The overland flow erosion is common and became more serious because of the climate warming inducing more runoff in the Tibet Plateau. The purposes of this study were to evaluate the effects of flow rate, slope gradient, shear stress, stream power, unit stream power and unit energy of water-carrying section on the soil detachment capacity for the soil in the Tibet Plateau of China due to the information is limited. To achieve this aim, laboratory experiments were performed under six flow rates (5, 10, 15, 20, 25 and 30 L min⁻¹) and six slope gradients (8.74%, 17.63%, 26.79%, 36.40%, 46.63 and 57.73%) by using a slope-adjustable steel hydraulic flume (4 m length, 0.4 m width, 0.2 m depth). The results indicated that soil detachment capacity ranged from 0.173 to 6.325 kg m⁻² s⁻¹ with 1.972 kg m⁻² s⁻¹ on average. The soil detachment capacity increased with power function as the flow rate and the slope gradient augmented (R² = 0.965, NRMSE = 0.177 and NSE = 0.954). The soil detachment capacity was more influenced by flow rate than by slope gradient in this study. The relation between soil detachment capacity and shear stress, stream power, unit stream power and unit energy of water-carrying section can be described by using the linear function and power function, the power function relationship performed better than the linear function in generally. The stream power exhibits the best performance in describing the soil detachment capacity among shear stress, stream power, unit stream power and unit energy of water-carrying section in this study. The erodibility value in this study was larger than and the critical shear stress was less than those for soil in the eastern China. There has a huge potential for the soil in the Tibet Plateau eroded by the water erosion when enough runoff exiting. More attention should be payed to the water erosion process and mechanism in the Tibet Plateau area in the future.

Many measures have been applied to quarry slopes for ecological restoration; however, the performance of these measures has not been clearly evaluated. Thus, research evaluating the effects of the ecological restoration of quarry slopes in Caidian District was carried out to quantify the performance of different ecological restoration methods, to evaluate the effect of ecological restoration projects and to learn the applicability of different restoration technologies in Caidian District. The research can provide a reference for scientific decision-making in the follow-up management of ecological environments in Caidian District. First, the ecological restoration process of quarries in Caidian District was described in detail by visiting the relevant design and construction units. Through observational analysis from the aspects of applicable slope gradient, slope flatness requirements, project cost, the vegetation coverage conditions, the species diversity conditions and construction difficulty, the advantages and disadvantages, as well as the applicability of different ecological restoration technologies were preliminarily clarified. Then, the comprehensive evaluation index system of the ecological restoration effects was established by using the fuzzy AHP method. The ecological restoration effects of each sample plot were evaluated quantitatively based on the data of the evaluation indexes obtained by the field investigation and sampling analysis. Finally, according to the evaluation results, the existing problems in the follow-up management of the ecological restoration of quarry slopes in Caidian District were analyzed, and corresponding countermeasures and suggestions were proposed. The results showed that the quantitative evaluation results obtained by the comprehensive evaluation system of ecological restoration were consistent with the observational analysis results, and the validity of the evaluation system was proven.

Background: To quantitatively evaluate the contribution of plant roots to soil shear strength, the generalized equivalent confining pressure (GECP), which is the difference in confining pressure between the reinforced and un-reinforced soil specimens at the same shear strength, was proposed and considered in terms of the function of plant roots in soil reinforcement. Methods: In this paper, silt loam soil was selected as the test soil, and the roots of Indigofera amblyantha were chosen as the reinforcing material. Different drainage conditions (consolidation drained (CD), consolidation undrained (CU), and unconsolidated undrained (UU)) were used to analyse the influences of different root distribution patterns (horizontal root (HR), vertical root (VR), and complex root (CR)) and root contents (0.25%, 0.50%, and 0.75%) on the shear strength of soil-root composites. Results: The cohesion (c) values of the soil-root composites varied under different drainage conditions and root contents, while the internal friction angle (φ ) values remain basically stable under different drainage conditions. Under the same root content and drainage conditions, the shear strength indexes ranked in order of lower to higher were HR, VR and CR. The GECP of the soil-root composites with a 0.75% root content was 1.5–2.0 times that with a 0.50% root content and more than 5 times that with a 0.25% root content under the CD and CU conditions. The GECP in reinforced soil followed the sequence of CD > CU > UU. The GECP of the plant roots increased as confining pressure increased under CD and CU conditions while showed a complex change to the confining pressure under the UU condition. Conclusion: It was concluded that the evaluation of plant root reinforcing soil based on GECP can be used to measure effectively the influences of roots on soil under different drainage conditions and root distribution patterns.

Matric suction induced by evapotranspiration is an important parameter for determining the hydraulic mechanisms of vegetation on slope stability. Despite evapotranspiration closely associated with atmospheric parameters and soil conditions, the influence of soil properties and illumination intensities on matric suction of vegetated soil has so far received the least research attention. In this paper, three kinds of soil, namely, fine sandy loam, sandy silt, and silty clay, were selected as experimental soils, and Indigofera amblyantha was chosen as the test plant. The test conditions were controlled, such as the use of homogeneous soil and uniform plant growth conditions. Each specimen was exposed to identical atmospheric conditions controlled in a laboratory for monitoring matric suction responses over 10 days. The results showed that illumination intensities play an important role in evapotranspiration, and the thermal energy from lighting had a direct impact on plant transpiration, whereas the lighting only affected plant photosynthesis. Plant roots in vegetated soil can effectively improve the air intake value of soil, and matric suction induced by plant transpiration in vegetated soil was 1.5–2.0 times that of un-evapotranspirated soil. There is a correlation between matric suction and the silt and clay contents, and the matric suction of silty clay was sensitive to changes in the soil moisture content. Compared to fine sandy loam, the water retention of sandy silt and silty clay was high, and a high level of matric suction was maintained in the corresponding time. The results for predicting soil water evapotranspiration based on matric suction have theoretical and practical significance for preventing soil erosion and shallow landslides. In addition, these results have great guiding significance for agricultural production, such as irrigation.