Complementary root and mycorrhizal foraging strategies for phosphorus acquisition among arbuscular and ectomycorrhizal trees in a subtropical forest

Phosphorus (P) availability is widely recognized as an important constraint on plant growth in many subtropical forest ecosystems, yet how contrasting mycorrhizal strategies mediate the use of inorganic and organic P forms remains unclear. In a subtropical forest, we integrated a 50‐ha survey of adult tree dominance, a seedling growth survey across six 1‐ha plots and a shade‐house experiment to examine how arbuscular mycorrhizal (AM) and ectomycorrhizal (ECM) trees adjust root‐fungal foraging strategies across gradients of inorganic and organic P availability. In the field, quadrats with higher inorganic P availability were dominated by AM trees, whereas ECM trees were dominant in soils with greater organic P availability. In both the field survey and the shade‐house experiment, the growth of AM seedlings increased with inorganic P availability, whereas that of ECM seedlings increased with organic P availability. The results of structural equation modelling showed that, in AM seedlings, inorganic P enhanced specific root area and mycorrhizal colonization, thereby increasing root P concentration and biomass. In ECM seedlings, organic P increased mycorrhizal colonization and acid phosphatase activity, elevating root P concentration and biomass. Our findings reveal functional complementarity between AM and ECM tree species in nutrient acquisition strategies. By providing a trait‐based framework, we offer mechanistic insight into variation in seedling performance and community assembly along soil P gradients in subtropical forests. Read the free Plain Language Summary for this article on the Journal blog.