Comparative Study on Commercial Log Production Managed under Different Conditions: Evaluating Plantation Grown Teak of Sri Lanka

Abstract

Several methods are available to assess the plantation timber volume at their maturity. However, most of those methods can not be applied to the teak (Tectona grandis L.f) plantations of Sri Lanka, due to different site qualities and different management practices since planting. Therefore it is essential to carry out a comparative study of commercial log production managed under different conditions. For this purpose, the use of height-diameter and relative taper curves for estimation and prediction of planted teak stands in dry and intermediate zones of Sri Lanka were evaluated. Even-age mature plantations which are subjected to clear fell was selected randomly. Standing tree measurements of 164 trees were taken at three sites to build up the height-diameter curve. At the same time, 158 trees were felled and took diameter measurements along the felled log to construct the relative taper curve. The resulted models are useful in generating accurate and localized predictions of standing tree height, total timber volume, commercial timber volume which would eventually lead to better estimations on differently managed teak plantation sites. By measuring the diameter at breast height alone, the developed log diameter-length tables could estimate the commercial log length according to specific diameter values which would finally lead to better commercial log estimation to compete with increasing demand along with different site conditions.

A new taper index based on form-factor: application to three bamboo species (Phyllostachys spp.)

“…The apparent culm volume (v) and culm surface area (s) for each sample were determined using the sectional measurement method (Inoue and Sakamoto 2017;West 2004). The results were used to calculate the normal form-factors (λ 0.1 , λ 0.2 , …, λ 1.0 and κ 0.1 , κ 0.2 , …, κ 1.0 ) and the breast height form-factors (λ b and κ b ) (Inoue 2005).…”

“…The stem diameter of a tree decreases gradually from the ground to the top. The rate of decrease in diameter along the stem is called the stem taper (Tenzin et al 2017;West 2004), and depends on various characteristics, including genetics, silviculture, site, and climatic characteristics (Ikonen et al 2006;Karlsson 2000;Nigh and Smith 2012;Pukkala et al 2019;Schneider et al 2018). Knowledge of the stem taper is indispensable for estimating the total or merchantable volume of trees (Tenzin et al 2017;Wijenayake et al 2019).…”

“…The rate of decrease in diameter along the stem is called the stem taper (Tenzin et al 2017;West 2004), and depends on various characteristics, including genetics, silviculture, site, and climatic characteristics (Ikonen et al 2006;Karlsson 2000;Nigh and Smith 2012;Pukkala et al 2019;Schneider et al 2018). Knowledge of the stem taper is indispensable for estimating the total or merchantable volume of trees (Tenzin et al 2017;Wijenayake et al 2019). Therefore, an effective way to quantify the stem taper has long been an important topic in ecological and forestry studies (Gregoire 2012;McTague and Weiskittel 2021).…”

Taper Equations for Evaluating Private Plantation Teak (<i>Tectona grandis</i>) in Thailand

“…The basic diameter should be at the lowest height along the stem so that the diameter is not affected by buttress swelling (Osumi 1959). Many studies have used the basic diameter of d 0.9 (i.e., diameter at length 0.9 from tree top to ground) (Osumi 1959, Wijenayake et al 2019, Yamada & Ohno 2016. Thus, d 0.9 was used as the basic diameter in this study.…”

“…Because the price of a teak log is determined primarily by its diameter (Keogh 2008, Wijenayake et al 2019, the use of taper equations is essential to obtain both log and stem volume and diameter at any height above ground and estimate the fair merchantable value or maximize the log product value of a standing teak tree . As Kozak (2004) summarized, although volume equations only predict the total or merchantable stem volume, taper equations predict, among others, the diameter at any height, merchantable height to any top diameter, log volume of any length at any height above ground, and merchantable volume.…”