Soil Salt Redistribution and Organ-Level Ion Allocation in Halophytes Across Sites with Different Planting Durations in Extremely Saline Soil

Soil salinization is a major constraint on ecological restoration in arid regions. This study was conducted in the highly saline coal-mining area of Dananhu, Hami, Xinjiang, China. Using a spatial chronosequence approach, we compared soil salt distribution between unplanted bare land and plots planted for 1, 2, and 3 years, as well as ion composition in the roots, stems, and leaves of three halophyte species. The results showed that: (1) Soil salt contents were lower in planted plots than in unplanted bare land. Surface-soil salinity and the sodium adsorption ratio (SAR) differed among plots with different planting durations, with higher values in the 2-year plots than in the 1- and 3-year plots. (2) Na+, SO42−, and Cl− were the dominant soil ions, and their relative proportions differed among plots, particularly in the surface soil. (3) The roots of Tamarix chinensis had a relatively high proportion of SO42−, whereas the leaves of Nitraria tangutorum had relatively high proportions of Na+ and Cl−. In contrast, the leaves of Phragmites australis had a relatively low proportion of Na+ and relatively high proportions of K+ and Ca2+. (4) Root Na+ contents in T. chinensis and P. australis were significantly positively correlated with SAR in the upper soil layer, whereas stem Na+ content in N. tangutorum was significantly negatively correlated with soil Cl−, Na+, and SAR. These findings highlight differences in soil ionic conditions and plant ion traits among plots with different planting durations.