Abstract: The response of the relationship between transpiration rate and leaf traits to environmental factors is important for clarifying ecophysiological coupling mechanism between carbohydrate metabolism and constructing modes of leaf traits. In this study, we investigated the relationships between transpiration rate (T_r) and leaf area and leaf thickness ofPhragmites australis under different soil moisture levels along a transect from the central to the edge of the wetland in Zhangye National Wetland Park, Gansu Province, China. Four plots were established withdifferent soil moisture levels as Ⅰ (95.70%), Ⅱ (67.50%), Ⅲ (50.70%) and Ⅳ (30.17%). The results showed that the height, coverage, and aboveground biomass of the wetland community showed an increase and then decrease trend with the decreases of soil moisture. The leaf area and T_r presented an increase and then decrease trend, while the leaf thickness displayed an increasing trend from plots Ⅰ to Ⅳ. T_r was significantly positively correlated with leaf area in plots Ⅰ and Ⅳ (P<0.01) and leaf thickness in plot Ⅰ (P<0.01), but negatively correlated with leaf thickness in plot Ⅳ (P<0.01). Meanwhile, positive correlations between T_r and leaf area, leaf thickness were found in plots Ⅱ and Ⅲ (P<0.05). In plots with saturated soil moisture (Ⅰ) andserious soil water deficit (Ⅳ), Phragmites australis built up through a small thin leaf mode, and a small thick leaf mode, respectively, to keep lowerT_r. In the moderate soil water condition (Ⅱ, Ⅲ), they built up through a large thin leaf resource investment strategy to achieve higher T_r. All these changes in plants reflect the phenotypic plasticity of plant adaptation to heterogeneous habitats.

Key words: Chengdu Plain, potassium, soil profile, land use pattern