Drivers of aboveground carbon in protected areas in Burkina Faso

Abstract

Grasslands, savannas, and forests within protected areas play a vital role in mitigating climate change and conserving biodiversity. While these landscapes are widely recognized for their ecological value, the contribution of biodiversity to enhancing aboveground carbon (AGC) storage is less understood. We investigated how environmental factors (climate, topography and soil conditions) affect biodiversity and AGC stock, and how functional trait diversity and species composition mediate the response of AGC to evolutionary drivers within the study area. The study was conducted in 133 plots in two protected areas (Bontioli Total Wildlife reserve and Nazinga Game Ranch) in Burkina Faso. We measured local environmental conditions, species composition and tree structural data (diameter at breast height, maximum height) for each plot. We used combined field observations with wood density values from literature to quantify phylogenetic diversity, functional trait diversity and dominance. We then estimated AGC using established allometric equations. We used structural equation models to assess the direct and indirect impacts of environmental factors on AGC stock, mediated by biodiversity metrics. Aboveground carbon stocks ranged from 5 to 165 Mg/ha, with notable association between phylogenetic diversity and functional trait metrics. These findings underscore the influence of both complementary interactions and trait-based selection. A strong positive relationship between phylogenetic diversity and functional richness across all vegetation types suggest that evolutionary divergence contribute to ecological function. However, the strength and direction of the relationship between phylogenetic diversity and community-weighted mean of maximum height differed among the vegetation types, suggesting that evolutionary influences on trait values are modulated by the unique environmental conditions of each ecosystem. This study highlights the intricate links between biodiversity, functional traits, and carbon storage, offering insights for managing and conserving forest ecosystems in support of SDGs 13 (Climate Action), 15 (Life on Land), and 12 (Responsible Consumption and Production).