Effect of density and moisture content on biological durability of stem and branch wood of Entandrophragma cylindricum (sapele)

Abstract

Branch wood is being promoted as supplement to stem wood but its natural durability is scarcely studied. This study compared the biological durability of branch wood of Entrandophragma cylindricum (sapele) to its stem wood for ground or other outdoor applications like garden furniture at two moisture levels (i.e., 9 ± 3 and 14 ± 2 % using kiln-drying and air-drying methods, respectively). The study followed a field test method according to EN 252-1989 in combination with percentage weight loss. Branch and stem wood samples were extracted from two natural forests in Ghana. Results indicated that branch wood of sapele was marginally denser than its stem wood. Percentage weight loss of branch wood compared to its stem wood was significantly higher by approximately 108 % at 14 ± 2 % moisture content (MC) but significantly lower by 53 % at 9 ± 3 % MC. The stem and branch woods at 14 ± 2 % MC were classified respectively as moderately durable and non-durable, but at 9 ± 3 % MC both were classified as moderately durable. Visual rating indicated that at 9 ± 3 % MC branch wood could have a better service life than stem wood. Density and MC correlated positively and negatively respectively with weight loss but the association was marginally stronger for stem wood (R2 = 0.86 %) than branch wood (R2 = 0.82 %). In conclusion, sapele branch wood material dried to 9 ± 3 % MC appeared more durable than branch wood at 14 ± 2 % MC or stem wood at either 9 ± 3 or 14 ± 2 % MC. Wood products manufacturers and users should consider using well dried branch wood of sapele to supplement stem wood for ground applications. Further research is encouraged to assess other properties of the branch wood in comparison with its stem wood for a firmer conclusion to be drawn on their utilization.