Within-tree and tree-age variation of selected anatomical properties of the wood of Ugandan-grown Eucalyptus grandis

Abstract

The challenges of utilizing Eucalyptus grandis thinnings prompted a study into its anatomical properties with the aim of identifying its potential based on the within-tree axial and tree-age variation. Fiber length, fiber diameter, vessel length, vessel diameter, vessel average, ray height, and ray frequency at 3, 6, 9, and 12 years were studied. Axial sample portions at 25, 50, and 75 percent of tree height were collected from western Uganda and prepared for maceration, microtomy, and microscopy. Analysis of variance and Tukey’s test were used to obtain axial and tree-age variation. Fiber length (819 to 1,077 lm) decreased axially in higher tree ages of 6, 9, and 12 years and increased with tree age. Fiber diameter (10 to 13.4 lm) varied inconsistently axially and decreased with tree age. Vessel length had no consistent axial pattern but decreased with tree age (338 to 548 lm). Vessel diameter showed higher values at 75 percent and increased with tree age (93 to 138 lm). Vessel average did not vary axially but decreased with tree age (8 to 11 vessels per mm2 ). Ray height did not vary axially but increased with tree age (107 to 278 lm). Ray frequency decreased with tree age (8 to 10 rays per mm2 ). E. grandis trees at the ages of 3, 6, 9, and 12 years have anatomical properties suitable for production of strong pulps although with a modest proportion of fines. Comparative research on cloned E. grandis varieties and their implied industrial potential would be appropriate to improve utilization of this fast-growing tree species.