Volume recovery and estimation of commercial volumes of Okan (Cylicodiscus gabunensis Harms) in southern Cameroon

Abstract

The objective of this study was to quantify the volume of residues and develop volume equations for estimation of commercial outside-bark volumes of Okan (Cylicodiscus gabunensis) at different logging stages. Two hundred and five stems with diameter at breast height (DBH) varying between 65 and 167 cm were cut and scaled (by successive logs) and followed at forest management unit 09 004b in South Cameroon. The relationships between the scaled volumes and the measured dendrometric variables were established using weighted regressions. The largest proportion (>63%) of the total volume of discarded waste was observed at the stump. Modelling the proportion of stem residues, although resulting in a low R² value, was best described by considering log length and quality class. Commercial volumes were estimated using DBH, the proportion of waste, grade quality and commercial length. Although difficult to estimate, commercial length offers better results compared with the use of grade quality. These results can contribute to better management of Okan’s commercial timber stocks in South Cameroon.

Keywords: commercial volume, Cylicodiscus gabunensis, Okan, quality rating, South Cameroon, volume recovery

Southern Forests 2019, 81(4): 345–356