Microbial-mediated carbon acquisition drives phosphorus turnover within soil initial development in oligotrophic tailing sites.

Metabolic strategies of indigenous functional microorganisms drive initial nutrient accumulation in oligotrophic environment. However, their specific roles in carbon-phosphorus interactions remain poorly understood. Here, phosphate tailings were investigated across different aging stages through controlled inoculation experiments with native phosphate-solubilizing bacteria (PSB) and microalgae. Results revealed that initial soil development was constrained by severe stoichiometric imbalance between microbial phosphorus demand and resource supply. Co-inoculation reduced insoluble inorganic phosphorus by 10.0 %-17.5 % while increasing organic carbon accumulation by 87.7 %-212.9 %. Metagenomic revealed this was primarily attributed to the carbon-fixing and organic phosphorus mineralization pathways. Enzymatic stoichiometry showed that microbial carbon acquisition (through both carbon fixation and fresh organic matter input) alleviated phosphorus limitation (R = 0.54, p < 0.01), reducing carbon:phosphorus imbalance by 51.8 %-98.6 %. Structural equation modeling (SEM) confirmed carbon acquisition precedes phosphorus turnover. This study demonstrate that targeted regulation of carbon availability overcomes nutrient constraints in oligotrophic tailings, enabling sustainable soil development from tailings.