RESUMOO presente estudo teve como objetivo avaliar os aspectos ecológicos e sucessionais de um fragmento de floresta subtropical via projeção da estrutura diamétrica de diferentes grupos ecológicos com uso da Matriz de Transição. Com base em medições de 2009 e 2012 de todas as árvores acima de 10 cm de DAP, foram realizadas projeções da distribuição diamétrica, bem como análise da dinâmica de três agrupamentos de espécies: Pioneiras; Não Pioneiras; e Floresta como um todo. Simulações da dinâmica dos agrupamentos foram feitas até 2027 após validação do método. O método de projeção se mostrou aderente em todos os casos, apresentando maior precisão quando utilizado o intervalo de classe de 5 cm. As análises indicaram tendência de substituição gradual das espécies pioneiras, sugerindo avanço sucessional no fragmento florestal estudado, bem como eficiência do método para análise da dinâmica dos grupos ecológicos estudados.Palavras-chave: dinâmica florestal, sucessão florestal, cadeia de Markov. Diametric Distribution Projection of Ecological Groups in a Mixed Tropical Forest ABSTRACTThis study aimed to evaluate the ecological and successional aspects of a subtropical forest fragment by projection of the diameter distribution of different ecological groups, using transition matrix model. Based on measurements of 2009 and 2012 of all trees above 10 cm of DBH, projection of the diameter distribution as well as analysis of forest dynamic were made for three species groups: Pioneer; Non Pioneers, and the whole forest. Simulations of the dynamics of the groups were made until 2027 after method validation. The projection method was adherent in all cases, with higher precision when using the 5cm class interval. The analysis made indicated a gradual substitution tendency of the pioneer species, suggesting a successional advance in the forest fragment under study, as well as an efficiency of the projection method for dynamics analysis of the ecological groups studied.

Weibull distributions have been widely used to describe tree stem diameter distributions. However, there is a scarcity of studies suggesting the best Weibull formulation. The parameters of the Weibull distribution are usually predicted either by the parameter prediction method (PPM) or by the parameter recovery method (PRM), although other methods have been proposed. Thus, this study aimed to evaluate the performance of eight Weibull formulations and to compare parameter prediction methods to describe diameter distributions of clonal eucalypt stands in Brazil. Data originated from re-measurements of 56 plots at ages 3, 5, and 6 years. Weibull distributions were fitted using the maximum likelihood method and evaluated in a goodness-of-fit-indicators ranking. The right-truncated two-parameters formulation showed the best results and was used to evaluate the parameter prediction methods. Stand attributes showed a strong relationship with shape and scale parameters. Regression models were developed and resulted in accurate estimates using PPM. PRM used a growth and yield system to estimate the stand attributes followed by the moment-based method. The Modified CDFR approach was also evaluated and presented the poorest results. While the PPM showed excellent results, PRM is recommended in older stands with inventory since it implicitly promotes compatibility among stand attributes.

The aim of this study was to evaluate the effects of age, site, and density factors on the dynamics of eucalyptus diameter distribution. Data were obtained from a continuous forest inventory measured at different occasions, stratified according to the factors evaluated and adjusted by the three-parameter Weibull function using nonthinned clonal plots of eucalyptus stands located in the Central region of the state of Minas Gerais. In order to evaluate the diameter distribution behavior, asymmetry and kurtosis measures and graphical analysis for fitted curves were used. In general, an increase was observed in diameter amplitudes with aging, as well as with improvement of site productivity and higher densities. The number of trees decreased in the lower classes and increased in the upper classes, resulting in diameter distribution curves, being displaced to the right and flattened with aging.

No abstract

Taper functions have been widely used for various purposes. Several functions were developed and successfully applied. However, most of these functions fail to account for the influence of stand-level and individual-tree effects of variation on the stem profile. Hence, we aimed in this study to assess how these factors influence the stem profile of black wattle (<i>Acacia mearnsii</i> De Wild.) trees in southern Brazil. There is a notable necessity for developing a domestic market for black wattle solid wood. The database was composed of 218 black wattle trees at age 10 years distributed across the state of Rio Grande do Sul, Brazil. A dimensionally compatible taper equation combining with the mixed-effect modeling approach was used. Additionally, auxiliary variables were included to build a generalized taper function that explains stem form variations. In general, all variables showed a significant influence on the stem profile, except the crown ratio. The inclusion of relative spacing and tree hierarchical position in the taper function resulted in higher accuracy when estimating stem diameters and total tree volume. This study indicates that accounting for attributes at the stand and individual-tree levels may improve stem profile predictions as well as the biological soundness of the taper function.