Mario Tomazello Filho

Influência de idade e da posição radial nas dimensões das fibras e dos vasos da madeira de Eucalyptus grandis Hill ex. Maiden

RESUMO – Objetivou-se neste trabalho avaliar a variacao das dimensoes das fibras e dos vasos da madeira de Eucalyptus grandis com quatro diferentes idades (10, 14, 20 e 25 anos), proveniente de talhoes comerciais. A amostragem do material na arvore foi feita atraves da coleta de tres discos, retirados da base e das extremidades das duas primeiras toras, ambas com o comprimento comercial de 3 m. De cada disco, retiraram-se cinco amostras, de dimensoes 1,0 x 1,0 x 1,0 cm, tomadas de pontos equidistantes, correspondentes a 0; 25; 50; 75; e 100% da secao, no sentido radial medula-casca, fazendo-se a medicao das fibras e dos vasos. Verificouse, em todos os parâmetros, o efeito da idade e da variacao radial, no sentido medula-casca, a excecao da largura e do diâmetro do lume das fibras; todos os demais parâmetros apresentaram correlacao positiva.

Wood density of loblolly pine trees as affected by crown thinnings and harvest age in southern Brazil

The Brazilian plantation forestry is well known for high yields. Such yields are not necessarily linked with acceptable wood quality. Pine plantations are an important source of timber in Brazil, and although pulp and paper production plays a dominant role, there is an increasing need for sawtimber, and even high-quality timber is in demand. The impacts of crown thinning on ring width, ring density and juvenile–mature wood of loblolly pine trees were analysed. The experimental design included no thinning, an extreme release from competition, and two practice-oriented variants with moderate and heavy thinnings. X-ray microdensitometry provided ring width and density for 1197 rings and 44 trees. Mean ring width at 1.3xa0m height varied from 6 to 9xa0mm, reaching a maximum of 22xa0mm during the first 3–6xa0years regardless of thinning intensity. Only occasional differences were verified in ring densities produced from the different thinning variants. The transition from juvenile to mature wood occurred between 13 and 17xa0years of age. From the analysis of wood density, extreme and early thinning delayed the production of mature wood in ~xa04xa0years compared with non-thinned or practice-oriented thinned stands. At the same harvest age, thinning had no effect on wood density. However, harvest age itself was a determinant for obtaining wood of higher density. Altogether, results indicated that regarding current market demands no constraints related to the analysed wood characteristics are to be expected, even if extreme thinning regimes are applied.

Avaliação da rugosidade superficial da madeira de Eucalyptus sp submetida ao fresamento periférico

Conduziu-se este trabalho, com o objetivo de avaliar a qualidade de superficie usinada da madeira de tres especies de Eucalyptus sp, para a producao de produtos madeireiros. Para os ensaios, foram confeccionados e usinados 48 corpos de prova de madeira de cada especie, nos tratamentos de usinagem em fresadora de eixo vertical, no sentido discordante, em sete velocidades. Na avaliacao da qualidade da superficie dos corpos de prova de madeira, utilizou-se o rugosimetro marca Taylor Hobson modelo Surtronic 3+, utilizando o filtro 2CR, com comprimento de amostragem com 0,80 Ie ou ln (mm) e cut-off de 0,80 λc (mm). Os resultados indicaram que a madeira do E. urophylla apresentou a melhor qualidade de superficie com os menores valores de coeficiente de variacao; a madeira do E. grandis mostrou-se intermediaria e a do E. dunnii apresentou o pior desempenho e o maior valor de coeficiente de variacao. Observou-se, tambem, que o desempenho dos tratamentos para a madeira das especies de Eucalyptus sp mostrou relacao da reducao da velocidade de avanco da usinagem com a rugosidade superficial; melhor na de 3-4 m.min-1 e pior na de 22 m.min-1. Constatou-se, tambem, que a qualidade da superficie da madeira usinada relacionou-se com a sua densidade e tipo de gra.

Variações dos teores de fibras celulósicas e amido no colmo de bambu

The basic density, cellulosic fibers and starch contents in the axial and radial directions were determined in three-year old culms of Bambusa vulgaris Schrad. The samples were obtained considering the useful length of the culm at the base and at 25, 50, 75 and 100% of the useful length. In the radial direction the culm wall thickness was divided in five equal parts. The results showed that the lowest values of the basic density were obtained in the basal position of the culm (0.660 g/cm3) and in the inner parts of the culm wall (0.690 g/cm3). The cellulosic fibers contents (38.7 to 40.1%) and starch percentages (26.2 to 29.7%) didnt vary significantly along the culm length. In the radial direction the cellulosic fiber concentration vary from 48.8 to 28.3%, being the highest value obtained in the outer portion of the culm. For the starch contents (20.0 to 35.1%) the highest value was observed in the inner portion of the bamboo culm.