Aboveground Biomass in West African Semi-Arid Ecosystems: Structural Diversity, Taxonomic Contributions and Environmental Drivers

Abstract

The role of plant diversity and biomass in ecosystem functioning and management is well recognized. However, the structural drivers of aboveground biomass (AGB) and their influence across savanna ecosystems remain understudied, particularly in semi-arid regions. Here, we hypothesized that (i) species richness and structural diversity would positively influence AGB across vegetation strata and (ii) environmental factors would play a secondary role compared to diversity metrics. We tested these hypotheses using data from 160 systematically established plots (0.1 ha each) in two savanna sites (Cassou and Kongoussi) in Burkina Faso. We examined how taxonomic diversity, structural diversity (CV-DBH, CV-height) and environmental factors contribute to AGB and aboveground carbon (AGC) stocks. A total of 97 woody species from 66 genera and 26 families were identified. Species richness had a significant positive effect on AGB in both strata, with a more pronounced influence in shrub layers. Structural diversity, particularly CV-DBH and CV-height, also contributed significantly to AGB, especially in Cassou. Elevation negatively influenced AGB at both sites, while NDVI and EVI2 were positively correlated with AGC in Kongoussi but not in Cassou. Species richness and structural diversity, especially in shrub strata, were the primary drivers of AGB, underscoring their importance for carbon sequestration. The study highlights the important role of structural diversity and taxonomic richness in determining AGB, particularly in shrub-dominated savannas. Management strategies focusing on the conservation of species diversity and enhancement of structural diversity are essential to optimize biomass accumulation and ecosystem functioning in semi-arid savanna ecosystems.