Plant phenotypic plasticity is a common feature that is crucial for explaining interspecific competition,dynamics and biological evolution of plant communities.In this study,we tested the effects of soil CaCO3 (calcium carbonate) on the phenotypic plasticity of a psammophyte,Artemisia ordosica,an important plant species on sandy lands in arid and semi-arid areas of China,by performing pot experiments under different CaCO3 contents with a two-factor randomized block design and two orthogonal designs.We analyzed the growth responses (including plant height,root length,shoot-leaf biomass and root biomass) of A.ordosica seedlings to different soil CaCO3 contents.The results revealed that,with a greater soil CaCO3 content,A.ordosica seedlings gradually grew more slowly,with their relative growth rates of plant height,root length,shoot-leaf biomass and root biomass all decreasing significantly.Root N/P ratios showed signfificant negative correlations with the relative growth rates of plant height,shoot-leaf biomass and root length of A.ordosica seedlings;however,the relative growth rate of root length increased significantly with the root P concentration increased,showing a positive correlation.These results demonstrate that soil CaCO3 reduces the local P availability in soil,which produces a non-adaptive phenotypic plasticity to A.ordosica seedlings.This study should prove useful for planning and promoting the restoration of damaged/degraded vegetation in arid and semi-arid areas of China.