Estimation of change of taper with age for Tectona grandis L. f. (Teak)

Abstract

Taper is the change of diameter over a specified length along the tree stem, which varies not only byspecies and site type, but also by diameter at breast height (dbh), height and other tree growthparameters. Taper is important for the foresters to estimate the upper stem diameters especia!ly involume calculations.

The main objective of the present study was to find out the variation of taper with different ages forTee/ana grandis L. f. (teak). For this reason, three teak plantations of 22, 27 and 35 years of agcwere selected from the Block Olin Kotagoda plantation, Ampara Forest Division. Selection of thesethree plantations from a single Block was done to minimise the effect of the site quality on treegrowth. Data were collected from randomly laid out 14 circular plots of 0.05 ha. The trees in sampleplots were measured for dbh, total height and sectional diameters at 5m and 10m along the stem.

In order to estimate the taper variation, the equation developed by Kozak et af (1969) for Douglas firin Western Colombia was used. This equation is given below and it is considered as one of the bestmio?dels developed to estimate the upner stem tree diameters.

mio?dels developed to estimate the upner stem tree diameters. 1 .~. 1 a: t dbh' =17" +hi(hl H)+b:(h- I H-);where d = diameter at height handH = total height

At the first stage, the data were fitted to the selected equation separately for each age and theregression parameters were estimated separately without changing the basic structure of the originalequation.It was observed that the parameter b() and b , were positive values and increased from age 22 to 27and then decreased from that to age 35. TIle parameter b, was a negative value which decreasedfrom age 22 to 27 and then increased from that to age 35.When the results were examined further, it was observed that the taper is decreasing with the ageproving that the teak tree stems become more conical with the age, i.e., the diameter differenceincreases with age for a fixed length along the stem.