Shallow fine roots enhance soil shear strength and play a critical role in vegetated slope stability. While prior research focused on factors like soil type, moisture, root arrangement, and plant species, the relationship between root characteristics and root-soil composite strength remains underexplored. This study employs direct shear tests on saturated Amorpha fruticosa root-loess composites to systematically investigate the influence of root content, root length, and key parameters (root area index - RAI, root length density - RLD, root volume ratio - Rv) on shear strength. Results show: ①under low vertical loads, shear strength increases significantly with root content, but this effect weakens under higher loads; ② reinforcement primarily enhances cohesion, with minimal impact on internal friction angle; ③ for root length ≥2 cm, an optimal root content (1%-1.5%) maximizes cohesion; ④ shear strength correlates strongly positively with RAI and Rv, but weakly with root content, biomass, RLD, and specific root length, indicating dominance of root-soil interface friction under saturation. This work clarifies the mechanical mechanisms of root reinforcement in saturated loess, identifies a specific optimal root content, defines key root characteristic-strength relationships (RAI, Rv, average diameter), and provides a new theoretical basis for the comprehensive understanding of the mechanical effects of vegetation slope protection in loess areas and the scientific design of ecological slopes.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |