Distribution diversity of fungi and bacteria communities in the pure plantation of Larix gmelinii and Fraxinus mandshurica
Authors: Wei Qing Yu , Li Wei , Zhang Yulong , Wei Xing 
Published: October 2020

BackgroundLarix gmelinii （larch）and Fraxinus mandshurica （ash）are two important tree species in northeast China and are infected by Ectomycorrhizal fungi and arbuscular mycorrhizal fungi, respectively.MethodUsing the high-throughput sequencing method, we analyzed the composition of Fungi and bacterial communities in the roots, Rhizosphere, and Non-rhizosphere soil of 21-year-old larch and ash pure plantations. Furthermore, we also analyzed the impact of soil environmental factors on the Fungi and bacterial community diversity according to soil nutrition. ResultsThere were differences in the fungal community diversity between larch and ash. Ascomycota increased gradually from the larch root to non-rhizosphere soil, whereas Streplophyta decreased sharply from the larch root to non-rhizosphere soil. However, the trend of Basidiomycota and Streplophyta under the ash forest was opposite to that of the larch. At the same time, it was found that Larix , Pyronemataceae _Unclassified, Cenococcum , and Ulmus were endemic to larch, whereas Anemone and Monographella were endemic to ash. The bacteria were similar under larch and ash forest. Proteobacteria decreased gradually from rhizosphere to non-rhizosphere soil, and the relative abundance of Acidobacteria , Actinobacteria , Chloroflexi , Rokubacteria , Gemmatimonadetes , Firmicutes, and Nitrospirae were the lowest in the roots of the two species. Pseudomonas , one of the Plant Growth-Promoting Rhizobacteria（PGPR）, had high relative abundance in the roots of the two tree species. The fungal and bacterial communities in the root, rhizosphere soil, and non-rhizosphere soil of the same tree species were different. The distribution diversity of the fungal and bacterial community of larch was non-rhizosphere soil > rhizosphere soil > root. The bacterial community diversity of the ash rhizosphere soil was the highest, whereas the fungal community diversity in the root was the highest. The Larix , the special fungus in the larch, were mainly distributed in the root and decreased sharply outside the root. The Pyronemataceae _Unclassified, Cenococcum, and Ulmus were mainly distributed in the rhizosphere soil. The special fungi of ash were mainly distributed in the rhizosphere. Burkholderiaceae -Unclassified, one of the PGPR, was mainly distributed in the roots of larch, but it was the opposite in the ash. Bacillus and Paenibacillus existed widely in the rhizosphere soil of ash. However, the abundance of Paenibacillus in larch was low, and it gradually increased from the root to the outside. The relative abundance of Streptomycetaceae _Unclassified was slightly high in the larch non-rhizosphere soil and ash rhizosphere soil. There was a correlation between PGPR and some fungi under the two tree species. Among them, Bacillus had a significant synergistic effect with Mortierella and Mucor under larch forest. There was a positive correlation between total nitrogen and bacteria in rhizosphere soil under larch forest, and its content was significantly higher than that of other treatments. There was a positive correlation between total phosphorus and fungi in ash rhizosphere soil, and the content was significantly lower than that in non-rhizosphere soil. However, the relationship between soil fungi and bacteria to soil nutrients was not significant.ConclusionTherefore, compared with the bacterial community, endomycorrhizal tree species have greater differences in the fungal community. The diversity of fungal and bacterial communities in ectomycorrhizal trees increase from rhizosphere soil to non-rhizosphere soil, while the diversity of fungal communities in endomycorrhizal trees is the highest in roots.