Species interactions mediate arbuscular mycorrhizal fungi successional dynamics and glomalin-related soil protein accumulation in volcanic ecosystems

Volcanic ecosystems provide a valuable model for studying microbial succession and soil formation following intense environmental changes. Arbuscular mycorrhizal fungi (AMF) and their metabolic product, glomalin-related soil protein (GRSP), play critical roles in ecosystem restoration and soil carbon sequestration. However, the changes and drivers of GRSP accumulation and AMF community succession in volcanic ecosystems remain poorly understood. In this study, soil samples were collected from different areas of the Huitengxile volcanic clusters to investigate the AMF community at various successional stages. We found that AMF diversity was significantly lower in early and middle successional stages compared to late successional stages, with the dominant genus shifting from Claroideoglomus to Glomus. The content of GRSP was relatively low in early successional stages, but its contribution to SOC was higher compared to other stages. Through network and cohesion analysis, we found that the proportion of negative cohesion, reflecting competitive interactions, increased with successional progression. In addition, late successional networks exhibited a more modular structure and greater robustness. These changes in network topology reflect the enhanced stability of the AMF network during succession. Phylogenetic analysis and the null model results indicated that AMF communities in late successional stages were phylogenetically clustered, dominated by deterministic processes, with variable selection playing a primary role. Biotic and abiotic factors jointly regulate AMF community assembly and GRSP contents, with the influence of AMF species interactions such as network complexity and network cohesion playing a dominant role. Overall, our study highlights the importance of AMF species interactions in regulating AMF community succession and GRSP production, and provides new insights for using AMF for ecosystem restoration.