Root Tensile Strength Research Articles

Stability Evaluation of Reinforced Slope Soil with Vetiver Grass against Erosion and Landslides Hazards by Using Finite Element Method

This work studied slopes with different geometric situations. The purpose is to select types of soil for embankment construction to stabilise the site by using nearby accessible filling materials. Then, PLAXIS-2D software was used including five (6) phases of sequential calculation such as soil, structure, mesh generation, conditions of flow and construction stage and the use of Vetiver grass for embakment stability reinforcement. Choices were made on soil properties, loading, water table effect, embankment geometry and reinforcement actions of vetiver grass. The method is based on using diverse filling materials and varied slope gradients with different heights. So, the slope analyse involves homogeneous soils, in addition to slope section by various soils strata. Results obtained showed that the increase in soil shear strength is related to the mechanical effects of vetiver roots and make the soil able to resist shear stress due to the presence of roots density within the soil mass and the root tensile strength. It is also noticed that the soil suction effects and roots reinforcement increased the apparent cohesion of the soil, showing an important role played by vetiver grass in stabilising shallow-seated slopes failure with significant effect on slopes stability.

Mechanical properties of Bermuda grass roots towards sandy and clay soil for slope reinforcement

Natural and man-made slope failure has been a phenomenon that has caused many deaths, destruction, and environmental damage. The use of bioengineering technique (grasses) has been widely approached for slope remediation work. However, slope failure still occurs even though it has been protected by a few grasses. Many previous findings have reported on root pull out and root tensile strength for different plant species. However, the type of soil was not taken into account. Therefore, this research was carried out to investigate the function of root mechanical properties in different types of soil. The dry and wet sieve analysis tests were performed to know the classification of the soil. In addition to that, the soil mineralogy test was also conducted to support the soil classification. Root tensile strength tests were carried out on well-grown and poorly-grown Bermuda grass toward sandy and clay soil in dry and wet conditions. The dry condition is considered the condition of Bermuda grass in hot weather, while the wet condition is the condition after the raining season. Bermuda grass was chosen since this type of grass is widely applied for slope stabilization. The site locations were chosen in Temerloh, Maran which consist of clay soil. The other locations chosen were Karak, Gambang, Kuantan, Dengkil, Batang Kali, Ulu Yam, Kuala Pilah, Gombak and Sabak Bernam consist of sandy soil. The results show that the single root of Bermuda grass has higher tensile strength in sandy soil with range values from 0.47 to 185 Mpa compared to clay soil with range values from 0.12 to 159.10 Mpa. In conclusion, the results indicate that soil is one of the factors that influence the growth of bioengineering techniques for slope reinforcement.

Soil moisture and hysteresis affect both magnitude and efficiency of root reinforcement

Plant roots can protect soil against shallow landslides. The mechanics of rooted soil failure under varying soil water content remain poorly understood. The aim of our study was to characterize the impact of soil water content on root mechanical traits and reinforcement to soil. One-year-old Symplocos setchuensis trees were replanted in shear boxes (0.4 × 0.4 × 0.5 m3), which were placed in a canopy gap on Jinyun Mountain, Chongqing, China. After three years of vegetation growth, root mechanical measurements and soil direct shear tests were performed at five levels of volumetric soil water content varying from 14.9 to 44.4 %, by either wetting or drying the soil. For each shear box, we measured soil shear strength, root area ratio, root tensile force, root water content, and root failure mode (slippage versus breakage) during or after the shearing process. Root area ratio and root failure modes were examined for different root diameter classes. With increasing volumetric soil water content, we found a persistent decrease in root tensile strength (ca. 15 %) and an increase in root water content (ca. 11 %), although the dependence on volumetric soil water content was not statistically significant for certain soil water content levels. We found that both additional shear strength of rooted soil and proportion of root failure in breakage increased first and then decreased, with peak values occurring at a soil water content of ca. 22 %. Altered root tensile force (68.0 % contribution to root reinforcement variation) and the change in proportion of root failure modes (breakage or slippage; 8.4 % contribution to root reinforcement variation) jointly contribute to the negative impact of soil water on observed root reinforcement. Soil shear strength was positively correlated with root area ratio and their relationship was linear. At high soil water content (>28 %), the slope of the linear relationship decreased rapidly with increasing soil water content, suggesting that increasing root biomass is not effective for enhancing root reinforcement in very wet soil conditions. Regarding hysteresis, root reinforcement magnitude and efficiency were higher in the drying process than in the wetting process when soil moisture was low. Our results highlight the vital role of soil water features in affecting soil-root mechanical interactions and such effects should be taken into account in future root reinforcement modelling and assessment

Contribution of fine roots mechanical property of Poaceae grasses to soil erosion resistance on the Loess Plateau

Plant roots play a key role in soil erosion process, but less studies are focused on analyze the soil erosion resistance in terms of grassland roots mechanical properties. The objective of this study was to examine the root diameter, root density, root tensile strength and soil shear strength for five typical and widely distributed Poaceae grasses in semi-arid regions, thus determine the contribution of roots of artificial grassland to soil erosion resistance. Results showed that the roots of five grasslands were densely distributed in the surface soils (0–10 cm). Bromus inermis had the strongest roots that characterized by the highest average tensile strength (40.2 MPa) The shear strength significantly increased as the vertical stress increased from 50 kPa to 300 kPa, but the degree varied with grassland types. Shear strength was also linearly correlated with root density when vertical pressure reached 300 kPa (p < 0.01, R2 = 0.47), indicating that high root density might help resist extreme external stress. Moreover, Bromus inermis showed a high soil cohesion of 122.7 kPa (next to the highest value of 128.71 kPa in Panicum virgatum). Overall, Bromus inermis showed the highest soil erosion resistance among these five grasslands, could be a good candidate in Poaceae artificial grasslands to improve soil shear strength for topsoil conservation. These findings have potential implications for understanding the contribution of Poaceae grasses’ roots on the topsoil reinforcement, and provide a theoretical basis for artificial grassland establishment on soil erosion resistance on the Loess Plateau.

Passive earth pressure of vegetation rooted soils based on limit analysis and quasi-static approach

Although it has been recognized that vegetation roots have a positive effect on the stability of geotechnical structures, few quantitative studies have been performed on the effects of vegetation roots on earth pressures. In this paper, based on the upper bound limit analysis theory and quasi-static method, a new method for calculating the seismic passive earth pressure of vegetation rooted soils is proposed, which considers both the hydrological and mechanical effects of vegetation roots on the passive earth pressure. The proposed method is validated by some existing solutions. The effects of root parameters of shrubs (root transpiration rate, root tensile strength, and root depth), angle of the soil slope surface with the horizontal, and wall interface friction angle on the seismic passive earth pressure coefficient are also investigated. The results show that the passive earth pressure coefficient increases with the increase of root transpiration rate, root tensile strength, root depth, angle of the soil slope surface with the horizontal, and wall interface friction angle. Compared with the mechanical effect, the hydrological effect of vegetation roots on the passive earth pressure coefficient is more obvious. The effects of root parameters on the passive earth pressure ranked in descending order of sensitivity are root transpiration rate, root tensile strength, and root depth. In addition, the effect of vegetation roots on the passive earth pressure becomes more significant with the increase of internal friction angle. The proposed method can provide a reference for the local reinforcement of multi-stage slopes with vegetation.

Root Distribution and Root Cohesion of Two Herbaceous Plants in the Loess Plateau of China

In order to understand the root morphology distribution and mechanical properties of typical herbaceous plants, and to evaluate the ability of soil reinforcement by the plant roots, root morphology investigation, single root tensile test in laboratory and root cohesion evaluation by the Wu-Waldron model were carried out on two local representative herbaceous plants, Kochia scoparia (L.) Schrad and Artemisia sacrorum Ledeb. in the Loess Plateau of China. The results showed that the root morphological indexes (root number, single root diameter, root cross-sectional area, root surface area, root volume and root area ratio) of the two herbaceous plants decreased with the increase in soil depth, and the ratio of root to shallow soil layer was the highest in the 0–10 cm soil layer. The efficiency of root reinforcement could be higher in the shallow soil layer less than 10 cm. A positive correlation was observed between the root tensile force and root diameter in power function or exponential function, and a negative correlation was observed between the root tensile strength and root diameter in power function. The root cohesion of Kochia scoparia (2.73 kPa, or 0.92 kPa–1.37 kPa) was greater than that of Artemisia sacrorum (1.60 kPa, or 0.54 kPa–0.8 kPa), which could be used as the preferred herbaceous plant species for soil erosion control. The results could provide a scientific basis for selecting dominant species in the fields of ecological slope protection and soil and water conservation plant engineering in the loess area.

Shearing behaviour of vegetated soils with growing and decaying roots

Plant roots affect the soil shear strength, but the temporal dynamics of roots such as growth and decay due to different mortality means have rarely been considered. This study investigates the effects of root growth and decay on the changes in root biomechanical properties and the shearing behaviour of vegetated soils. Columns of compacted soils were grown with a grass species, Cynodon dactylon. The grass was grown for 6 months, followed by burning or herbicide applications to introduce root decay. The top part of each column was used for direct shear tests, whilst the roots collected from the bottom part were used for the measurements of root tensile and chemical properties. The vegetated soils displayed greater shear strength and larger dilatancy, which were attributable to the growth-induced increase in the root cellulose content, and thus the root tensile strength and modulus. Root decay, upon burning or herbicide use, caused significant declines in the root tensile properties, which translated to the reductions in soil dilatancy and soil shear strength lower than those of the fallow soil. Herbicide use introduced a much faster and significant loss of root reinforcement than burning because of the more severe decay and loss of root biomechanical properties.

Whole plant traits of coastal dune vegetation and implications for interactions with dune dynamics

AbstractCoastal dunes are important protective features against sea level rise and coastal storms. Interactions between dune plant aboveground structures and sediment trapping that allow for dune building and maintenance are well established. More recently, studies documenting belowground biomass for promoting erosion resistance in dominant dune species have been conducted, yet a knowledge gap remains regarding species‐specific characterization of whole plants, specifically with respect to roots, rhizomes, and belowground stems. Our objective was to quantify above‐ and belowground traits of four dominant dune grasses to document the potential for species‐specific effects on dune growth, maintenance, and erosion resistance. We examined above‐ and belowground traits among four prominent dune grasses of the Atlantic and Gulf Coasts of North America: Ammophila breviligulata, Panicum amarum, Spartina patens, and Uniola paniculata. Whole plant samples of each species were collected from the foredune at the US Army Engineer Research and Development Center's Field Research Facility in Duck, North Carolina, USA, and quantified for several above‐ and belowground traits (e.g., stem height, rhizome number and length, root surface area by diameter class, root tensile strength, and mycorrhizal percent infection). Belowground factors known to impact important dune processes, such as rhizome length, mycorrhizal percent infection, and root traits, differed substantially among species. When visualized in multivariate space, all species significantly differed in suites of above‐ and belowground traits. When considering belowground only, Ammophila and Spartina were similar, despite differences in biomass allocation. Species separated along axes related to mycorrhizal association, biomass allocation, and root construction. The four co‐occurring dune grass species were dissimilar in suites of plant traits. Belowground trait differences were driven by those describing root construction, biomass allocation, and mycorrhizal infection. Dissimilarity in above‐ and belowground suites of traits may demonstrate different approaches for surviving the dune environment. Incorporating belowground traits into modeling will enhance predictions of dune response to climate change through interactions between vegetation and dune dynamics that facilitate coastal resistance and resilience.

The role of roots traits of climax community species to shear strength in the Loess Hilly Region, China

the climax community species, especially their roots, have been found very helpful to increase slope stability and reinforce the soil on the Loess Plateau of China. However, the effect of root-soil shear resistance is poorly understood on plant roots mechanical traits and chemical compositions on the Loess Plateau. Thus, this study evaluated the correlations among root mechanical properties, root chemical compositions and root parameters traits, and effects of root traits on soil shear resistance. In this study, the roots of climax community species (Bothriochloa ischaemum (L.) Keng. (B. ischaemum), Carex tristachya Thunb. (C. tristachya), Artemisia gmelinii Web. (A. gmelinii), and Artemisia giraldii Pamp. (A. giraldii)) were subjected to be a series of laboratory tests of biochemical, biomechanical and direct shear strength with different soil layers. The findings of the study revealed that (1) Over 65% of the total measured root parameter traits were distributed in the upper 20 cm of the soil, and they decreased with increasing soil layer. There was the highest Tr by B. ischaemum as a failure (386.5 MPa), followed by C. tristachya (30.97 MPa), A. gmelinii (24.67 MPa), A. giraldii (8.95 MPa). The tensile properties (Tr (root tensile strength) and Tf (tensile force)) were significantly correlated with root diameter. The contents of root lignin were significantly correlated with root diameter while cellulose and hemicellulose showed no obvious trend with root diameter. Tr was significantly positive correlation from cellulose and lignin. (2) The presence of plant roots enhanced the soil cohesion by 13.34～115.05%. The soil cohesion is negatively correlated with the soil layers whether the root-soil composites or the soil without roots. (3) The root-soil composite cohesion can be explained by RSAD (root surface area density), followed by RLD (root length density) and D (root diameter), and the internal friction angle can be explained by Tr, followed by cellulose and lignin. These conclusions were provided theoretical guidance and data accumulation for the mechanical traits, soil reinforcement and slope stability of climax community species roots in the Loess Plateau of China.

Root Functional Traits and Water Erosion-Reducing Potential of Two Indigenous C4 Grass Species for Erosion Control of Mudstone Badlands in Taiwan

In southern Taiwan, mudstone badland accounts for over 1000 km2 of the upstream region of watersheds. Rainstorms often induce interrill and surface erosion on the mudstone slopes. Furthermore, the large quantity of soils detached by surface runoff result in severe sedimentation in reservoirs. Thus, soil erosion control of mudstone badlands represents one of the most pressing problems in reservoir watershed management. Cynodon dactylon (L.) Pers. (Bermuda grass) and Eremochloa ophiuroides (Munro) Hack. (Centipedegrass) are two native predominant C4 grass species appearing on mudstone badlands. They play a key role in erosion control and the revegetation of mudstone slopes. Nevertheless, their root functional traits and water erosion-reducing potential have not been investigated. In this study, the root traits were examined. Vertical pullout and tensile tests were conducted to measure root pullout resistance and root tensile strength. Hydraulic flume tests were also performed to evaluate their water erosion-reducing potentials. The results demonstrated that the root systems of C. dactylon and E. ophiuroides grasses all belonged to the fibrous M-type. C. dactylon had remarkably better root traits compared to those of E. ophiuroides. Furthermore, the root tensile resistance of C. dactylon was remarkably higher than that of E. ophiuroides. In addition, hydraulic flume tests showed that C. dactylon has remarkably smaller soil detachment rates than that of E. ophiuroides. Altogether, our data clearly show that C. dactylon has better root traits, root pullout resistance, root tensile resistance and water erosion-reducing potential than E. ophiuroides and is more suitable for erosion control of mudstone badland. Further studies on large-scale implementation techniques of these species for efficient vegetation restoration are needed.

Root Traits and Erosion Resistance of Three Endemic Grasses for Estuarine Sand Drift Control

In southern Taiwan, rivers sporadically cease to flow and dry up in winter. The exposed dry riverbeds are very vulnerable to wind erosion. The strong northeast monsoon often induces serious estuarine sand drift and fugitive dust, which cause damages to agricultural crops, human health and infrastructures. Giant reed (Arundo formosana), common reed (Phragmite australis) and the wild sugarcane (Saccharum spontaneum) are pioneer grass species in estuary areas. They have great potential to reduce wind erosion and control windblown dust on agricultural lands. Nevertheless, their root traits, biomechanical characteristics and wind erosion resistance have not been investigated. In this research, the root traits were investigated utilizing the hand digging technique and the WinRHIZOPro System. Root pullout resistance and root tensile strength were estimated using vertical pullout and root tensile tests. Wind tunnel tests were executed to evaluate the wind erosion resistance using six-month-old plants. The results demonstrated that the growth performance and root functional traits of S. spontaneum are superior to those of A. formosana and P. australis. Additionally, the root anchorage ability and root tensile strength of S. spontaneum plants are notably greater than those of A. formosana and P. australis plants. Furthermore, the results of the wind tunnel tests showed that the wind erosion resistance of A. formosana is remarkably higher than those of S. spontaneum and P. australis. This study demonstrates that A. formosana and S. spontaneum are superior to P. australis, considering root traits, root anchorage ability, root tensile strength and wind erosion resistance. Taken together, our results suggest that S. spontaneum and P. australis are favorable for riverbed planting, while A.formosana is applicable for riverbank planting in estuary areas. These results, together with data on the acclimation of estuarine grasses in waterlogged soils and brackish waters, provide vital information for designing planting strategies of estuary grasses for the ecological engineering of estuarine sand drift control.

Vetiver root cohesion at different growth sites in Bogor, Indonesia

Abstract. Fata YA, Hendrayanto, Erizal, Tarigan SD, Wibowo C. 2022. Vetiver root cohesion at different growth sites in Bogor, Indonesia. Biodiversitas 23: 1683-1692.The plant root system, including the root system of vetiver grass, plays a critical role in enhancing soil cohesion, shear strength, and vegetated slope stability. Numerous studies on mechanical reinforcement of vetiver grass-roots have been conducted, with the majority of studies focusing on ground-planted vetiver with good maintainedor naturally grown vetiver, while mechanical reinforcement of vetiver grass roots planted in landslide areas at various growth sites with less maintenance is still uncommon.The purpose of this study was to examine the vetiver grass-roots cohesion that grew in the different growth sites that had been affected by landslides. Vetiver grass root samples were collected in January 2021, at the age of 8 months. Vetiver grass roots were collected from vetiver plants growing in the affected landslide areas of (a) bareland, (b) shrubland, and (c) bushland. The root tensile strength of root samples was determined using a Universal Testing Machine (UTM) with a capacity of 3 tons, and the measurement accuracy of the load cell was 1/10000. The test was conducted in accordance with ASTM D638-14 guidelines. Three repetitions were performed on roots representing the root length class of 10 cm. The results indicated that the growth sites influenced the morphological and architectural properties of the vetiver grass-roots. The vetiver grass that grew in bushland exhibited a higher root density than bareland or shrubland. The roots were denser and had a greater range of lengths. Short roots less than 10 cm in length were the most prevalent, and the majority of them were found near the soil surface. The greater the soil depth, the less the quantity of roots.The tensile strength (TR) tends to get smaller with longer roots, and vetiver grass rootsgrew in bareland have the highestTR(15-59 MPa) relative to their growth in bushland (9-37 MPa) and shrubland (16-29 MPa). The ratio of root fiber area to root growth area (RAR) also tends to get smaller with deeper roots. Likewise, is the tensile strength increasing caused by roots (tR) and root cohesion (CR) which are a function of RAR. The CR??of vetiver roots growing in bushland (0.015-0.275 kPa) were relatively higher than those growing in bareland (0.02-0.168 kPa) and shrubland (0.002-0.028 kPa) in the same root length class, at the same depth.

Influence of Super Absorbent Polymer on Root Characteristics and Anchorage of Amorpha fruticosa on Rocky Slope

Super absorbent polymer (SAP), known as a water retention agent, has a high capacity for water absorption, which can help enhance the soil structure. This paper studied the effects of SAP dosages on the root characteristics and anchorage of Amorpha fruticosa on rock slopes. The internal relationship between root growth effect and soil was discussed, and a specific reference was provided for the rational application of SAP on slopes. Using the pull-out and tensile resistance tests, we systematically studied the changes of soil properties, root distribution, root tensile strength, and root anchorage under six different SAP dosages. The results indicated that: (1) With the increase in SAP dosage, the natural soil water content and water content after 24 h of watering increased significantly, whereas the contents of TN, TP, and TK decreased dramatically. (2) With the increase in SAP dosage, the amount and length of first-order and secondary lateral roots decreased significantly, and there was no significant difference in diameter. The amount of downslope first-order and unembedded secondary lateral roots is greater than upslope. The amount of upslope embedded secondary lateral roots is greater than in downslope. (3) Tensile strength: embedded secondary root &gt; non-embedded secondary root &gt; first-order lateral root; upslope root &gt; downslope root. (4) With the increase in SAP dosage, the plant anchorage drops noticeably. This study concluded that 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.

Influence of growth media on the biomechanical properties of the fibrous roots of two contrasting vetiver grass species

Different artificial (non-soil) growth media have been used to cultivate plants for measuring their root biomechanical properties and estimating root reinforcement to soil. However, the effect of growth media on root tensile strength and Young's modulus has rarely been investigated. We studied the effects of three contrasting growth media (hydroponic, rice husk ash, and lateritic soil) on the biomechanical properties of the fibrous roots of two contrasting vetiver species (Chrysopogon nemoralis and Chrysopogon zizanioides). After growing in the different media for 7 weeks, the tensile strength and Young's modulus of both species were measured via uniaxial tensile tests. Roots grown in the ash were the strongest (10.21 ± 0.8 and 9.46 ± 1.1 MPa for C. nemoralis and C. zizanioides, respectively) and stiffest (275.98 ± 20.6 and 172.74 ± 26.3 MPa, respectively), followed by those grown in the soil (9.1 ± 0.9 and 6.18 ± 0.5 MPa for strength; 182.3 ± 16.9 and 81.88 ± 5.3 MPa for modulus) and then those grown hydroponically (5.99 ± 0.5 and 5.87 ± 0.5 MPa for strength; 107.06 ± 10.8 and 82.13 ± 7.8 MPa for modulus). Irrespective of the growth treatments, root strength and modulus were correlated with root diameter by a negative power law model (R2 ranged between 0.11 and 0.68; p-value <0.05). The shape and scale factors of the strength–diameter and modulus–diameter correlations were different among the growth treatments. We caution the use of the tensile properties of roots grown in artificial media and laboratory conditions for predicting root reinforcement to natural soil on slopes.

Root tensile strength of terrace hedgerow plants in the karst trough valleys of SW China: Relation with root morphology and fiber content

Root tensile strength is commonly affected by root morphology and fiber content, which combinedly affect the effectiveness of terrace hedgerow on controlling soil erosion in sloping farmland. However, the relationships between these root characteristics are still elusive. This study aimed to compare the root tensile strength, root morphologies, and root fiber contents, and quantify their differences among different plant species. Complete root systems of three terrace hedgerow plant species, i.e., O. bodinieri, V. villosa, and D. lablab L. were sampled for detecting root morphologies and fiber contents at different slope positions on a representative hillslope in karst trough valley. Single root specimens were collected to measure root tensile properties for these three plant species. Results showed that most root morphological parameters were the highest in O. bodinieri, followed by D. lablab L. Three plant species presented the same dominant diameter class as < 1.0 mm, and root volumes as < 1.50 cm3. Cellulose with contents closing to 50% was the main fiber type, and increased significantly linearly with the increasing root diameter in both O. bodinieri and V. villosa. The highest tensile strength and Young's modulus were found in D. lablab L., while the best ultimate tensile force and ultimate elongation were displayed in O. bodinieri. Root diameter showed negative power relationships with tensile strength and Young's modulus, a positive power relationship with ultimate tensile force, and a positive linear relationship with ultimate elongation. Our results will deepen the understanding of the terrace hedgerow functions for controlling soil erosion worldwide.

Soil reinforcement potential of cultivated cardoon (Cynara cardunculus L.): First data of root tensile strength and density

Plant roots play a key role in erosion control by increasing soil resistance to shear stress. Root tensile strength data have been published for natural systems, less is available on cultivated crops. Cardoon (Cynara cardunculus L.) is raising a growing interest as multipurpose crop for marginal lands. In this work we measured cardoon roots tensile strength, topsoil root area ratio, root length density and estimated soil reinforcement potential. Root samples were collected in late spring and at the beginning of fall and were subjected to tensile strength tests in laboratory. Tensile strength (σmax) ranged between 1.57 and 254.78 MPa, decreasing with by a power-law relationship with high determination coefficients (>0.75), with differences between summer and fall roots. We measured root length density (RLD) and root area ratio (RAR) in surface soil (top 5 cm) at different positions in the row and inter-row. RAR was used to calculate soil reinforcement potential (Cr = 1.2 * ∑σmax (kPa) * RAR (cm2 cm−2)). Average RLD was quite high 8.68 cm cm−3 with a mean value of 9.183 cm cm−3 on the row and 8.179 cm cm−3 on the inter-row, though differences between row and inter-row, were not significant. RAR was on average 0.017 cm2 cm−2. Average soil reinforcement was 194 kPa with values ranging from 67.34 kPa to 265 kPa. This is not to be interpreted as absolute reinforcement values, due to drawbacks of the simple model used, but they are useful for comparisons within the framework of crop choices. Cardoon produces a dense mat of fine roots that can contribute to increase soil cohesion, thus providing important ecosystem services.

喀斯特坡地2种地埂篱根-土复合体抗剪和抗冲性能综合评价

PDF HTML阅读 XML下载 导出引用 引用提醒 喀斯特坡地2种地埂篱根-土复合体抗剪和抗冲性能综合评价 DOI: 10.5846/stxb202010292774 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点研发计划项目（2016YFC0502303）；中央高校基本业务费专项资金项目（XDJK2018B044）；岩溶环境重庆市重点实验室开放课题项目（Cqk201803）；西南大学资源环境学院"光炯"项目（202008） Comprehensive evaluation of shear strength and anti-scourability of root-soil complex of two grass hedgerows in karst slope land Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:分析喀斯特地区不同地埂篱根系的形态和力学特性，量化其根-土复合体抗剪和抗冲性能的强弱，探寻该地区地埂篱根系固土抗蚀性能的评价因子，为喀斯特坡地水土流失治理中植被恢复措施的科学应用提供参考。选取重庆酉阳龙潭槽谷为研究区，分上、中、下坡分别布设拉巴豆和光叶苕子2种地埂篱，采用根系扫描仪和电子万能试验机测定其根系形态和力学参数，应变控制式直剪仪测定复合体抗剪强度，原状土冲刷水槽法测定复合体抗冲指数。结果表明：（1）抗剪复合体中，拉巴豆平均根长密度和根表面积密度分别高出光叶苕子59.32%和16.86%；抗冲复合体中，拉巴豆平均根长密度、根表面积密度和根体积密度较之光叶苕子高出30.48%、57.78%、92.98%；拉巴豆根系极限抗拉力和抗拉强度均显著高于光叶苕子。（2）2种地埂篱根系均能增强土壤的抗剪和抗冲性能，其中拉巴豆和光叶苕子复合体粘聚力较之对照土体分别增强了113.06%-124.37%和51.56%-87.12%，抗冲指数最高达到对照土体的2.81倍和2.45倍。（3）不同坡位，下坡2种植物的根长密度显著高于上、中坡；拉巴豆根系抗拉特性在下坡表现最优，光叶苕子在上坡表现更好；拉巴豆复合体粘聚力和抗冲指数均表现为下坡 > 中坡 > 上坡。（4）主成分分析显示，2种地埂篱下坡的根-土复合体抗剪和抗冲性能综合评分最高，根表面积密度、根系抗拉强度、根系木质素含量对根-土复合体抗剪和抗冲性能的贡献度最高，可作为表征复合体抗剪和抗冲性能的重要参数。 Abstract:Grass hedgerows are beneficial for preventing soil erosion on karst slopes, and their roots play a vital role. This paper aimed to analyze the morphological and mechanical properties of the root system of different hedgerows, to quantify the shear strength and anti-scourability of the root-soil complex, to explore the evaluation factors of the soil erosion resistance of the hedgerows in karst area and to provide reference for the scientific application of plant restoration measures in soil erosion control on karst slopes. Dolichos lablab L. and Vicia villosa hedgerows were planted on the upper, middle and down slopes of karst bedding slope in Youyang, Chongqing. The physical properties, root morphology and fiber content, tensile properties, shear strength index and anti-scouring index of the root-soil complex were measured. (1) The mean root length density and root surface area density of Dolichos lablab L. were 59.32% and 16.86% higher than those of Vicia villosa in the shear complex. The mean root length density, root surface area density and root volume density of Dolichos lablab L. were 30.48%, 57.78% and 92.98% higher than those of Vicia villosa in the souring complex. The ultimate tensile force and tensile strength of Dolichos lablab L. root were significantly higher than those of the Vicia villosa. (2) The roots of the two kinds of grass hedgerows could enhance the shear strength and anti-scourability of soil. Compared with the control check, the cohesion of Dolichos lablab L. and Vicia villosa complex was 113.06%-124.37% and 51.56%-87.12%, respectively, and the anti-scouring index was 2.81 and 2.45 times higher than the control check. (3) In different slope positions, the root length density was significantly higher in the lower slope than in the upper and middle slope. The tensile strength of Dolichos lablab L. root was the best in the downslope and the Vicia villosa was the best in the upslope. The cohesion and anti-scouring index of Dolichos lablab L. complex were both downslope > middle slope > upslope. (4) The principal component analysis showed that the comprehensive scores of the shear strength and anti-scourability of the root-soil complex of the two kinds of grass hedgerows were the highest in the down slope. Root surface area density, root tensile strength and root lignin content had the highest contribution to the shear strength and anti-scourability performance of the root-soil complex, which could be used as important parameters to characterize the shear strength and anti-scourability of the root-soil complex. When grass hedgerow measures are implemented in karst areas, planting on the low slope should be carried out in order to give full play to the soil and water conservation effect. 参考文献 相似文献 引证文献

三江并流区水电站消落带适生草本植物根系固土能力

PDF HTML阅读 XML下载 导出引用 引用提醒 三江并流区水电站消落带适生草本植物根系固土能力 DOI: 10.5846/stxb202104201025 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: S157.2 基金项目: 国家自然科学基金项目（42167046）；云南澜沧江黄登水电站库周消落带治理试验工程科研合作项目（H20200133）；云南省教育厅科学研究基金项目（2020Y165） Soil-fixing capacity of suitable herbaceous plant roots in the water-level-fluctuating zone of hydropower station in the Three Parallel Rivers Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:三江并流区生态脆弱敏感，水电站库周消落带土壤侵蚀严重，为研究消落带适生草本植物的根系固土效应，并为重建植被、控制土壤侵蚀提供依据，以生长期为18个月的风车草(Cyperus alternifolius L.)、美人蕉(Canna indica L.)、花叶芦竹(Arundo donax var. versicolor)和菖蒲(Acorus calamus L.)4种草本植物为研究对象，采用自制的原位剪切仪测定根土复合体和素土的抗剪强度；用根系拉力试验机测定根系的抗拉强度，用Wu和Waldron模型(WWM)对根系提高土体抗剪强度进行预测，并评价模型的可靠性。结果表明：①4种适生草本植物根系都能增强土体的抗剪强度，风车草、美人蕉、花叶芦竹和菖蒲根系使土体的抗剪强度分别提高了403.89%、248.32%、388.50%和200.71%；②4种草本植物根系的抗拉强度均与直径呈现负幂函数关系；③根系抗拉强度较大、破坏面上根面积比较高和根系直径(D)<1 mm细根较多的草本植物，固土效应更加显著；④4种草本植物根系对土体强度增量的WWM模型计算值是实测值的9.37-43.85倍，该模型对高含水率土壤中草本植物根系的预测精度较低。风车草、美人蕉、花叶芦竹和菖蒲的根系均有较强的固土能力，尤其是风车草和花叶芦竹，是三江并流区黄登水库消落带植被重建和固土抗蚀的优选物种。 Abstract:The Three Parallel Rivers area is located in the northwest of Yunnan Province and is the core area of an important ecological barrier in Southwest China. The area has serious soil erosion, but is rich in hydropower resources, so a large number of hydropower stations have been planned and built. With the operation of the power station, the long-term and repeated changes of the reservoir's water level have made it difficult for many native plants to survive, and a large-scale water level fluctuation zone has been formed around the reservoir. The erosion of the soil in the water-level fluctuating zone is intensified under the effects of rainfall and changes in water level of the reservoir. Therefore, studying the mechanism of soil consolidation by herbaceous plant roots in the reservoir water level fluctuating zone and selecting suitable plants with strong soil-fixing ability is of great significance for restoring vegetation in the water level fluctuating zone of the reservoir, controlling soil erosion, and improving the stability of the reservoir bank. In this study, four herbaceous plants including Cyperus alternifolius L., Canna indica L., Arundo donax var. versicolor, and Acorus calamus L. with a growth period of 18 months were taken as research objects. The self-made in-situ shearing instrument was used to measure the shear strength of the root-soil complexes and the rootless soil; the root tensile testing machine was used to measure the tensile strength of the roots. The Wu and Waldron model (WWM) was used to predict the increment in the shear strength of the soil by the root system and to evaluate the reliability of the model. The results showed that:① the roots of the four suitable herbaceous plants could increase the shear strength of the soil. Compared with the rootless soil, the shear strength of root-soil complexes with roots of Cyperus alternifolius L., Canna indica L., Arundo donax var. versicolor, and Acorus calamus L. were increased by 403.89%, 248.32%, 388.50% and 200.71%, respectively; ② The tensile strength of the roots of the four herbaceous plants all showed a negative power function relationship with the diameter; ③ Herbs with higher root tensile strength, higher root area ratio on the damaged surface, and more fine roots with D<1 mm, the soil-fixing effect were more significant; ④ The calculated value of the WWM model for the 4 herbaceous plant roots to increase the soil shear strength was 9.37-43.85 times of the measured value, so the model had a low prediction accuracy for the herbaceous plant roots. In conclusion, the root systems of Cyperus alternifolius L., Canna indica L., Arundo donax var. versicolor, and Acorus calamus L. all had strong soil-fixing ability, especially the root systems of Cyperus alternifolius L. and Arundo donax var. versicolor, which were the preferred species for vegetation reconstruction and soil consolidation in Huangdeng Reservoir hydro-fluctuating zone in the Three Parallel Rivers area. 参考文献 相似文献 引证文献

Morphological traits and root anchorage ability of native pioneer tree species for reforestation of mudstone badlands

ABSTRACT Mudstone badlands occupy a large area in southwestern Taiwan. Mudstone soils with poor cementation property are particularly vulnerable to water erosion and landslides during rainy seasons. Broussonetia papyrifera, Hibiscus taiwanensis and Macaranga tanarius are major pioneer tree species occurring on mudstone badlands. Therefore, these species are beneficial for slope stabilization and forest restoration to control erosion and landslide. Nevertheless, information on their morphological traits and root biomechanical properties are lacking. In this research, root morphological traits of these species were inspected utilizing WinRHIZOPro Image Analysis System. Root anchorage ability and root tensile strength of 1-year-old B. papyrifera, H. taiwanensis and M. tanarius saplings were evaluated using uprooting testing and root tensile testing. The results show, compared to H. taiwanensis, B. papyrifera and M. tanarius plants had markedly greater root traits. Moreover, the root anchorage abilities of M. tanarius and B. papyrifer plants were notably higher than that of H. taiwanensis. In addition, root tensile strength of M. tanarius plants was markedly higher than those of B. papyrifera and H. taiwanensis plants. The results clearly demonstrate that M. tanarius outperforms B. papyrifera and H. taiwanensis, in these traits. Taken together, the priority for selecting these species for reforestation of mudstone badlands follows as: M. tanarius > B. papyrifera > H. taiwanensis. These results, together with the information on ecological succession following erosion and landslide, allow us to develop the reforestation plan and management strategy of mudstone badlands.

Biomechanical properties of the growing and decaying roots of Cynodon dactylon

Root growth and decay may affect root reinforcement to soil erosion and stability. We measured the effects of growth and decay on the tensile strength of Cynodon dactylon roots considering different causes of mortality common to agricultural land conversion (i.e. burning and herbicide application). We applied three treatments to C. dactylon grass: (i) growth duration (60, 120 and 180 days), (ii) decay duration after burning (30, 60, 120, 180 and 360 days) and (iii) decay duration after herbicide application (15, 30 and 60 days). The diameter, tensile strength and cellulose and lignin contents of root samples (n = 303) in different treatments were measured. Tensile strength–diameter relations followed a negative power law regardless of treatment (R2 > 0.6). The increase in median tensile strength values due to grass growth was consistent with the increase in cellulose and lignin contents. Root decay by herbicide application caused significantly greater and faster reduction in tensile strength than burning treatment because of the faster reduction of cellulose and lignin contents. Root decay due to different causes of plant mortality can increase susceptibility to erosion and slope instability during the conversion of agricultural land. Measures on slope safety and erosion are vital when using herbicides for weed clearance in farmlands due to the faster deterioration of root chemical composition and root tensile strength (compared with burning).