The Congo River Basin forest-savanna mosaic landscape. Smoke from burning vegetation can also be seen. Photo by T. Drake.
The charring of terrestrial biomass (e.g., trees and grasses) produces black carbon, which is resistant to microbial degradation and thus cycles differently than its unburned precursor material. A portion of this charred biomass enters waterways as dissolved black carbon (DBC), which is then routed through river networks and subsequently delivered to coastal oceans. Since river systems are a globally significant sink for this refractory component of terrestrial carbon, we set out to constrain sources and fluxes of DBC from the second-largest watershed on Earth: the Congo River Basin.
Sasha Wagner and Travis Drake (ETH Zurich) led a paper entitled “Du feu à l'eau: Source and flux of dissolved black carbon from the Congo River” that was recently published in Global Biogeochemical Cycles. In this study, they found that the Congo River exports over 800,000 metric tons of DBC per year and was largely controlled by the basin’s unique North‐South bimodal hydrologic regime. Compound-specific stable carbon isotopes also revealed a seasonal shift in DBC source from forest-dominant landscapes early in the year to mixed forest-savanna landscapes later in the year. Detailed assessments of the production, mobility, and fate of DBC produced by fires within the Congo River Basin is key to balancing fire-derived carbon budgets globally.
