EFFECT OF AGE AND HEIGHT ON THE PHYSICAL AND MECHANICAL PROPERTIES AND THE CALORFIC VALUE OF Hevea brasiliensis

ABSTRACT

Many of Ghana’s commercial timber species are threatened due to high demand resulting to pressure on the traditional species. The need to investigate the potential utilization of some Lesser-used Timber Species to ascertain their suitability for use is very paramount. Some physico-mechanical properties and calorific value of 20, 30 and 40-year old Hevea brasiliensis were investigated. The moisture content (MC) ranged between 13.02% (base of 40-year old) and 15.26% (crown of 20-year old). All the ages (20, 30 and 40-years) recorded gradual increase in MC from their bases to their crowns (14.57 to 15.26%, 13.55 to 14.52% and 13.02 to 13.38% respectively). Density also increased along the boles of the various trees (495.28 to 529.38Kg/m3 for 20-years, 502.28 to 546.88Kg/m3 for 30-years and 553.07 to 558.14Kg/m3 for 40-years). Longitudinal swelling and shrinkage both increased along the boles of the various trees (1.62 to 1.93% and 0.63 to 1.12%, 1.19 to 1.55% and 0.61 to 0.75%, 0.87 to 1.47% and 0.07 to 0.12% respectively) from the base to the crown. Tangential swelling and shrinkage ranged from 2.26 to 2.73% and 2.50 to 3.37% (20-years), 2.01 to 2.53% and 2.30 to 3.21% (30-years), 1.49 to 1.73% and 2.29 to 3.21% (40-years) increasing from the base to the crown and 20-years to 40-years respectively. Volumetric swelling and shrinkage both recorded increases along the boles of all the trees but reduced from age 20-years to 40-years (5.50 to 7.76% and 5.87 to 7.63%, 4.56 to 6.39% and 5.73 to 6.87%, 4.51 to 6.18% and 5.47 to 6.85%, respectively). The greatest resistance to compressional forces parallel and perpendicular to the grain were recorded by the 40-year old tree (34.51 to 35.24N/mm2 and 4.79 to 5.30N/mm2) followed by the 30-years (31.77 to 33.39N/mm2 and 4.55 to 4.77N/mm2) and 20-years (26.60 to 32.84N/mm2 and3.78 to 4.40N/mm2). MOR recorded an increase in values from age 20 to 40-years but reduced along the boles from base to crown (58.74 to 60.88N/mm2, 59.07 to 66.60N/mm2 and 59.56 to 67.24N/mm2 respectively). The average calorific values recorded were 15.99, 18.09 and 18.17MJ/Kg respectively for the various ages making them good sources of firewood. In general the 20-year old tree and the crown portions of the 30 and 40year old H. brasiliensis would be suitable for general light works such as tool handles, packaging and pencils due to their lesser densities and the great propensity to swell and shrink. The base and middle portions of the 30 and 40-year old trees were heavy and strong with less MC and would be ideal for furniture production and also as good fuel wood. This work intends to generate greater interests by stakeholders to move into massive cultivation of H. brasiliensis plantations leading to the creation of job opportunities and a source of constant supply of raw material to both the local and international markets.