Abstract: Cultivating Aralia elata under larch plantations is a typical economic industry in mountainous areas of eastern Liaoning. However, the effects of A. elata cultivation on soil organic carbon and microbial communities remain unclear. We analyzed soil carbon pool components and microbial community characteristics in 0-10 cm and 10-20 cm soil layers between plots with understory planting of A. elata (experimental group) and non-planting plots (control group) in the compound ecosystem of larch plantations intercropped with A. elata in eastern Liaoning mountainous areas. The results showed that: (1) Compared with the control group, understory cultivation of Aralia elata significantly increased the contents of soil total carbon, soil organic carbon and its main components including dissolved organic carbon, particulate organic carbon and mineral-associated organic carbon. The amplitude of enhancement was higher in the 0-10 cm soil layer than in the 10-20 cm layer. (2) A. elata planting markedly increased the Simpson diversity of bacteria but decreased that of fungi. The community structure exhibited specific differentiation across different soil layers. There were significant differences among bacterial communities, whereas distinct variations of fungal communities mainly occurred in the 0-10 cm soil layer. (3) Compared with that in the control, understory A. elata planting decreased the relative abundances of bacterial phyla Acidobacteriota and Chloroflexota, and fungal phylum Basidiomycota, while increased those of bacterial phyla Pseudomonadota and Verrucomicrobiota, and fungal phylum Ascomycota. Soil organic carbon and its main components showed negative correlations with the relative abundance of Chloroflexota, but positive correlations with that of Verrucomicrobiota. This study revealed the patterns and correlations of significant increases in soil organic carbon and its main components, as well as changes in microbial community diversity and key taxa under the intercropping system of larch plantations and A. elata. Our findings provide an important theoretical basis for the coordinated ecological and economic development of this compound planting mode in Northeast China.

Key words: the mountainous area of eastern Liaoning, under-forest economy, soil organic carbon, microbial community diversity, ecological effect