Debris flows are a type of natural disaster induced by vegetation-water-soil coupling under external dynamic conditions. Research on the mechanism by which underground plant roots affect the initiation of gulley debris flows is currently limited. To explore this mechanism, we designed 14 groups of controlled field-based simulation experiments. Through monitoring, analysis, calculation, and simulation of the changes in physical parameters, such as volumetric water content, pore-water pressure, and matric suction, during the debris flow initiation process, we revealed that underground plant roots change the pore structure of soil masses. This affects the response time of pore-water pressure to volumetric water content, as well as hydrological processes within soil masses before the initiation of gully debris flows. Underground plant roots increase the peak volumetric water content of rock and soil masses, reduce the rates of increase of volumetric water content and pore-water pressure, and increase the dissipation rate of pore-water pressure. Our results clarify the influence of underground roots on the initiation of gulley debris flows, and also provide support for the initiation warning of gully debris flow. When the peak value of stable volumetric water content is taken as the early warning value, the early warning time of soil with underground plant roots is delayed by 534 to 1253 s. When the stable peak value of pore-water pressure is taken as the early warning value, the early warning time of soil with underground plant roots is delayed by 193 to 1082 s. This study provides a basis for disaster prevention and early warning of gully debris flows in GLP, and also provides ideas and theoretical basis under different vegetation-cover conditions area similar to GLP.
In this study, we present an on-chip analytical method using a microfluidic device to characterize the mechanical properties in growing roots. Roots are essential organs for plants and grow under heterogeneous conditions in soil. Especially, the mechanical impedance in soil significantly affects root growth. Understanding the mechanical properties of roots and the physical interactions between roots and soil is important in plant science and agriculture. However, an effective method for directly evaluating the mechanical properties of growing roots has not been established. To overcome this technical issue, we developed a polydimethylsiloxane (PDMS) microfluidic device integrated with a cantilevered sensing pillar for measuring the protrusive force generated by the growing roots. Using the developed device, we analyzed the mechanical properties of the roots in a model plant, Arabidopsis thaliana. The root growth behavior and the mechanical interaction with the sensing pillar were recorded using a time-lapse microscopy system. We successfully quantified the mechanical properties of growing roots including the protrusive force and apparent Young's modulus based on a simple physical model considering the root morphology. (c) 2025 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.
AimsPlant roots play a crucial role in soil stability and erosion prevention. Most studies currently focus on the macro-biomechanical properties of roots based on apparent diameter or stele size. However, these analyses cannot explain the factors affecting macro-biomechanical properties of roots from an endogenous perspective.MethodsTensile tests, scanning electron micrography (SEM), image-based strain measurement and compositional tests were conducted on roots of typical species (Robinia pseudoacacia, Pinus tabuliformis, Vitex negundo, Syzygium aromaticum) in the Loess Plateau to explore the influence of stele on enhancing and pores on weakening mechanical properties.ResultsRoot breakages in tension can be categorized into simultaneous and successive brittle breakage, with most simultaneous brittle breakages occurring in fine roots and most successive brittle breakages occurring in coarse roots, respectively. The negative regression between tensile strength (Tr) and diameter (Dr) was attributed to the decrease in cellulose content. The positive regression between Tr and stele percentage was attributed to the dominant distribution of cellulose within the stele of root. Pores in plant root could weaken the macro-biomechanical properties, with trees generally having higher porosity than shrubs in this research species. The non-uniformity coefficient (UC) of pores reflected their distribution form. The fine roots, with higher UC, showed more random pore distribution, more scattered macro-biomechanical properties than coarse roots.ConclusionsOur results explained the intrinsic characteristics that influence the macro-biomechanical properties along root diameters. This finding provides valuable insights for understanding the mechanical properties of plant roots and providing soil reinforcement theoretical basis.
As the central accumulation area of the Loess Plateau in Shaanxi Province, China, Loess landslides occur frequently, which seriously affect the safety of people's lives and properties. The prediction and early warning of landslides are the hot spots of geological disaster research, and the prediction of the stability of Loess landslides can provide a reference basis for the prevention and management of landslides. This study takes a typical Loess landslide site in Ganquan County, Yan'an City, as the research object. By collecting soil samples from the landslide body for indoor simulation tests and analyzing and testing the changes in the basic physical and mechanical properties of the soil under different plant root densities and different precipitation conditions, the stability of shallow Loess landslides on the Loess Plateau was simulated using Geo-Studio software. The analysis shows that the stability coefficient of the natural root density of Zhangzi slope soil is 0.889, which belongs to the unstable state, and under the condition of 1.5 times root density, its stability coefficient increases to 1.246, which belongs to the stable state, while at 2 times root density, its stability coefficient decreases to 0.973, which belongs to unstable state, and the stability of its root-soil complex is 1.5 times root density > 2.0 times root density > natural root density. Under different soil water content conditions, the stability of the slope shows a trend of decreasing with increasing water content. Under the condition of 10% soil water content, the stability coefficient of the landslide slope is 1.123, which is the basic stability state; under the condition of 20% soil water content, the stability coefficient drops to 0.886, which is the unstable state; under the condition of 30% soil water content, the stability coefficient is 0.724, which indicates that precipitation has a great influence on the stability of Loess landslides.
Shallow slope instability poses a significant ecological threat, often leading to severe environmental degradation. While vegetation, particularly woody plants, is commonly employed in slope stabilization, herbaceous vegetation offers distinct and underexplored advantages. This paper reviews the role of herbaceous plants in enhancing slope stability, analyzing their mechanical and ecological mechanisms. Through an extensive review of the literature, this review challenges the prevailing view that woody vegetation is superior for slope stabilization, finding that herbaceous plants can be equally or more effective under certain conditions. The key findings include the identification of specific root parameters and species that contribute to soil reinforcement and erosion control. The review highlights the need for further research on optimizing plant species selection and management practices to maximize the slope stabilization effects. These insights have practical implications for ecological slope engineering, offering guidance on integrating herbaceous vegetation into sustainable land management strategies.
Under long-term loading, the mechanical properties of geogrids in eco-bag reinforced soil retaining walls (ERSW) gradually weaken due to creep and photo-oxidative aging. In contrast, the continuously growing roots transfer their tensile strength to soil shear strength. However, the reinforcing effect of plant roots within retaining walls is often overlooked in current research and design. This study investigated the reinforcement effect of plant roots and geogrids on ERSW stability through theoretical derivations using the Swedish circle method for roots penetrating potential sliding surface and two-wedge method for shallow roots. The results showed that their synergistic reinforcement effect affords the highest overall stability of ERSW under loading. Additionally, the compensation ability of roots was investigated by vertically loading a scaled ERSW model with palm leaves and designing 16 sets of controlled tests with two geogrid lengths, three geogrid spacings, and four root lengths. The horizontal displacement of the facing, horizontal earth pressure behind the eco-bags, and geogrid tensile strain under various conditions decrease by 5.47%, 3.71%, and 4.17%, respectively, with increases in the unit length of the geogrid, and by 3.625%, 1.411%, and 4.713%, respectively, with increases in the unit length of roots. In the three parameters, the compensation rates of the root for the geogrid length are 0.66, 0.38, and 1.13, respectively. The reduction rates of the three parameters are 34.38%, 45.26%, and 58.62% with the geogrid spacing decreasing from 30 cm to 20 cm under the no-root condition, and the rates change to 56.25%, 21.14%, and 63.22% with a geogrid spacing of 30 cm and the addition of 15 cm long roots, respectively. In the three parameters, the compensation rates of 15 cm length roots for the geogrid spacing are 1.64, 0.47, and 1.08, respectively. Therefore, roots provide a compensatory effect on geogrid strength, enhancing the long-term stability of ERSW.
Background: Root cutting caused by underground coal mining subsidence is among the leading causes of plant damage in western China. Detection of root cutting stress is of great importance in evaluating the degree of plant damage and changes in physiological conditions in underground coal mining disturbance conditions. Methods: The present study assessed the use of chlorophyll fluorescence OJIP transient data to evaluate the disturbance characteristics of root cutting stress on leaf photosynthetic mechanisms in the typical shrub Artemisia ordosica Krasch. Different root cutting ratios (10%, 20%, 30%, 50%, 75%, and 100%) were established on the roots of A. ordosica in the field, and the OJIP transient and JIP parameters of the leaves were measured. Results: The overall OJIP curves and each OJIP step in leaves decreased as the root cutting ratio increased, but the impact was relatively small for root cutting ratios of less than 30%. Through the analysis of JIP parameters and the established energy pipeline model, it was found that the energy capture efficiency and electron transfer efficiency of photosystem II decreased as the root cutting ratio increased. Therefore, we also inferred that the threshold for the plant root cutting ratio at which leaf photosynthetic mechanisms begin to change is 30-50%. Conclusion: These results indicate that OJIP transient analysis can serve as a non-destructive, rapid technique for detecting plant root cutting stress in coal mining subsidence areas, which is of great value for non-destructive monitoring of plant root damage.
Context Plant roots can increase soil shear strength and reinforce soil. However, wetting and drying alternation (WD) could lead to soil structure destruction, soil erosion and slope instability.Aims This study tried to explore the effects of wetting and drying alternation on shear mechanical properties of loess reinforced with root system.Methods Direct shear testing was conducted on alfalfa (Medicago sativa L.) root system-loess composites with three soil bulk densities (1.2 gcm-3, 1.3 gcm-3 and 1.4 gcm-3) under 0, 1, 2 and 3 cycles of wetting and drying alternation (WD0, WD1, WD2 and WD3).Key results The morphological integrity of the root-loess composites was obviously better than the non-rooted loess after WD. Under the three soil bulk densities, negative power-law relationships were observed between the shear strength, cohesion and internal friction angle and the cycles of WD. WD deteriorated the soil shear strength. The most obvious decrease in soil shear strength occurred under WD1, which was 13.00-22.86% for the non-rooted loess and 17.33-25.09% for the root-loess composites. The cohesion was decreased more than the internal friction angle by WD.Conclusions The most obvious damage to the soil was under WD1. The roots inhibited the deterioration effect of WD on the shear property of loess, and the inhibition by the roots decreased with the cycles of WD.Implications The results could provide new insights into the mechanical relationship between plant roots and loess under WD, and provide a scientific basis for the ecological construction in the loess areas. Wetting and drying alternation (WD) on the mechanical properties of root-soil composites is not clear at present, or if roots can inhibit the deterioration of soil under WD. This paper investigated the effect of WD on the shear strength of root-loess composites. WD was found to deteriorate soil shear strength and cohesion, while roots inhibited the deterioration of WD on the shear property of loess. The results provide a scientific basis for ecological construction in loess areas.