Background This study explored the soil organic carbon (SOC) distribution characteristics and soil carbon (C) sink potential of different types of economic forests in the Yellow River Delta, as well as improving soil capacity, thereby clarifying the influence of economic forests on SOC, soil structure and fertility, and the effects of different economic forests and their planting patterns on soil improvement were discussed.

Methods Typical economic forest tree species (i.e. Ziziphus jujuba, Prunus persica var. nectarina, Pyrus bretschneideri and P. persica var. nectarina + P. bretschneideri) in the Yellow River Delta were selected as the research objects, and Populus alba farmland shelterbelt was selected as the control. Soil samples from the 0–20 cm and 20–40 cm soil layers of different treatments were collected to measure SOC, moisture physical and available nutrient indicators. The soil improvement effects of different economic forests were comprehensively evaluated by correlation analysis and fuzzy mathematics membership function method.

Results 1) The mean values of SOC content and density in the 0–40 cm soil layer ranged from 3.85 to 10.76 g/kg and 0.97 to 3.00 kg/m². Respectively, which were higher in the economic forest than in the P. alba, increasing by 49.76% and 51.12% compared with P. alba. The soil water-holding capacity was shown as follows: P. persica var. nectarina + P. bretschneideri > P. alba > single stand economic forest; the content of soil available nutrient in P. bretschneideri soil was the highest, and P. alba was the lowest. 2) The SOC content and density and soil water-holding capacity and available nutrient contents in the 0–20 cm soil layer were exceeded that of 20–40 cm. 3) SOC content and density were significantly correlated with soil water content, soil water storage capacity, pH, available phosphorus and available potassium content.

Conclusions This study has revealed that soil C sink potential and available nutrient content in P. bretschneideri is the best, followed by P. persica var. nectarina and Z. jujuba; P. persica var. nectarina + P. bretschneideri has the best soil water storage performance, followed by single stand; P. bretschneideri and P. persica var. nectarina + P. bretschneideri are the planting modes with good soil C sink potential and soil improvement effect in this area. This result may provide a certain degree of reference for study on soil C sink and soil quality improvement of economic forests in the Yellow River Delta region.