Revising volume tables to adapt to changes in timber resources in cameroon

Abstract

Knowledge of extractable timber volumes is essential to both forestry management and logging inspections. In central Africa, estimations of timber volumes mainly rely on single-entry volume tables that are specific to each species and predict extractable volumes based on tree diameters. Recently, however, many forestry managers have been reporting inconsistencies between commercial volumes estimated by applying the volume tables imposed by the government and the volumes calculated from measurements of the length and diameter of felled logs. In order to check the accuracy of the volume tables imposed by the Cameroon government, we took destructive samples of 12 key species for Cameroon’s timber trade to develop new volume tables. These were compared with those imposed by the Cameroon government and with 52 other volume tables available from the literature. In four logging concessions, chosen as representative of the different ecological conditions in Cameroon, 732 trees were felled and their volumes estimated by taking measurements of successive bole segments. The single-entry volume tables, calculated as a function of diameter only, were then fitted by the generalised least squares method. Our study confirms that there are inconsistencies between the volumes measured and the volumes estimated with the volume tables imposed by the Cameroon government. Accordingly, our study proposes new volume tables and a correction chart. Finally, the inconsistencies in the majority of the volume tables tested all produced a similar bias, which is probably due to changes in the resource and in logging practice.