Root Disturbance Effects of Four Halophytes on Soil Physiochemical Charismatics in Intertidal Ecotone of the Yellow River Estuary

Four representative halophytes, Tamarix chinensis (Tc), Phragmites australis (Pa), Suaeda salsa (Ss), and Spartina alterniflora (Sa), in the Yellow River Estuary wetland were selected to clarify the root disturbance on soil nutrient elements, salt ions, and their stoichiometric ratios. The results showed that the average total organic carbon (TOC) content of Tc, Pa, Ss, and Sa in the rhizosphere (RS) group was 5.19, 2.15, 2.05, and 2.14 times higher than those in the non-rhizosphere (CK) group, respectively. The total nitrogen (TN) content of Tc in the RS group was about 3.44 times that of the CK group. The average soil salinity reduced by 41.35%, due to the root disturbance of Tc. Soil ions, including K⁺, Ca²⁺, Mg²⁺, Na⁺, Cl^-, and SO₄^2- reduced by 33.86-62.86%. The root disturbance of Pa reduced soil salinity and soil ions by 35.47% and 16.93%-46.85%, respectively. However, the root disturbance effects in Sa and Ss were not obvious. The disturbance of roots played a crustal role in affecting the spatial heterogeneity of soil properties in the coastal wetlands above the intertidal zone (Tc and Pa), but its effect was greatly weakened below the intertidal zone (Sa and Ss). These findings are important for understanding how halophytes can impact soil nutrient levels and salt concentrations in coastal wetlands, which is crucial for effective management and restoration.