Caracterización química y análisis de la variación axial y radial de la anatomía y densidad de la madera de Eucalyptus grandis W. Hill ex Maiden

The Eucalyptus genus, recognized worldwide for its rapid growth and adaptability, is predominant in Uruguay, where it accounts for 72% of all plantations. Among its species, Eucalyptus grandis stands out for its advantages in the national context and it is expected to continue expanding due to its ability to thrive in diverse conditions and its stability in the face of climate change. Consequently, studying its anatomical, chemical, and physical properties is essential; this knowledge not only deepens the understanding of the species' characteristics but also aids in identifying potential uses and promotes more efficient utilization, thereby maximizing its added value.

This study, conducted in the Cerro Largo department of Uruguay, aimed to compare the anatomy and basic apparent density of healthy wood from 30-year-old Eucalyptus grandis trees at different radial positions and trunk heights, as well as to characterize their chemical composition and dendrometric features. The specific objectives included: performing dendrometric characterization of the studied trees, comparing the anatomy of healthy wood across the radius and at different trunk heights, characterizing its chemical composition using descriptive statistics and evaluating variations in basic apparent density radially and with trunk height.

In a stand at the Estación Experimental Prof. Bernardo Rosengurtt (EEBR) of the Faculty of Agronomy, five healthy trees with similar diameters and no cracks were randomly selected. Various heights (stump, first branch, and total) were measured, along with diameter measurements taken every meter until reaching 8 cm at the thin end. Discs were collected from each tree at heights of 0.5 m, 1 m, and 1.5 m, resulting in a total of 15 samples. In the laboratory, four samples per disc were extracted, and each was then sectioned into four subsamples from pith to bark, identified according to their radial location and methodological use: anatomy, chemistry, or density.

Dendrometrically, the trees averaged 25.84 m in total height, 9.41 m to the first branch, and 0.21 m in stump height. The average diameter at breasy height - DBH was 25.96 cm, showing a progressive decrease in diameter with increasing height. In terms of anatomy, fibers had an averaged length of 986.310 µm, a diameter of 21.100 µm, and a cell wall thickness of 3.484 µm, with significant differences based on radial position -these increased from pith to bark- without significant variations based on height or interaction between height and radial position. Chemically, the averages obtained were: 7.571% moisture content, 6.255% extractives, 2.044% soluble lignin, 28.317% insoluble lignin, 73.293% holocellulose, and 0.310% ash. The average basic apparent density was measured at 0.413 g/cm³, decreasing with height while increasing radially from pith to bark, without significant interaction between height and radial position.