Vegetation Position Impacts Soil Carbon Losses on the Slope of the Loess Plateau of China

Vegetation restoration changes hydrological processes and impacts soil carbon loss through runoff and sediment. However, the impact of vegetation positions on soil carbon transportation during erosion remains unclear. In this study, four vegetation positions (no vegetation [Position A], upper-slope [Position B], middle-slope [Position C], and down-slope [Position D]) were established to study the effects of vegetation distribution on soil carbon losses through simulated rainfall experiments. The findings revealed showed runoff and sediment yields in the following order: positions A > B > C > D. Soil organic carbon (SOC) lost through sediment was much higher than that lost through runoff, whereas soil inorganic carbon (SIC) showed the opposite trend. However, SIC was lost substantially more than SOC during the erosion process. Soil total carbon (STC) lost through runoff under different vegetation positions was in the following order: positions A (1714.88 g) > B (1454.67 g) > C (990.90 g) > D (914.78 g). Similarly, STC lost through sediment was higher under positions A and B than under positions C and D. Position D resulted in the highest reduction in STC (38.14 %), SOC (36.73 %), and SIC (38.76 %). Based on our results, we suggest revegetating the down-slope area to reduce runoff, sediment, and soil carbon losses. This study provides a scientific basis for the regulation of vegetation restoration on soil carbon dynamics in the water erosion process.