Biomechanical optimisation strategy for selecting native shrubs and herbaceous plants with superior soil and water conservation properties in combating land degradation in central-western Inner Mongolia

Toenhance the biomechanical database ofplant root systems for soil reinforcement and erosion control inarid and semi-arid regions, and toprovide ascientific basis for selecting superior native shrub and herb species inforestry and grassland measures for desertification control incentral and western Inner Mongolia, this study investigated the root-soil interfacial friction characteristics offive typical native plant species – Caragana korshinskii and Hippophae rhamnoides, the semi-shrub Hedysarum mongolicum, and the perennial herbs Medicago sativa and Astragalus adsurgens – intwo widely distributed non-zonal soils: loessial soil and aeolian sandy soil. Single-root pull-out tests were conducted onindoor-prepared root-soil composite samples toexamine their responses tovarying soil moisture levels. The results showed that within asoil moisture range of4.6% to20.6%, the single-root pull-out resistance and shear strength ofall five species inboth soil types followed aquadratic model Y =ax2 + bx + c (with all multiple correlation coefficients >0.5), initially increasing and then decreasing with rising moisture content. Peak values occurred at8.6% moisture, with consistently higher values observed inloessial soil than inaeolian sandy soil. This indicates anoptimal soil moisture level for maximising root-soil interfacial friction resistance. Among the species, Hippophae rhamnoides and Medicago sativa exhibited superior pull-out performance inboth soils, with Hippophae rhamnoides showing greater sensitivity to environmental variations in loessial soil. Redundancy analysis identified soil type and moisture content as key factors explaining variations in root pull-out shear strength. These findings demonstrate that mixed-species plantations, leveraging complementary root traits, can form more complex and stable root-soil structures, thereby enhancing surface soil mechanical stability. Further research is needed to elucidate the adaptive mechanisms linking plant traits, environmental conditions, and biomechanical characteristics.