Abstract: Aims The symbiotic relationship between arbuscular mycorrhizal fungi (AMF) and plant roots enhances nutrient acquisition in plant communities and plays a vital role in sustaining key functions and ecological processes in grassland ecosystems. However, the response patterns of soil AMF communities to varying grazing intensities remain under debate, and the mechanisms by which these communities influence soil multifunctionality (SMF) under grazing disturbance are not yet fully understood. Methods To address these knowledge gaps, this study investigated mountain meadow steppes on the northern slope of the Tianshan Mountains in Xinjiang under three grazing intensities: ungrazed, lightly grazed, and heavily grazed. High-throughput sequencing was used to characterize the composition of soil AMF communities and to construct their co-occurrence networks. A weighted average method, based on cluster analysis, was applied to comprehensively evaluate SMF and to analyze how AMF community characteristics vary with grazing intensities and how these variations influence SMF. Important findings The results indicated that the dominant AMF genera in the three grazing treatments were Glomus and Diversispora. As grazing intensity increased, AMF community diversity, as along with network stability, complexity, cohesion, and SMF, exhibited a unimodal pattern—increasing initially and then declining at higher grazing levels. Linear regression and structural equation modeling indicated that grazing influences SMF mainly by modulating AMF community diversity and altering the complexity and stability of AMF networks. The effect of AMF community diversity on SMF was largely indirect, mediated through its effects on network structure, while its direct impact was relatively weak. Overall, this study highlights that the complexity and stability of AMF co-occurrence networks enhance the role of community diversity in shaping SMF and strengthen the interdependent relationship between biodiversity and ecosystem functioning. These findings offer valuable theoretical insights for the restoration and sustainable management of degraded grassland ecosystems.

Key words: arbuscular mycorrhizal fungi, co-occurrence network analysis, stability, network complexity, soil multifunctionality, grazing