VARIATION OF STEM TAPER WITH DIFFERENT AGES IN Tectona grandis L.f. (Teak)

Abstract

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Taperisthe rate of change of diameter over a specified length along the tree stem, which varies not only by species but also by diameter at breast height, tree height and other tree parameters. Taper is important for the foresters to predict the upper stem diameters especially in volume calculations. Although itis difficult to find taper studies in Sri Lanka, studies have been carried out in Canada and New Zealand (Hewage, 2002). Themain objective ofthe current study is to find out the variation of stem taper with different ages of Tectona grandis Lf (Teak). Three plantations ( 22 year, 27 year and 35 year) were selected in block 01 of Kotagoda teak plantation in Ampara Forest Division for this purpose by selecting differentagesin same site, it is assumed that the site difference is not significant. The selection of sample plotswere carried out randomly within the sub blocks separately. Data were collected from twelve 0.05ha circular plots and each tree was measured for total height, dbh, sectional diameters at 5m and 10malong the stem. These were used to estimate the parameters for the selected equation originally constructed for Douglas fir in Coastal Central Colombia by Kozak et. al. (1969).Furthermore in this study,separate models were constructed with different parameter sets with the similar basic model structured for three different ages of teak. These three models were tested to find whether they significantly vary from each other. Then finally an attempt was made to construct a common model with new parameters to apply for all age gradations simultaneously by pooling the data. These tests revealed that, the different models constructed were not sensitive for different ages, and therefore it canbe recommended to use the common model for the prediction of upper diameters or the taper for teak irrespective oftheir age gradation. Finallya sensitivity analysis was carried out for the re-calibrated models developed in 1969 by Kozak et.a!. for Douglas fir and in 2002 by C. Hewage for Caribean pine. The results indicated the high sensitivityproving that the inability of using the models constructed for different species to predict the stemtaper of some other species.