Seleção de clones de Eucalyptus para crescimento e qualidade da madeira aliada à estabilidade biomecânica de árvores

Abstract

The impacts caused by the dragging force of strong winds are difficult to control for two fundamental reasons: the first is in the unpredictability of its occurrence and its intensity, the second reason is resultant of an important trade-off involving some allometric reactions of trees that can be modified by breeding. This study had the objective of proposing a methodology to align the improvement of the tree dimension with its properties of biomechanic resistance to environmental forces, such as wind dragging, gravity and water accumulation by rain or snow. We used 20 Eucalyptus spp. clones, at the age of five years and three months, cultivated in spacing of 10 x 4 m, at the Bom Sucesso farm, located in the municipality of Vazante, Minas Gerais, Brazil. The evaluation was done by destructive sampling and non-destructive analysis, conducted in three trees for each clone. Basic density (Db), Elasticity ( E) and Specific Elasticity (SE) Module, Esbeltez Index (EI), Critical Height (Hcrit), Safety Factor (f), Residual Deformation (DRL) and maximum Proportion of Wood Traction (MPWT) were evaluated. For the estimations of the genetic and phenotypic parameters and the prediction of the genotypic values, the Selegen-REML/PLUP computer program was used. In the growth study, the DAP traits and height presented very high heritability, of 0.74 and 0.83, respectively, and clones 39 (DAP) and 44JC (height) were highlighted regarding genetic gain. In the study of the wood properties, the heritability traits were very high for Db and E, with values of 0.90 and 0.80, respectively. For DRL, the heritability was of 0.51, of considerable magnitude. Clone 180 was highlighted as superior, considering the purpose of resistance to static flexing of the wood, wood density and growth in DAP, and clone 319, in addition to being superior for Db and E, was also for growth in height. The estimation for heritability for the IE, Hcrit and f are of good magnitude, with the values of 0.67, 078 and 0.65, respectively. For clone 65, we can predict that the trees are mechanically more stable, productive and generators of sawn wood with lower levels of defects. Clones 180, 319, 48 and 35 presented the lowest MPWT, with amplitude of 8 to 10%, which, theoretically, can be classified as producers of bet ter quality wood for primary processing.