No abstract

, Alexandre Miguel do Nascimento 2 e Marcos Antônio de Rezende 3 RESUMO -Durante o crescimento, as árvores produzem diferentes tipos de tecido lenhoso. O xilema produzido nos primeiros anos até certa idade cambial é denominado lenho juvenil e apresenta propriedades físicas, mecânicas, químicas e anatômicas diferentes do xilema produzido após certa idade cambial, isto é, quando as células do câmbio já amadureceram. Dessa forma, um prévio conhecimento sobre a qualidade da matéria-prima produzida é de fundamental importância para melhor aplicabilidade do material. Com base nesse contexto, este trabalho objetivou, a partir de dados de comprimento de traqueídeos e densidade da madeira, delimitar a idade de transição entre os lenhos juvenil e adulto. Para isso, coletaram-se três árvores de Pinus elliottii var. elliottii Engelm., com 35 anos de idade, provenientes da Estação Experimental de Itapetininga, localizada em São Paulo, Brasil. De cada árvore, retiraram-se discos de aproximadamente 5 cm de espessura, extraídos a 0,05 m do solo, que foram utilizados para determinação radial da densidade pelo método de atenuação da radiação gama e comprimento dos traqueídeos. Os resultados da análise de regressão linear indicaram que o lenho juvenil está limitado aos sete primeiros anos de crescimento da árvore e o lenho adulto é formado após os 20 anos de idade. No lenho adulto há diferenças significativas entre as idades médias obtidas através do comprimento dos traqueídeos e da densidade da madeira.Palavras-chave: Densidade da madeira, Idade de transição, Qualidade da madeira. DELIMITATION THE JUVENILE AND MATURE WOOD OF Pinus elliottii ENGELM

This study aimed to evaluate the effect of thermal treatment on the physical properties of juvenile and mature woods of Eucalyptus grandis. Boards were taken from 30-year-old E. grandis trees. The boards were thermally modified at 180 °C in the Laboratory of Wood Drying and Preservation at UNESP, Botucatu, Sao Paulo state, Brazil. The results showed that thermal modification caused: (1) decrease of 6.8% in the density at 0% equilibrium moisture content of mature wood; (2) significant decreases of 14.7% and 35.6% in the maximum volumetric swellings of juvenile and mature woods, respectively; (3) significant decreases of 13.7% and 21.3% in the equilibrium moisture content of juvenile and mature woods, respectively. The influence of thermal modification in juvenile wood was lower than in mature wood and caused greater uniformity in the physical variations between these types of wood in E. grandis.

Identifying wood species using wood anatomy is an important tool for various purposes. The traditionally used method is based on the macroscopic description of the physical and anatomical characteristics of the wood. This requires that the identifier has thorough technical knowledge about wood anatomy. A possible alternative to this task is to use intelligent systems capable of identifying species through an analysis of digital images. In this work, 21 species were used to generate a set of 2000 macroscopic images. These were produced with a smartphone under field conditions, from samples manually polished with knives. Texture characteristics obtained through a gray level co-occurrence matrix were used in developing classifiers based on support vector machines. The best model achieved a 97.7% accuracy. Our study concluded that the automated identification of species can be performed in the field in a practical, simple and precise way.

The present study is aimed at evaluating the anatomical characteristics of Eucalyptus grandis wood and the transition age between the juvenile and mature woods. Four trees of 23-year-old E. grandis were used. The juvenile, transition and mature wood zones were found by fiber length measurement from the pith to the bark. Samples were taken from juvenile wood, transition wood and mature wood and the anatomical properties of the wood were determined. The results showed that: (1) the fiber length, cell wall thickness, slenderness ratio, cell wall fraction and tangential vessel diameter increase from pith to bark; (2) fibers, axial parenchyma, ray parenchyma cells and vessels are equally distributed from pith to bark; (3) the transition zone between juvenile and mature wood occurs between the age of 8 and 13 years.