WOOD PROPERTIES AND NATURAL DURABILITY OF Artocarpus altilis (PARKINSON EX F.A. ZORN) FOSBERG

Abstract

Preferred timber species are increasingly becoming unavailable due to overexploitation of natural forests. There is a growing shift in demand to Lesser-Used Species (LUS), like Artocarpus altilis as substitutes in Nigeria. Knowledge on wood quality and durability of LUS would enhance efficient utilisation. However, there is limited information on wood properties and natural durability of Artocarpus altilis. Therefore, physico-mechanical, anatomical and chemical properties, as well as, natural durability of Artocarpus altilis were investigated. Four trees of Artocarpus altilis were purposively selected and felled based on maturity (45.0±0.5 years) at Gambari Forest Reserve, Oyo State, Nigeria. Billets (500 cm) were obtained from base, middle and top of merchantable height of each tree. Each billet was partitioned into corewood, innerwood and outerwood and processed into various dimensions using standard procedures. Physical (density, kg/m 3 ; shrinkage, %) and mechanical (impact bending, J/m2 ; Modulus of Rupture- MOR, N/mm2 ; Modulus of Elasticity-MOE, N/mm2 ; shear strength, N/mm 2 ; Maximum Compressive Strength parallel to grain MCS//, N/mm2 ) properties were determined using standard methods. Cell morphology (Runkel Ratio, vessel diameter, µm) and chemical properties (cellulose, %; hemicelluloses, %; and ash content, %) were determined following standard procedures. In a factorial arrangement, graveyard experiment and Accelerated Biological Test (ABT) following White Rot (WR) and Brown Rot (BR) fungi biodegradation were used to assess weight loss for 48 and 20 weeks, respectively. Data were analysed using descriptive statistics, Pearson Product Moment Correlation and ANOVA at α0.05. Density decreased significantly from base (602.7±64.5) to top (570.7±56.0) and from outerwood (629.3±54.3) to corewood (590.4±59.4). Shrinkage ranged from 4.9±0.8 (base) to 6.2±0.5 (top) and increased from corewood (5.1±0.8) to outerwood (6.4±0.7). Impact bending increased from base (14.3±3.9) to top (16.5±4.0) and varied from 14.5±3.1 (corewood) to 17.6±4.4 (outerwood). The MOR and MOE were highest at base (42.1±8.8, 3993±1983) and least at top (32.9±5.4, 3145±520.4), but decreased from corewood (37.6±1.9, 3630.1±555.5) to outerwood (36.6±7.2, 2986.0±410.6), respectively. Shear strength and MCS// decreased significantly from base (9.7±1.7, 23±4.1) to top (8.5±0.9, 18±2.7) and from corewood (10.8±1.4, 22.5±2.5) to outerwood (8.5±1.1, 18±3.6), respectively. Runkel Ratio was highest at top (0.7±0.2), least at base (0.5±0.2) but decreased from corewood (0.7±0.2) to outerwood (0.6±0.2). Vessel diameter varied from base (238.0±64.8) to top (238.6±57.8) and increased from corewood (238.7±53.5) to outerwood (249.0±61.8). Cellulose, hemicellulose and ash content were highest at base (47.8±0.7, 27.8±1.2, 0.93±0.4) and least at middle (47.1±0.4, 27.1±0.7, 0.92±0.4), respectively. Weight loss decreased from base (26.5±10.1) to top (24.6±8.6) and increased from outerwood (24.6±5.4) to corewood (27.8±2.4) in graveyard experiment. In ABT, weight loss varied from base (WR: 4.4±2.1, BR: 5.3±2.5) to top (WR: 4.8±1.7, BR: 5.5±2.9). White rot caused the highest weight loss at corewood (4.8±2.9) and least at outerwood (4.6±2.0), while BR caused least weight loss at corewood (5.1±2.2) and highest at outerwood (6.0±6.1). The MOR was positively correlated with MOR (r=0.54) and impact bending (r=0.56). Artocarpus altilis could be categorised as medium density wood with mechanical properties being superior at the base and corewood. The chemical properties indicated species suitability for light construction and papermaking.