Abundant herbaceous and shrub roots play an important role in preventing water and soil erosion and increasing shallow slope stability. In order to make a quantitative analysis on the contribution of root system to sl...Abundant herbaceous and shrub roots play an important role in preventing water and soil erosion and increasing shallow slope stability. In order to make a quantitative analysis on the contribution of root system to slope stability under dif- ferent slope gradient, an unconsolidated and undrained triaxial compression test was conducted to measure the shear strengths of soil and root-soil composite in the two slopes in eastern Qinghai Province. In addition, under the protection of plant roots, the effect of gradient on stability of soil slope was investigated by limit equilibrium method. The results showed that the stability coefficient of soil slope planted with two kinds of brush was decreased with the increase in slope gradient, and the sta- bility coefficient increment of soil slope containing Atriplex canescens roots was higher than that containing Caragana korshinskii roots. When the slope gradient ranged from 25° to 50°, the stability coefficient of soil slope planted with Atriplex canescens or Caragana korshinskii ranged from 0.80 to 1.38. However, when the slope gradient exceeded 55°, the increment of stability coefficient of soil slope became small.展开更多
To investigate the influence of root system architectural properties of three indigenous （cold- adapted） shrubs on the hillslope stability of loess deposits in the Xining Basin, northeast part of Qinghai-Tibet Plate...To investigate the influence of root system architectural properties of three indigenous （cold- adapted） shrubs on the hillslope stability of loess deposits in the Xining Basin, northeast part of Qinghai-Tibet Plateau （QTP）, indoor direct shear tests have been conducted on the remolded rooted soil of three shrubs. Test results show that root system architectural indices （root area ratio （RAR）, root length density （RLD） and root density （RD）） of the shrubs decline with depth and the relationship between RAR, RD and depth is exponential, while a power relationship describes the relationship between RLD and depth. The cohesion force of remolded rooted soil for the shrubs initially increases with depth, but it then demonstrates a slightly decreasing trend, which can be described with a power relationship. Power relationships also describe relationships between cohesion force and RAR, RLD and RD for the shrubs. As the growth period increases from lO to 17 months, the incremental increase in RAR is 48.32% ~ 21o.25% for Caragana korshinskii Kom and 0.56% ~ 166.85% for ZygophyUum xanthoxylon （Bunge） Maxim. This proportional increase is notably larger than that for RLD and RD. The increment in RAR is marginally greater for C. korshinskff than it is for Z. xanthoxylon. Correspondingly, the cohesion force incremental rates of remolded rooted soil for C. korshinskii and Z. xanthoxylon are 12.41% ~ 25.22% and 3.45% ~ 17.33% respectively. Meanwhile, as root content increases, the contribution by roots to cohesion force increases markedly until a threshold condition is reached.展开更多
Deformation modulus is the important parameter in stability analysis of tunnels, dams and mining struc- tures. In this paper, two predictive models including Mamdani fuzzy system （MFS） and multivariable regression a...Deformation modulus is the important parameter in stability analysis of tunnels, dams and mining struc- tures. In this paper, two predictive models including Mamdani fuzzy system （MFS） and multivariable regression analysis （MVRA） were developed to predict deformation modulus based on data obtained from dilatometer tests carried out in Bakhtiary dam site and additional data collected from longwall coal mines. Models inputs were considered to be rock quality designation, overburden height, weathering, unconfined compressive strength, bedding inclination to core axis, joint roughness coefficient and fill thickness. To control the models performance, calculating indices such as root mean square error （RMSE）, variance account for （VAF） and determination coefficient （R^2） were used. The MFS results show the significant prediction accuracy along with high performance compared to MVRA results. Finally, the sensitivity analysis of MFS results shows that the most and the least effective parameters on deformation modulus are weatherin~ and overburden height, respectively.展开更多
Traditional vegetation techniques for the control of concentrated flow erosion are widely recognized, whereas only a few studies have experimentally investigated the impacts of belowground roots on the erodibility of ...Traditional vegetation techniques for the control of concentrated flow erosion are widely recognized, whereas only a few studies have experimentally investigated the impacts of belowground roots on the erodibility of topsoils in semi-arid areas. To quantify the effects of root architectures on soil erodibility and its relevant structural properties, simulated flow experiments were conducted at six-week intervals from 18 July to 20 October in 2012 in the hilly Loess Plateau. Five treatments were: 1) bare(control), 2) purple alfalfa(Medicago sativa), representing tap roots(T), 3) switchgrass(Panicum virgatum), representing fibrous roots(F), 4) purple alfalfa and switchgrass, representing both tap and fibrous roots(T + F), and 5) natural recovery(N). For each treatment, soil structural properties and root characteristics were measured at an interval of six weeks. Soil anti-scouribility was calculated. Results showed that grass planting slightly reduced soil bulk density, but increased soil aggregate content by 19.1%, 10.6%, 28.5%, and 41.2% in the treatments T, F, T + F, and N, respectively. Soil shear strength(cohesion and angle of internal friction(φ)) significantly increased after the grass was planted. As roots grew, soil cohesion increased by 115.2%–135.5%, while soil disintegration rate decreased by 39.0%–58.1% in the 21 th week compared with the recorded value in the 9th week. Meanwhile, root density and root surface area density increased by 64.0%–104.7% and 75.9%–157.1%, respectively. No significant differences in soil anti-scouribility were observed between the treatments of T and F or of T + F and N, but the treatments of T + F and N performed more effectively than T or F treatment alone in retarding concentrated flow. Soil aggregation and root surface-area density explained the observed soil anti-scouribility during concentrated flow well for the different treatments. This result proved that the restoration of natural vegetation might be the most appropriate strategy in soil reinforcement in the hilly Loess Plateau.展开更多
Coastal erosion is currently a major problem along the southern coast of Chongming Island, Shanghai. To enhance the erosion protection ability of coastal shelterbelts, two woody tree species, Taxodium ascendens and Sa...Coastal erosion is currently a major problem along the southern coast of Chongming Island, Shanghai. To enhance the erosion protection ability of coastal shelterbelts, two woody tree species, Taxodium ascendens and Salix babylonica, were planted separately into Phragmites australis ＋ Scirpus mariqueter communities in 2006. Two years later, we investigated whether either of these experiments reduced erosion and increased stability in the native herbaceous plant community. We also examined soil stability and root length density under T. aseendens added, S. babylonica added and native herbaceous vegetation conditions along an intertidal gradient from the soil surface to a depth of 40 cm in each experiment, thus to determine the capacity of T. ascendens and S. babylonica to contribute to shoreline stabilization. Topsoil under the native vegetation had greater stability at the middle and higher intertidal zones because its soil stability index and root length density were significantly higher than in the T. ascendens or S. babylonica planted communities. The effect of T. ascendens on soil stability was not generally better than that of the native vegetation. Only at the 20-30 cm soil depth of the middle intertidal zone and in the 10-20 cm layer of the higher intertidal zone the soil stability index and root length densities under the T. ascendens added condition were significantly higher （P 〈 0.05） than those of the native vegetation. The S. babylonica planted soil had greater stability in the deeper soil layer than the soil under either the native vegetation or the T. ascendens added condition, and its soil stability index and root length density were significant higher （P 〈 0.05） than those of other vegetation conditions at the 30 40 cm soil depth for the lower intertidal zone and at the 20-40 cm layer for middle and higher intertidal zones.展开更多
Increasing the local charge density of flexible side-chain cations in the hydrophilic segments of anion exchange membranes(AEMs)is helpful for improving their properties.However,due to limitations of structural design...Increasing the local charge density of flexible side-chain cations in the hydrophilic segments of anion exchange membranes(AEMs)is helpful for improving their properties.However,due to limitations of structural design strategies and available synthetic methods,very few AEMs with more than four flexible side-chain cationic groups in hydrophilic segments have been reported.In order to further improve the hydroxide conductivity,alkaline stability and dimensional stability,herein we report a series of AEMs containing eight flexible side-chain cations in hydrophilic segments,based on poly(aryl ether sulfone)s(PAES).The synthesis,ion exchange capacity(IEC),water absorption,dimensional swelling,alkaline stability and hydroxide conductivity of the obtained membranes(PAES-8TMA-x)were examined and the relationships between structures and properties of different types of AEMs were also systematically compared.The resulting AEMs with IEC values of1.76–2.76 mmol g^-1 displayed comprehensively desirable properties,with hydroxide conductivities of 62.7–92.8 m S cm^-1 and dimensional swelling in the range of 8.3%to15.8%at 60℃.The IEC and hydroxide conductivity for a representative sample,PAES-8TMA-0.35,maintained 82.2%and 79.6%of the initial values after being immersed in2 mol L^-1 Na OH at 90℃ for 480 h,respectively.This study expands the design and preparation of AEMs containing high local densities of flexible side chain cations,and provides a new strategy for new AEM materials.展开更多
As common soil fungi that form symbioses with most terrestrial plants,arbuscular mycorrhizal(AM) fungi play an important role in plant adaptation to chromium(Cr) contamination.However,little information is available o...As common soil fungi that form symbioses with most terrestrial plants,arbuscular mycorrhizal(AM) fungi play an important role in plant adaptation to chromium(Cr) contamination.However,little information is available on the underlying mechanisms of AM symbiosis on plant Cr resistance.In this study,dandelion(Taraxacum platypecidum Diels.) was grown with and without inoculation of the AM fungus Rhizophagus irregularis and Cr uptake by extraradical mycelium(ERM) was investigated by a compartmented cultivation system using a Cr stable isotope tracer.The results indicated that AM symbiosis increased plant dry weights and P concentrations but decreased shoot Cr concentrations.Using the Cr stable isotope tracer technology,the work provided possible evidences of Cr uptake and transport by ERM,and confirmed the enhancement of root Cr stabilization by AM symbiosis.This study also indicated an enrichment of lighter Cr isotopes in shoots during Cr translocation from roots to shoots in mycorrhizal plants.展开更多
基金Supported by Scientific Research Fund for Middle-aged and Young Scientists of Qinghai University(2012-QGY-5)"123 High-level Personnel Training Project"of Qinghai UniversityProject of Geological Resources and Geological Engineering Innovation Team of Qinghai University(4056051201)~~
文摘Abundant herbaceous and shrub roots play an important role in preventing water and soil erosion and increasing shallow slope stability. In order to make a quantitative analysis on the contribution of root system to slope stability under dif- ferent slope gradient, an unconsolidated and undrained triaxial compression test was conducted to measure the shear strengths of soil and root-soil composite in the two slopes in eastern Qinghai Province. In addition, under the protection of plant roots, the effect of gradient on stability of soil slope was investigated by limit equilibrium method. The results showed that the stability coefficient of soil slope planted with two kinds of brush was decreased with the increase in slope gradient, and the sta- bility coefficient increment of soil slope containing Atriplex canescens roots was higher than that containing Caragana korshinskii roots. When the slope gradient ranged from 25° to 50°, the stability coefficient of soil slope planted with Atriplex canescens or Caragana korshinskii ranged from 0.80 to 1.38. However, when the slope gradient exceeded 55°, the increment of stability coefficient of soil slope became small.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.41162010,41572306)provincial key project in science and technologies of Qinghai(Grant No.2003-N-134)+1 种基金Excellent Talents in University of New Century by Ministry of Education of the People’s Republic of China(Grant No.NCET–04–G983)International Science&Technology Cooperation Program of China(Grant No.2011DFG93160)
文摘To investigate the influence of root system architectural properties of three indigenous （cold- adapted） shrubs on the hillslope stability of loess deposits in the Xining Basin, northeast part of Qinghai-Tibet Plateau （QTP）, indoor direct shear tests have been conducted on the remolded rooted soil of three shrubs. Test results show that root system architectural indices （root area ratio （RAR）, root length density （RLD） and root density （RD）） of the shrubs decline with depth and the relationship between RAR, RD and depth is exponential, while a power relationship describes the relationship between RLD and depth. The cohesion force of remolded rooted soil for the shrubs initially increases with depth, but it then demonstrates a slightly decreasing trend, which can be described with a power relationship. Power relationships also describe relationships between cohesion force and RAR, RLD and RD for the shrubs. As the growth period increases from lO to 17 months, the incremental increase in RAR is 48.32% ~ 21o.25% for Caragana korshinskii Kom and 0.56% ~ 166.85% for ZygophyUum xanthoxylon （Bunge） Maxim. This proportional increase is notably larger than that for RLD and RD. The increment in RAR is marginally greater for C. korshinskff than it is for Z. xanthoxylon. Correspondingly, the cohesion force incremental rates of remolded rooted soil for C. korshinskii and Z. xanthoxylon are 12.41% ~ 25.22% and 3.45% ~ 17.33% respectively. Meanwhile, as root content increases, the contribution by roots to cohesion force increases markedly until a threshold condition is reached.
文摘Deformation modulus is the important parameter in stability analysis of tunnels, dams and mining struc- tures. In this paper, two predictive models including Mamdani fuzzy system （MFS） and multivariable regression analysis （MVRA） were developed to predict deformation modulus based on data obtained from dilatometer tests carried out in Bakhtiary dam site and additional data collected from longwall coal mines. Models inputs were considered to be rock quality designation, overburden height, weathering, unconfined compressive strength, bedding inclination to core axis, joint roughness coefficient and fill thickness. To control the models performance, calculating indices such as root mean square error （RMSE）, variance account for （VAF） and determination coefficient （R^2） were used. The MFS results show the significant prediction accuracy along with high performance compared to MVRA results. Finally, the sensitivity analysis of MFS results shows that the most and the least effective parameters on deformation modulus are weatherin~ and overburden height, respectively.
基金Strategic Priority Research Program-Climate Change:Carbon Budget and Relevant Issues of Chinese Academy of Sciences(No.XDA05060300)
文摘Traditional vegetation techniques for the control of concentrated flow erosion are widely recognized, whereas only a few studies have experimentally investigated the impacts of belowground roots on the erodibility of topsoils in semi-arid areas. To quantify the effects of root architectures on soil erodibility and its relevant structural properties, simulated flow experiments were conducted at six-week intervals from 18 July to 20 October in 2012 in the hilly Loess Plateau. Five treatments were: 1) bare(control), 2) purple alfalfa(Medicago sativa), representing tap roots(T), 3) switchgrass(Panicum virgatum), representing fibrous roots(F), 4) purple alfalfa and switchgrass, representing both tap and fibrous roots(T + F), and 5) natural recovery(N). For each treatment, soil structural properties and root characteristics were measured at an interval of six weeks. Soil anti-scouribility was calculated. Results showed that grass planting slightly reduced soil bulk density, but increased soil aggregate content by 19.1%, 10.6%, 28.5%, and 41.2% in the treatments T, F, T + F, and N, respectively. Soil shear strength(cohesion and angle of internal friction(φ)) significantly increased after the grass was planted. As roots grew, soil cohesion increased by 115.2%–135.5%, while soil disintegration rate decreased by 39.0%–58.1% in the 21 th week compared with the recorded value in the 9th week. Meanwhile, root density and root surface area density increased by 64.0%–104.7% and 75.9%–157.1%, respectively. No significant differences in soil anti-scouribility were observed between the treatments of T and F or of T + F and N, but the treatments of T + F and N performed more effectively than T or F treatment alone in retarding concentrated flow. Soil aggregation and root surface-area density explained the observed soil anti-scouribility during concentrated flow well for the different treatments. This result proved that the restoration of natural vegetation might be the most appropriate strategy in soil reinforcement in the hilly Loess Plateau.
基金Supported by the National Key Technologies Research and Development Program of China during the 11th Five-Year Plan Period (No. 2006BAC01A14)the Key Project of the Science and Technology Commission of ShanghaiMunicipality,China (Nos. 10dz1200602 and 10dz1200902)
文摘Coastal erosion is currently a major problem along the southern coast of Chongming Island, Shanghai. To enhance the erosion protection ability of coastal shelterbelts, two woody tree species, Taxodium ascendens and Salix babylonica, were planted separately into Phragmites australis ＋ Scirpus mariqueter communities in 2006. Two years later, we investigated whether either of these experiments reduced erosion and increased stability in the native herbaceous plant community. We also examined soil stability and root length density under T. aseendens added, S. babylonica added and native herbaceous vegetation conditions along an intertidal gradient from the soil surface to a depth of 40 cm in each experiment, thus to determine the capacity of T. ascendens and S. babylonica to contribute to shoreline stabilization. Topsoil under the native vegetation had greater stability at the middle and higher intertidal zones because its soil stability index and root length density were significantly higher than in the T. ascendens or S. babylonica planted communities. The effect of T. ascendens on soil stability was not generally better than that of the native vegetation. Only at the 20-30 cm soil depth of the middle intertidal zone and in the 10-20 cm layer of the higher intertidal zone the soil stability index and root length densities under the T. ascendens added condition were significantly higher （P 〈 0.05） than those of the native vegetation. The S. babylonica planted soil had greater stability in the deeper soil layer than the soil under either the native vegetation or the T. ascendens added condition, and its soil stability index and root length density were significant higher （P 〈 0.05） than those of other vegetation conditions at the 30 40 cm soil depth for the lower intertidal zone and at the 20-40 cm layer for middle and higher intertidal zones.
基金supported by the Six Talent Peaks Project of Jiangsu Province(XCL-078)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(KYCX20-2528)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions of China。
文摘Increasing the local charge density of flexible side-chain cations in the hydrophilic segments of anion exchange membranes(AEMs)is helpful for improving their properties.However,due to limitations of structural design strategies and available synthetic methods,very few AEMs with more than four flexible side-chain cationic groups in hydrophilic segments have been reported.In order to further improve the hydroxide conductivity,alkaline stability and dimensional stability,herein we report a series of AEMs containing eight flexible side-chain cations in hydrophilic segments,based on poly(aryl ether sulfone)s(PAES).The synthesis,ion exchange capacity(IEC),water absorption,dimensional swelling,alkaline stability and hydroxide conductivity of the obtained membranes(PAES-8TMA-x)were examined and the relationships between structures and properties of different types of AEMs were also systematically compared.The resulting AEMs with IEC values of1.76–2.76 mmol g^-1 displayed comprehensively desirable properties,with hydroxide conductivities of 62.7–92.8 m S cm^-1 and dimensional swelling in the range of 8.3%to15.8%at 60℃.The IEC and hydroxide conductivity for a representative sample,PAES-8TMA-0.35,maintained 82.2%and 79.6%of the initial values after being immersed in2 mol L^-1 Na OH at 90℃ for 480 h,respectively.This study expands the design and preparation of AEMs containing high local densities of flexible side chain cations,and provides a new strategy for new AEM materials.
基金supported by the Knowledge Innovation Program of Chinese Academy of Sciences (No.KZCX2-YW-BR-17)the National Natural Science Foundation of China(No.41101246)the State Key Laboratory of Urban and Regional Ecology, Research Center of Eco-Environmental Sciences,Chinese Academy of Sciences(No.SKLURE2008-1-03)
文摘As common soil fungi that form symbioses with most terrestrial plants,arbuscular mycorrhizal(AM) fungi play an important role in plant adaptation to chromium(Cr) contamination.However,little information is available on the underlying mechanisms of AM symbiosis on plant Cr resistance.In this study,dandelion(Taraxacum platypecidum Diels.) was grown with and without inoculation of the AM fungus Rhizophagus irregularis and Cr uptake by extraradical mycelium(ERM) was investigated by a compartmented cultivation system using a Cr stable isotope tracer.The results indicated that AM symbiosis increased plant dry weights and P concentrations but decreased shoot Cr concentrations.Using the Cr stable isotope tracer technology,the work provided possible evidences of Cr uptake and transport by ERM,and confirmed the enhancement of root Cr stabilization by AM symbiosis.This study also indicated an enrichment of lighter Cr isotopes in shoots during Cr translocation from roots to shoots in mycorrhizal plants.
