Effect of Herbivore Predation and Water-Wave Disturbance on the Survival of Wild Extinct Aquatic Plant Eriocaulon heleocharioides (Eriocaulaceae) in the Reintroduction Site

摘要

The effects of two factors, an alien herbivore and water-wave disturbance, on the decline of a wild extinct annual amphibious herb, Eriocaulon heleocharioides (Eriocaulaceae), was examined in a reintroduction site where the species existed. The numbers of surviving individ-uals after sowing seeds in three plot types were measured every two weeks. Surviving individuals were recorded only in plots sheltered by a net from all sides (Close). There were no surviving indi-viduals to the reproductive stage in sheltered plots with opened corners (Semi-Close) and the plots without sheltering (Open). The effect of sheltering and vanishing water-wave structure (VWS) revealed that plot closing prevents aquatic organisms and mitigates the water waves. However, Semi-Close allowed aquatic organisms enter and water-wave disturbance as well. Thus, the overall survival is mainly promoted by the prevention of aquatic organisms to enter. The water-wave miti-gation could additionally reduce the decline of the plants. To prevent herbivores is most essential for the design and management of the reintroduction site. The mitigation of water-wave distur-bance could further help to reduce the decline of this plant.