Phylogeny, Functional Types, and Environment Drive Different Leaf C:N:P Stoichiometric Patterns of Alpine Shrubs in Xizang, China

Concentrations of leaf carbon (C), nitrogen (N), phosphorus (P), and their stoichiometric ratios are essential for understanding plant nutrient uptake strategies and ecosystem functions such as primary productivity and nutrient cycling. Climate and soil factors and plant genetics all pose important impacts on the variation of leaf C:N:P stoichiometry. However, which factor determines the geographic variation of leaf C:N:P stoichiometry in alpine shrubs remains unclear. In this study, we analyzed 218 samples composed of 24 shrub species from 80 shrubland sites in Xizang to explore the geographic variations of leaf C:N:P stoichiometry in response to changes in climate, soil properties, phylogeny, and shrub functional types The stoichiometric ratios of leaf C:N:P exhibit significant geographical variation particularly along longitudinal and altitudinal gradients. However, the primary drivers of these variations differed among elements. Phylogeny accounted for the majority of the variation in leaf N content (62.02%), whereas leaf C content and the C:N ratio were primarily influenced by shrub functional types (63.96% and 57.78%, respectively). In contrast, leaf P content and the C:P ratio were predominantly regulated by environmental factors (64% and 60%, respectively). Among the environmental variables, soil pH emerged as the primary driver of leaf C:N:P stoichiometric variation, exerting a greater impact than climatic factors and soil nutrient content. This study highlights the critical roles of phylogeny, shrub functional types, and environmental factors in shaping the geographical patterns of elemental composition and stoichiometric traits, contributing to a deeper understanding of plant adaptive strategies and trait evolution under diverse environmental conditions.