Experimental study of root morphology and biomechanical properties of six slope protection plants in low-latitude alpine regions

Background The study aims to investigate the root morphology and biomechanical properties of six slope-protection plant species and analyze their efficacy on soil reinforcement capacity，so as to provide valuable insights for erosion control and ecological restoration in low-latitude alpine regions.Methods The seeding program with PVC pipes was designed via orthogonal experimental design considering the interspecific competition. After one-year growth，root scanning，single-root tensile tests，and single-root pull-out tests were conducted respectively. Meanwhile，principal component analysis (PCA) was applied to quantitatively evaluate soil-consolidation and slope-protection effects of the plants. Results The results showed that: 1) Lolium perenne，Caragana sinica and Piptanthus concolor had superior root morphology in general when sown in mixtures；Under monoculture，herbaceous plants generally outperformed shrubby plants in root morphology；The most competitive plants in the mixture were Lolium perenne and Caragana sinica； 2) Medicago sativa exhibited the highest mean tensile force (5.62 N)，while Poa annua demonstrated maximum tensile strength (139.10 MPa).；For the pull-out test，the maximum average pull-out force and pull-out strength were found in Medicago sativa (5.421 N) and Poa annua (220.13 MPa)；Depending on the root diameter interval，the biomechanical properties of different plants showed distinct rates of change with the root diameter； 3) Among the six slope-protection plant species， Piptanthus concolor achieved the optimal slope stabilization performance，while Hippophae rhamnoides performed the poorest effectiveness.The ideal seeding ratio was determined as: Lolium perenne (15 g/m²)，Medicago sativa (10 g/m²)，Poa annua (5 g/m²)，Caragana sinica (15 g/m²)，Piptanthus concolor (22.5 g/m²)，and Hippophae rhamnoides (7.5 g/m²). Conclusions The plants investigated in this experiment feature distinctive root morphological structures and superior biomechanical properties. These attributes are complementary advantages for effective slope protection，thereby offering theoretical references for vegetation restoration on slopes in low-latitude alpine regions.