关键词: 海拔梯度, 功能性状, 权衡策略, 环境因子, 大叶金顶杜鹃

Abstract: Aims This study aimed to quantify variation in flower and leaf functional traits of Rhododendron faberi subsp. prattii along an altitudinal gradient, identify their trade-off strategies and environmental drivers, and thereby improving our understanding of plant adaptive mechanisms to climate change in alpine ecosystems. Methods Rhododendron faberi subsp. prattii individuals were sampled at five elevations ranging from 3190 to 3596 m on Balang Mountain in western Sichuan, China. We measured morphological traits, dry matter content, and carbon (C), nitrogen (N), and phosphorus (P) contents of flowers and leaves, along with temperature, light, and soil environmental factors. Important findings With increasing altitude, flower thickness, leaf thickness, leaf biomass, leaf C content, and leaf C:P ratio increased significantly, whereas leaf dry matter content, specific leaf area, and leaf P content decreased. Flower dry weight and leaf area showed unimodal patterns, while flower C content and C:N ratio first increased and then decreased. Principal component analysis revealed that PC1 axis for floral traits captured a trade-off between an "display strategy" strategy (specific flower area and C:P ratio) and "structural maintenance" (dry matter and P content), whereas PC2 axis captured a transition from "resource acquisition" (N content and fresh mass) to "resource conservation" (C content and C:N ratio). For leaf traits, the PC1 axis captured a shift from N content to leaf mass and C:N ratio, while the PC2 axis exhibits synchronous changes in leaf area and fresh weight. Trait network analysis revealed that nutrient-related traits (e.g., flower N content) dominated the phenotype network at low elevations, whereas structural traits (e.g., flower fresh weight, flower dry weight, and leaf dry matter content) gradually became central at mid-to-high elevations. Network complexity peaked at 3509 m, whereas at 3596 m, the edge density was highest and the degree of modularity was lowest. Environmental driver analysis indicated that elevation indirectly drove trait differentiation through combined effects of light, temperature, and soil factors. Growing-season light intensity was the primary environmental factor influencing floral trait trade-offs; leaf trait variations were more closely associated with mean annual temperature, growing season duration, and accumulated temperature; soil available P significantly regulated both flower and leaf traits. In summary, in high-altitude environments, Rhododendron faberi subsp. prattii enhances the synergy between flower and leaf functional traits and adopts resource-conservative strategies to optimize the allocation of resources between growth and reproduction, thereby improving its adaptation to alpine conditions.

Key words: altitudinal gradient, functional traits, trade-off strategies, environmental factors, Rhododendron faberi subsp. prattii