Sex-Specific Adaptive Strategies of Populus euphratica Along Developmental and Canopy Gradients Based on Leaf Trait Networks

To reveal the variation patterns and differences in the adaptation strategies of leaf functional traits between male and female Populus euphratica in an arid desert environment, this study evaluated the effects of sex, developmental stage, and their interaction on 31 leaf traits using variance partitioning and trait network analysis. Furthermore, we analyzed the topological characteristics of the trait networks across two dimensions: developmental stage and vertical canopy gradient. The results indicated that sex moderately explained the variation in leaf nutrient characteristics (N and K) and physiological resistance indicators (Pro). Meanwhile, developmental stage largely accounted for variations in traits such as leaf dry weight, leaf width, specific leaf area, and photosynthetic physiology. The interaction between sex and developmental stage significantly influenced leaf anatomical structures and water-use strategies. Leaf trait network analysis revealed that during development, the male network exhibited higher connectivity and shorter average path lengths, with its core traits shifting from photosynthetic physiological indicators to nutrient and water transport characteristics; female plants exhibited higher network modularity during key developmental stages, with core nodes concentrated on leaf area, biomass, and structural traits. Along the vertical canopy gradient, the male leaf trait network showed pronounced topological reorganization in the mid-to-upper layers, suggesting a stronger capacity to respond to environmental fluctuations. Conversely, the core hubs of the female leaf trait network shifted from morphogenesis toward a synergy between structure and metabolism, which may be associated with maintaining system stability at different canopy heights. These findings suggest that female and male P. euphratica may adopt “conservative” and “acquisitive” ecological adaptation strategies, respectively, potentially leading to differentiated patterns of trait variation and coordination. This study provides a theoretical basis for understanding the potential ecological adaptation mechanisms and evolutionary strategies underlying sexual dimorphism in desert plants.