Effects of different ecological type earthworm on soil fungal community structure and diversity in an organic tea plantation

The aging of tea trees, degradation of soil fertility in tea gardens and poor soil biodiversity have become important factors limiting the yield and quality of organic tea. Earthworms play an important part in the regulation of soil ecosystem services. Introduction of two widely reared earthworm species as pioneers was tested through field experiment in a tea plantation of China. Field experiment was aimed to explore the effects of inoculation of different ecological types of earthworms on soil fungal community in organic tea gardens. Four treatments were set up, including: Eisenia fetida inoculation (300·m⁻²) (E), Metaphire guillelmi inoculation (100·m⁻²) (P), simultaneous inoculation of Eisenia fetida (150·m⁻²) and Metaphire guillelmi (50·m⁻²) (EP); control treatment (CK). The soil fungal community was investigated through high throughput sequencing. Results showed that the community structure and functional groups of soil fungi changed significantly. The inoculation of earthworms significantly increased the number of Operational Taxonomic Unit in soil fungi, and the number of dominant OTU increased from 100 to 269. Inoculating earthworms increased the α diversity of soil fungal community, Shannon, Simpson, and Fisher index have increased as well (P<0.05). Ascomycota and basidiomycota are dominant fungal groups in tea garden soil. Ascomycota further increased in single earthworm treatment and slightly decreased in double earthworm treatment. Under EP treatment, the highest relative abundance of mortierellomycota was 10.16%, while the highest relative abundance of xylariales increased to 29.43%. EP treatment showed the best population uniformity, more unknown fungi appeared with a proportion of 29.61%. Xylariales can decompose litter decomposition. From this, it can be seen that EP treatment exhibits stronger ability to decompose dead branches and leaves than the single earthworm inoculation treatment, which is more beneficial for increasing soil nutrients in organic tea gardens. Compared with conventional organic tea gardens, inoculation with earthworms reduces the content of saprotrophic while improving the growth of pathotroph-saprotroph-symbiotroph. However, single earthworm introduction provoked the growth of pathotrophs, especially those that were facultatively saprotrophic and symbiotrophic. EP treatment not only reduced the specific saprophytic and promoted the growth of facultative saprophytic, but also significantly increased the proportion of saprotrophic and symbiotrophic community and reduced the growth of pathotrophs. Reduce the relative abundance of pathogenic fungi commonly in organic tea gardens, such as Fusarium, which are prone to canker disease. Generally, in biologically and physically degraded soil systems, mutual promotion between earthworm species over competition. The introduction of both earthworm species showed an effect of pathogen control. Mixing inoculation with different ecological types of earthworms can help control potential pathogens, providing a sustainable solution for improving soil biodiversity and enhancing soil quality in organic tea gardens. Inoculating earthworms is an effective and feasible ecological measure to improve soil quality in organic tea gardens.