Soil microbial community composition and co-occurrence network responses to mild and severe disturbances in volcanic areas

Soil physicochemical properties and vegetation types are the main factors affecting soil microorganisms, but there are few studies on the effects of the disturbance following volcanic eruption. To make up for this lack of knowledge, we used Illumina Miseq high-throughput sequencing to study the characteristics of soil microorganisms on both shores of a volcanically disturbed lake. Soil microorganisms in the two sites were subjected to different degrees of volcanic disturbance and showed significant heterogeneity. Mild volcanic disturbance area had higher enrichment of prokaryotic community. Co-occurrence network analysis showed that a total of 12 keystone taxa (9 prokaryotes and 3 fungi) were identified, suggesting that soil prokaryote may play a more significant role than fungi in overall community structure and function. Compared with severe volcanic disturbance area, the soil microbial community in mild volcanic disturbance area had the higher modular network (0.327 vs 0.291). The competition was stronger (positive/negative link ratio, P/N: 1.422 vs 1.159). Random forest analysis showed that soil superoxide dismutase was the most significant variable associated with soil microbial community. Structural equation model (SEM) results showed that keystone had a directly positive effect on prokaryotic (λ = 0.867, P < 0.001) and fungal (λ = 0.990, P < 0.001) multifunctionality while had also a directly positive effect on fungal diversity (λ = 0.553, P < 0.001), suggesting that keystone taxa played a key role in maintaining ecosystem stability. These results were important for understanding the effects of different levels of volcanic disturbance on soil ecosystems.