LAUSR

Abstract Interactions between plants will shift between competition and facilitation along environmental stresses, which has already been widely demonstrated in terrestrial ecosystems. Reestablishment of submerged macrophytes in eutrophic aquatic ecosystems has been recognized as a pivotal measure in the process of ecological restoration. However, little is known about the interactions between neighbor species and target species of submerged macrophytes along a nutrient gradient in freshwater ecosystems. Here, we carried out a mesocosm factorial experiment to investigate the responses of three target species (Potamogeton perfoliatus, Myriophyllum spicatum and Vallisneria natans) to the presence/absence of neighbor species (Potamogeton malaianus) under five nutrient levels. Results showed that the neighbor species has a strong negative effect on the performance of P. perfoliatus, whereas has weak effects on the performances of M. spicatum and V. natans (negative and neutral, respectively). Along the experimental nutrient gradient, the neighborhood effects shifted from facilitation to competition, whereas no significant facilitative effects were found in the study. Strong negative neighborhood effects were found in high nutrient levels due to the higher periphyton biomass. Multiple regression analysis suggested that the neighborhood effects are significantly affected and largely explained by the periphyton attached on target species. Overall, our results suggested that periphyton may be a potential factor mediating the neighborhood effects on restoration of submerged macrophytes in eutrophic freshwater ecosystems.