Abstract:
The purpose of this study was four-fold: First, to estimate merchantable logging
residues left in the forest after logging; second, to investigate the natural durability of
stem and branch wood of five species; third, to compare the bending strength of solid
and finger-jointed lumber; and finally to investigate the influence of anatomical
properties on natural durability and mechanical properties of wood. The five wood
species were Entandrophragma cylindricum (sapele), Entandrophragma angolense
(edinam), Khaya ivorensis (mahogany), Terminalia superba (ofram), and Pterygota macrocarpa (koto/kyere). Forest residues were quantified with Smalian‟s equation,
natural durability test was measured on percentage weight loss in accordance with EN
252-1989, whereas bending strengths of solid and finger-jointed lumber (produced
with PVA adhesive) were evaluated in accordance with BS 373-1957, and the
anatomical properties assessed using IAWA Committee protocol and using ImageJ
software. Results showed 25% of merchantable logging residues of felled trees were
left in the forest unextracted. Unlike branchwood of mahogany, ofram and koto whose
natural durability were comparable to their stemwood, branchwood of sapele and
edinam dried to 9±3%MC were significantly (p<0.05) better than their stemwood
counterparts. Bending test showed significant (p<0.05) MOE differences from 9.4%
to 23.5% higher in solid branchwood of edinam, mahogany and ofram, whereas MOR
differences were from 16.5% to 23.5% higher in branchwood of edinam and
mahogany compared to their stemwood counterparts with MC and wood type having
significant effect (p=0.000). Branchwood finger-jointed lumber combinations
produced joint efficiencies in MOE ranging from 59% to 110%, and those in MOR
ranged from 30% to 68%. Expectedly, finger-joint efficiencies in MOE and MOR
correlated inversely with wood density. But unlike the MOEs, MORs of all finger jointed combinations were significantly lower (p<0.05) than those of stemwood of
their respective species. As a characteristic of hardwoods, sizes and quantities of some
wood cells were either significantly (p<0.05) more or less in stemwood than in
branchwood. As expected, fibre and parenchyma proportions respectively correlated
inversely and positively with percentage weight loss. Also, fibre and vessel
proportions correlated positively and inversely respectively with MOE and MOR. In
conclusion, wood residues are of substantial quantities, and solid wood or finger jointed lumber of branches are not inferior to those of stemwood of the same species
and therefore branches could be extracted for use to supplement stemwood so as to
help in addressing the challenge being posed by timber shortages to industry and also
help in reducing the depletion rate of Ghana‟s forest cover.
Description:
A Thesis in the Department of CONSTRUCTION AND WOOD
TECHNOLOGY EDUCATION of FACULTY OF TECHNICAL
EDUCATION, Submitted to the School of Graduate Studies, University
of Education, Winneba in partial fulfilment of the requirements for award
of the Doctor of Philosophy (Wood Science and Technology) degree.
JULY, 2014