INTERSPECIFIC VARIATION AND THRESHOLD DYNAMICS OF SOIL SEPARATION CAPACITY IN SHRUB ROOT-SOIL COMPLEXES UNDER SEQUENTIAL FREEZE–THAW CYCLES AND CONTROLLED HYDRODYNAMIC CONDITIONS

In regions characterized by seasonal freeze-thaw cycles and intense hydrodynamic conditions, shrub root-soil complexes play a pivotal role in mitigating soil erosion.However, the interspecific differences in soil separation capacity and their relationship with freeze-thaw frequency and water flow velocity remain poorly understood.This study aimed to elucidate these complex interactions and identify thresholds governing soil stabilization.Soil samples were collected from a 25 hillside in the Wuying National Nature Reserve, northeastern China, which experiences a temperate continental monsoon climate.Controlled laboratory experiments were then conducted to simulate the effects of freeze-thaw cycles and hydrodynamic forces on soil separation capacity.We selected three shrub species, Amorpha fruticosa, Swida alba, and Lespedeza bicolor, and subjected their root-soil complexes to 0-20 freeze-thaw cycles and varied flow rates (2, 6, and 10 L/min) in controlled laboratory simulations.Amorpha fruticosa consistently exhibited the highest soil separation capacity, surpassing Lespedeza bicolor and Swida alba.Soil separation capacity increased with both water flow velocity and freeze-thaw cycles, stabilizing at lower cycle counts under higher flow conditions.Critical thresholds emerged after 10 cycles at 2 L/min and 5 cycles at 6 and 10 L/min.These findings underscore the importance of species-specific root traits and the synergistic influence of freeze-thaw processes and hydrodynamic forces in shaping soil stability.The identified thresholds offer insights for managing erosion-prone landscapes under shifting environmental regimes.