Spatial distributions of salt-based ions, a case study from the Hunshandake Sandy Land, China

Soil water soluble base ion salt-based ion concentrations are critical parameters for estimating soil buffer capacity and vegetation productivity. Ionic content clearly covaries with the distribution of plant communities. Previous studies on salt-based ions in soils focused primarily on ion migration and its relationships with vegetation growth. Few studies have sought to characterize larger scale spatial distribution of salt-based ions or correlation with climatic and plant community characteristics. This study used ion chromatography to analyze the salt-based ion content (Ca(2+), Mg(2+), Na(+) and K(+)) of surface soils from the Hunshandake sandy lands. Statistical methods were used interpret spatial variation. Results showed that the average content of salt-based ions in Hunshandake sandy land was 86.57 mg/kg. Average values ranked as Ca(2+) > Na(+) > K(+) > Mg(2+) but concentrations also exhibited uneven spatial distributions. Horizontal spatial variation in Ca(2+), Mg(2+) and Na(+) ions showed these ions gradually decrease from northwest to southeast. Potassium ions (K(+)) showed no obvious spatial variation trends. Ions varied significantly across different soil layers but their average concentrations ranked as K(+)>Na(+)>Ca(2+)>Mg(2+) (from shallow to deep). The 20–30 cm soil layer contained the highest salt ion concentrations. Of the four base ions, only K(+) ions appeared in surface samples. In terms of water soluble base ion available salt-based ions, Ca(2+) occurred in the highest concentrations along the north and west side of the study area. K(+) ions occurred in the highest concentrations along the south and east sides of the study area. Na(+) concentrations did not show a consistent spatial pattern. Statistical analysis detected significant correlations of normalized ion concentration parameters (Ca(2+)/CECT, K(+)/CEC, effective water soluble base ion salt-based ions) and the total species number, average species number and total biomass of the plant communities (P <0.05). This study can help inform understanding of soil water transport in sandy areas and provide a reference for interpreting ecosystems in arid regions.