Soil texture and exchangeable ions primarily control soil erosion resistance in estuaries of Laizhou Bay

Estuaries are irreplaceable ecological habitats and the primary deposition areas for sediment and pollutants from rivers. However, many estuaries are subject to an elevated risk of soil erosion owing to the increasing occurrence of flood events and reduced sediment supply. Soil erosion resistance in estuaries, as one of the most important parameters to assess and model soil erosion in estuaries, remains unclear. In this study, soil samples were collected from eight estuaries in Laizhou Bay, China, to characterize soil erosion resistance using soil erodibility (Kd) and soil critical shear stress (τc); additionally, the controlling soil properties were identified using a partial least-squares regression (PLSR) model. The Kd of the eight estuaries ranged from 15.21 to 772.08 cm3/N s. The τc of the eight estuaries ranged from 0.33 to 3.35 Pa. The results of the PLSR analysis indicated that the increased soil electrical conductivity at 25 °C water temperature (EC25), exchangeable sodium (Na+), and clay content contributed to high Kd values, whereas increased exchangeable calcium (Ca2+) and exchangeable potassium (K+) levels were correlated with low Kd values. The τc was negatively correlated with clay content, EC25, exchangeable magnesium (Mg2+), silt content, and total porosity and positively correlated with sand content, K+, and soil bulk density. The Di River estuary exhibited the highest EC25 and lowest Ca2+ among all the estuaries, resulting in the largest Kd. The Bailang River estuary exhibited the highest τc owing to its having the lowest Mg2+ content. These findings indicate that soil erosion resistance is not determined by any individual soil property; future studies should consider the interactions among the physical, chemical, and biological properties of soil.