Effects of root growth on salt leaching and soil structure improvement in saline soils: A case study of Suaeda salsa

Halophytes reduce soil salinity through significant shoot salt accumulation and facilitation of salt leaching. However, quantitative evidence on how Suaeda salsa L. (S. salsa) roots interact with saline soil to facilitate salt leaching remains limited. This study investigated the effects of S. salsa planting on salt removal, soil salinity, and soil quality under four soil salinity levels (0.1 % none-saline, 0.6 % lightly saline, 1.1 % moderately saline, and 2.6 % severely saline soils) using soil column experiments. Results showed that S. salsa planting significantly reduced soil salinity in the 0–20 cm layer. In lightly to moderately saline soils (0.6 %–1.1 % salt content), above-ground Na removal accounted for 12.1 %–19.3 % of soil total Na; in severely saline soils (2.6 % salt content), this dropped to 4.3 %. Compared with bare saline soil, S. salsa planting improved soil quality through increasing total soil porosity (TSP) by 51.6 %–109.6 %, pore connectivity (PC) by 144.5 %–550.7 % in the 0–20 cm layer; enhancing saturated hydraulic conductivity (Ks) by 100.7 %−373.8 %, and reducing bulk density (BD) by over 4.0 % in 0–100 cm soil profile. Correlation analysis revealed that root length (RL) and root average diameter (RAD) were positively correlated with TSP, PC, connected pore numbers (CPN), and Ks but negatively correlated with BD and soil moisture (SM). Root-induced soil quality improvements promoted salt leaching in the 0–20 cm layer, achieving desalination rates of 45.5 %–54.8 % in lightly to moderately saline soils and 24.6 % in severely saline soils. Furthermore, S. salsa planting reduced topsoil salt accumulation, decreasing salinity by over 55.0 % in the 0–20 cm layer compared to uncultivated soils. Therefore, continuous cultivation of S. salsa is an effective biological strategy for remediating saline-alkali land by improving soil quality and promoting salt removal.