Contribution of Hydrological Connectivity in Maintaining Aquatic Plant Communities in Remnant Floodplain Ponds in Agricultural Landscapes

The expansion of the agricultural landscape has led to the fragmentation of floodplains. These remnant floodplain ponds serve as important habitats for aquatic plants. Hydrological connectivity between floodplain ponds, facilitated by artificial watercourses, plays an important role in providing a migration course for mobile animals, such as fish. However, little is known about the contribution of artificial watercourses to the dispersal of aquatic plants, which are passive dispersers, between floodplain ponds. This study aimed to elucidate the effects of hydrological connectivity through artificial watercourses and environmental factors on the structure and composition of aquatic plant communities in lowland floodplain ponds. Vegetation and environmental surveys of 20 floodplain ponds were conducted in the agricultural landscape of northern Japan. Path analysis was used to clarify the effects of local- and landscape-scale environmental variables on aquatic plant communities with respect to species richness and species coverage. The path analysis results suggested that both hydrological connectivity between floodplain ponds and eutrophication were influential determinants of the species richness of aquatic plant communities. The study findings indicate that water quality management, connectivity conservation, and restoration should be prioritized to maintain aquatic plant communities in degraded floodplain ponds.