**3.1 Wood characteristics**

The average values of fiber dimensions, morphological ratios and basic density are summarized in **Table 3**. Fiber morphology showed considerable differences between genotypes, except for length measurements. Fiber length corresponded from 813.6 μm (clone E) to 836.6 μm (clone D); fiber diameter from 16.9 μm (clone D) to 18.5 μm (clone B); fiber wall thickness from 3.8 μm (clone B) to 4.5 μm (clone D); and lumen width from 8.0 μm (clone D) to 10.9 μm (clone B).


*FL–fiber length; FD–fiber diameter; FWT–fiber wall thickness; FLW–fiber lumen width; RR–Runkel ratio; WP–Wall proportion; FC–flexibility coefficient; SR–slenderness ratio; LSF–Luces's shape factor; BD–basic density. Means and coefficients of variation (%). Means followed by the same letter do not differ from each other by the Tukey test (p > 0.05).*

## **Table 3.**

*Fiber dimensions, morphological ratios, and basic density of the five elite Eucalyptus spp. clones.*

*Wood Quality and Pulping Process Efficiency of Elite* Eucalyptus *spp. Clones Field-Grown… DOI: http://dx.doi.org/10.5772/intechopen.106341*

**Figure 3.**

*Pearson's correlation (a) and hierarchical cluster analyses (b) for fiber dimensions and wood density of*  Eucalyptus *spp. clones. BD–basic density; FL–fiber length; FD–fiber diameter; FWT–fiber wall thickness; FLW–fiber lumen width.*

Regarding the morphological ratios, clone B had the lowest RR (Runkel ratio), WP (wall proportion) and LSF (Luce's factor): 0.76, 43.5%, and 0.49, respectively. The highest values for the same ratios were found for clone D (1.19 to RR, 54.8 to WP and 0.64 to LSF). In the same way but with opposite results, clone B showed the highest flexibility coefficient (0.59), and clone D presented the lowest value (0.46). Slenderness ratio values ranged from 44.8 (clone E) to 49.7 (clone D).

Mean wood density ranged from 446 to 501 kg m−3, with the highest basic density for clones D and E and differing significantly between clone B. In **Figure 3a** it can be verified that wood density presented a significant inverse correlation with the fiber lumen width (p-value = 0.006) and a positive correlation with fiber wall thickness (p-value = 0.02). Correlations are also verified between fiber diameter and fiber wall thickness (p-value <0.001) and between fiber wall thickness and fiber lumen width (p-value <0.001). Taking to account the fiber dimensions and basic density, cluster analysis showed the formation of two main groups (**Figure 3b**). Group 1 comprised clones B and C, while group 2 contained clones A, D and E.
