Structure et stock de biomasse d'une forêt claire de type miombo du Haut-Katanga, en République Démocratique du Congo

Abstract

Estimating biomass and monitoring its evolution in the world’s different ecosystems is an important challenge at the global level, particularly to guide political decisions in the management of these environments accumulating carbon in their biomass. However, biomass stocks in "miombo" woodlands and factors that influence them are still poorly quantified despite the large size of this ecoregion in Africa. This master thesis focuses on the analysis of the structure of a 10-ha permanent inventory system in a "miombo" woodland and attempts to identify the structural, architectural, compositional and diversity factors influencing biomass. The classification of miombo as a "savanna" or as a "forest" is also discussed throughout this study. Dendrometric measurements were carried out in the Mikembo sanctuary, 30 km northeast of Lubumbashi, Democratic Republic of Congo (11°28’57" - 11°29’5" S, 27°40’12" - 27°40’28" E; 1200 m altitude). Comparisons with other study sites, comparisons between different site plots and comparisons between the different dominant species into the site are made by combining inventory data, species-specific and site-specific allometries and bibliographic data. The 10-ha inventory system has a high biomass density (154,2 tons per hectare) compared to other estimates in "miombo" woodlands. The presence of Marquesia macroura, typical of wet miombo and capable of reaching a large trunk diameter, is largely responsible for the high biomass value at this site, despite the abundance of Julbernardia paniculata. The heights and crown diameters of Mikembo trees are higher than the average for African savannas. The hypothesis is that the site was once a "muhulu" dry forest that was degraded by fires and charcoal harvesting and has been regenerating since its protection was enforced. Comparison between the site plots shows excellent potential for estimating above-ground biomass by basal area and basal area weighted architectural attributes, which are measurable by remote sensing methods. Comparison between dominant species of the site shows a particular architecture compared to other studies that have used a similar method in rainforest ; the crown size in juvenile age does not seem to show any difference between canopy dominant species and undergrowth species. The master thesis provides a direction towards which future work could be carried out to estimate biomass in miombo. The studied site is rather particular compared to other sites studied in miombo, with a higher value of above-ground biomass and taller trees. Wet miombo carbon storage capacities could be increased regionally in the event of increased fire protection.