The scaling relationship between leaf nitrogen and phosphorus concentrations in vascular epiphytes

Introduction: The scaling relationship between leaf nitrogen (N) and phosphorus (P) concentrations reflects plant adaptation strategies and evolutionary dynamics. While extensively studied in terrestrial plants, vascular epiphytes-a key yet understudied component of global biodiversity-remain poorly understood. Methods: We compiled leaf N and P data from 38 epiphyte species across tropical seasonal rainforests and subtropical montane forests in China, supplemented by a global literature synthesis. Standardized major axis (SMA) regression analyzed N-P scaling exponents (β) across forest types, functional groups, and habitats. Results: Epiphytes exhibited a distinct global N-P scaling exponent (β=0.78), significantly higher than terrestrial plants. Facultative epiphytes showed lower β in epiphytic (0.69) versus terrestrial habitats (0.91). No significant variation occurred among functional groups or forest types, suggesting conserved nutrient allocation strategies. Discussion: The elevated β underscores epiphytes' reliance on atmospheric nutrient inputs and adaptive P retention. Habitat-driven differences highlight niche specialization, while functional group uniformity reflects stoichiometric constraints of canopy living. These findings redefine epiphyte nutrient ecology within broader plant stoichiometry theory.