## 5 Conclusions  
In this study, we took _Amorpha fruticosa_ as the object to study soil properties, root distribution, single root tensile properties, and root-soil tensile properties under the six dosages of super absorbent polymer on moderately weathered slopes. The pull-out and indoor root tensile tests were conducted to analyze the upward and downward slope root tensile strength and root anchorage. The following findings were drawn from the data gathered during the testing process:  
1. The water retention agent effectively reduces soil bulk and increases soil water content. SAP can improve the environmental conditions at the root-soil interface, and enhances soil water storage capacity. 2. The soil nutrient content was found to be related to three factors: plant growth consumption, water retention agent adsorption, and active groups in the water retention agent. The first two reasons work against soil nutrient increase, while the third reason works in favor of nutrient growth. Three of these factors interact, and because the soil fertility in this experiment may be insufficient, the soil nutrients decline as the water-retention agent content increases. 3. The number and length of lateral roots decreases as the amount of SAP increases. When the soil moisture is sufficient, the water retention agent changes the soil structure due to its water absorption characteristics, limiting soil moisture transportation to the root system to a certain extent, thereby inhibiting the growth of the root system. Besides, we suppose that since _Amorpha fruticosa_ is a woody shrub with tolerance to water stress and low or moderate water requirements, SAP does not provide additional benefits. 4. The tensile strength of the upslope root is greater than that of downslope root. The primary contributors to root anchoring are the upslope lateral roots. Mechanical stimulation enhances the tensile strength of the root system by increasing the quantity and diameter of up-slope lateral roots that resist the external load pressure, hence strengthening the slope stability. Simultaneously, water retention agents alter the water content of the root system, which results in changes to the root system's internal structure in terms of lignin, cellulose, and xylem fiber area, which influences the anchorage of the root system. 5. Plant anchorage decreases as SAP increases. SAP increases the water content below the root-soil plate, causing the soil pore water pressure to increase, so the soil is hydraulically fractured, the friction between the root-soil decreases, and the plant anchorage is weakened. 6. The significant addition of SAP could enhance the tensile strength of upslope embedded secondary lateral roots but would adversely affect soil nutrients, root distribution, and root anchorage. The addition of SAP in this test had no significant effect on improving slope stability. From the perspective of reinforcement capacity, we cannot blindly pursue the survival rate and other high dosage use of water retention agents to increase the risk of slope destabilization. The results of this study provide an essential reference for studying the effect of water retention agents on soil physicochemical properties, plant root distribution, and anchorage, and also have important reference significance for improving the stability of rocky slopes. However, we lacked the study of water retention agent on plant root microstructure and did not consider the interaction between plant consumption, water retention agent adsorption properties, and active groups. To have a better understanding of the influence of water retention agent dosage on root anchoring, additional research on water retention agent structure and root morphology is required. Writing--original draft preparation, S.H. ; methodology, H.S. ; writing--review and editing, H.S. and Y.Z. All authors have read and agreed to the published version of the manuscript. This research was funded by the Sichuan Youth Science and Technology Innovation Research Team Special Program (2019)DTD0007). Not applicable.