Background
Studies on the relationship between biodiversity and ecosystem productivity have suggested that species richness and functional diversity are the main drivers of ecosystem processes. ...Several patterns on this relationship have been found, including positive, unimodal, negative, and neutral trends, keeping the issue controversial. In this study, taxonomic diversity and functional diversity as drivers of above-ground biomass (AGB) were compared, and the mechanisms that influence biomass production were investigated by testing the complementarity and the mass-ratio hypotheses.
Methods
Using data from 414 permanent sample plots, covering 23% of temperate forest in the Sierra Madre Oriental (México), we estimated the above-gound biomass (AGB), taxonomic and functional diversity indices, as well as community weighted mean values (CWM) for three functional traits (maximum height, leaf size and wood density) for trees ≥7.5 cm DBH, in managed and unmanaged stands. To compare taxonomic diversity differences between managed and unmanaged stands we carried out a rarefaction analysis. Furthermore, we evaluated the relationship between AGB and taxonomic and functional diversity metrics, as well as CWM traits throught spatial autoregressive models.
Results
We found a hump-shaped relationship between AGB and species richness in managed and unmanaged forests. CMW of maximum height was the most important predictor of AGB in both stands, which suggested that the mechanism underlaying the AGB-diversity relationship is the dominance of some highly productive species, supporting the mass-ratio hypothesis. Above-ground biomass was significantly correlated with three of the five functional diversity metrics, CWM maximum height and species richness. Our results show the importance of taking into account spatial autocorrelation in the construction of predictive models to avoid spurious patterns in the AGB-diversity relationship.
Conclusion
Species richness, maximum height, functional richness, functional dispersion and RaoQ indices relate with above-ground biomass production in temperate mixed-species and uneven-aged forests of northern Mexico. These forests show a hump-shaped AGB-species richness relationship. Functional diversity explains better AGB production than classical taxonomic diversity. Community weighted mean traits provide key information to explain stand biomass in these forests, where maximum tree height seems to be a more suitable trait for understanding the biomass accumulation process in these ecosystems. Although the impact of forest management on biodiversity is still debated, it has not changed the AGB-diversity relationships in the forests of the Sierra Madre Occidental, Mexico.
Se desarrollaron diagramas de manejo de densidad (DMD) con datos de 218 sitios permanentes establecidos en rodales puros de Pinus cooperi en Durango, México. Los DMD se basan en el índice de ...espaciamiento relativo y en tres ecuaciones no lineales que incluyen variables de rodal. La primera relaciona el diámetro cuadrático con la densidad y la altura dominante; la segunda estima el volumen con la biomasa aérea, el diámetro cuadrático y la altura dominante; y la tercera estima la biomasa a partir del diámetro cuadrático, la altura dominante y la densidad. La densidad máxima se estimó mediante regresión cuantílica ajustando la relación densidad-altura dominante. Las ecuaciones explicaron el 92 % (biomasa) y el 99 % (volumen) de la varianza observada en los datos. Los DMD fueron aplicados en la cuantificación y proyección del volumen y la biomasa en rodales de la especie, como apoyo en la toma de decisiones multiobjetivo.
Antecedentes: El modelado de nicho ecológico es una herramienta utilizada para delimitar y estimar las áreas de distribución de una especie y representarlas en forma de mapa.
Hipótesis: El modelado ...de nicho ecológico y los valores dasométricos proyectados a un espacio geográfico y ambiental permiten identificar áreas potenciales para la producción de semillas.
Especie de estudio: Pinus chihuahuana y Pinus leiophylla
Sitio de estudio: Provincias fisiográficas Sierra Madre Occidental, Mesa del Centro, Faja Volcánica Transmexicana, Sierra Madre del Sur y la subprovincia Carso Huasteco.
Métodos: Se utilizaron registros de P. chihuahuana y P. leiophylla y variables ambientales los cuales fueron procesados con el algoritmo MaxEnt, para seleccionar las áreas potenciales semilleras se usaron los datos dasométricos del Sistema Biométrico Forestal para el manejo de los bosques de México (SiBiFor).
Resultados: Se estimaron 3,671,978 ha como zonas de alta idoneidad para P. chihuahuana en la Sierra Madre Occidental y 420,860 ha para P. leiophylla en la Faja Volcánica Transmexicana. Las variables con mayor contribución al modelo para P. chihuahuana fueron la temperatura media anual y la temperatura mínima del mes más frío, para P. leiophylla fueron temperatura media anual y la vegetación. Las zonas con mejor calidad de sitio (relación altura-diámetro) para P. chihuahuana ( r 2 = 0.77, p < 0.01) y P. leiophylla ( r 2 = 0.73, p < 0.01) mostraron un coeficiente de determinación elevado.
Conclusiones: Este estudio ilustra una aproximación en la delimitación de áreas idóneas con potencial, las cuales podrían ser empleadas para la producción de semillas en México.
La estimación del crecimiento y rendimiento de las especies forestales maderables es clave para planear y proyectar la cosecha de manera sustentable. El objetivo de la presente investigación fue ...ajustar cuatro modelos de crecimiento en diámetro, altura, área basal y volumen para Pinus leiophylla, Pinus lumholtzii y Pinus strobiformis de la región de Guadalupe y Calvo, Chihuahua. Mediante un muestreo selectivo se recolectaron 26 árboles de P. lumholtzii, 26 de P. strobiformis y 30 árboles de P. leiophylla para generar 219, 249 y 385 perfiles de cada una de las especies, respectivamente. Los modelos de crecimiento evaluados fueron los de Chapman-Richards, Schumacher, Hossfeld I y Weibull. Los criterios de selección de los mejores modelos fueron el coeficiente de determinación, la raíz del error medio cuadrático, la significancia de los parámetros estimados y las tendencias del crecimiento. Se determinó que todos los modelos presentaron ajustes significativos; sin embargo, por las tendencias del crecimiento que generan, los que mejor representaron el comportamiento biológico de las variables analizadas fueron los de Chapman-Richards, Hossfeld I y Schumacher. Con base en las edades a las que ocurre el máximo incremento en volumen y el turno, se infiere que las tres especies presentan lento crecimiento.
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.
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.
We present a new set of equations for tree level volume and aboveground biomass estimation for ocote pine (Pinus oocarpa Schiede ex Schltdl). These equation systems are the first developed for this ...species in Nicaragua. The first system includes a taper function, a merchantable volume equation, and volume equations for stem, coarse branches, and whole trees. The second system estimates whole tree and individual tree component biomass (stem wood, bark, branches, and needles). Data from 112 sampled trees were used for models’ development. Seemingly Unrelated Iterative Regression and the Generalized Method of Moments were used to simultaneously fit the volume and biomass equations systems, respectively; both methods ensure additivity and compatibility between equations. Weighted regression and a second-order continuous autoregressive error structure were used to correct heteroscedasticity and autocorrelation within the hierarchical dataset. The predictive power of the new proposed equations is higher than the currently used models for P. oocarpa in the country. These equation systems represent a scientific advancement that will enhance forest inventories, optimize timber management of the species, and facilitate accurate monitoring of forest carbon dynamics. Additionally, the new equations will contribute to a more precise accounting of CO2 emissions from the country’s forestry sector.
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 < 0.05) between pellets and gasifiers, with an average of 31% Tier 3 in ISO (International Organization for Standardization) for the T-LUD and 14% (ISO Tier 1) for EGWCS, with 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.
A challenge in community ecology is the development of ecosystem baselines, allowing the assessment of the variation in the ecological dynamics through different temporal and spatial scales. To our ...best knowledge, no studies have been carried out in seasonal evergreen forests of Belize to establish a baseline for future monitoring. Hence, a floristic study of the woody plant species diversity and composition was carried out at the Billy Barquedier National Park (BBNP) to develop an ecosystemic baseline for the assessment of the originally implemented conservation strategies. A thorough floristic survey was performed from May to August 2015 in 42 rectangular plots (500 m2) randomly allocated along the 100 to 500 m elevation gradient of the BBNP. Species richness, diversity, composition, and aboveground biomass were assessed. Likewise, information of a series of indicators on protection and risk situation (e.g., IUCN Red List of threatened species, CITES categories), and restoration for each relevant species are also provided. The BBNP is an important forest with 67 woody species distributed in 30 plant families. Terminalia amazona and Corozo palm Attalea cohune are the most important species in the reserve, in terms of abundance, frequency, and biomass. A clear trend between biodiversity metrics, elevation, and aboveground biomass was noted. This study contributes to understand relevant ecological topics as well as provides key elements for the management and conservation of the BBNP area and Belize.
Temperate mixed forests in Mexico are considered highly important ecosystems because of their high levels of biodiversity and capacity to store carbon. The aim of this study was to evaluate temporal ...and between-forest soil respiration (CO2 efflux) variability, and to assess the effect of vegetation diversity metrics on soil CO2 fluxes in mixed-uneven-aged forests in Durango, Northwestern Mexico. Soil CO2 efflux, soil moisture, and soil temperature were measured in three temperate forest types. A generalized linear model (GLM) was fitted to analyze the relationship between soil CO2 fluxes and stand variables, diversity metrics, soil moisture, and soil temperature. Furthermore, a two-way analysis of variance was used to assess the effect of forest type, month of the year, and their interaction on soil respiration. Annual average, minimum, and maximum soil CO2 efflux rate values were 3.81 (±2.94), 2.28 (±1.47), and 7.97 (±2.94) µmol m−2 s−1, respectively. Soil respiration was positively related to species richness, aboveground biomass, and quadratic mean diameter; however, forest type did not contribute to understanding the dynamics of soil CO2 fluxes. The results highlight the importance of seasonality, species diversity and aboveground biomass stocks to preserve the ecosystem processes driving soil respiration in temperate forests.
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