Leaf Functional Trait Adaptation of Woody and Herbaceous Plants to Flooding Gradients in an Aquatic–Terrestrial Ecotone, Taihu Lake

Investigating the adaptive mechanisms of different plant growth forms to flooding gradients is essential for formulating scientific vegetation allocation models to support ecological restoration in aquatic–terrestrial ecotones and mitigate ecological risks associated with summer flooding. This study focused on 38 adaptable species under three flooding gradients in the Taihu Lake aquatic–terrestrial ecotone. We systematically measured leaf morphological traits, photosynthetic physiological parameters, and stoichiometric characteristics. Employing analysis of variance, correlation networks, and principal component analysis, we elucidated how flooding environments shape leaf functional trait patterns of woody and herbaceous plants. The results indicated the following. (1) With increasing flooding stress, herbaceous plants increase the leaf area (LA) and leaf dry weight (LDW), whereas woody plants decrease them, indicating that herbaceous plants demonstrate stronger adaptability than woody plants. (2) Woody plants constructed a leaf functional trait network centered on stomatal conductance (Gs), adopting a conservative resource-use strategy. In contrast, herbaceous plants formed a network centered on leaf nitrogen content (Nmass), employing a rapid resource acquisition strategy to adapt to the ecotone environment. (3) The synergistic changes in leaf traits of different growth forms were affected by flooding in distinct ways. Integrating the leaf economics spectrum and adaptive evaluation values for each species can further our understanding of plant adaptation strategies in different flooding environments and guide species selection and configuration for aquatic–terrestrial ecotone restoration.