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Department of Forestry and Environmental Science
UNIVERSITY OF SRI JAYEWARDENPURA, SRI LANKA ../ |
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FORESTRY AND ENVIRONMENT SYMPOSIUM |
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Department of Forestry and Environmental Science
UNIVERSITY OF SRI JAYEWARDENPURA, SRI LANKA ../ |
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FORESTRY AND ENVIRONMENT SYMPOSIUM |
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| FORESTRY SYMPOSIUM 1996 | |||
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TREES OF DIFFERENT SITE CLASSES N D Ruwanpathirana*, Hiran S Amarasekera**,M P De Silva*** * State Timber Corporation, Nuwaraeliya ** University of Sri Jayewardenepura *** University of Ruhuna Large extents of under-utilized Pinus plantations are available in Sri Lanka. Utilization of timber requires information in terms of wood quality. Specific gravity of wood is the best single criterion that determines the strength and quality of wood. Variation of specific gravity in even-aged trees grown in three site classes, which representing low, medium and high growth rates were investigated. Low growth site had mean DBH of 17 cm and mean height of 13m; medium growth site mean DBH of 25 cm and mean height of 21 m, high growth site had mean DBH of 35 cm and mean height of 24 m. Five straight and clean boled trees were selected from each site and sample discs of 2 cm thickness were extracted from 20%, 40%, 60%, 80% height levels and from breast height level (1.3 m). From each disc two strips of approximately 2 cm wide were cut along the North- South and East-West axis through the pith. Specific gravity was measured according to the Archimedes method using the samples extracted from pith to bark at all height levels. Altogether specific gravity was measured for 2020 samples It was observed that specific gravity decreased with the increase of height in all trees irrespective of the site (except 80% level in low site and 40% level in height). The pattern of radial variation of specific gravity was broadly similar at all height levels of all sites: high close to the pith, decreasing to a minimum within 3-5 cm followed by a steady and rapid increase towards the bark. Overall mean specific gravity variation between site classes was 0.412 in low growth site, 0.363 in medium growth site and 0.373 in high growth site, and these differences were not significant at the 0.05 level. However, breast height level samples show a decrease in specific gravity with the growth rate: specific gravity was highest (0.458) in low growth site, low in medium growth site (0.405) and lowest in high growth site (0.398). Collection of data on other wood properties such as shrinkage and strength properties is now in progress. This will be helpful in determining the most appropriate utilization of Pine timber.
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