Effects of tides on interspecific interactions and plastic growth responses of Bolboschoenus planiculmis

Abstract

Interspecific interactions between marsh plants can be shifted by abiotic factors. In estuaries, diverse factors such as salinity, soil, and tide can affect these relationships; however, the effects of tides are still poorly understood. In this study, we evaluated the effects of tidal stress on interspecific interactions and the plastic growth responses of Bolboschoenus planiculmis in a greenhouse experiment. Simulated tide changed the nature of interspecific interactions between B. planiculmis and Carex scabrifolia; the interaction was negative (competitive) in the nontidal treatment but became neutral in the tidal treatment for B. planiculmis. Both tide and interspecific interactions decreased the biomass of B. planiculmis. The tide caused thinner stems which is in agreement with an avoidance strategy and decreased sexual reproduction in B. planiculmis; however, other plastic growth responses were not observed. Carex scarbifolia decreased biomass under tidal stress without any plastic ability under tidal stress. These results can help to explain the real distribution of these two species in the field. Bolboschoenus planiculmis with effective ability to avoid tidal stress would dominate at a low elevation; however, it may be outcompeted by its competitor C. scabrifolia at a high elevation. These findings indicate that tidal stress can alter interactions between stress-tolerant species and competitors in estuaries.