Characteristics of Dissolved Carbon Loss on Loess Slopes and Its Response to Soil and Water Conservation Measures

［Objective］ The implementation of soil and water conservation measures has led to a notable reduction in the loss of soil carbon pools, while simultaneously facilitating effective control of soil erosion. However, there is a paucity of systematic understanding of the processes of carbon loss, flux characteristics and the factors that influence them under different soil and water conservation measures. ［Methods］ In this study, a comparative analysis of the characteristics and influencing factors associated with the loss of dissolved organic carbon (DOC) and inorganic carbon (DIC) from loess slopes under different soil and water conservation measures was conducted. These measures included terraces, grasslands, upper terraces and lower grasslands, and the upper terraces and lower bare soil. To this end, a simulated rainfall test in the field was employed to quantify the benefits of the above-mentioned soil and water conservation measures in reducing the loss of dissolved carbon from the slopes. ［Results］ The dissolved carbon concentration on the slope surface under each soil and water conservation measure remained relatively constant throughout the rainfall process. However, the flux of dissolved carbon loss was significantly lower than that observed on bare ground (p<0.05). Furthermore, the loss of dissolved inorganic carbon contributed to 79.5%—83.1% of the total carbon loss. The retention benefits of grassland, the upper terraces and lower grasslands, the upper terraces and lower bare soil measures for dissolved carbon on slopes were 76.9%, 56.3%, 47.6% and 18.0%, respectively. The volume of flow production on the slope surface was identified as the determining factor affecting the flux of dissolved carbon loss. Furthermore, the flux of carbon loss was found to be significantly positively correlated with the flow volume. ［Conclusion］ This study enhances our understanding of the mechanisms through which soil carbon loss is mitigated by diverse soil and water conservation measures. It offers a scientific foundation for evaluating the carbon sink benefits of soil and water conservation on the slopes of the Loess Plateau.