Microbial community composition and Co-occurrence network analysis of the rhizosphere soil of the main constructive tree species in Helan Mountain of Northwest China

To understand the microbial diversity and community composition of the main constructive tree species, Picea crassifolia , Betula platyphylla , and Pinus tabuliformis , in Helan Mountain and their response to changes in soil physicochemical factors, high throughput sequencing technology was used to analyze the bacterial and fungal diversity and community structure. RDA and Pearson correlation analysis were used to explore the influence of soil physicochemical factors on microbial community construction, and co-occurrence network analysis was conducted on the microbial communities. The results showed that the fungal and bacterial diversity was highest in B. platyphylla , and lowest in P. crassifolia . Additionally, the fungal/bacterial richness was greatest in the rhizosphere soils of P. tabuliformis and B. platyphylla . RDA and Pearson correlation analysis revealed that NN and AP were the main determining factors of the bacterial community, while NN and SOC were the main determining factors of the fungal community. Pearson correlation analysis between soil physicochemical factors and the alpha diversity of the microbial communities revealed a significant positive correlation between pH and the bacterial and fungal diversity, while SOC, TN, AP, and AN were significantly negatively correlated with the bacterial and fungal diversity. Co-occurrence network analysis revealed that the soil bacterial communities exhibit richer network nodes, edges, greater diversity, and greater network connectivity than the fungal communities, indicating that the bacterial communities bacteria exhibit more complex and stable interaction patterns in soil. The research results can provide guidance for understanding the interactions between microorganisms in forest ecosystems and the relationships between microbial community composition and ecosystem functions.