Trophic associations outweigh consumer diversity in structuring arbuscular mycorrhizal fungal communities in plantation forests

Arbuscular mycorrhizal fungi (AMF) form mutualistic associations with most terrestrial plants, playing essential roles in nutrient cycling and plant productivity. While protistan predation can influence AMF richness and composition, the extent to which trophic interactions, alongside environmental factors, shape AMF diversity and community structure in plantation ecosystems remains unclear. Here, we analyzed 432 samples from two microhabitats (216 rhizosphere soils and 216 roots) of dominant afforestation species (Pinus tabuliformis and Ulmus pumila) across two seasons (spring and autumn). We assessed the effects of biotic (plant biomass, litter, root traits, protistan consumer diversity, and trophic network properties) and abiotic (soil physicochemical) factors on AMF α- and β diversity. Trophic associations, quantified by network edge number and connectance, as well as plant-related variables, emerged as primary predictors of AMF diversity across species, microhabitats, and seasons. Root traits were key determinants in root-associated AMF diversity, while litter characteristics influenced rhizosphere AMF communities. Notably, protistan consumer diversity significantly affected AMF β diversity, but not α-diversity, whereas trophic network properties consistently exerted strong direct effects on both diversity metrics. Overall, trophic associations had a stronger influence on AMF diversity than consumer richness alone. These findings highlight the critical yet often underappreciated role of trophic interactions in regulating mycorrhizal community dynamics in afforested landscapes.