Moderate grazing drives contrasting microbial network reorganization and functional shifts in desert and meadow steppes of Inner Mongolia

Grazing strongly influences soil microbial communities and their roles in ecosystem functioning. However, it remains unclear how moderate grazing mediates microbial network organization and functional pathways under contrasting environmental contexts, which is critical for understanding the mechanisms sustaining grassland ecosystem resilience. Here, we investigated soil bacterial and fungal communities in desert and meadow steppes of Inner Mongolia after seven years of moderate grazing using high-throughput amplicon sequencing, network topology analysis, and module-based functional prediction. Our results revealed pronounced steppe-specific responses. In meadow steppes, grazing significantly increased fungal network complexity, hub centrality, and functional redundancy, particularly enhancing carbon and energy cycling potentials. In contrast, desert steppes exhibited simplified bacterial-dominated networks, reduced modularity, and limited functional shifts, with a relative increase in pathogen-associated guilds. Partial Least Squares Path Modeling further demonstrated that microbial functions in meadow steppes were regulated primarily by plant diversity, whereas those in desert steppes were constrained by abiotic stressors such as soil moisture. These findings highlight distinct microbial strategies under grazing across arid and mesic ecosystems and underscore the importance of context-specific management to sustain belowground biodiversity and ecological resilience in temperate grasslands.