Impact of rainfall events on the river dissolved carbon transportation in a vegetation restoration watershed

Rainfall-driven riverine dissolved carbon (DC) transport is crucial for research on the carbon cycle. However, the relationship between river DC and discharge during rainfall events in the vegetation restoration area remains unclear. This study aims to elucidate the evolving patterns of DC concentrations in rivers of small watersheds undergoing vegetation restoration on the Loess Plateau during rainfall events. It quantified the relationship between rainfall, floods, and river DC using high-frequency sampling, continuous hydrology, and climate monitoring, along with hysteresis analysis. Results indicated that disparities in carbon sources and previous hydrological conditions mainly influenced the trends and hysteresis patterns of river dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) concentrations. During intermittent rainfall, depletion of proximal DOC sources in preceding events led to scarcity in subsequent events, while activation of DIC sources replenished the river in subsequent events. Rainfall significantly affected river DC flux in the vegetation restoration watersheds. The output flux range for DOC and DIC was 0.37–9.12 kg/h and 2.21–39.95 kg/h, respectively. Thus, measures must be implemented to mitigate the additional carbon losses resulting from revegetation. These research findings can serve as a scientific basis for ecological environmental protection in the Loess Plateau and for predicting river carbon flux during vegetation restoration.