Abstract
INTRODUCTION: Phosphorus (P) limitation constrains the growth of Macadamia integrifolia in subtropical soils, despite intrinsic adaptations such as cluster roots and rhizosphere P mobilization. However, the role of arbuscular mycorrhizal fungi (AMF) in enhancing P acquisition under varying P availability and inoculum identity remains unclear. METHODS: We conducted a controlled pot experiment with three P levels (P0, P1, P2) and two AMF treatments (indigenous consortium and Glomus mosseae), assessing seedling growth, biomass allocation, organ-level P concentrations, rhizosphere soil properties, and fungal community composition. RESULTS: Seedling growth and biomass allocation responded non-linearly to P, with maximal aboveground biomass at P1. Notably, G. mosseae inoculation under P1 increased aboveground biomass by 42.9% and root P concentration by 18.4%, whereas the indigenous AMF consortium enhanced leaf P and rhizosphere P under low-P conditions. AMF colonization was strongly associated with total plant biomass but decoupled from short-term P uptake efficiency. Rhizosphere fungal α-diversity and community composition varied with P supply and AMF identity, with Glomeromycota enrichment and reduced saprotroph abundance in inoculated treatments. DISCUSSION: These findings demonstrate context-dependent AMF effects that integrate strain-specific functional traits with intrinsic plant P-acquisition strategies, highlighting functional differentiation between growth promotion and immediate nutrient acquisition. This study provides quantitative guidance for optimizing growth and P-use efficiency in low-P-adapted woody crops.