Soil organic carbon distribution in relation to land use and its storage in a small watershed of the Loess Plateau, China

Soil organic carbon (SOC) is an important component in agricultural soil, and its stock is a major part of global carbon stocks. Estimating the SOC distribution and storage is important for improving soil quality and SOC sequestration. This study evaluated the SOC distribution different land uses and estimated the SOC storage by classifying the study area by land use in a small watershed on the Loess Plateau. The results showed that the SOC content and density were affected by land use. The SOC content for shrubland and natural grassland was significantly higher than for other land uses, and cropland had the lowest SOC content. The effect of land use on the SOC content was more significant in the 0–10 cm soil layer than in other soil layers. For every type of land use, the SOC content decreased with soil depth. The highest SOC density (0–60 cm) in the study area was found in shrublandII (Hippophae rhamnoides), and the other land uses decreased in the SOC density as follows: natural grassland > shrublandI (Caragana korshinskii) > abandoned cropland > orchard > level ground cropland > terrace cropland > artificial grassland. Shrubland and natural grassland were the most efficient types for SOC sequestration, followed by abandoned cropland. The SOC stock (0–60 cm) in this study was 23,584.77 t with a mean SOC density of 4.64 (0–60 cm).