Root disturbance effects of diverse halophytes on soil nutrient elements and salt ions in intertidal ecotone of the Yellow River Estuary wetland

Abstract

Four representative halophytes of Tamarix chinensis (Tc), Phragmites australis (TPa), Suaeda salsa (Ss) and Spartina alterniflora (Sa) in the Yellow River Estuary wetland were selected to clarify the root disturbance effects on soil nutrient elements, salt ions and their stoichiometric ratios. The results showed that the average TOC content of Tc, TPa, Ss, and Sa in the rhizosphere (RS) group were 5.19, 2.15, 2.05, and 2.14 times of those in the non-rhizosphere (CK) group, respectively. TN content of Tc in the RS group was about 3.44 times of the CK group. The average soil pH and salinity reduced by 3.60% and 41.35%, respectively, due to the root disturbance of Tc. Soil ions including K+, Ca2+, Mg2+, Na+, Cl- and SO42- reduced by 33.86%-62.86%. The root disturbance of TPa reduced soil pH and salinity by 1.09% and 35.47%, respectively, and soil ions reduced by 16.93%-46.85%. However, the root disturbance effects in Sa and Ss were not obvious. The results of Mantel test and PCA demonstrated that the root disturbance diversified the soil characteristics. 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 TPa), and 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 efforts.