Qualidade de Tectona grandis L.f. para produção de madeira serrada

Abstract

In the search for greater production of wood in a short time, forestry companies have invested heavily in genetic improvement. Additionally, studies are necessary about the quality of sawn wood to determine whether the clonal material has characteristics equal to or greater than the seminal material. Therefore, it aimed to analyze the production of pith, heartwood, sapwood and bark, in addition to evaluating the basic density and mechanical properties of Tectona grandis wood of seminal and clonal origin, in addition to assessing the quality of sawn wood submitted to drying in open air and in a kiln. Six trees were collected by genetic material, approximately 15 years old, two clonal materials (C1 and C2) and one of seminal origin (S). From each tree, the diameter at chest height and commercial height were measured, and discs were sectioned in the regions of 0% (base of the tree), 25%, 50%, 75% and 100% (top) in relation to the commercial height, and two logs approximately one meter from the basal region. From the discs, the proportions of pith, heartwood, sapwood and bark were measured, determining the maximum angular deviation, pith eccentricity and basic density. The specimens of the mechanical tests of compression parallel to the fibers, Janka hardness and shear, were made from one of the logs. To evaluate the wood before and after the drying processes in the open air and in the kiln, another log was used, which was unfolded in boards and quantified the yield of sawn wood, the presence of knots and defects (bowing, crooking and cracking). As a result, clone C2 showed a lower proportion of bark (11%). The C2 presented a percentage of heartwood approximately (51%) up to half of the commercial height, whereas for C1 and S, this percentage was up to (25%) of the height. The three materials did not differ statistically for maximum angular deviation, pith eccentricity, basic density and Janka hardness. They were classified with moderately intercrossed grain, had an average basic density of 0.52 g.cm- ³ and values of parallel compression to the fibers and Janka hardness greater than 40 MPa. There was no statistical difference between the materials for total yield (77.58%) and commercial (55.72%) of sawn wood. After the drying processes, the bowing and crooking rates were less than 5 mm.m-1 , but the seminal material showed a higher incidence of cracking before and after drying in the air and in a kiln. It is concluded that the quality of the sawn wood of the three genetic materials is satisfactory. Kiln drying triggered a lower proportion of defects in the three materials, and clonal materials showed lower proportions of drying defects compared to seminal material.