Abstract: Clarifying the responses of plant functional traits to environmental changes is crucial for understanding plant adaptation strategies and ecosystem functions. While most studies have focused on aboveground plant traits, with limited research on belowground traits, especially the covariation of leaf and fine root traits in wetlands.This study took the typical wetland plant Phragmites australis in the lower reaches of the Yellow River as the object, measured its key leaf (i.e., specific leaf area, leaf dry matter content and nitrogen concentration) and fine root (i.e., specific root length, root tissue density and nitrogen concentration) traits, and combined with environmental factor analysis to explore the variation patterns and influencing factors of plant traits under the gradient of wetland degradation.With the intensification of wetland degradation, leaf and fine root traits of P. australis presented a coordinated change from acquisition to conservation strategy, manifested as a significant decrease in specific leaf area, leaf nitrogen concentration and root nitrogen concentration, while leaf dry matter content and root tissue density significantly increased. However, specific leaf area and specific root length showed a significant negative correlation, with the latter increasing along the degradation gradient, indicating a certain functional divergence in morphological strategies between aboveground and belowground organs. Further analysis revealed that soil nutrient availability was the key environmental factor driving trait variation during degradation. As nutrient availability decreased, both the leaves and fine roots of P. australis shifted toward a “conservative” strategy characterized by high tissue density and low nitrogen concentration. By integrating leaf and root traits, this study reveals that P. australis adapts to nutrient limitation in degraded wetlands through the coordinated aboveground-belowground adjustments. These findings deepen our understanding of plant adaptive strategies under environmental change and offer a theoretical foundation for the functional restoration of degraded wetland ecosystems.

Key words: wetland ecosystem, habitat degradation, plant functional traits, ecological strategy, soil nutrient