Quantifying erosion-induced carbon emissions from SOC decomposition across sediment pathways in the yellow river...

Soil erosion not only leads to soil loss but also redistributes soil organic carbon (SOC) and releases carbon dioxide (CO₂) that contributes significantly to regional carbon emissions. Great efforts have been made to prevent soil erosion in the Yellow River Basin (YRB) in China in the past decades. Only few studies have paid attention to carbon emissions from soil loss. This study integrates the China Soil Loss Equation (CSLE) with a transport-limited sediment delivery (TLSD) model to quantify sediment redistribution and associated carbon emissions across five depositional processes (slope, reservoir, plain, river channel, and regional output) in the YRB.

The CSLE-TLSD model calibrated to a significantly improved Nash-Sutcliffe efficiency of 0.5690, compared to 0.5628 for the CSLE model. Results reveal that 28.50 ± 4.43% of eroded SOC was decomposed during transport, releasing 2.48 ± 0.11 × 10⁸ t CO₂ in the YRB from 1990 to 2020. Striking spatial disparities emerged in different regions: the upper reaches exhibited a SOC decomposition ratio of 49.66 ± 4.40%, in sharp contrast to 22.96 ± 10.35% in the middle reaches. The five provinces with the highest carbon emission rate from 1990 to 2020 were Shanxi (15.45 t CO₂/km²), Shaanxi (14.23 t CO₂/km²), Shandong (13.10 t CO₂/km²), Qinghai (11.98 t CO₂/km²), and Gansu (11.25 t CO₂/km²).

These findings underscore the necessity of incorporating erosion-driven carbon flux dynamics into terrestrial carbon accounting frameworks, particularly in basins undergoing intensive anthropogenic modification.