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.

Prediction of aboveground biomass and carbon stock of Balanites aegyptiaca, a multipurpose species in Burkina Faso

“…Branch contributed for approximately 64% of TAGB in the two climatic zones, whereas leaf represented the smallest portion (<3%) in both zone. These results are consistent with several published studies in the tropical African savanna species as Vitellaria paradoxa, Combretum glutunosum, Terminalia laxiflora and Afzelia africana ( Mensah et al., 2016 ; Balima et al., 2019 ; Dimobe et al., 2019 ).…”

“…This trend being observed at the components and tree levels between the two climatic zones, suggests that climate does not affect aboveground biomass distribution within B. aegyptiaca tree component, and the C content. Similar results were recently found by Balima et al. (2019) on Afzelia Africana, and these authors concluded that this might be related to a low climatic variation between two neighboring climatic zone as the case of our study.…”

“…This difference could also be explained by the presence of the lignin in the woody parts and absent in the foliage. These results support the hypothesis stating that the more biomass is allocated to a given tree component, the more the C will be stored in that component, and lower C is shared in the parts that physiological functions are intense ( Negi and Durgapal, 2003 ; Bayen et al., 2016 ; Dimobe et al., 2018 ; Balima et al., 2019 ; Meng et al., 2019 ).…”

“…Scientist considered that allocating more resources to stem and branch when the size increases is to promote height and crown growth to increase the competitiveness for light relative to neighbor trees ( Dimobe et al., 2018 ; Meng et al., 2019 ). Leaf biomass proportion decreased with increasing dbh in both climatic zones suggesting that the species has the same specific ecological and physiological responses towards environmental conditions ( Balima et al., 2019 ).…”

“…This leads to a general lack of allometric adapted equations to estimate biomass in West African savanna ecosystems (Dimobe et al, 2018). Some studies were carried out in West Africa in arid environments, but these works are unfortunately limited (Sawadogo et al, 2010;Bayen et al, 2016;Dimobe et al, 2018;Balima et al, 2019) in Burkina Faso, Chabi et al (2016) in Benin, Tredennick et al (2013) in Mali and Mbow et al (2013) in Senegal.…”