Abstracts Category : Other

The Natural Durability, Anatomy and Chemical Composition of the Stem and Branch Woods of Two Commercial Hardwood Timbers [Aningeria robusta (A. Chev) and Terminalia ivorensis (A. Chev)].

by Sitsofe Kang-Milung

To enhance wood economic value and effective utilization, knowledge of its properties, which impact its service behaviour, is indispensable. The biochemical properties of the sapwoods and heartwoods along the stems and branches of T. ivorensis and A. robusta were studied to provide adequate information to enhance their efficient utilization, especially branchwood, whose use could widen the raw material base of the timber industry. Macerated samples and microtomed sections (radial, longitudinal and tangential), TAPPI and field tests respectively were employed to determine tissue dimensions and proportions, chemical component percentages and the natural durability. Analyses of variance (ANOVA) were used to test for differences between axial and radial position and tree portions and correlation and regression analysis were used to determine the relationships among the biochemical properties. Stemwood recorded wider vessel lumen diameter, greater fibre and vessel proportions with less parenchyma than the branchwood. Fibre length, diameter, lumen diameter and double wall thickness were greater for T. ivorensis stemwood (1296.7-1508.6, 19.8-23.4, 13.3-17.3 and 6.0-6.5m respectively) than branchwood (1046.0-1116.5, 19.2-21.2, 13.1-15.2 and 5.7-6.3m respectively). Similarly, A. robusta stemwood recorded greater values (1182.9-1302.3, 22.9-23.9, 15.3-18.6 and 6.2-7.6m respectively) than branchwood (995.1-1145.3, 20.1-22.42, 15.1-17 and 4.9-5.6m respectively). Fibre proportions decreased up their stems (51.5-42.5%) and branches (51.2-40.0%). Their sapwood and heartwood vessel and parenchyma percentages were greater at bases than top. Vessel lumen diameters increased with stem height but decreased along branches. T. ivorensis had 39.0-41.9%, 18.1-23.6%, 31.6-32.9% and 1.58-9.9% and A. robusta 39.1-40.5%, 32.6-34.0%, 24.9-26.6% and 0.37-1.6% cellulose hemicellulose, lignin and extractives percentage respectively. the amounts were greater for stemwoods, except for more branchwood hemicellulose percentages. Extractives and lignin were also greater for heartwoods than sapwoods, which also had more cellulose and hemicelluloses. A. robusta was rated non-durable; it was completely degrade; lost 100% weight and hardness. Natural durability of T. ivorensis decreased with height along the stem and branch, was greater for stem heartwood (moderately durable to very durable) than branch heartwood (moderately durable) and for heartwood than sapwood. Chemical components were great determinants of natural durability, while the anatomical features were poor determinants of natural durability for T. ivorensis. The biochemical properties of the branchwoods of T. ivorensis and A. robusta, compare favourably with their stemwoods and with utilizable hardwoods. The branchwoods could suitably be utilized to avoid wastage and increase the raw material base of the wood industry. A Thesis submitted to the Department of Wood Science and Technology, College of Agriculture and Natural Resources in partial fulfilment of the requirements for the