LAUSR

Background For better understanding the mechanism of Reaumuria soongarica community formation in a salt stressed grassland ecosystem, we designed a field experiment to test how leaves salt secretion changes the competitive relationship between species in this plant communities. Results Among the three species ( R. soongarica, Stipa glareosa and Allium polyrhizum ) of the salt stressed grassland ecosystem, the conductivity of R. soongarica rhizosphere soil was the highest in five soil layers (0–55 cm depth). The high soil conductivity can increase the daily salt secretion rate of plant leaves of R. soongarica . In addition, we found the canopy size of R. soongarica was positively related to the distance from S. glareosa or A. polyrhizum . The salt-tolerance of R. soongarica was significantly higher than the other two herbs ( S. glareosa and A. polyrhizum ). Moreover, there was a threshold (600 µS/cm) for interspecific competition of plants mediated by soil conductivity. When the soil conductivity was lower than 600 µS/cm, the relative biomass of R. soongarica increased with the soil conductivity increase. Conclusions The efficient salt secretion ability of leaves increases soil conductivity under the canopy. This leads the formation of a “saline island” of R. soongarica. Meanwhile R. soongarica have stronger salt tolerance than S. glareosa and A. polyrhizum. These promote the competitiveness of R. soongarica and inhibit interspecies competition advantage of the other two herbs ( S. glareosa and A. polyrhizum ) in the plant community. It is beneficial for R. soongarica to establish dominant communities in saline regions of desert grassland.