Root mechanical properties comparison of two herbaceous plants in western Sichuan plateau

Western Sichuan plateau is an ecologically fragile area and a frequent geological disasters zone in China．Studying mechanical properties of suitable plants' roots is crucial for slope ecological protection and soil and water conservation．Mechanical characteristics of Cynodon dactylon and Poa pratensis L. roots were compared through single-root tensile tests．Results showed that average single-root tensile force（8.06 N）and tensile strength（42.94 MPa）of Cynodon dactylon were approximately 2.9 times and 1.7 times higher than Poa pratensis L. （2.79 N and 25.30 MPa）, respectively．Root tensile force exhibited a positive power-function correlation with root diameter, as thicker roots increased material basis for bearing tensile forces, such as cell walls and vascular tissues．However, tensile strength decreased with root diameter in a power-function, attributed to dilution of overall strength by new low-strength cortical tissues added during root thickening．Key factors contributing to significantly higher tensile strength of Cynodon dactylon compared to Poa pratensis L. and other grass species lied in its smaller cortical area ratio and larger middle stele area ratio．Cynodon dactylon increased soil shear strength by 19.6 and 3.2 kPa at soil depths of 0～15（inclusive）cm and 15～30 cm, respectively．Poa pratensis L. contributed shear strength increases of 9.2 and 4.1 kPa at same depths．In ecological engineering, Poa pratensis L. was suitable for deep soil reinforcement, while Cynodon dactylonwas beneficial for surface erosion resistance．Combined application of two species could optimize mechanical stability of different soil layers, achieving synergistic effects in soil and water conservation and slope protection．A scientific basis for ecological restoration of slopes in western Sichuan Plateau was provided．