Abstract: This study compared the variation of branch and leaf morphology, nutrient content with developmental stage and canopy height and sex differences between male and female Populus euphratica under the same habitat to elucidate their adaptation differences during individual development. The results showed that C, N, P, and K contents of branches and leaves of both male and female plants were closely correlated with canopy height and were not significantly correlated with individual developmental stage. As canopy height increased, leaf C, N and P contents of both male and female plants gradually increased, and K contents gradually decreased, while the element contents of current-year branches gradually increased. Leaf C, N and current-year branch C, N, P and K contents of both male and female plants were significantly positively correlated with leaf area, leaf thickness, leaf dry weight and branch thickness, and negatively correlated with leaf shape index and branch length. Leaf P contents were significantly positively correlated with leaf thickness and branch dry weight. Leaf K contents were significantly positively correlated with leaf shape index and significantly negatively correlated with leaf thickness. Among individuals with same diameters, both leaf area and leaf thickness were significantly greater in males than in females, while branch and leaf C, N, P, and K contents were not significantly different between males and females. When comparing males and females at the same canopy height in each diameter class, branch length was shorter and leaf area was larger in males, and leaf C, N, P and K contents were significantly greater in females than in males at the top of canopy. Our results indicated that male poplar plants had a greater capacity for light energy acquisition and lower water dissipation, while female plants had more abundant C, N, P and K in their branches and leaves. Such sexual difference was related to their morphology and canopy height.

Key words: Populus euphratica Oliv., dioecious, branch morphology, leaf morphology, nutrient content.