Spatial Variation and Seasonal Dynamics of Leaf Stoichiometry in Vascular Epiphytes

Understanding spatial and seasonal variations in leaf stoichiometry is essential for understanding plant nutrient-use strategies and their implications for ecosystem biogeochemical cycling. Although broad-scale stoichiometric patterns have been well documented for terrestrial plants, comparable evidence for vascular epiphytes remains limited. Here, we examined spatial and seasonal variation in leaf stoichiometry of vascular epiphytes by integrating field data from subtropical and tropical forests in southwestern China with a global literature synthesis. At the global scale, leaf nitrogen and phosphorus concentrations (LNC and LPC) of vascular epiphytes were significantly related to climate variables, whereas no clear latitudinal pattern was detected for leaf N:P ratios. At the regional scale, vascular epiphytes in the subtropical montane moist forest exhibited higher LNC and LPC and lower C:N and C:P ratios than those in the tropical seasonal rainforest. At the local scale, LPC of epiphytes was positively correlated with host LPC, whereas LNC showed a weak but statistically significant association with N availability in canopy soils. Seasonally, evergreen epiphytes exhibited higher leaf nutrient concentrations during the rainy season, and deciduous species showed significantly higher stem N, P, and K concentrations during the dry season, indicating contrasting seasonal nutrient-use strategies. Our results demonstrate that leaf stoichiometry of vascular epiphytes is jointly shaped by climate, canopy-level nutrient dynamics, and seasonal regulation, and differs fundamentally from patterns commonly observed in terrestrial plants. These findings highlight the importance of considering canopy-specific processes and fine-scale species turnover when assessing large-scale stoichiometric patterns and forest nutrient cycling.