Riparian Vegetation Adapts to the Antiseasonal Water Fluctuations: Insights From Plant Functional Traits

Plant functional traits (PFTs) reflect plant responses to environmental changes, with different species exhibiting distinct trait combinations along environmental gradients, illustrating trade-offs in survival strategies. However, the patterns of functional traits in reservoir water-level fluctuation zones—where hydrological regimes are artificially regulated—remain poorly understood. This study hypothesized that (1) intracommunity functional traits vary along water-level gradients, (2) functional traits converge among species within the same water fluctuation zone and (3) trade-offs in functional traits are evident in morphology, shoots and roots. To test these hypotheses, we analysed plant community properties and measured intra- and interspecies trait variation across spatial and environmental gradients. Correlation analysis identified key drivers of ecological adaptation strategies. Results showed that water fluctuations were the primary factor shaping PFTs, with traits converging horizontally along longitudinal gradients but diverging along lateral gradients. Flooding stress induced niche differentiation in dominant plants, leading to distinct survival strategies: Cynodon dactylon exhibited a high conservation-stasis strategy, while Xanthium sibiricum adopted a fast investment-escape strategy, both maintaining high homeostasis. Cyperus rotundus displayed a conservation-stasis strategy in severely flooding zones but shifted to a fast investment-escape strategy in moderately flooded zones. This study demonstrates that plants employ diverse adaptive strategies under reservoir-induced hydrological conditions, providing insights for revegetation in water-level fluctuation zones as a nature-based solution.