Phosphate‐Solubilizing Bacteria Enhance Carbon Accumulation by Mediating Microbial Functions in Alpine Restoration

ABSTRACT Phosphorus availability critically limits microbial growth and soil organic carbon (SOC) persistence, yet how phosphate‐solubilizing bacteria (PSB) mediate microbial metabolic functions to influence SOC fate remains less investigated. Herein, we conducted an in situ full‐factorial experiment on the eastern Tibetan Plateau by introducing three PSB (i.e., Pseudomonas tolaasii , P. moorei , and P. chlororaphis ) to investigate their effects on SOC. This study investigated the regulation of PSB on SOC accumulation via microbial functions, including bacterial metabolism, fungal guild, and life‐history strategies. The findings indicated that PSB addition increased SOC via two opposing pathways: bacterial communities increased SOC through intensified competition and niche contraction, while fungal communities promoted SOC via increased phylogenetic diversity and symbiotrophic dominance. Bacterial metabolic pathways, particularly energy, nucleotide, and amino acid metabolism, were enhanced, thereby alleviating limitations in adenosine triphosphate (ATP) and biosynthesis. Concurrently, carbon degradation functions (e.g., aromatic and hydrocarbon degradation) declined, while photoautotrophic bacterial abundance increased. Fungal functional groups shifted from saprophytic to symbiotrophic models. These functional changes are not only potential drivers of increased SOC but also depend on the dynamics of soil and plant phosphorus. Our findings demonstrate that PSB facilitates SOC accumulation in alpine ecosystems by reprogramming microbial metabolism and ecological niche, highlighting the need to incorporate P‐mediated microbial processes into terrestrial carbon models.