The effect of quality attributes in determination of price for plantation-grown Teak (Tectona grandis) logs in Sri Lanka

Abstract

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Teak (Tectona grandis) is one o f the highly demanded timber species in Sri Lanka. When buying teak logs, customers assess their quality by visual appraisal o f surface characteristics such as visible defects. Hence, the buyers’ preference for logs with desired attributes is reflected by the price achieved in the market. In this study, w e examined the influence o f visually observable quality attributes o f plantation grown teak logs on their market price. A set o f 650 randomly selected teak logs were assessed for dimensions, shape defects, surface defects and end-defects. Length o f the log, mid-circumference (under bark), diameter at top-end and butt-end, number o f knots per meter, average diameter o f the knots, bend fraction, percentage o f heartwood, shape o f the log, presence o f buttress, position o f the hollow s, presence o f felling damages, splits and heart rot were recorded using standard methods. Selling prices o f logs were obtained from the records o f log storing facilities. By using the multiple linear regressions, a price-quality m odel was developed to explain the impact o f quality attributes on selling price. The regression model achieved a strong coefficient o f determination (R2) o f 0.87. Accordingly, the length, mid-circumference, number o f knots per meter, bend fraction, hollow position, presence o f buttresses and presence o f heart rot were found to have a significant influence on the price. The relative price reduction due to presence o f a specific log defect was further examined using the derived price-quality model. The presence o f high number o f knots had the highest detrimental impapt on price, follow ed by the higher bend fraction, presence o f hollow s at top end and/or middle o f the log, presence o f heart rot and presence o f buttresses respectively. These findings have implications in the improved management o f teak plantations