Characteristics of plant communities in the riparian zone of the Xiangxi River in the Three Gorges Reservoir

The Xiangxi River, a key tributary of the Three Gorges Reservoir, exhibits dynamic changes in riparian vegetation in response to periodic fluctuations in water levels. This study systematically investigated plant community composition and structural variation along the Xiangxi River riparian gradient using quadrat-based surveys, bidirectional clustering, and redundancy analysis. A total of 74 vascular plant species belonging to 67 genera and 30 families were recorded, with Asteraceae constituting the most dominant family (13 genera and 15 species). Annual herbaceous plants accounted for 54.05% of the flora. Biodiversity indices, including Shannon diversity, Pielou evenness, Simpson dominance, and species richness, initially declined and then increased with elevation. Cluster analysis revealed a transition from annual and perennial herbaceous assemblages at low and middle elevations to mixed herbaceous-grass shrub communities at higher elevations. Redundancy analysis identified elevation, inundation duration, and soil moisture content as dominant drivers of plant spatial distribution, while soil factors such as available potassium exerted secondary influences. These findings provide a scientific basis for understanding vegetation dynamics and inform ecological restoration strategies in reservoir riparian zones.