The total tree height (h) and diameter at breast height (dbh) relationship is an essential tool in forest management and planning. Nonlinear mixed effect modeling (NLMEM) has been extensively used, ...and lately the artificial neural network (ANN) and the resilient backpropagation artificial neural network (RBPANN) approach has been a trending topic for modeling this relationship. The objective of this study was to evaluate and contrast the NLMEN and RBPANN approaches for modeling the h-dbh relationship for the Durango pine species (Pinus durangensis Martínez) for both training and testing datasets in a mixed-species forest in Mexico. The knowledge of this relationship is important for forest management and planning in Mexican Forestry. The total dataset considered 1000 plots (each plot 0.10 ha) (11,472 measured trees) randomly selected from 14,390 temporary forest inventory plots and the dataset was randomly divided into two parts: 50% for training and 50% for testing. An unsupervised clustering analysis was used to group the dataset into 10 cluster-groups based on the k-means clustering method. An RBPANN was performed for tangent hyperbolicus (RBPANN-tanh), softplus (RBPANN-softplus), and logistic (RBPANN-logistic) activation functions in the cross product of the covariate or neurons and the weights for the ANN analysis. Also, a different vector of hidden layers was used for training of ANNs. For both training and testing, 10 classical statistics (e.g., RMSE, AIC, BIC, and logLik) were computed for the residual values and to assess the approaches for the h-dbh relationship. For training and testing, the ANN approach outperformed the NLMEM approach, and the RBPANN-tanh had the best performance in both the training and testing of ANNs.
Key message
The oak species
Q. crassifolia
produces reliable annual rings with better climatic sensitivity than many conifer species commonly used for hydroclimatic reconstructions in Mexico.
Most ...dendrochronological research in Mexico has been done with conifers, but broadleaf species have been underutilized. Mexican oaks are found among those species receiving limited attention for dendrochronological purposes, despite Mexico being a primary center of oak diversity with over 160 species. The objectives of this study were: (1) date the annual radial increments of oaks (
Quercus crassifolia
Bonpl.), and (2) analyze the dendrochronological potential and climatic response of the species to reconstruct historical climatic variability and the influence of ocean–atmospheric modes. The study was located at the Barajas site, municipality of Tepehuanes, Durango, Mexico. Wood samples consisted of 60 cross sections, 30 of them obtained at the base of the stem, and 30 more ca. 20–30 cm above the first cross section, which were analyzed by dendrochronological techniques. A tree-ring width chronology 177 years long (1840–2016) was developed indicating suitable values of series intercorrelation (0.52), mean sensitivity (0.26), signal-to-noise ratio (8.98), first-order autocorrelation (0.21), rbar (0.28), and expressed population signal (0.86) for the period 1890–2016. Dendrochronological parameters were similar or superior to those obtained from conifer species in the region. The chronology shows the strongest relationship with October–May precipitation, explaining ca. 60% of its variability (1951–1984,
r
= 0.78,
p
< 0.01), but a negative response to the average seasonal October–May temperature (1902–2016,
r
= -0.50,
p
< 0.01). The annual growth rings of
Q. crassifolia
showed a negative association (1890–1977,
r
= – 0.67,
p
< 0.01) with the El Niño-Southern Oscillation (reconstructed Southern Oscillation Index), and positive with the Pacific Decadal Oscillation Index (1948–2015,
r
= 0.39,
p
< 0.01, the reconstructed Palmer Drought Severity Index (1890–2012,
r
= 0.73,
p
< 0.01), and the seasonal winter–spring Standard Precipitation Index (1890–2016,
r
= 0.76,
p
< 0.01).
Sustainable forest management requires accurate biometric tools to estimate forest site quality. This is particularly relevant for prescribing adequate silvicultural treatments of forest management ...planning. The aim of this research was to incorporate topographic and climatic variables into dominant height growth models of patula pine stands to improve the estimation of forest stand productivity. Three generalized algebraic difference approach (GADA) models were fit to a dataset from 66 permanent sampling plots, with six re-measurements and 77 temporary inventory sampling plots established on forest stands of patula pine. The nested iterative approach was used to fit the GADA models, and goodness-of-fit statistics such as the root mean square error, Akaike’s Information Criterion, and Bias were used to assess their performance. A Hossfeld IV GADA equation type that includes altitude, slope percentage, mean annual precipitation, and mean annual minimum temperature produced the best fit and estimation. Forest site productivity was negatively affected by altitude, while increasing the mean annual minimum temperature suggested the fastest-growing rates for dominant tree height.
•A statistical framework is provided to predict the yield of patula pine stands.•The Weibull and Johnson's SB functions modeled stand diameter distributions.•The Bayesian approach produced robust ...parameter estimates for probability density functions.•The Weibull function fits best empirical diameter distributions; its implementation is simple.•The diameter distribution model could improve southern Mexico's forest management strategies.
Characterization of the diameter distribution of forest stands managed for timber production provides accurate estimates of existing wood volume by diameter class and area unit. It provides the basis for determining the stand's ecological and economic value, its structure, the potential for ecosystem services, and appropriate management practices. Patula pine is one of the most important conifers in southern Mexico and requires biometric tools to improve management strategies. This study aimed to use the Bayesian approach to estimate the parameters of Johnson's SB (JSB) and Weibull (W) probability density functions (pdf) and to model the diameter distribution of patula pine stands in southern Mexico. We used data from 462 diameter distributions derived from 66 permanent 400 m2 sampling plots. The results indicated that the Bayesian approach was appropriate for estimating the JSB and W pdf parameters. Due to the similarity between the nonparametric tests and the goodness-of-fit statistics of the functions, the graphical analysis helped to select the W function as the better option to adequately model the diameter distribution of the analyzed stands. The equations developed for parameter prediction of the W function with stand variables allowed us to characterize and project the theoretical distribution of diameter classes in a simple accurate way with variables easily obtained from forest inventories. The Bayesian approach proved to be an effective method for estimating the pdf parameters used. This allowed for the correct characterization of the observed diameter distribution, and its implementation was easy for executing the procedure. Diameter distribution models are a powerful tool for forest inventory and management of patula pine stands analyzed in southern Mexico.
In recent decades, droughts associated with climate change have increased in frequency and intensity. Given this trend, the understanding of climate variability over time has raised great interest. ...The main objective of this study was to reconstruct the standardized precipitation-evapotranspiration index (SPEI) from tree rings of Pinus durangensis Martinez at a representative site in the western region of the Durango State, Mexico. To this end, we used radii of 286 cross-sections, which were processed through conventional dendrochronological techniques. In addition, chronologies of total ring and early and latewood were generated, covering 296 years. In parallel, we analyzed the association between the chronologies obtained and the cumulative SPEI for 3, 6, 9, and 12 months. The earlywood residual chronology (EWres) showed the closest association with the six-month cumulative SPEI for February–May (SPEI6FM). Thus, the SPEI6FM for the past 296 years was reconstructed through a simple linear regression model. In this reconstruction, 18% of the years were wet, 16% dry, and 66% average. In addition, an increase in the frequency of droughts was observed from 1880 onwards, which might have been related to the rise in temperature due to climate warming. Therefore, the annual rings of P. durangensis are suitable for use as a proxy for the reconstruction of historical climatic events in this region of northern Mexico.
Las plantaciones forestales comerciales contribuyen al incremento de la producción maderable en bosques con manejo forestal en el estado de Michoacán, México; sin embargo, no se considera el uso de ...ecuaciones que permitan predecir, de manera eficiente, la dinámica de crecimiento en diámetro, lo cual es imprescindible para la planeación y evaluación de labores silvícolas. El objetivo fue ajustar y comparar ecuaciones en diferencia algebraica (DA) para la elaboración de curvas de crecimiento e incremento en diámetro e índice de diámetro para plantaciones comerciales de Pinus pseudostrobus en Michoacán, México. La base de datos utilizada proviene de análisis troncales de 41 árboles y para la generación de las curvas de crecimiento, se consideró como índice de diámetro al diámetro medio que alcanzan las plantaciones a la edad de referencia de 20 años. Las ecuaciones de Korf, Levakovic ll, Monomolecular y Weibull presentaron alta precisión de acuerdo con los estadísticos de ajuste; pero la mayor precisión se obtuvo con la ecuación anamórfica de Korf, la cual generó curvas que describieron adecuadamente el patrón de crecimiento en diámetro y sugirió que el punto de crecimiento máximo sucede a los seis años. Las ecuaciones de índice de diámetro son herramientas que permiten describir de forma adecuada el patrón de crecimiento, además, son útiles para estimar el punto de crecimiento máximo; esta información servirá de apoyo para conducir a las plantaciones de P. pseudostrobus a mayor rendimiento maderable.
Forests experience disturbances, such as fire, that affect their functioning, structure, and species composition. The objective of this work was to compare the species diversity and forest structure ...at sites affected by different degrees of fire severity, 9 years after a forest fire event. We used the differenced Normalized Burn Ratio (dNBR) index. Vegetation was sampled in three severity levels: high (HS), moderate (MS), and low (LS) and included the unburned (U) level as control. In addition, we calculated the species richness (S), the Shannon index (H), and the Evenness Index (E). The structural diversity of tree diameters and heights was measured applying the indices H, E, and the coefficient of variation (CV). The differences in the indices calculated across the fire severity levels were determined through analyses of variance (ANOVA) and Tukey’s multiple comparison tests. The results showed no significant differences (p ≤ 0.05) in the species diversity indices between fire severity levels. The structural diversity of tree diameters and heights was lower at the HS level. dNBR was negatively related to structural diversity; thus, it is concluded that HS tends to reduce structural variability in terms of diameter, height, and age. These results provide a baseline to understand how fire can modify forest structure and species diversity.
Understanding the ecological role of fire in forests is essential for proper management and conservation programs. The objectives of this study were: (1) to reconstruct the history of fires in a ...temperate forest in Sierra Madre Occidental; and (2) to interpret the impacts of fire and climate on forest structure. Sixty tree cross-sections with fire scars were analyzed, and descriptive statistics of fire history were generated. Additionally, growth cores were analyzed, and the ages of trees of different diameter categories were calculated. The synchrony between fire history and tree establishment was determined, and precipitation and Palmer Drought Severity Index (PDSI) values were correlated with the number of trees established per year. The presence of 137 fire scars was determined, which allowed the reconstruction of 41 fire events over the period 1855–2019; however, only the period 1940–2015 was used to compare tree recruitment, as tree establishment was detected in this period. The mean fire interval (MFI) was 2.28 years in general, and 12.17 years for extensive fires. As regards vegetation, a continuous recruitment pattern was observed, typical of a frequent low-intensity fire regime, although peak regeneration occurred after extensive fires. The correlation analysis showed that the number of trees established per year was influenced by the wet conditions that occurred in December of the previous year and the dry conditions in September and October of the previous year. This finding demonstrates the historical influence of fire and climate on the structure of the current stand in the study area. Therefore, the present study highlights the importance of including fire in forest management programs, considering the natural fire regime to which the species in this ecosystem are already adapted.
In the middle of the last century, the Mexican government applied a forest administration policy based on state control through concessions to parastatal enterprises. In the 1980s, communities began ...to regain control of their forests and promote community forestry, with Ixtlán playing a leading role. This study compared three forest management plans (FMPs) that have been implemented in the community of Ixtlán de Juárez, in southern Mexico, and their contributions to the productivity and conservation of forest resources. The information was obtained from three FMPs, considering the silvicultural regimes, the original stand or sub-stand structure, and the species that promoted cutting regeneration. These FMPs represent different management periods; the forest inventory of the first FMP indicates the condition of the forest originated under state control, while the two subsequent ones evaluate the condition of the forest under community forestry. Sub-stand variables of the three FMPs were compared using the nonparametric Kruskal–Wallis test. The results indicated that, in the first FMP, the sub-stands were of old growth, and intensive thinning was applied. In the two subsequent plans, alternate strip clearcutting and single-tree selection were implemented. It was shown that, with increased management intensity in the sub-stands, better characteristics were obtained in terms of increment in basal area and volume variables, promoting regeneration and establishment of Pinus and displacing dominance of Quercus genus, without affecting forest richness and diversity.
Gmelina arborea es una especie que ostenta valor económico en los mercados forestales, esencialmente por la versatilidad de su biomasa, su rápido crecimiento y la calidad de su madera. Los objetivos ...principales de esta investigación fueron evaluar la dendrometría, la biomasa, el suelo y las propiedades físicas y mecánicas de la madera en dos rodales de 18 años. En parcelas rectangulares de 1000 m2 se recabó información dasométrica de 20 árboles, además de fracciones de madera para ensayos físicos-mecánicos en laboratorio. En términos estadísticos, la G. arborea del rodal mezclado presentó mayor diámetro (7.3 %) y biomasa del fuste (5.1 %), además de un impacto en las propiedades mecánicas (8.1 %) y la dureza en sus diferentes ejes (long. 6.2 %, rad. 1.5 % y tang. 6.3 %). Se deduce que los rodales mezclados contribuyen a una mayor biomasa y a madera de mejor resistencia y calidad en G. arborea.
Gmelina arborea is a species that holds economic value in forest markets, primarily due to the versatility of its biomass, rapid growth, and timber quality. The main objective of this research was to evaluate the dendrometry, biomass, soil, and the physical and mechanical properties of the wood in two 18-year-old stands. In rectangular plots of 1000 m², dasometric information from 20 trees was collected, in addition to wood fractions for physical-mechanical tests in the laboratory. Statistically, mixed-stand G. arborea exhibited a larger diameter (7.3%) and stem biomass (5.1%), as well as an impact on mechanical properties (8.1%) and hardness on its various axes (long. 6.2%, rad. 1.5%, and tang. 6.3%). It is inferred that mixed stands contribute to greater biomass and better resistance and quality of wood in G. arborea.
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