Effect of age and wood position in a tree on selected physical and mechanical properties of coppiced African rosewood ( Pterocarpus erinaceus Poir)

Abstract

Ghana's non-coppiced African rosewood is being overexploited and leading to serious environmental degradation, especially in the Savannah Zone. The coppiced timber of any age is not being exploited owing to inadequate information on properties. This study aimed at evaluating the age and tree position influence on some physico-mechanical properties of the coppiced type of wood to promote their utilization. Ten trees of five age groups (20, 24, 32, 37 and 42 years) were extracted from natural forest in the zone and test specimens taken from five different tree sections. Density and mechanical properties were evaluated in accordance with ASTM D143-48 and BS 373 protocols respectively. Results indicated that Air-dry density at 12% MC (ranged from 678 Kg/m³ to 893 Kg/m³), compression strength (ranged from 72–78 N/mm²), shear strength (ranged 16–21 N/mm²), and Janka hardness strength (ranged from 8–12 N/mm²) were significantly (P < 0.05) influenced by age and wood position in the tree, and values were comparable to the same properties of some structural timber species. Age had a positive whereas wood position in trees had inverse correlation with the physico-mechanical properties. It is recommended that since the coppiced is not inferior to non-coppiced rosewood and some structural timbers, regarding air-dry density, compression strength//grain, shear//grain, and Janka hardness, it should be utilized to supplement the non-coppiced timber to augment supply to meet demand in order to reduce the negative environmental impact being caused by overexploitation of the non-coppiced trees.