Steud, and encino colorado Quercus sideroxyla Humb. & Bonpl. in two gasifiers (top-lit-up-draft (T-LUD) and electricity generation wood camp stove (EGWCS)) in order to determine the reduction of footprint carbon. In accordance with conventional methodologies, we determined the extracts and chemical components (lignin, cellulose, holocellulose), and the immediate analyses were carried out (volatile materials, fixed carbon, ash content and microanalysis of said ash), as well as the evaluation of emission factors (total suspended particulate matter (PM2.5), CO, CO2, CH4, black carbon (BC), elemental carbon (EC), and organic carbon (OC)). The results were statistically analyzed to compare each variable among species and gasifiers. The raw material analyzed showed how the pH ranged from 5.01 to 5.57, and the ash content ranged between 0.39 and 0.53%. The content values of Cu, Zn, Fe, Mg, and Ca ranged from 0.08 to 0.22, 0.18 to 0.19, 0.38 to 0.84, 1.75 to 1.90, and 3.62 to 3.74 mg kg−1, respectively. The extractive ranges from cyclohexane were 2.48–4.79%, acetone 2.42–4.08%, methanol 3.17–7.99%, and hot water 2.12–4.83%. The range of lignin was 18.08–28.60%. The cellulose content ranged from 43.30 to 53.90%, and holocellulose from 53.50 to 64.02%. The volatile material range was 81.2–87.42%, while fixed carbon was 11.30–17.48%; the higher heating value (HHV) of raw material and pellets presented the ranges 17.68–20.21 and 19.72–21.81 MJ kg−1, respectively. Thermal efficiency showed statistically significant differences (p Arbutus xalapensis being the species with the highest energy yield. The use of improved combustion devices, as well as that of selected raw material species, can reduce the impact of global warming by up to 33% on a cooking task compared to the three-stone burner

Estimating biomass of mixed and uneven-aged forests using spectral data and a hybrid model combining regression trees and linear models

The Sierra Madre Occidental mountain range (Durango, Mexico) is of great ecological interest because of the high degree of environmental heterogeneity in the area. The objective of the present study was to estimate the biomass of mixed and uneven-aged forests in the Sierra Madre Occidental by using Landsat-5 TM spectral data and forest inventory data. We used the ATCOR3 ® atmospheric and topographic correction module to convert remotely sensed imagery digital signals to surface reflectance values. The usual approach of modeling stand variables by using multiple linear regression was compared with a hybrid model developed in two steps: in the first step a regression tree was used to obtain an initial classification of homogeneous biomass groups, and multiple linear regression models were then fitted to each node of the pruned regression tree. Cross-validation of the hybrid model explained 72.96% of the observed stand biomass variation, with a reduction in the RMSE of 25.47% with respect to the estimates yielded by the linear model fitted to the complete database. The most important variables for the binary classification process in the regression tree were the albedo, the corrected readings of the short-wave infrared band of the satellite (2.08-2.35 µm) and the topographic moisture index. We used the model output to construct a map for estimating biomass in the study area, which yielded values of between 51 and 235 Mg ha-1. The use of regression trees in combination with stepwise regression of corrected satellite imagery proved a reliable method for estimating forest biomass.This research was supported by SEPPROMEP (Project: Seguimiento y Evaluación de Sitios Permanentes de Investigación Forestal y el Impacto Socioeconómico del anejo Forestal en el Norte de México)S

Secondary Succession under invasive species (Pteridium aquilinum) conditions in a seasonal dry tropical forest in southeastern Mexico

The role of invasive species in ecosystem functioning represents one of the main challenges in ecology. Pteridium aquilinum is a successful cosmopolitan invasive species with negative effects on the ecological mechanisms that allow secondary succession. In this study, we evaluated the influence of P. aquilinumon secondary succession under different disturbances in a seasonal dry forest of the Yucatán Peninsula. We determined species richness, composition and the relative importance value in four sampling units. Fabaceae followed by Asteraceae, Meliaceae, Rubiaceae, Sapindaceae and Verbenaceae were the most species rich families. A dissimilarity analysis determined significant differences in beta diversity between sampling units. With a generalized linear model we found that species richness was best explained by site conditions, followed by calcium and soil organic matter. Also, the generalized linear model showed that abundance resulted in a strong correlation with site conditions and soil characteristics. Specific soil conditions related to phosphoro and calcium were also detected as beneficiary to the successional processes. Our results suggest that applying fire restriction and periodic cutting of the bracken fern, this can increase a higher diversity of species

Individual Tree Diameter and Height Growth Models for 30 Tree Species in Mixed-Species and Uneven-Aged Forests of Mexico

Lack of knowledge of individual tree growth in species-rich, mixed forest ecosystems impedes their sustainable management. In this study, species-specific models for predicting individual diameter at breast height (dbh) and total tree height (h) growth were developed for 30 tree species growing in mixed and uneven-aged forest stands in Durango, Mexico. Growth models were also developed for all pine, all oaks, and all other species of the genus Arbutus (strawberry trees). A database of 55,158 trees with remeasurements of dbh and h of a 5-year growth period was used to develop the models. The data were collected from 217 stem-mapped plots located in the Sierra Madre Occidental (Mexico). Weighted regression was used to remove heteroscedasticity from the species-specific dbh and h growth models using a power function of the tree size independent variables. The final models developed in the present study to predict dbh and total tree height growth included size variables, site factors, and competition variables in their formulation. The developed models fitted the data well and explained between 98 and 99% and of the observed variation of dbh, and between 77 and 98% of the observed variation of total tree height for the studied species and groups of species. The developed models can be used for estimating the individual dbh and h growth for the analyzed species and can be integrated in decision support tools for management planning in these mixed forest ecosystemsThis study was supported by the National Forestry Commission (CONAFOR) and the Mexican National Council for Science and Technology (CONACYT)S