Evaluation of an Acacia mangium Provenance Trial after Seven Years, on the Ibi - Batéké Plateau, Democratic Republic of the Congo

This study reports on the evaluation of 46 Acacia mangium provenances and varieties, which were planted in 2006 on the Ibi-Batéké Plateau, Democratic Republic of the Congo. After seven years, tree height and diameter, biomass and carbon stocks of the 46 Acacia mangium provenances, together with soil carbon and nitrogen concentrations, were compared with savannah soils in which Acacia was no present. Heights and diameters of 20 to 25 trees per provenance were measured. Carbon in the biomass was determined by the direct method. In total, 25 trees were harvested and weighed for each carbon compartment (leaves, branches, litter, trunks and roots). Ninety soil samples were collected at three different depths in the provenance plots and on the savannah and analyzed for their C and N concentrations. There were differences in height and diameter growth and in accumulated carbon among trees of different origins (provenances). Finally, soil C and N differed under different provenances, and with depth. Carbon and nitrogen tended to decrease with depth. The results of the study revealed better performance for provenances originating from Papua New Guinea, Australia, Malaysia, Vietnam, China, Fiji and the Philippines.