Variation of basic density, calorific value and volumetric shrinkage within tree height and tree age of Ugandan grown Eucalyptus grandis wood

Abstract

Insufficient knowledge on Ugandan grown Eucalyptus grandis W. Hill ex Maiden wood properties, high demand, and processing challenges led to a study into its physical properties. We obtained the variation of basic density (BD), calorific value (CV) and volumetric shrinkage (VS) within tree height and tree-age of E. grandis, and its appropriate use based on these properties. Trees with good boles were harvested from Kabarole District in western Uganda to produce specimens as prescribed by British Standards and ASTM standard wood testing procedures. Secondary data reviews and statistical analysis using ANOVA, Tukey’s test and multivariate analysis were done to obtain property estimates and their variation within trees and amongst tree ages. The mean BD of E. grandis is 413.6, 380.5, 471.0, and 501.1 kg m−3 at 3, 6, 9, and 12 years, respectively, showing significant increase with tree age (p = 0.003). The pattern of BD with tree height showed a reduction with tree height although with higher values in the middle portion of the tree. The CV increases (p = 0.014) with tree age and reduces with tree height with values of 14,560.32, 15,447.3, 16,079.11, and 16,932.6 kJ kg−1 at 3, 6, 9, and 12 years, respectively. The percentage VS was 11.02, 9.84, 12.31, and 14.45 for 3-, 6-, 9-, and 12-year-old trees, respectively, and it did not vary significantly (p = 0.088) with tree height. Basing on these property values, E. grandis wood could be used for scaffolding, light constructions and fuel wood production. Its seasoning needs to be longer with well monitored drying schedules to reduce seasoning defects caused by the high VS. Further studies on strength properties, seasoning schedules, panel products properties and tree-age chemical variations would improve the knowledge about its wood quality and would enhance its efficient utilization.