Soil organic carbon loss driven by water erosion in northeast China's black soil region (1991-2019)

Soil erosion is a primary driver for the mobilization and loss of soil organic carbon, as well as a key dynamic process within the terrestrial carbon cycle. Nevertheless, the impact of soil erosion on soil organic carbon (SOC) in the black soil region remains to be fully elucidated. The RUSLE model was applied to analyze the spatiotemporal characteristics of soil and associated SOC erosion in the Northeast Black Soil Region of China over the past 30 years (1991 to 2019). The findings of the study demonstrated that the rates of soil erosion and SOC erosion ranged from 0.46 to 1.05 t ha^-1 yr^-1 (mean = 0.68 ± 0.17 t ha^-1 yr^-1) and from 0.002 to 0.021 t C ha^-1 yr^-1 (mean = 0.007 ± 0.004 t C ha^-1 yr^-1), respectively, with periodic fluctuations in response to precipitation and land use/land cover (LULC) variations. The total annual soil and associated SOC erosion were ∼7.4 × 10⁷ t yr^-1 and ∼1.29 × 10⁶ t C yr^-1, respectively. The annual SOC yield showed a significant (r = -0.42, p < 0.01) decreasing trend during the past three decades. Spatially, the subregion of being prone to SOC erosion was identified. The Changbai-Wanda mountains hilly region contributed over 52% of the total soil erosion and 88% of the total SOC erosion. The primary land use types associated with SOC loss exhibit regional heterogeneity. The cropland, forest, grassland, and barren contributed 14%-93%, 0-12%, 1%-72%, and 5%-65% of the SOC loss in the different subregions, respectively. Overall, cropland and barren were the primary sources of SOC loss, accounting for 40.1% and 57.7% of the total loss, respectively. The present findings provide useful insights with respect to sustainable land resource management in the Northeast Black Soil Region of China and enhance our understanding of the impact of soil erosion on the carbon cycle.