Phosphorus Acquisition Strategy of Different Wild Rhododendron Species Modulates Soil Phosphorus Cycle in Subtropical Montane Forest Ecosystems

Montane forests are commonly limited by phosphorus (P) scarcity, yet Rhododendron species persist via specialized P-acquisition strategies. However, the microbial processes governing P utilization among wild Rhododendron species remain unclear. We collected soil and root samples from three wild Rhododendron species—Rhododendron latoucheae Franch. (R. latoucheae), Rhododendron fortunei Lindl. (R. fortunei) and Rhododendron simsii Planch. (R. simsii)—in a montane forest and analyzed soil P fractions, acid phosphatase activity, and fungal community traits to investigate their relationships with P cycling. The results showed significant differences in P fraction contents between non-rhizosphere and rhizosphere soils among the three species. In R. fortunei, rhizospheric NaOH-Po decreased tenfold while H2O-Pi increased by 9.13 mg/kg, indicating a shift toward labile P. In contrast, R. latoucheae and R. simsii showed increases in moderately labile P by 32.54% and 22.09%, respectively. R. latoucheae exhibited the lowest acid phosphatase activity in non-rhizosphere soil (4.810 ± 0.560 μmol/d/g), which increased significantly in the rhizosphere. Fungal community analysis revealed a significant enrichment of Podila in the rhizosphere of R. latoucheae (10.84%) and R. simsii (9.17%), while Penicillium (6.80%), Trichoderma (3.65%) and Mortierella (5.83%) were dominant in the R. fortunei rhizosphere. R. latoucheae mineralized organic P through acid phosphatase hydrolysis driven by nutrient scarcity. R. fortunei likely mobilizes inorganic P through ericoid mycorrhizal-associated secretion of organic acids and the activity of specialized phosphate-solubilizing fungi facilitated by high substrate availability. Soil nutrients (SOC, TN, NO3−-N) influenced fungal abundances and indirectly shaped soil P fractions, whereas fungal taxa abundance in the rhizosphere directly drove P turnover. Our results confirm that different wild Rhododendron species employ distinct P-acquisition strategies mediated by rhizosphere fungi and enzyme activities, and provide new insights into microbial-driven P cycling in montane forests.