Variation of teak stem taper with age

Variation of stem taper with age for Tectona grandis (teak)
by
Mohomed Nafees and Upul Subasinghe

Taper is the rate of change of diameter over a specific length along the tree stem. Taper varies not only by species, but also by dbh, tree height and other tree parameters. Taper is important for the foresters to predict the upper stem diameters especially in volume calculations.

The main objective of the present study to find out the variation of stem taper with different ages of teak. Three plantations (22, 27 and 35 years old) were selected in Block 01 of Kotagoda teak plantation in Ampara Forest Division for the data collection. Since the plantations were selected from the same Block, it was assumed that the site variation is not significant. Data were collected from 12 sample plots (0.05 ha circular). Dbh, total height, sectional diameters at 5 m and 10 m intervals along the main stem were measured for all the trees in the sample plots.

The the taper for all the trees were separately estimated using the collected data by applying the equation developed by Kozak et al in 1969. For this reason, the 1969 equation was re-parameterized for three ages of the selected plantations separately. Then those three models were statistically tested to identify whether they were significantly different from each other. The results revealed that, the equations were not different from each other proving that the taper does not vary in significant manner for teak with the age. Therefore, a common model was finally developed to estimate the taper for teak irrespective of age. For this reason, the pooled data of all three plantations were re-fitted to 1969 model estimate a completely new set of paramters.