Effect of<i>Elymus nutan</i>s on the assemblage of arbuscular mycorrhizal fungal communities enhanced by soil available nitrogen in the restoration succession of revegetated grassland on the<scp>Qinghai‐Tibetan</scp>Plateau

The succession of arbuscular mycorrhizal fungi (AMF) communities during ecosystem development has received widespread attention, but the ecological mechanism that drives the succession of AMF communities during the restoration process in alpine meadow ecosystems remains unclear. Here, we treated ‘Black Beach’ (severely degraded alpine meadow) as the baseline for restoration (0 year), and selected the revegetated grassland of Elymus nutans with different planting times (3, 7, 10, and 14 years) to analyze the species composition of the AMF community in mixed roots (at the whole‐plant‐community scale) and in E. nutans roots (at the single‐plant‐species scale). A total of 46 AMF phylotypes (mixed roots: 44; E. nutans roots: 46) were identified in both root systems, predominantly belonging to Glomeraceae. AMF species richness showed a single‐peak curve change across the restoration time and reached its peak at 3 years in both root systems. In mixed roots, the soil available nitrogen not only directly changed the AMF species composition but also indirectly changed the AMF species composition through plant richness. In the E. nutans roots, only the soil available nitrogen drove changes in AMF species composition through changes in plant richness. Our results indicate that E. nutans , a key species in the restoration process of revegetated grassland, can enhance its regulation to assemble the AMF community through soil available nitrogen at the two research scales, suggesting that the scientific management of soil nitrogen availability during restoration succession could strengthen the mutual symbiosis of ‘plant‐AMF,’ thereby retarding the occurrence of secondary degradation of revegetated grassland.