Soil origin, mycorrhizal plant partners and environmental factors affect the growth and development of SongRong (Tricholoma matsutake). In order to clarify the relationships of fungi–bacteria networks and various influence factors in the habitat of SongRong, we chose three collection sites with a Quercus mongolica pure forest (plot A without SongRong was used as the control sample site), Q. mongolica mixed Rhododendron dauricum (plot B) and Q. mongolica mixed with R. dauricum and Pinus densiflora (plot C). By using high-throughput sequencing, we obtained a total of 4930 fungal and 55501 bacterial amplicon sequence variants (ASVs) based on internally transcribed spacer ribosomal RNA (ITS rRNA) and 16S ribosomal RNA (16S rRNA) sequencing via the Illumina NovaSeq platform. In the habitat soil of SongRong (plot B and plot C), alpha or beta diversity and species compositions of fungi and bacteria were different from plot A. The fungal–bacterial networks follow the selection rule that few dominant genera account for the greater relative abundance. Forest types, but not the host itself, drove the fungal–bacterial networks of the forest soil, and soil physicochemical characteristics and texture affected their abundance. The abundance of Tricholoma was affected by the fungal and bacterial abundance in the habitat.

Host plants are known to determine the distribution and development of ectomycorrhizal fungi such as Tricholoma matsutake; however, we found that the fruit body distribution of T. matsutake was different in Quercus mongolica pure or mixed forests. To clarify the fungal and other microbial composition rules of host plants, ectomycorrhizal root tip samples of Q. mongolica mixed with different plants were selected for study. By using high-throughput sequencing, we obtained 5229 fungal and 38,834 bacterial amplicon sequence variants (ASVs) as determined by internally transcribed spacer ribosomal RNA (ITS rRNA) and 16S ribosomal RNA (16S rRNA) sequencing via the Illumina NovaSeq platform. Among the neighboring plants, there were no significant differences in fungal or bacterial alpha diversity, but there was a significant difference (p < 0.05) in ectomycorrhizal alpha diversity. The fungal, bacterial and ectomycorrhizal fungal communities in the ectomycorrhizosphere of Q. mongolica all showed differences in beta diversity and species composition. In addition, the physical and chemical properties of the soil and the relationships among species could affect the relative abundance of fungi, bacteria and ectomycorrhizal fungi, but the soil microbial pool had little effect on microbial composition. Using PICRUSt2, some significantly up-regulated (p < 0.05) metabolic functions in ectomycorrrhizospheric microbial communities were predicted, which would be an interesting research field for ectomycorrhizal microecology.