Effects of different herbage intercropping patterns on the soil fungal community structure in Camellia oleifera forest

The intercropping of Camellia oleifera with leguminous and gramineous herbage not only helps to improve soil fertility and soil quality but also effectively enhances its production potential and ecological advantages. Therefore, exploring the effects of different herbage intercropping patterns on the soil fungal community of young C. oleifera forest will provide a scientific basis for ecosystem diversity management and increase the comprehensive benefit of C. oleifera production.

We set 5 different intercropping patterns: C. oleifera × Dactylis glomerata, C. oleifera × Trifolium repens, C. oleifera × Medicago sativa, C. oleifera × D. glomerata + T. repens, C. oleifera × D. glomerata + M. sativa in this study, and determined the most efficiency intercropping pattern for improving the soil environment of C. oleifera. The fungal community was analyzed by high-throughput Illumina sequencing of the 16SrRNA gene, and the driving factors were clarified based on soil physicochemical properties.

Compared with single-species cropping, mixed-species intercropping showed higher contents of SOC, TN and TP. The contents of total K and Mg were the highest in soils of single D. glomerata intercropping, followed by the CK soils, and the lowest content was found in soils with the two mixed intercropping. Herbage intercropping generally reduced the contents of available nutrients. The content of NO₃ in CK was the highest, and the content of NH₄ in M. sativa was the highest. For trace elements, the contents of Zn, Fe and Mn were the highest in CK, followed by single species cropping and the lowest contents were found in the mixed species intercropping pattern. The content of As in the soil was generally reduced by planting herbage. The sequencing data showed that there were 586 OTUs of fungus species shared by the five different intercropping patterns, among which 120 OTUs were found in intercropping and mixed species intercropping, and Ascomycota, Basidiomycota and Mortierellomycota were dominant phyla in fungi. Additionally, intercropping increased the soil fungal richness. According to RDA analysis, the most important soil properties that determine the dominant genus (relative abundance >1%) in the fungus community were pH, TN, NH₄ and PO₄.

Multiple herbage intercropping, especially the soybean and grass species intercropping, improves the stability of the soil environment and the diversity of fungi. Therefore, intercropping can increase the survival rate of young C. oleifera forest, improve the rational property of soil, promote the growth of C. oleifera, and improve the economic benefits of forest land.