Soil organic and inorganic carbon distribution driven by erosion at various spatial scales on the Loess Plateau of China

Sediment deposition from upslope erosion zones is generally considered to be fertile for agricultural production and ecological restoration. However, how the distribution of soil organic carbon (SOC) and inorganic carbon (SIC) driven by erosion differed with spatial scales remains poorly understood. Here, the profile distribution and driving factors of SOC and SIC at the erosion and deposition topographies were investigated across multiple spatial scales on the Loess Plateau of China. Results showed that SIC, the major carbon (C) form, responded sensitively to erosion like SOC. At the plot scale, minimal differences in SOC and SIC were observed between erosion and deposition zones, except for a significant accumulation of deposited SOC in the cropland plot with the lowest vegetation biomass. At the small-catchment scale, SOC and SIC were higher in deposition topography for the sub-catchment with a smaller area and steeper slope, and SIC was depleted in deposited sediments for the sub-catchment with opposite characteristics. At the regional scale, the enrichment of SOC in deposition topography was greater in sites with more intense soil erosion, but the higher SOC in erosion topography was found in sites with light erosion and a more pleasant climate. In addition, SIC depleted for deposited sediments in sites with higher MAP. The variations of SOC were greater in surface soils, but the variations of SIC were greater in deep soils. ΔSOC and ΔSIC (Δ = Deposition – Erosion) were negatively related with vegetation biomass, catchment area, MAT, and MAP but positively related with slope gradient and erosion modulus, indicating that they were enhanced by the magnitude of erosion. As to soil factors, ΔSOC and ΔSIC at different scales were negatively affected by initial C but positively influenced by Δclay+silt. In conclusion, SOC and SIC can be enriched, unchanged, or depleted in deposited sediments than eroded soils relating to the spatial scales and the variations all strengthened by erosion magnitude at each scale.