Abstract:

【Objective】The epidermal morphology of plant roots critically determines their anti-pullout performance through root-soil interface friction modulation. Elucidating how root bark topography influences pullout resistance is fundamental for understanding vegetation-mediated slope stabilization mechanisms.【Method】Using Pyracantha fortuneana and Amorpha fruticosa as model slope-protection shrubs, we conducted single-root pullout tests to quantify frictional resistance. Fractal dimension (D) and contour arithmetic mean roughness (Ra) parameters were utilized to characterize root epidermis morphology, with subsequent correlation analysis between these descriptors and pulling resistance.【Result】P. fortuneana demonstrated significantly higher pullout resistance than A. fruticosa. The pulling resistance of P. fortuneana increased progressively with root diameter, whereas A. fruticosa exhibited no significant correlation between pulling resistance increment and root diameter, except for the highest resistance increase observed within the (3,4] mm diameter range. Microscopic analysis revealed distinct root bark morphologies: P. fortuneana displayed prominent undulating contours, while A. fruticosa maintained a relatively smooth surface. The morphological parameters Ra and D effectively characterized epidermal features. For P. fortuneana, fissured root bark morphology was optimally quantified by Ra values, which showed a strong positive correlation with pullout resistance—higher Ra values corresponded to greater resistance. In contrast, A. fruticosa’s serrated root bark morphology was best described by D values, with pullout resistance increment demonstrating a strong positive correlation with increasing D. Mechanistic divergence was evident: P. fortuneana generated resistance through a particle-embedded friction mechanism, while A. fruticosa relied on direct root-soil interface contact. The interlocked soil particles within P. fortuneana’s root bark contributed substantially to enhanced frictional resistance during pullout processes.【Conclusion】This study establishes quantitative relationships between root epidermal morphology and pullout resistance mechanisms, providing critical insights for optimizing slope-protection species selection based on root-surface architectural features.

Key words: pulling friction, root bark microscopic character, contour arithmetic mean deviation(Ra), the fractal dimension