Competition between Salicornia europaea and Atriplex prostrata (Chenopodiaceae) along an experimental salinity gradient

Salicornia europaea L. is a halophyte that often occupies the lowest and most saline (>3.5% total salt) areas of salt marshes. Atriplex prostrata Boucher is less salt tolerant than S. europaea and often grows in a less saline (<2.0% total salts) zone adjacent to S. europaea. The purpose of this experiment was to determine the competitive outcome when these two species are grown at different salinities to ascertain the extent salinity and competition affect plant zonation. Plants were grown in a de Wit replacement series at 85, 170, and 340 mM NaCl in half-strength Hoagland's no. 2 nutrient solution for two months. There was a significant effect of salt concentration, competition, and their interaction on biomass production of S. europaea plants. However, only salt concentration significantly affected biomass production of A. prostrata plants. Results of this experiment confirmed the results of other studies that demonstrated that the more salt tolerant species were less competitive at lower salinities. Atriplex prostrata was the better competitor at 85 mM NaCl, whereas S. europaea was the better competitor at 340 mM NaCl because growth of A. prostrata was inhibited. At 170 mM NaCl, A. prostrata biomass production decreased more than S. europaea biomass in mixed culture.