Abstract: Using pure forests of Phyllostachys prominens (PP) as the control, we compared the ecological stoichiometry of bamboo leaves in mixed forests of Ph. prominens and Ph. edulis (PM), as well as Ph. prominens and broadleaved-conifer mixed trees (PB), under competitive conditions. By measuring the carbon (C), nitrogen (N), phosphorus (P), and potassium (K) content in mature and senescent leaves of Ph. prominens across these different forest types, we analyzed nutrient resorption patterns and employed partial least squares structural equation modeling (PLS-SEM) to explore the effect of interspecific competition on bamboo's nutrient utilization strategies. The results show that: Compared to PP, N and P contents in both mature and senescent leaves of Ph. prominens were significantly reduced in PM and PB, while C content remained unchanged. K content was significantly higher in PB than in PP and PM. The C/N, C/P, and N/P ratios in Ph. prominens leaves were significantly higher in PM and PB compared to PP, with PB showing significantly higher values than PM. Conversely, the N/K ratio was significantly lower in PM and PB than in PP. N and P resorption efficiency (NRE and PRE) was significantly higher in PM and PB compared to PP, with PM exhibiting the highest K resorption efficiency (KRE). PLS-SEM analysis revealed that interspecific competition significantly influenced NRE and PRE by regulating the nutrient content in mature leaves and the stoichiometric ratios in senescent leaves. In conclusion, Ph. prominens employs distinct nutrient-use strategies in response to interspecific competition: when competing with broadleaved-conifer mixed forests, it prioritizes P utilization and resorption, whereas it enhances K-use efficiency when competing with Ph. edulis, thereby improving its ecological adaptability and growth potential.