Alternate wetting-drying frequency differentially regulates phosphorus speciation transformation via microbial community and metabolic strategy in rubber plantation soil

Phosphorus (P) is critical for forest ecosystems but is increasingly affected by soil alternate wetting and drying (AWD) under climate change. Yet, how AWD frequency reshapes soil P fractions through microbial community shifts and metabolic strategies remains elusive. We examined P fraction allocation, bacterial/fungal communities, and C/N/P functional potentials under continuous moisture (W), low-frequency (3DW), and high-frequency (6DW) AWD in rubber plantation soil. Both AWD treatments reduced P activity and soil total P, available P, and microbial P, while increasing r-strategist abundance and recalcitrant polymer degradation genes (e.g., tpx , xylH , xylF ). Notably, 3DW induced a stronger r-strategist proliferation than 6DW and additionally enriched P uptake and transport genes (e.g., phnC , ugpE ). Consequently, AWD promoted P redistribution from labile to stable pools, decreasing Resin-P and NaHCO 3 -Po but increasing NaHCO 3 -Pi, NaOH-Po, and HCl-P. The two AWD frequencies differed in efficacy, 6DW exerted stronger effects on Resin-P, NaOH-Po, and Sonic-Po, whereas 3DW more strongly influenced NaHCO 3 -Po. Labile P fractions correlated with P mineralization, solubilization, nitrogen fixation, and denitrification, driven by Firmicutes , Basidiomycota , and Chytridiomycota . Recalcitrant P pools linked to P uptake/transport, nitrification, and complex carbon decomposition, associated with Proteobacteria and Myxococcota . Structural equation modeling revealed that microbial community structure and metabolic functions primarily governed P fraction allocation and availability under AWD, with direct contributions from pH, TN, and NO 3 - -N. These findings advance mechanistic understanding of P dynamics under changing precipitation regimes and inform sustainable P management in tropical plantation soils.