WOOD DENSITY AND GROWTH RING STRUCTURE OF PINUS PATULA PLANTED IN MALAWI, AFRICA

Growth ring structure and wood density were compared among five families of Pinus patula planted in Malawi, Africa. The vertical and radial variations of wood density and growth characteristics were investigated in stems of 30-year-old Pinus patula planted at a spacing of 2.74 x 2.74 m. The pattern of ring width with cambial aging was broadly similar at all stem heights: wide to the 4th growth ring, decreasing gradually up to the 10th ring and then very narrow towards the bark. In all the families, the first complete growth ring was the widest, ranging from 20 to 50 mm across the families. This trend was different from other similar studies carried out in Zimbabwe and South Africa where the growth ring width increased from the 1st to the 3rd ring with the highest ring width of 19 mm. Specific gravity varied with height above the ground for all the trees. The average specific gravity was 0.56. Weak to medium correlations between latewood percentage and specific gravity were observed. The study shows that selection for density in Pinus patula could be made at least by the age of 10 years.