Investigation of the Effect of Growth Rate on the Quality of Teak (Tectona grandis L.f.) Wood

Teak was established as a plantation species since 1680 in Sri Lanka. Recently several private sector companies have involved in planting teak with shorter rotation. This study was designed to study how wood quality of teak varies with fast growth rates.

Based on diameter at breast height and total tree height, three different crown classes namely, suppressed, co-dominant and dominant were selected from a 45-year-old state plantation at Melsiripura, Kurunegala. Three trees from each crown class were studied. Sample disks were extracted at breast height from each tree, to measure ring width and specific gravity of each ring. Percentage heartwood was also measured.

The mean ring width values obtained for suppressed (2.65 mm), co-dominant (3.54 mm) and dominant (4.67 mm) crown classes were significantly different. Ring width values indicate the growth rate. Mean specific gravity values obtained for these classes (0.6231, 0.6473 and 0.6346) were not significantly different. Specific gravity is a measure of wood quality. Regression coefficients between ring width and specific gravity were very low: in suppressed R2 = 2.1%, in co-dominant R2 = 0.0% and in dominant R2 = 0.0%. These results show that the differences in specific gravity in the crown classes cannot be explained by the differences in growth rate, indicating that there is no relationship between growth rate and specific gravity. Based on these results it can be concluded that ring width is a property that depends on the growth rate but specific gravity seems to be an inherent property independent of growth rate variation. Hence, fast growth rates with shorter rotations will not likely to reduce specific gravity in teak.

Wood property patterns were found similar between the crown classes, indicating that these trends are inherent in teak. Ring width fluctuates close to the pith, and then decreases forming almost a constant value towards the bark; specific gravity remains almost a constant value from pith to bark.

D.N. Jayawardana and H.S. Amarasekera

Department of Forestry and Environmental Science, University of Sri Jayewardenepura, Sri Lanka