Aboveground biomass allometric equations and distribution of carbon stocks of the African oak (Afzelia africana Sm.) in Burkina Faso

Abstract

The significant role of tropical forest ecosystems in the global carbon budget has increased the need for accurate estimates of tropical forest biomass. The lack of large-scale biomass allometric equations hampers the understanding of the spatial distribution of tree biomass and carbon stocks and their influencing factors in West Africa. This study aimed to develop allometric equations to estimate aboveground biomass of African oak (Afzelia africana Sm.) in Burkina Faso and to analyze factors affecting the variability of tree biomass and carbon storage. Sixty individual trees were destructively sampled in four protected areas along two climatic zones. In each climatic zone, log–log models were tested and fitted to each aboveground biomass component and to the total aboveground biomass. Carbon content in tree aboveground components was evaluated using the ash method. All validated equations showed good fit and performance with high explained variance. Allometric equations differed between the Sudano-sahelian zone and the Sudanian zone, except for leaf biomass equations. Both biomass allocation and carbon content varied significantly between tree components but not between climatic zones. Carbon content in tree components followed the patterns of biomass allocation with branches accounting for the highest proportion. In the two climatic zones, carbon contents were 50.18–52.62% for leaves, 54.78–54.94% for stems and 54.96–55.99% for branches. Dry biomass ranged from 509.05 to 765.56 kg tree-1 at site level and from 620.21 to 624.48 kg tree-1 along climatic zones. Carbon content varied from 53.90% in the Sudano-sahelian zone to 54.39% in the Sudanian zone. This study indicated that climate does not influence aboveground biomass production and carbon sequestration of Afzelia africana along the Sudanosahelian and the Sudanian climatic zones of Burkina Faso. Future studies on climate–growth relationships should contribute to better understanding climate effects on biomass production and carbon storage.