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Basic Density And Strength Properties Of Pines In Uganda
Abstract
Basic density and strength properties and their variations in 25 year - old Pinus caribaea, P. oocarpa and P. kesiya grown in Katugo, Uganda were investigated. Six trees for each species were selected representing three diameter classes. The trees were felled after measuring their diameter at breast height. Three disks were cut from each tree at 1.3 m, 45% and 75% of total tree height for growth ring width and basic density assessment. For strength properties determination, a central plank measuring 65 mm thick was extracted from each sample tree starting at breast height upwards. Basic density was determined using water displacement. Tests of various strength properties were done in accordance with standard procedures. The data were analyzed using the Statistical Analysis System. Results for the studied properties of Pinus caribaea, P. kesiya and P. oocarpa respectively were as follows: Basic density: 424, 431,and 444 kg/m3; Modulus of rupture: 54.51, 56.31 and 60.69 N/mm2; Modulus of elasticity: 8590,8752 and 8825 N/mm2; Work to maximum load: 0.088. 0.099 and 0.101 mmN/mm3; Maximum compression strength: 33.38, 33.83and 34.66 N/mm2; Maximum shear strength: 9.43, 9.80 and 10.37 N/mm2 and cleavage: 11.79,12.15 and 12.48 n/mm. There were no significant differences in all wood properties between the three species. Between tree variations in wood properties were statistically insignificant (p<0.05) in all the species, indicating a low potential of improving wood quality through selection. Growth rate had no significant influence on wood properties. Wood properties studied decreased significantly from stump upwards the stem and increased from pith outwards in the three species. Strength properties of the three pine species were strongly correlated to basic density with regression coefficients (R2) of above 0.88. Wood strength property values obtained in this study were within the range of pines grown in Kenya and Tanzania. These findings indicate that there are possibilities of expanding the use of these species through promotion. Butt end logs and inner wood can be used for non-structural applications and the outer wood for structural purposes.
TJFNC Vol. 76 2007: pp. 88-93
