Quantifying the contributions of isolated and connected pores to soil permeability in alpine meadow soils

Study region: Typical alpine meadow soils on the central Qinghai-Tibet Plateau Study focus: This study applied the DHC-FVAM (Dual-Porosity Hydraulic Conductivity–Flow Velocity in Alpine Meadows) model to quantify contributions of connected and isolated pores to soil permeability during frozen soil thawing. Despite their established roles in permeability, quantitative insights remain limited. New hydrological insights for the regions: The results show that during the initial thawing stage, connected pores contribute 62.83 % more to total soil permeability than isolated pores, with values of (1.53 ± 1.13) × 10−10 m/s and (8.87 ± 0.30) × 10−11 m/s, respectively. Upon complete thawing, this contribution rises to 83.74 % greater, with permeability values of (2.20 ± 1.17) × 10−10 m/s and (8.67 ± 0.30) × 10−11 m/s, respectively. As frozen soil transitions from initial to complete thawing, the volume fraction of connected pores increases by 10.49 %, and connectivity rises by 155 %, driving the nonlinear permeability surge. This surge is attributed to the freeze-thaw-induced coalescence of isolated pores into connected pores, where the increase in connectivity enhances flow path efficiency and reduces tortuosity, thereby amplifying soil water transport capacity in a nonlinear manner. These findings highlight the dominant role of connected pores in water transport in alpine meadow soils, improving understanding of hydrological processes in alpine regions and offering a scientific foundation for climate-adaptive water management and ecological conservation.