The distribution of soil C and N along the slope is regulated by vegetation type on the Loess Plateau

Soil carbon (C) and nitrogen (N) dynamics significantly contribute to greenhouse gas emissions from terrestrial ecosystems. However, uncertainty exists regarding the distribution of soil C and N along slopes of various vegetation types. To examine differences in soil C and N on the slope, this study selected three vegetation restoration types of grasslands (Artemisia sacrorum and Artemisia capillaris), shrublands (Caragana korshinskii) and forestlands (Robinia pseudoacacia) with five slope positions (top, upper, middle, lower, and foot). The results showed that the distribution of soil C and N were regulated by the vegetation type. Soil C and N stocks in grasslands and shrublands increased from the top to the foot slope, but this pattern was not observed in forestlands. The lowest coefficients of variation (CVs) of soil C and N along the slope were observed in the shrublands, with the highest soil C (17.0 Mg ha−1) and N (1.9 Mg ha−1) stocks on the entire slope. The primary factors influencing soil C and N distribution along the slope differed depending on the vegetation type. The primary factors influencing soil C and N in grassland slopes were pH and belowground biomass C/N, while those in shrublands and forestlands were pH, litter biomass C/N, and soil inorganic N (NH4+ and NO3–). Moreover, variations in mineral-associated organic C and mineral-associated organic N dominated the soil C and N dynamics. This study showed that vegetation types regulated the distribution of soil C and N throughout the slope. The shrublands were the optimal vegetation type on the entire slope, which can help in boosting soil C and N stocks in Central Loess Plateau.