Caracterización anatómica de la madera de híbridos de Eucalyptus grandis y Eucalyptus dunnii y evaluación de su potencial para la producción de celulosa y papel

Uruguay has been the scene of various investigations with Eucalyptus hybrids. In this case, hybrids between Eucalyptus dunnii and Eucalyptus grandis were studied in order to combine the most desirable characteristics of both species. The general objective of this work was to biometrically characterize the cellulose fibers of 201, 3-year-old trees of the mentioned hybrids, measuring the length and width of the cellulose fiber to obtain the slenderness index as a quality indicator. A maceration was done out to visualize and measure a total of 25 fibers from each tree using an optical microscope. To complement the measured data, UPM provided the diameter at breast high, height, volume, basic density and pulp yield for each tree. The observed fibers were libriform, presenting an average fiber length of 808,0 μm and an average fiber width of 13,63 μm. For fiber length and width hybrids presented significant differences, with E. dunnii x E. grandis being the one with the longest and thinnest fibers, presenting an average of 814,2 μm long and 13,34 μm wide. While E. grandis x E. dunnii presented shorter and wider fibers with averages of 795,2 μm long and 14,25 μm wide. The average slenderness index was 59,87% and like the length and width, it presented significant differences between hybrids with E. dunnii x E. grandis being the one with highest average slenderness of 61,55%, while that of E. grandis x E. dunnii was 56,33%. As well as the anatomical characteristics, volume, basic density and pulp yield also showed significant differences between hybrids, with E. dunnii x E. grandis showing differences the highest averages in the three variables mentioned. Likewise, the correlation between volume, basic density, pulp yield and slenderness were analyzed and all the correlations were positive and significant. When analyzing the importance of the variables on pulp yield, it was found that the one with the greatest influence is basic density, followed by volume and finally slenderness, with importance values of 57,80%, 57,66% and 50,94% respectively. This was represented in a regression tree, where a total of 37 individuals are in the group with the highest pulp yield. Regarding the comparison between the 29 families analyzed, we obtained two different clusters. These are mostly grouped by crossing, that is, on the one hand, those E. dunnii x E. grandis families and on the other hand, those E. grandis x E. dunnii. All the results obtained were used to generate a database useful for genomic selection.