The functional diversity of plants dispersed via three upland rivers in humid subtropical monsoon climate

The plant diversity of riparian zones has significantly deteriorated due to human disturbances, making their restoration a key focus in research. However, restoration efforts often fail due to the lack of available propagules. Hydrochory, i.e., plants dispersed via water, which plays a critical role in transporting propagules downstream and is pivotal for riparian habitat recovery. Although hydrochory is closely related to the establishment and restoration of downstream riparian vegetation, most previous studies have concentrated mainly on the species richness and the number of propagules dispersed by water, but have overlooked the functional diversity. We explored the temporal variations in functional traits composition and functional diversity of hydrochorous propagules in three upland rivers within the upper Yangtze River catchment, situated in a humid subtropical monsoon climate. We find that during the high flows of summer, these rivers transport more species and exhibit higher functional diversity. This underscores the critical role of high summer flows for breaking the dispersal bottleneck of species with limited dispersal ability, and emphasizes the importance of hydrochory during the flood season for the recovery of riparian vegetation and maintaining high river flows is a critical strategy for restoration in the era of global flow regulation.