Higher diversity, denser stands and greater biomass in peri-urban forests than in adjacent agroforestry systems in Western Burkina Faso: implications for urban sustainability.

Urban and peri-urban forests greatly contribute to the well-being of urban dwellers in West Africa. However, increasing urban densification and spatial expansion negatively affect the functioning of urban ecosystems. Therefore, highlighting the negative impacts of land use change on the ecological attributes of urban landscapes is fundamental for sustainable urban planning. This study aimed to assess the impacts of land use on woody species diversity, structure and carbon storage in peri-urban areas in Burkina Faso. Forest inventories were conducted in 167 plots across two peri-urban forests and their adjacent agroforestry systems. We found a total diversity of 91 woody species representing 69 genera and 26 families. Diversity indices were significantly higher (p-value < 0.0001) in the peri-urban forests than in the agroforestry systems, highlighting a negative impacts of land use on tree diversity. Besides, peri-urban forests had significantly lower tree diameter (15.749 ± 9.194 cm), but higher basal area (5.030 ± 4.407 m2. ha-1) and denser stands (317.308 ± 307.845 ind. ha-1) compared to the agroforestry systems. Tree aboveground biomass was significantly higher (p-value < 0.0001) in the peri-urban forests (18.198 ± 23.870 Mg. ha-1) than in the agroforestry systems (7.821 ± 6.544 Mg. ha-1). Multivariate analyses revealed that denser stands hold higher diversity in peri-urban areas, and that stand basal area mostly drives carbon storage than tree density and diversity. These findings highlight the potential of peri-urban forests to conserve plant biodiversity and mitigate climate change. The study advocates for a sustainable urban land use and planning.

Aboveground biomass allocation, additive biomass and carbon sequestration models for Pterocarpus erinaceus Poir. in Burkina Faso.

Efforts to develop allometric models for accurate estimation of biomass and carbon sequestration in Sub-Saharan African savanna ecosystems remain inconclusive. Most available allometric models are not site-specific, and hence do not account for the effects of regional climate variabilities on tree growth and capacity to sequester carbon. In contrast, site-specific biomass allometric models constitute a robust tool for forest and carbon emission management in the context of the reducing emissions from deforestation and degradation program (REDD+). Although site-specific models have been developed for several tropical tree species, such models do not exist for Pterocarpus erinaceus in Burkina Faso. In this study, we investigated biomass fraction patterns and used a system of additive allometric models for predicting aboveground biomass and carbon stocks of P. erinaceus components. Thirty P. erinaceus trees were destructively sampled to estimate the biomass of their stems, branches and leaves. The biomass fraction of each component was assessed and its relationship with tree diameter at breast height (dbh) examined. The best allometric equations of the tree components, selected from three non-linear models with dbh, height (ht) and crown diameter (Cd) as predictors, were combined to develop an additive allometric model, using the Seemingly Unrelated Regressions (SUR) method. The Ash method was then used to estimate the carbon content of the different components. Leaf and stem biomass fractions decreased when the dbh increased, whereas a reverse trend was observed for branch biomass. Dbh was the most correlated independent variable with all biomass components. AGB = e-3.46(dbh)1.62+e-2.45(dbh)2.31+e-2.68(dbh) was the most appropriate additive allometric equation for estimating the biomass of P. erinaceus trees. The carbon content of the leaves, branches and stems was 55.73%, 56.68% and 56.23%, respectively. The developed allometric equations can be used to accurately estimate the aboveground biomass of P. erinaceus in the savannas of Burkina Faso and other similar ecosystems in Sub-Saharan Africa.