Effects of soil stoichiometry of the CaCO 3 /available phosphorus ratio on plant density in Artemisia ordosica communities

In soil, CaCO 3 can reduce the availability of phosphorus in arid and semi-arid regions, thereby influencing plant growth. However, the effects of soil stoichiometry of the CaCO 3 /available phosphorus ratio (CaCO 3 /AP ratio) on plant density are unknown. In this study, we examined 4 Artemisia ordosica communities located in arid and semi-arid regions, and performed a pot experiment with an orthogonal design to examine the relationships between the soil CaCO 3 /AP ratio and plant density. The results showed that the soil stoichiometry of the CaCO 3 /AP ratio had a greater effect on growth of A. ordosica than either CaCO 3 or AP as single factor. The influence of the soil CaCO 3 /AP ratio on density of A. ordosica was related to the climatic zone and the types and/or amplitudes of increases in the soil CaCO 3 /AP ratio. When the soil CaCO 3 /AP ratio was within the same amplitude and was less than 2.5, the A. ordosica density increased in the semi-arid region, whereas the density decreased with increasing soil CaCO 3 /AP ratios in the arid region. In the semi-arid region, when the soil CaCO 3 /AP ratio was within the same amplitude and the increase in the soil CaCO 3 content was greater than the increase in soil AP, the A. ordosica density increased with increasing soil CaCO 3 /AP ratios. This means that the relationship between the soil CaCO 3 /AP ratio and the A. ordosica density remained the same. In the arid region, an increase in the soil CaCO 3 /AP ratio as a result of increased soil CaCO 3 content and decreased soil AP resulted in increased density of A. ordosica . Therefore, the relationship between soil CaCO 3 /AP ratios and density of A. ordosica was altered by these changes in soil chemistry. Thus, the soil stoichiometry of the CaCO 3 /AP ratio is an important factor affecting the density of A. ordosica in arid and semi-arid regions.