Characteristics of soil organic carbon distribution in different economic forests in Gangu County, Gansu Province, China

Abstract SOC (Soil organic carbon) is an important indicator of soil nutrients and is essential for maintaining ecosystem functions and preventing land degradation. In this study, five types of economic forest plots were selected as sample plots ( Malus pumila , Juglans regia , Zanthoxylum bungeanum , Prunus persica , and Prunus armeniaca ) in Gangu County, Gansu Province, and wasteland was used as a control to investigate the changes of soil organic carbon content in 0-100 cm of different economic forests in Gangu County. The results showed that the soil organic carbon content of different economic forests in Gangu County ranged from 9.17 ± 0.15–17.20 ± 0.13 g/kg, and the soil organic carbon content at 0-100 cm depth ranged from high to low: apple ( Malus pumila ), pepper ( Zanthoxylum bungeanum ), walnut ( Juglans regia ), apricot ( Prunus armeniaca ), peach ( Prunus persica ) and wasteland. The SOC content of the five forest types and the wasteland showed apparent surface aggregation, with the highest SOC content of 17.20 g/kg for Malus pumila and the lowest SOC content of 12.65 g/kg for the wasteland in the 0–10 cm surface layer; in the 80–100 cm deep layer, the highest SOC content of 14.90 g/kg for Juglans regia and the lowest SOC content of 9.17 g/kg for the wasteland. SWC (Soil water concent, SWC) and S-UE were the most influential factors on the SOC content of Juglans regia ; S-CAT (Soil catalase, S-CAT) was the most influential factor on the SOC content of Malus pumila ; SBD (Soil bulk density, SBD) was the most influential factor on the SOC content of Prunus armeniaca , Prunus persica , and Zanthoxylum bungeanum ; the SOC content of the control wasteland was more influenced by S-CAT and soil fungi. The number of S-CAT and soil fungi more influenced the SOC content of the control wasteland. Overall, the mean SOC content of Malus pumila and Prunus persica in 0-100 cm soils is relatively high among the five economic forest species. Therefore, Malus pumila is the preferred choice for economic forest planting in Gangu County. In the future economic development and ecological restoration practice of Gangu County, it is recommended to plant a mixed forest planting pattern of Malus pumila and Zanthoxylum bungeanum , which is conducive to improving the potential carbon sink function of economic forests in the region.