Understanding how dominant plants respond to nitrogen(N)addition is critical for accurately predicting the potential effects of N deposition on ecosystem structure and functionality.Biomass partitioning serves as a va...Understanding how dominant plants respond to nitrogen(N)addition is critical for accurately predicting the potential effects of N deposition on ecosystem structure and functionality.Biomass partitioning serves as a valuable indicator for assessing plant responses to environmental changes.However,considerable uncertainty remains regarding how biomass partitioning shifts with increasing N inputs in sandy ecosystems.To address this gap,we conducted a greenhouse N fertilization experiment in April 2024,using seeds from 20 dominant plant species in the Horqin Sandy Land of China representing 5 life forms:annual grasses,annual forbs,perennial grasses,perennial forbs,and shrubs.Six levels of N addition(0.0,3.5,7.0,14.0,21.0,and 49.0 g N/(m2•a),referred to as N0,N1,N2,N3,N4,and N5,respectively)were applied to investigate the effects of N inputs on biomass partitioning.Results showed that for all 20 dominant plant species,the root biomass:shoot biomass(R:S)consistently declined across all N addition treatments(P<0.050).Concurrently,N addition led to a 23.60%reduction in root biomass fraction,coupled with a 12.38%increase in shoot biomass fraction(P<0.050).Allometric partitioning analysis further indicated that N addition had no significant effect on the slopes of the allometric relationships(leaf biomass versus root biomass,stem biomass versus root biomass,and shoot biomass versus root biomass).This suggests that plants can adjust resource investment—such as allocating more resources to shoots—to optimize growth under favorable conditions without disrupting functional trade-offs between organs.Among different life forms,annual grasses,perennial grasses,and annual forbs exhibited increased allocation to aboveground biomass,enhancing productivity and potentially altering community composition and competitive hierarchies.In contrast,perennial forbs and shrubs maintained stable biomass partitioning across all N addition levels,reflecting conservative resource allocation strategies that support long-term ecosystem resilience in nutrient-poor environments.Taken together,these findings deepen our understanding of how nutrient enrichment influences biomass allocation and ecosystem dynamics across different plant life forms,offering practical implications for the management and restoration of degraded sandy ecosystems.展开更多
It has been well recognized that sand particles significantly affect the mechanical properties of reconstituted sandy clays,including the hosted clay and sand particles.However,interrelation between the permeability a...It has been well recognized that sand particles significantly affect the mechanical properties of reconstituted sandy clays,including the hosted clay and sand particles.However,interrelation between the permeability and compressibility of reconstituted sandy clays by considering the structural effects of sand particles is still rarely reported.For this,a series of consolidation-permeability coefficient tests were conducted on reconstituted sandy clays with different sand fractions(ψ_(ss)),initial void ratio of hosted clays(e_(c0))and void ratio at liquid limit of hosted clays(e_(cL)).The roles of ψ_(ss) in both the relationships of permeability coefficient of hosted clay(k_(v-hosted clay))versus effective vertical stress(σ'_(v))and void ratio of hosted clay(e_(c-hosted clay))versus σ'_(v) were analyzed.The results show that the permeability coefficient of reconstituted sandy clays(k_(v))is dominated by hosted clay(k_(v)=k_(v-hosted clay)).Both ψ_(ss) and σ'_(v) affect the k_(v) of sandy clays by changing the e_(c-hosted clay) at any given σ'_(v).Due to the partial contacts and densified clay bridges between the sand particles(i.e.structure effects),the e_(c-hosted clay) in sandy clays is higher than that in clays at the same σ'_(v)v.The k_(v)-e_(c-hosted clay) relationship of sandy clays is independent of σ'_(v) and ψ_(ss)but is a function of e_(cL).The types of hosted clays affect the k_(v) of sandy clays by changing the e_(cL).Based on the relationship between permeability coefficient and void ratio for the reconstituted clays,an empirical method for determining the k_(v) is proposed and validated for sandy clays.The predicted values are almost consistent with the measured values with k_(v-predicted)=k_(v-measured)=0.6-2.5.展开更多
Bentonite is a very useful material for improving soil properties,which enhances the ability of plants to grow and produce in different conditions.The experiment was carried out in an agricultural nursery in one of th...Bentonite is a very useful material for improving soil properties,which enhances the ability of plants to grow and produce in different conditions.The experiment was carried out in an agricultural nursery in one of the areas of the City of Diwaniyah,in a house covered with green netting,with a shade rate of 25%,to study the effect of bentonite and humic acid on the growth and flowering of a Catharanthus roseus L.plant in sandy soil.The experiment included two factors:the first factor was bentonite clay,and the second factor was humic acid.Using a randomized complete block design(R.C.B.D)with three replications,data were analyzed using the analysis of variance(ANOVA)method,and comparison was made according to the least significant difference(L.S.D)test at a probability level of 0.05.The experiment consisted of adding bentonite clay at 0,2,6,and 8 g L-1,humic acid at 0,0.5,1,and 10 g L-1.The results showed that adding bentonite clay and humic acid to sandy soil can have a significant positive effect on the growth and flowering of the Catharanthus roseus plant grown in poor sandy soil conditions.Bentonite,clay and humic acid were added at concentrations of 8 and 10 g L-1,which led to an increase in plant height and number of leaves and leaf area.They reached 30.07,23.84 cm2,76.62,63.42 cm2 for leaf-1 and 24.73,20.22 cm2 for leaf-1,respectively.The results also showed an increase in the content of nitrogen(N),phosphorus(P),and potassium(K)in leaves by 2.27,1.92,1.99%and 1.51,1.22,1.77%.This also led to an increase in chlorophyll pigment and anthocyanin at the highest concentration and gave the highest value.Therefore,adding bentonite and humic acid together gave the highest values in vegetative and chemical characteristics,compared to treatments without addition.展开更多
The progressive failure characteristics of geomaterial are a remarkable and challenging topic in geotechnical engineering.To study the effect of salt content and temperature on the progressive failure characteristics ...The progressive failure characteristics of geomaterial are a remarkable and challenging topic in geotechnical engineering.To study the effect of salt content and temperature on the progressive failure characteristics of frozen sodium sulfate saline sandy soil,a series of uniaxial compression tests were performed by integrating digital image correlation(DIC)technology into the testing apparatus.The evolution law of the uniaxial compression strength(UCS),the failure strain,and the formation of the shear band of the frozen sodium sulfate saline sandy soil were analyzed.The test results show that within the scope of this study,with the increase of salt content,both the UCS and the shear band angle initially decrease with increasing salt content before showing an increase.In contrast,the failure strain and the width of the shear band exhibit an initial increase followed by a decrease in the samples.In addition,to investigate the brittle failure characteristics of frozen sodium sulfate saline sandy soil,two classic brittleness evaluation methods were employed to quantitatively assess the brittleness level for the soil samples.The findings suggest that the failure characteristics under all test conditions in this study belong to the transition stage between brittle and ductile,indicating that frozen sodium sulfate saline sandy soil exhibits certain brittle behavior under uniaxial compression conditions,and the brittleness index basically decreases and then increases with the rise in salt content.展开更多
In Switzerland,the Opalinus Clay has been selected as a potential host rock for the deep geological disposal of radioactive waste due to its low hydraulic conductivity and favorable swelling properties.During the oper...In Switzerland,the Opalinus Clay has been selected as a potential host rock for the deep geological disposal of radioactive waste due to its low hydraulic conductivity and favorable swelling properties.During the operational phase of the repository,the host rock will be exposed to pH values as high as 13.5 due to concrete degradation,which will certainly affect its hydraulic properties.This study investigates the effect of pH increase on the water retention properties of Opalinus Clay.A series of samples from the lower sandy facies of the Mont Terri site in Switzerland,at initial dry state,were exposed to a hyperalkaline solution of pH=13.5 and to the synthetic water of pH=7.5 at different water contents.After equilibrium,the total suction was measured with a dew point potentiometer and microstructural analyses were conducted via mercury intrusion porosimetry(MIP)and nitrogen adsorption-desorption technique.It was found that the total suction decreased with hydration and pH increase.Since the two investigated solutions have the same osmotic suction,the decrease in total suction was attributed to the decrease in matric suction.Indeed,the total porosity increased with saturation and pH increase.This was confirmed by MIP data that evidenced an increase in the proportion of macropores,and by Barret eJoynereHalenda(BJH)data that showed mesopore generation.The specific surface area(SSA)also increased.The previous results were due to mineral hydration and,exclusively in the case of alkaline solution,to(1)the dissolution of quartz and calcite and(2)the acid-base reactions,which were concentrated at the edges of the clay particles,leading to an increase in negatively charged groups and thus to a face-to-face association of the clay particles(dispersion),causing an increase in the repulsive forces between the clay particles.In addition,the weakening of covalent bonds led to the primary dissolution of clay minerals,i.e.silicon and aluminum detachment.展开更多
Tunnel face ground loss(TFGL)emerging in shield tunnelling can trigger ground movement and impose threats to surrounding structures.However,the impact of cutterhead vibration on TFGL in sandy soils with varying degree...Tunnel face ground loss(TFGL)emerging in shield tunnelling can trigger ground movement and impose threats to surrounding structures.However,the impact of cutterhead vibration on TFGL in sandy soils with varying degrees of saturation has been largely unexplored.To fill this gap,an innovative numerical model based on computational fluid dynamics-discrete element method(CFD-DEM)and adhesive rolling resistance linear contact algorithm is established for the simulation of TFGL.Meanwhile,algorithms are proposed to account for the effects of cutterhead vibration and support pressure.Results from the validated model reveal that the TFGL can be exacerbated by seepage and opening enlargement,but mitigated by apparent cohesion.The cutterhead vibration can merely exacerbate the relatively small TFGL,which implies the unjamming effect of the particle at the opening.The balanced support pressure(BSP)required for TFGL prevention rises remarkably with the increases in opening ratio,vibration amplitude,and frequency.The maximum BSP in unsaturated sandy ground reaches up to 0.18γD,which is significantly less than that of 1.62γD observed in saturated sandy ground.The tangential and radial intervals with the largest TFGL are located within the ranges of 82.5°-97.5°,and 0.3D≤r_(loss)≤0.45D,respectively.The increase in support pressure can alter the time-dependent development of TFGL from linear to stepwise,leading to convergence.The support pressure required for convergence is increased by cutterhead vibration and seepage,but decreased by apparent cohesion.Lastly,the prospects of the numerical study on TFGL under cutterhead vibration are also discussed.展开更多
In recent years,intensive human activities have increased the intensity of desertification,driving continual desertification process of peripheral meadows.To investigate the effects of restoration on soil microbial co...In recent years,intensive human activities have increased the intensity of desertification,driving continual desertification process of peripheral meadows.To investigate the effects of restoration on soil microbial communities,we analyzed vegetation-soil relationships in the Hulun Buir Sandy Land,northern China.Through the use of high-throughput sequencing,we examined the structure and diversity in the bacterial and fungal communities within the 0-20 cm soil layer after 9-15 a of restoration.Different slope positions were analyzed and spatial heterogeneity was assessed.The results showed progressive improvements in soil properties and vegetation with the increase of restoration duration,and the following order was as follows:bottom slope>middle slope>crest slope.During the restoration in the Hulun Buir Sandy Land,the bacterial communities were dominated by Proteobacteria,Actinobacteria,and Acidobacteria,whereas the fungal communities were dominated by Ascomycota and Basidiomycota.Eutrophic bacterial abundance increased with the restoration duration,whereas oligotrophic bacterial and fungal abundance levels decreased.The soil bacterial abundance significantly increased with the increasing restoration duration,whereas the fungal diversity decreased after 11 a of restoration,except that at the crest slope.Redundancy analysis showed that pH,soil moisture content,total nitrogen,and vegetation-related factors affected the bacterial community structure(45.43%of the total variance explained).Canonical correspondence analysis indicated that pH,total phosphorus,and vegetation-related factors shaped the bacterial community structure(31.82%of the total variance explained).Structural equation modeling highlighted greater bacterial responses(R^(2)=0.49-0.79)to changes in environmental factors than those of fungi(R^(2)=0.20-0.48).The soil bacterial community was driven mainly by pH,soil moisture content,electrical conductivity,plant coverage,and litter dry weight.The abundance and diversity of the soil fungal community were mainly driven by plant coverage,litter dry weight,and herbaceous aboveground biomass,while there was no significant correlation between the soil fungal community structure and environmental factors.These findings highlighted divergent microbial succession patterns and environmental sensitivities during sandy grassland restoration.展开更多
Sandy braided river deposits are widely preserved in ancient stratigraphic records and act as a significant type of hydrocarbon reservoir.Due to the frequent and rapid migration of channels within the riverbed,the sed...Sandy braided river deposits are widely preserved in ancient stratigraphic records and act as a significant type of hydrocarbon reservoir.Due to the frequent and rapid migration of channels within the riverbed,the sedimentary architecture is highly complex.In this paper,a flume experiment was conducted to reveal the detailed depositional process and establish a fine sedimentary architecture model for sandy braided rivers.The result showed that(1)Three types of braid channels,including the lateral migration channel,the confluence channel,and the deep incised channel,were recognized based on geometry,scale,distribution,and spatial patterns;they are interconnected,forming a complex channel network.(2)Braid channels were characterized by lateral migration,abandonment,filling,and chute cutoff.Lateral migration of channels shaped the braid bars and dominated the formation,growth,and reworking of braid bars.(3)Controlled by the fast and frequent variations of the braid channel network,braid bars were continuously formed,reworked,reshaped,and composited of multiple accretions with different types,orientations,scales,and preservation degrees.Symmetrical and asymmetrical braid bars pre-sented significantly different composition patterns.(4)Dominated by the continuous reworking of braid channels,temporary deposits were limited preserved,braid channel deposits account for 54.3 percent of the eventually preserved braided river deposits,and four types of amalgamate patterns were recognized.Braid bars were cut and limited preserved,only accounting for 45.7 percent of the eventually preserved braided river deposits.(5)During the experiment,only 28 percent of near-surface temporary deposits were eventually preserved in fragmented forms with the final experimental braided river;the shape,spatial patterns,and most of the deposits observed during the depositional process were largely reworked and poorly preserved.(6)The scale of eventually preserved braid bars and braid channels is significantly smaller than the temporary deposits from geomorphic observations.The aspect ratio of the eventually preserved braid bars and the width-to-depth ratio of the eventually preserved braid channel are also significantly different from that of the temporary ones measured from topography data.展开更多
Sandy cobble soil exhibits pronounced heterogeneity.The assessment of the uncertainty surrounding its properties is crucial for the analysis of settlement characteristics resulting from volume loss during shield tunne...Sandy cobble soil exhibits pronounced heterogeneity.The assessment of the uncertainty surrounding its properties is crucial for the analysis of settlement characteristics resulting from volume loss during shield tunnelling.In this study,a series of probabilistic analyses of surface and subsurface settlements was conducted considering the spatial variability of the friction angle and reference stiffness modulus,under different volumetric block proportions(Pv)and tunnel volume loss rates(ηt).The non-intrusive random finite difference method was used to investigate the probabilistic characteristics of maximum surface settlement,width of subsurface settlement trough,maximum subsurface settlement,and subsurface soil volume loss rate through Monte Carlo simulations.Additionally,a comparison between stochastic and deterministic analysis results is presented to underscore the significance of probabilistic analysis.Parametric analyses were subsequently conducted to investigate the impacts of the key input parameters in random fields on the settlement characteristics.The results indicate that scenarios with higher Pv or greaterηt result in a higher dispersion of stochastic analysis results.Neglecting the spatial variability of soil properties and relying solely on the mean values of material parameters for deterministic analysis may result in an underestimation of surface and subsurface settlements.From a probabilistic perspective,deterministic analysis alone may prove inadequate in accurately capturing the volumetric deformation mode of the soil above the tunnel crown,potentially affecting the prediction of subsurface settlement.展开更多
Investigating the spatiotemporal evolution of vegetation and its response mechanisms to natural and anthropogenic elements is crucial for regional vegetation restoration and ecological preservation.The Mu Us Sandy Lan...Investigating the spatiotemporal evolution of vegetation and its response mechanisms to natural and anthropogenic elements is crucial for regional vegetation restoration and ecological preservation.The Mu Us Sandy Land(MUSL),which is situated in the semi-arid zone of northwestern China adjacent to the Loess Plateau,has been at the forefront of desertification and oasis formation over the past two millennia.This study is based on the synthesis of the Normalized Difference Vegetation Index(NDVI)data from MOD13A3 data in the MODIS(Moderate-Resolution Imaging Spectroradiometer)dataset(2002-2021)and climate data(temperature and precipitation)at annual and monthly scales from the National Earth System Science Data Center.A range of analytical methods,including univariate linear regression,Theil-Sen trend analysis and Mann-Kendall significance test,correlation analysis,residual analysis,and Hurst index,were used to explore the response mechanisms of the NDVI to climate change and human activities and to predict the future trends of the NDVI in the MUSL.The results showed that through the method of correlation analysis,in terms of both spatially averaged correlation coefficients and area proportion,the NDVI was positively correlated with temperature and precipitation in 97.59%and 96.51%of the study area,respectively,indicating that temperature has a greater impact on the NDVI than precipitation.Residual analysis quantified the contributions of climate change and human activities to the NDVI changes,revealing that climate change and human activities contribute up to 30.00%and 70.00%,respectively,suggesting that human activities predominantly affect the NDVI changes in the MUSL.The Hurst index was used to categorize the future trend of the NDVI into four main directions of development:continuous degradation(0.05%of the study area),degradation in the past but improvement in the future(54.45%),improvement in the past but degradation in the future(0.13%),and continuous improvement(45.36%).In more than 50.00%of the regions that have been degraded in the past but were expected to improve in the future,the NDVI was expected to exhibit a stable trend of anti-persistent improvement.These findings provide theoretical support for future ecological protection,planning,and the implementation of ecological engineering in the MUSL,and also offer a theoretical basis for the planning and execution of construction projects,environmental protection measures,and the sustainable development of vegetation.展开更多
Eco-geological vulnerability assessment is a significant research topic within the field of eco-geology,but it remains poorly studied.The Mu Us Sandy Land,located in the central part of the farming-pastoral ecotone in...Eco-geological vulnerability assessment is a significant research topic within the field of eco-geology,but it remains poorly studied.The Mu Us Sandy Land,located in the central part of the farming-pastoral ecotone in northern China,plays a critical role in maintaining the ecological security pattern in this region.However,this sandy land also faces severe sandy desertification and ecological degradation.This study conducted a regional eco-geological vulnerability assessment of the Mu Us Sandy Land using a comprehensive index evaluation method based on eco-geological theories and survey results.To construct an appropriate index system for the eco-geological vulnerability assessment of the Mu Us Sandy Land,the study considered the sandy land’s unique characteristics and identified 15 factors of five categories,namely geology,meteorology,soil,topography,and vegetation.The paper calculated the comprehensive weights of all the indices using the analytic hierarchy process(AHP)and the entropy weight method(EWM).Furthermore,it established the eco-geological vulnerability index(EGVI)and obtained the assessment results.The results showed that the eco-geological vulnerability of the Mu Us Sandy Land gradually intensifies from east to west,manifested as vulnerable eco-geological conditions overall.Specifically,extremely vulnerable zones are found in the northwestern and southeastern parts of the study area,highly vulnerable zones in the western and southern parts,moderately vulnerable zones in the central part,and slightly and potentially vulnerable zones in the eastern and southern parts.Areas with high spatial autocorrelations include the northern Uxin Banner-Otog Banner-Angsu Town area,the surrounding areas of Hongdunjie Town in the southeastern part of the study area,the Hongshiqiao Township-Xiaohaotu Township area,Otog Front Banner,and Bainijing Town,which should be prioritized in the ecological conservation and restoration.Additionally,the paper proposed suggestions for the ecological conservation and restoration of county-level administrative areas in the study area.Overall,the findings provide a valuable reference for the ecological conservation and restoration of the Mu Us Sandy Land and other desert areas in arid and semi-arid regions.展开更多
The soil packing,influenced by variations in grain size and the gradation pattern within the soil matrix,plays a crucial role in constituting the mechanical properties of sandy soils.However,previous modeling approach...The soil packing,influenced by variations in grain size and the gradation pattern within the soil matrix,plays a crucial role in constituting the mechanical properties of sandy soils.However,previous modeling approaches have overlooked incorporating the full range of representative parameters to accurately predict the soaked California bearing ratio(CBR_(s))of sandy soils by precisely articulating soil packing in the modeling framework.This study presents an innovative artificial intelligence(AI)-based approach for modeling the CBR_(s)of sandy soils,considering grain size variability meticulously.By synthesizing extensive data from multiple sources,i.e.extensive tailored testing program undertaking multiple tests and extant literature,various modeling techniques including genetic expression programming(GEP),multi-expression programming(MEP),support vector machine(SVM),and multi-linear regression(MLR)are utilized to develop models.The research explores two modeling strategies,namely simplified and composite,with the former incorporating only sieve analysis test parameters,while the latter includes compaction test parameters alongside sieve analysis data.The models'performance is assessed using statistical key performance indicators(KPIs).Results indicate that genetic AI-based algorithms,particularly GEP,outperform SVM and conventional regression techniques,effectively capturing complex relationships between input parameters and CBR_(s).Additionally,the study reveals insights into model performance concerning the number of input parameters,with GEP consistently outperforming other models.External validation and Taylor diagram analysis demonstrate the GEP models'superiority over existing literature models on an independent dataset from the literature.Parametric and sensitivity analyses highlight the intricate relationships between grain sizes and CBR_(s),further emphasizing GEP's efficacy in modeling such complexities.This study contributes to enhancing CBR_(s)modeling accuracy for sandy soils,crucial for pertinent infrastructure design and construction rapidly and cost-effectively.展开更多
Due to space constraints in urban areas,metro tunnels are typically constructed in pairs,with a small clearance.The interaction between twin tunnels leads to a significantly more complex ground deformation and stress ...Due to space constraints in urban areas,metro tunnels are typically constructed in pairs,with a small clearance.The interaction between twin tunnels leads to a significantly more complex ground deformation and stress distribution than that observed in a single tunnel scenario,particularly if the tunnels are excavated in sequence.A series of physical model tests were conducted to investigate soil deformation and stress disturbances caused by the excavation of twin tunnels.The test results indicate that the interaction between the twin tunnels was observed.Due to the soil arching effect,the excavation of Tunnel 2 increases the soil stress acting on Tunnel 1.An analytical method was proposed to determine soil stress considering the soil arching effect and the interaction between twin tunnels.The method categorized the relative locations between twin tunnels into non-influenced,partially influenced,and fully influenced scenarios.For non-influenced and fully influenced scenarios,the soil stresses above twin tunnels were calculated based on a symmetric major principal stress trace.For the partially influenced scenario,however,the soil arch above Tunnel 2 was asymmetric due to the interaction,and the stress distribution was obtained based on a new asymmetric major principal stress trace.The soil stress on Tunnel 1 was influenced by the load transferred from Tunnel 2 and calculated based on the force equilibrium.A comparison of the analytical and test results indicates that the proposed method effectively predicts the soil stress in the cover layer above twin tunnels excavated sequentially,considering the interaction and soil arching effects.展开更多
Mongolian pine (Pinus sylvestiris Linnaeus var. mongolica Litvinov) as a valuable conifer tree species has been broadly introduced to the sandy land areas in 揟hree North?regions (North, northwest and northeast of Chi...Mongolian pine (Pinus sylvestiris Linnaeus var. mongolica Litvinov) as a valuable conifer tree species has been broadly introduced to the sandy land areas in 揟hree North?regions (North, northwest and northeast of China), but many problems occurred in the earliest Mongolian pine plantations in Zhanggutai, Zhangwu County, Liaoning Province (ZZL). In order to clarify the reason, comprehensive investigations were carried out on differences in structure characteristics, growth processes and ecological factors between artificial stands (the first plantation established in ZZL in 1950s) and natural stands (the origin forests of the tree species in Honghuaerji, Inner Mongolia) on sandy land. The results showed that variation of diameter-class distributions in artificial stands and natural stands could be described by Weibull and Normal distribution models, respectively. Chapman-Richards growth model was employed to reconstruct the growth process of Mongolian pine based on the data from field investigation and stem analysis. The ages of maximum of relative growth rate and average growth rate of DBH, height, and volume of planted trees were 11, 22 years, 8, 15 years and 35, 59 years earlier than those of natural stand trees, respectively. In respect of the incremental acceleration of volume, the artificial and natural stands reached their maximum values at 14 years and 33 years respectively. The quantitative maturity ages of artificial stands and natural stands were 43 years and 102 years respectively. It was concluded that the life span of the Mongolian pine trees in natural stands was about 60 years longer than those in artificial stands. The differences mentioned above between artificial and natural Mongolian pine forests on sandy land were partially attributed to the drastic variations of ecological conditions such as latitude, temperature, precipitation, evaporation and height above sea level. Human beings' disturbances and higher density in plantation forest may be ascribed as additional reasons. Those results may be potentially useful for the management and afforestation of Mongolian pine plantations on sandy land in arid and semi-arid areas.展开更多
The concentrations of the foliar and surface soil nutrients and the variation with species and stand age were studied inPinus spp. plantations in Zhanggutai area, northeast China. The results showed that the total N, ...The concentrations of the foliar and surface soil nutrients and the variation with species and stand age were studied inPinus spp. plantations in Zhanggutai area, northeast China. The results showed that the total N, total P and C: N ratio of the soil inP. sylvestris var.mongolica stands were significantly higher in comparison with those inP. tabulaeformis andP. densiflora stands. ForP. sylvestris var.mongolica, the foliar P concentration appeared to decrease with age, and the foliar N and K concentrations did not show a consistent change with age. As for the different tree species of the similar age, the foliar N and P concentrations were significantly different (p<0.05), being withP. sylvestris var.mongolica>P. densiflora>P. tabulaeformis. The foliar N: P ratio ofP. densiflora significantly was higher thanP. sylvestris var.mongolica andP. tabulaeformis, while the foliar K was no obvious difference between the three tree species. There were significant correlation (p<0.05) between soil total N and P, soil organic matter and total P, foliar N and P, but it did not show significant correlations between soil and foliar nutrient concentrations, which might attribute to the excessive litter raking, overgrazing and low soil moisture in this area. Based on the foliar N: P ratio, we introduced a combination threshold index of N: P ratio with their absolute foliar nutrient concentrations to determine the possible limiting nutrient. According to the critical N: P ratio and their absolute foliar N, P concentrations, theP. sylvestris var.mongolica stands showed a decreased N limitation degree with age, theP. densiflora stands showed unlimited by N and P in the whole, and theP. tabulaeformis stands showed co-limited by N and P. No significant difference in soil nutrient concentrations of the surface soils was found between 45, 29, 20-yr-oldPinus sylvestris var.mongolica plantation stands. Keywords coniferous trees - foliar nutrient concentration - limiting nutrients - N - P ratio - Zhanggutai sandy land CLC number S718.55 Document code A Article ID 1007-662X(2004)01-0011-08 Foundation item: This research was supported by Key Knowledge Innovation Project (KZCX3-SW-418) of Chinese Academy of Sciences.Biography: CHEN Guang-sheng (1978-), male, master candidate in Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. ChinaResponsible editor: Song Funan展开更多
The experiment was conducted at the Ganqika Sandy Land Ecological Station in Ke抏rqinzuoyihouqi County, Inner Mongolia, in a growing season from April 28 to October 28, 2001. Peat and weathered coal were added to the ...The experiment was conducted at the Ganqika Sandy Land Ecological Station in Ke抏rqinzuoyihouqi County, Inner Mongolia, in a growing season from April 28 to October 28, 2001. Peat and weathered coal were added to the aeolian sandy soil in different ratios. Two-year-old Pinus sylvestris var. mongolica seedlings and plastic pots were used in the experiment. The experimental results indicated that: 1) the peat and weathered coal could significantly improve the physical and chemical prop-erties of aeolian sandy soil, and thus promoted the growth of seedlings; 2) the effect of peat on seedling growth, including height, base diameter, root length and biomass, presented an order of 8%>10%>5%>2%>0 in terms of peat contents, and the effect of weathered coal on seedling growth presented an order of 5%>8%>10%>2%>0 in terms of weathered coal contents for height and basal diameter, 5%>8%>2% >10%>0 for root length, and 5%>2%>8% >10%>0 for biomass; 3) the effects of peat were generally greater than that of weathered coal. Meanwhile, 8% peat was the best treatment to promote the growth of P. sylvestris var. mongolica seedlings.展开更多
Calamagrostis epigejos (L.) Roth. is a perennial grass with slender and long rhizome segments between interconnected neighbor ramets. To investigate the phenotypic plasticity in response to the heterogeneous soil wate...Calamagrostis epigejos (L.) Roth. is a perennial grass with slender and long rhizome segments between interconnected neighbor ramets. To investigate the phenotypic plasticity in response to the heterogeneous soil water supply, ramet pairs of the species were subjected to heterogeneous water supply by which either mother ramets or daughter ramets were in high or low soil water supply, respectively, in the Maowusu (Mu Us) Sandy Land of Nei Mongol. The results showed that the phenotypic characteristics of the individual ramets of C epigejos were greatly influenced by the heterogeneous water supply. The ramets treated with high water supply significantly produced more new rhizomes and more offspring (ramets), and accumulated more shoot biomass, and allocated more biomass to their shoots than those treated with low water supply. In comparison with the daughter ramets in homogeneous soil water supply, phenotypic characteristics, in terms of new rhizome growth, the production of new offspring, and the biomass allocation pattern, of the daughter ramets within the pairs of the species were not significantly changed, no matter that high or low soil water supply to mother ramets. The phenotypic responses of mother ramets to soil water supply were similar to those of daughter ramets. From these results, it is inferred that the interconnected ramets of C epigejos response phenotypically to their local soil water rather than to the soil water experienced by the interconnected ramets. The interconnected ramets of C epigejos might be independent of each other in water relationship, although they are physically interconnected with rhizome segments. The physiological independence of interconnected ramets might facilitate the risk spreading and thus enhance the genet survivorship under the frequent drought stresses in Mu Us Sandland.展开更多
[Objective] This study aimed to investigate the artificial vegetations on soil physicochemical properties of sandy land. [Method] The soil physicochemical proper- ties in five representative lands respectively covered...[Objective] This study aimed to investigate the artificial vegetations on soil physicochemical properties of sandy land. [Method] The soil physicochemical proper- ties in five representative lands respectively covered by Artemisia ordosica, Salix cheilophila, Hedysarum scoparium, Populus simonii and Amorpha fruticosa, all of which were planted artificially at the same year were measured in the present study, using a bare soil as the control. [Result] Artificial vegetation improved the soil physicochemical properties by different extents in the lands covered by different plants. The soil physicochemical properties such as bulk density under A. Fruticosa and H. Scoparium were improved greatly. The frequency distribution of soil particle size under artificial vegetations exhibited a bimodal curve. The average soil particle size under A. fruticosa was the smallest, and the soil was very poorly sorted. The soil nutrients in the sandy land were not significantly improved by artificial vegeta- tion. [Conclusion] Artificial vegetation has a certain impact on soil properties in sandy land, as it greatly improves the soil physical properties but not the chemical properties.展开更多
A new species, Spirulina (Arthrospira) bayannurensis B. Sh. Li et C. Qiao sp. nov. was firstly collected from the Lake of Bayannur, Mu Us Sandy Land, Inner Mongolia Autonomous Region in China on April 30, 199...A new species, Spirulina (Arthrospira) bayannurensis B. Sh. Li et C. Qiao sp. nov. was firstly collected from the Lake of Bayannur, Mu Us Sandy Land, Inner Mongolia Autonomous Region in China on April 30, 1996 The morphological characteristics of the new species are described and illustrated by light micrographs, scanning and transmission electron micrographs. The type specimen of this new species is kept in Herbarium of Inner Mongolia Agricultural University.展开更多
This paper analyzed the water-retention mechanism of feldspathic sandstone （fine-（〈 1 mm diam.） and gravel-sized （2-3 cm diam.） in Mu Us Sandy Land, Northwest China. The objective of this study is to study the e...This paper analyzed the water-retention mechanism of feldspathic sandstone （fine-（〈 1 mm diam.） and gravel-sized （2-3 cm diam.） in Mu Us Sandy Land, Northwest China. The objective of this study is to study the effect of feldspathic sandstone amendment on water retention in sandy land. The results showed that as the proportion of fine feldspathic sandstone in the sandy land soil increased, the soil texture changed from sand to silt loam, the capillary po- rosity gradually increased from 26.3% to 44.9%, and the soil saturated hydraulic conductivity decreased from 7.10 ram/rain to 0.07 mm/min. Feldspathic sandstone gravel formed micro-reservoirs in the sandy land soil, playing the role of a ＇water absorbent＇ and ＇water retaining agent＇ in sandy land. Amendment with feldspathic sandstone can increase water retention in the arable layer of sandy land by 67%. This study provides a theoretical basis for the amelioration of sandy land on a large scale. It can be concluded that amendment with feldspathic sandstone can improve the physical properties of sandy land soil and increase soil water retention.展开更多
基金supported by the National Grassland Technology Innovation Centre(Preparation)Project(CCPTZX2023B02-2)the National Natural Science Foundation of China(32071845)the Key Science and Technology Project of Inner Mongolia Autonomous Region(2021ZD001505).
文摘Understanding how dominant plants respond to nitrogen(N)addition is critical for accurately predicting the potential effects of N deposition on ecosystem structure and functionality.Biomass partitioning serves as a valuable indicator for assessing plant responses to environmental changes.However,considerable uncertainty remains regarding how biomass partitioning shifts with increasing N inputs in sandy ecosystems.To address this gap,we conducted a greenhouse N fertilization experiment in April 2024,using seeds from 20 dominant plant species in the Horqin Sandy Land of China representing 5 life forms:annual grasses,annual forbs,perennial grasses,perennial forbs,and shrubs.Six levels of N addition(0.0,3.5,7.0,14.0,21.0,and 49.0 g N/(m2•a),referred to as N0,N1,N2,N3,N4,and N5,respectively)were applied to investigate the effects of N inputs on biomass partitioning.Results showed that for all 20 dominant plant species,the root biomass:shoot biomass(R:S)consistently declined across all N addition treatments(P<0.050).Concurrently,N addition led to a 23.60%reduction in root biomass fraction,coupled with a 12.38%increase in shoot biomass fraction(P<0.050).Allometric partitioning analysis further indicated that N addition had no significant effect on the slopes of the allometric relationships(leaf biomass versus root biomass,stem biomass versus root biomass,and shoot biomass versus root biomass).This suggests that plants can adjust resource investment—such as allocating more resources to shoots—to optimize growth under favorable conditions without disrupting functional trade-offs between organs.Among different life forms,annual grasses,perennial grasses,and annual forbs exhibited increased allocation to aboveground biomass,enhancing productivity and potentially altering community composition and competitive hierarchies.In contrast,perennial forbs and shrubs maintained stable biomass partitioning across all N addition levels,reflecting conservative resource allocation strategies that support long-term ecosystem resilience in nutrient-poor environments.Taken together,these findings deepen our understanding of how nutrient enrichment influences biomass allocation and ecosystem dynamics across different plant life forms,offering practical implications for the management and restoration of degraded sandy ecosystems.
基金supported by the National Natural Science Foundation of China (Grant Nos.52278334 and 4197724)Fundamental Research Funds for the Central Universities (Grant No.2242024k30066).
文摘It has been well recognized that sand particles significantly affect the mechanical properties of reconstituted sandy clays,including the hosted clay and sand particles.However,interrelation between the permeability and compressibility of reconstituted sandy clays by considering the structural effects of sand particles is still rarely reported.For this,a series of consolidation-permeability coefficient tests were conducted on reconstituted sandy clays with different sand fractions(ψ_(ss)),initial void ratio of hosted clays(e_(c0))and void ratio at liquid limit of hosted clays(e_(cL)).The roles of ψ_(ss) in both the relationships of permeability coefficient of hosted clay(k_(v-hosted clay))versus effective vertical stress(σ'_(v))and void ratio of hosted clay(e_(c-hosted clay))versus σ'_(v) were analyzed.The results show that the permeability coefficient of reconstituted sandy clays(k_(v))is dominated by hosted clay(k_(v)=k_(v-hosted clay)).Both ψ_(ss) and σ'_(v) affect the k_(v) of sandy clays by changing the e_(c-hosted clay) at any given σ'_(v).Due to the partial contacts and densified clay bridges between the sand particles(i.e.structure effects),the e_(c-hosted clay) in sandy clays is higher than that in clays at the same σ'_(v)v.The k_(v)-e_(c-hosted clay) relationship of sandy clays is independent of σ'_(v) and ψ_(ss)but is a function of e_(cL).The types of hosted clays affect the k_(v) of sandy clays by changing the e_(cL).Based on the relationship between permeability coefficient and void ratio for the reconstituted clays,an empirical method for determining the k_(v) is proposed and validated for sandy clays.The predicted values are almost consistent with the measured values with k_(v-predicted)=k_(v-measured)=0.6-2.5.
文摘Bentonite is a very useful material for improving soil properties,which enhances the ability of plants to grow and produce in different conditions.The experiment was carried out in an agricultural nursery in one of the areas of the City of Diwaniyah,in a house covered with green netting,with a shade rate of 25%,to study the effect of bentonite and humic acid on the growth and flowering of a Catharanthus roseus L.plant in sandy soil.The experiment included two factors:the first factor was bentonite clay,and the second factor was humic acid.Using a randomized complete block design(R.C.B.D)with three replications,data were analyzed using the analysis of variance(ANOVA)method,and comparison was made according to the least significant difference(L.S.D)test at a probability level of 0.05.The experiment consisted of adding bentonite clay at 0,2,6,and 8 g L-1,humic acid at 0,0.5,1,and 10 g L-1.The results showed that adding bentonite clay and humic acid to sandy soil can have a significant positive effect on the growth and flowering of the Catharanthus roseus plant grown in poor sandy soil conditions.Bentonite,clay and humic acid were added at concentrations of 8 and 10 g L-1,which led to an increase in plant height and number of leaves and leaf area.They reached 30.07,23.84 cm2,76.62,63.42 cm2 for leaf-1 and 24.73,20.22 cm2 for leaf-1,respectively.The results also showed an increase in the content of nitrogen(N),phosphorus(P),and potassium(K)in leaves by 2.27,1.92,1.99%and 1.51,1.22,1.77%.This also led to an increase in chlorophyll pigment and anthocyanin at the highest concentration and gave the highest value.Therefore,adding bentonite and humic acid together gave the highest values in vegetative and chemical characteristics,compared to treatments without addition.
基金supported by the National Natural Science Foundation of China(Grant Nos.42372312,and 42172299)the Pyramid Talent Training Project of Beijing University of Civil Engineering and Architecture(Grant No.JDYC20220807).
文摘The progressive failure characteristics of geomaterial are a remarkable and challenging topic in geotechnical engineering.To study the effect of salt content and temperature on the progressive failure characteristics of frozen sodium sulfate saline sandy soil,a series of uniaxial compression tests were performed by integrating digital image correlation(DIC)technology into the testing apparatus.The evolution law of the uniaxial compression strength(UCS),the failure strain,and the formation of the shear band of the frozen sodium sulfate saline sandy soil were analyzed.The test results show that within the scope of this study,with the increase of salt content,both the UCS and the shear band angle initially decrease with increasing salt content before showing an increase.In contrast,the failure strain and the width of the shear band exhibit an initial increase followed by a decrease in the samples.In addition,to investigate the brittle failure characteristics of frozen sodium sulfate saline sandy soil,two classic brittleness evaluation methods were employed to quantitatively assess the brittleness level for the soil samples.The findings suggest that the failure characteristics under all test conditions in this study belong to the transition stage between brittle and ductile,indicating that frozen sodium sulfate saline sandy soil exhibits certain brittle behavior under uniaxial compression conditions,and the brittleness index basically decreases and then increases with the rise in salt content.
文摘In Switzerland,the Opalinus Clay has been selected as a potential host rock for the deep geological disposal of radioactive waste due to its low hydraulic conductivity and favorable swelling properties.During the operational phase of the repository,the host rock will be exposed to pH values as high as 13.5 due to concrete degradation,which will certainly affect its hydraulic properties.This study investigates the effect of pH increase on the water retention properties of Opalinus Clay.A series of samples from the lower sandy facies of the Mont Terri site in Switzerland,at initial dry state,were exposed to a hyperalkaline solution of pH=13.5 and to the synthetic water of pH=7.5 at different water contents.After equilibrium,the total suction was measured with a dew point potentiometer and microstructural analyses were conducted via mercury intrusion porosimetry(MIP)and nitrogen adsorption-desorption technique.It was found that the total suction decreased with hydration and pH increase.Since the two investigated solutions have the same osmotic suction,the decrease in total suction was attributed to the decrease in matric suction.Indeed,the total porosity increased with saturation and pH increase.This was confirmed by MIP data that evidenced an increase in the proportion of macropores,and by Barret eJoynereHalenda(BJH)data that showed mesopore generation.The specific surface area(SSA)also increased.The previous results were due to mineral hydration and,exclusively in the case of alkaline solution,to(1)the dissolution of quartz and calcite and(2)the acid-base reactions,which were concentrated at the edges of the clay particles,leading to an increase in negatively charged groups and thus to a face-to-face association of the clay particles(dispersion),causing an increase in the repulsive forces between the clay particles.In addition,the weakening of covalent bonds led to the primary dissolution of clay minerals,i.e.silicon and aluminum detachment.
基金the National Natural Science Foundation of China(Grant Nos.52178385 and 52020105002)the Natural Science Foundation of Guangdong Province,China(Grant No.2024B1515040017)for their financial support.
文摘Tunnel face ground loss(TFGL)emerging in shield tunnelling can trigger ground movement and impose threats to surrounding structures.However,the impact of cutterhead vibration on TFGL in sandy soils with varying degrees of saturation has been largely unexplored.To fill this gap,an innovative numerical model based on computational fluid dynamics-discrete element method(CFD-DEM)and adhesive rolling resistance linear contact algorithm is established for the simulation of TFGL.Meanwhile,algorithms are proposed to account for the effects of cutterhead vibration and support pressure.Results from the validated model reveal that the TFGL can be exacerbated by seepage and opening enlargement,but mitigated by apparent cohesion.The cutterhead vibration can merely exacerbate the relatively small TFGL,which implies the unjamming effect of the particle at the opening.The balanced support pressure(BSP)required for TFGL prevention rises remarkably with the increases in opening ratio,vibration amplitude,and frequency.The maximum BSP in unsaturated sandy ground reaches up to 0.18γD,which is significantly less than that of 1.62γD observed in saturated sandy ground.The tangential and radial intervals with the largest TFGL are located within the ranges of 82.5°-97.5°,and 0.3D≤r_(loss)≤0.45D,respectively.The increase in support pressure can alter the time-dependent development of TFGL from linear to stepwise,leading to convergence.The support pressure required for convergence is increased by cutterhead vibration and seepage,but decreased by apparent cohesion.Lastly,the prospects of the numerical study on TFGL under cutterhead vibration are also discussed.
基金supported by the National Ecological Environment Survey and Assessment(2024-vertical-0107)the Fundamental Research Funds for the Central Public-interest Scientific Institution(2023YSKY-26)the Hulun Buir Grassland Ecological Restoration Comprehensive Survey Project(DD20230474).
文摘In recent years,intensive human activities have increased the intensity of desertification,driving continual desertification process of peripheral meadows.To investigate the effects of restoration on soil microbial communities,we analyzed vegetation-soil relationships in the Hulun Buir Sandy Land,northern China.Through the use of high-throughput sequencing,we examined the structure and diversity in the bacterial and fungal communities within the 0-20 cm soil layer after 9-15 a of restoration.Different slope positions were analyzed and spatial heterogeneity was assessed.The results showed progressive improvements in soil properties and vegetation with the increase of restoration duration,and the following order was as follows:bottom slope>middle slope>crest slope.During the restoration in the Hulun Buir Sandy Land,the bacterial communities were dominated by Proteobacteria,Actinobacteria,and Acidobacteria,whereas the fungal communities were dominated by Ascomycota and Basidiomycota.Eutrophic bacterial abundance increased with the restoration duration,whereas oligotrophic bacterial and fungal abundance levels decreased.The soil bacterial abundance significantly increased with the increasing restoration duration,whereas the fungal diversity decreased after 11 a of restoration,except that at the crest slope.Redundancy analysis showed that pH,soil moisture content,total nitrogen,and vegetation-related factors affected the bacterial community structure(45.43%of the total variance explained).Canonical correspondence analysis indicated that pH,total phosphorus,and vegetation-related factors shaped the bacterial community structure(31.82%of the total variance explained).Structural equation modeling highlighted greater bacterial responses(R^(2)=0.49-0.79)to changes in environmental factors than those of fungi(R^(2)=0.20-0.48).The soil bacterial community was driven mainly by pH,soil moisture content,electrical conductivity,plant coverage,and litter dry weight.The abundance and diversity of the soil fungal community were mainly driven by plant coverage,litter dry weight,and herbaceous aboveground biomass,while there was no significant correlation between the soil fungal community structure and environmental factors.These findings highlighted divergent microbial succession patterns and environmental sensitivities during sandy grassland restoration.
基金funded by two projects of the National Natural Science Foundation of China(No.41802123,42130813).
文摘Sandy braided river deposits are widely preserved in ancient stratigraphic records and act as a significant type of hydrocarbon reservoir.Due to the frequent and rapid migration of channels within the riverbed,the sedimentary architecture is highly complex.In this paper,a flume experiment was conducted to reveal the detailed depositional process and establish a fine sedimentary architecture model for sandy braided rivers.The result showed that(1)Three types of braid channels,including the lateral migration channel,the confluence channel,and the deep incised channel,were recognized based on geometry,scale,distribution,and spatial patterns;they are interconnected,forming a complex channel network.(2)Braid channels were characterized by lateral migration,abandonment,filling,and chute cutoff.Lateral migration of channels shaped the braid bars and dominated the formation,growth,and reworking of braid bars.(3)Controlled by the fast and frequent variations of the braid channel network,braid bars were continuously formed,reworked,reshaped,and composited of multiple accretions with different types,orientations,scales,and preservation degrees.Symmetrical and asymmetrical braid bars pre-sented significantly different composition patterns.(4)Dominated by the continuous reworking of braid channels,temporary deposits were limited preserved,braid channel deposits account for 54.3 percent of the eventually preserved braided river deposits,and four types of amalgamate patterns were recognized.Braid bars were cut and limited preserved,only accounting for 45.7 percent of the eventually preserved braided river deposits.(5)During the experiment,only 28 percent of near-surface temporary deposits were eventually preserved in fragmented forms with the final experimental braided river;the shape,spatial patterns,and most of the deposits observed during the depositional process were largely reworked and poorly preserved.(6)The scale of eventually preserved braid bars and braid channels is significantly smaller than the temporary deposits from geomorphic observations.The aspect ratio of the eventually preserved braid bars and the width-to-depth ratio of the eventually preserved braid channel are also significantly different from that of the temporary ones measured from topography data.
基金supported by the Natural Science Foundation of Beijing Municipality(No.8222004),Chinathe National Natural Science Foundation of China(No.51978019)+3 种基金the Natural Science Foundation of Henan Province(No.252300420445),Chinathe Doctoral Research Initiation Fund of Henan University of Science and Technology(No.4007/13480062),Chinathe Henan Postdoctoral Foundation(No.13554005),Chinathe Joint Fund of Science and Technology R&D Program of Henan Province(No.232103810082),China。
文摘Sandy cobble soil exhibits pronounced heterogeneity.The assessment of the uncertainty surrounding its properties is crucial for the analysis of settlement characteristics resulting from volume loss during shield tunnelling.In this study,a series of probabilistic analyses of surface and subsurface settlements was conducted considering the spatial variability of the friction angle and reference stiffness modulus,under different volumetric block proportions(Pv)and tunnel volume loss rates(ηt).The non-intrusive random finite difference method was used to investigate the probabilistic characteristics of maximum surface settlement,width of subsurface settlement trough,maximum subsurface settlement,and subsurface soil volume loss rate through Monte Carlo simulations.Additionally,a comparison between stochastic and deterministic analysis results is presented to underscore the significance of probabilistic analysis.Parametric analyses were subsequently conducted to investigate the impacts of the key input parameters in random fields on the settlement characteristics.The results indicate that scenarios with higher Pv or greaterηt result in a higher dispersion of stochastic analysis results.Neglecting the spatial variability of soil properties and relying solely on the mean values of material parameters for deterministic analysis may result in an underestimation of surface and subsurface settlements.From a probabilistic perspective,deterministic analysis alone may prove inadequate in accurately capturing the volumetric deformation mode of the soil above the tunnel crown,potentially affecting the prediction of subsurface settlement.
基金funded by the Shaanxi Provincial Department of Science and Technology(2023JCYB449)the Yan'an University Project(YDBK2017-19)+1 种基金the Yan'an Science and Technology Bureau's List System Project(2023SLJBZ002)the Shaanxi Provincial Department of Education Natural Science Special Project(23JK0725,24JK0716).
文摘Investigating the spatiotemporal evolution of vegetation and its response mechanisms to natural and anthropogenic elements is crucial for regional vegetation restoration and ecological preservation.The Mu Us Sandy Land(MUSL),which is situated in the semi-arid zone of northwestern China adjacent to the Loess Plateau,has been at the forefront of desertification and oasis formation over the past two millennia.This study is based on the synthesis of the Normalized Difference Vegetation Index(NDVI)data from MOD13A3 data in the MODIS(Moderate-Resolution Imaging Spectroradiometer)dataset(2002-2021)and climate data(temperature and precipitation)at annual and monthly scales from the National Earth System Science Data Center.A range of analytical methods,including univariate linear regression,Theil-Sen trend analysis and Mann-Kendall significance test,correlation analysis,residual analysis,and Hurst index,were used to explore the response mechanisms of the NDVI to climate change and human activities and to predict the future trends of the NDVI in the MUSL.The results showed that through the method of correlation analysis,in terms of both spatially averaged correlation coefficients and area proportion,the NDVI was positively correlated with temperature and precipitation in 97.59%and 96.51%of the study area,respectively,indicating that temperature has a greater impact on the NDVI than precipitation.Residual analysis quantified the contributions of climate change and human activities to the NDVI changes,revealing that climate change and human activities contribute up to 30.00%and 70.00%,respectively,suggesting that human activities predominantly affect the NDVI changes in the MUSL.The Hurst index was used to categorize the future trend of the NDVI into four main directions of development:continuous degradation(0.05%of the study area),degradation in the past but improvement in the future(54.45%),improvement in the past but degradation in the future(0.13%),and continuous improvement(45.36%).In more than 50.00%of the regions that have been degraded in the past but were expected to improve in the future,the NDVI was expected to exhibit a stable trend of anti-persistent improvement.These findings provide theoretical support for future ecological protection,planning,and the implementation of ecological engineering in the MUSL,and also offer a theoretical basis for the planning and execution of construction projects,environmental protection measures,and the sustainable development of vegetation.
基金This research was jointly supported by the project of the China Geological Survey(DD20242481)Key Laboratory of Airborne Geophysics and Remote Sensing Geology,MNR(2020YFL33)。
文摘Eco-geological vulnerability assessment is a significant research topic within the field of eco-geology,but it remains poorly studied.The Mu Us Sandy Land,located in the central part of the farming-pastoral ecotone in northern China,plays a critical role in maintaining the ecological security pattern in this region.However,this sandy land also faces severe sandy desertification and ecological degradation.This study conducted a regional eco-geological vulnerability assessment of the Mu Us Sandy Land using a comprehensive index evaluation method based on eco-geological theories and survey results.To construct an appropriate index system for the eco-geological vulnerability assessment of the Mu Us Sandy Land,the study considered the sandy land’s unique characteristics and identified 15 factors of five categories,namely geology,meteorology,soil,topography,and vegetation.The paper calculated the comprehensive weights of all the indices using the analytic hierarchy process(AHP)and the entropy weight method(EWM).Furthermore,it established the eco-geological vulnerability index(EGVI)and obtained the assessment results.The results showed that the eco-geological vulnerability of the Mu Us Sandy Land gradually intensifies from east to west,manifested as vulnerable eco-geological conditions overall.Specifically,extremely vulnerable zones are found in the northwestern and southeastern parts of the study area,highly vulnerable zones in the western and southern parts,moderately vulnerable zones in the central part,and slightly and potentially vulnerable zones in the eastern and southern parts.Areas with high spatial autocorrelations include the northern Uxin Banner-Otog Banner-Angsu Town area,the surrounding areas of Hongdunjie Town in the southeastern part of the study area,the Hongshiqiao Township-Xiaohaotu Township area,Otog Front Banner,and Bainijing Town,which should be prioritized in the ecological conservation and restoration.Additionally,the paper proposed suggestions for the ecological conservation and restoration of county-level administrative areas in the study area.Overall,the findings provide a valuable reference for the ecological conservation and restoration of the Mu Us Sandy Land and other desert areas in arid and semi-arid regions.
文摘The soil packing,influenced by variations in grain size and the gradation pattern within the soil matrix,plays a crucial role in constituting the mechanical properties of sandy soils.However,previous modeling approaches have overlooked incorporating the full range of representative parameters to accurately predict the soaked California bearing ratio(CBR_(s))of sandy soils by precisely articulating soil packing in the modeling framework.This study presents an innovative artificial intelligence(AI)-based approach for modeling the CBR_(s)of sandy soils,considering grain size variability meticulously.By synthesizing extensive data from multiple sources,i.e.extensive tailored testing program undertaking multiple tests and extant literature,various modeling techniques including genetic expression programming(GEP),multi-expression programming(MEP),support vector machine(SVM),and multi-linear regression(MLR)are utilized to develop models.The research explores two modeling strategies,namely simplified and composite,with the former incorporating only sieve analysis test parameters,while the latter includes compaction test parameters alongside sieve analysis data.The models'performance is assessed using statistical key performance indicators(KPIs).Results indicate that genetic AI-based algorithms,particularly GEP,outperform SVM and conventional regression techniques,effectively capturing complex relationships between input parameters and CBR_(s).Additionally,the study reveals insights into model performance concerning the number of input parameters,with GEP consistently outperforming other models.External validation and Taylor diagram analysis demonstrate the GEP models'superiority over existing literature models on an independent dataset from the literature.Parametric and sensitivity analyses highlight the intricate relationships between grain sizes and CBR_(s),further emphasizing GEP's efficacy in modeling such complexities.This study contributes to enhancing CBR_(s)modeling accuracy for sandy soils,crucial for pertinent infrastructure design and construction rapidly and cost-effectively.
基金supported by the National Natural Science Foundation of China(Grant No.52308463)the Shanghai Rising-Star Program(Grant No.23YF1449100)the Fundamental Research Funds for the Central Universities(Grant No.2023-2-ZD08).
文摘Due to space constraints in urban areas,metro tunnels are typically constructed in pairs,with a small clearance.The interaction between twin tunnels leads to a significantly more complex ground deformation and stress distribution than that observed in a single tunnel scenario,particularly if the tunnels are excavated in sequence.A series of physical model tests were conducted to investigate soil deformation and stress disturbances caused by the excavation of twin tunnels.The test results indicate that the interaction between the twin tunnels was observed.Due to the soil arching effect,the excavation of Tunnel 2 increases the soil stress acting on Tunnel 1.An analytical method was proposed to determine soil stress considering the soil arching effect and the interaction between twin tunnels.The method categorized the relative locations between twin tunnels into non-influenced,partially influenced,and fully influenced scenarios.For non-influenced and fully influenced scenarios,the soil stresses above twin tunnels were calculated based on a symmetric major principal stress trace.For the partially influenced scenario,however,the soil arch above Tunnel 2 was asymmetric due to the interaction,and the stress distribution was obtained based on a new asymmetric major principal stress trace.The soil stress on Tunnel 1 was influenced by the load transferred from Tunnel 2 and calculated based on the force equilibrium.A comparison of the analytical and test results indicates that the proposed method effectively predicts the soil stress in the cover layer above twin tunnels excavated sequentially,considering the interaction and soil arching effects.
基金The research was supported by innovation research project of Chinese Academy of Sciences (KZCX3-SW-418) and by Nature Science Foundation of Liaoning Province (20021006).
文摘Mongolian pine (Pinus sylvestiris Linnaeus var. mongolica Litvinov) as a valuable conifer tree species has been broadly introduced to the sandy land areas in 揟hree North?regions (North, northwest and northeast of China), but many problems occurred in the earliest Mongolian pine plantations in Zhanggutai, Zhangwu County, Liaoning Province (ZZL). In order to clarify the reason, comprehensive investigations were carried out on differences in structure characteristics, growth processes and ecological factors between artificial stands (the first plantation established in ZZL in 1950s) and natural stands (the origin forests of the tree species in Honghuaerji, Inner Mongolia) on sandy land. The results showed that variation of diameter-class distributions in artificial stands and natural stands could be described by Weibull and Normal distribution models, respectively. Chapman-Richards growth model was employed to reconstruct the growth process of Mongolian pine based on the data from field investigation and stem analysis. The ages of maximum of relative growth rate and average growth rate of DBH, height, and volume of planted trees were 11, 22 years, 8, 15 years and 35, 59 years earlier than those of natural stand trees, respectively. In respect of the incremental acceleration of volume, the artificial and natural stands reached their maximum values at 14 years and 33 years respectively. The quantitative maturity ages of artificial stands and natural stands were 43 years and 102 years respectively. It was concluded that the life span of the Mongolian pine trees in natural stands was about 60 years longer than those in artificial stands. The differences mentioned above between artificial and natural Mongolian pine forests on sandy land were partially attributed to the drastic variations of ecological conditions such as latitude, temperature, precipitation, evaporation and height above sea level. Human beings' disturbances and higher density in plantation forest may be ascribed as additional reasons. Those results may be potentially useful for the management and afforestation of Mongolian pine plantations on sandy land in arid and semi-arid areas.
基金Key Knowledge Innovation Project (KZCX3-SW-418) of Chinese Academy of Sciences.
文摘The concentrations of the foliar and surface soil nutrients and the variation with species and stand age were studied inPinus spp. plantations in Zhanggutai area, northeast China. The results showed that the total N, total P and C: N ratio of the soil inP. sylvestris var.mongolica stands were significantly higher in comparison with those inP. tabulaeformis andP. densiflora stands. ForP. sylvestris var.mongolica, the foliar P concentration appeared to decrease with age, and the foliar N and K concentrations did not show a consistent change with age. As for the different tree species of the similar age, the foliar N and P concentrations were significantly different (p<0.05), being withP. sylvestris var.mongolica>P. densiflora>P. tabulaeformis. The foliar N: P ratio ofP. densiflora significantly was higher thanP. sylvestris var.mongolica andP. tabulaeformis, while the foliar K was no obvious difference between the three tree species. There were significant correlation (p<0.05) between soil total N and P, soil organic matter and total P, foliar N and P, but it did not show significant correlations between soil and foliar nutrient concentrations, which might attribute to the excessive litter raking, overgrazing and low soil moisture in this area. Based on the foliar N: P ratio, we introduced a combination threshold index of N: P ratio with their absolute foliar nutrient concentrations to determine the possible limiting nutrient. According to the critical N: P ratio and their absolute foliar N, P concentrations, theP. sylvestris var.mongolica stands showed a decreased N limitation degree with age, theP. densiflora stands showed unlimited by N and P in the whole, and theP. tabulaeformis stands showed co-limited by N and P. No significant difference in soil nutrient concentrations of the surface soils was found between 45, 29, 20-yr-oldPinus sylvestris var.mongolica plantation stands. Keywords coniferous trees - foliar nutrient concentration - limiting nutrients - N - P ratio - Zhanggutai sandy land CLC number S718.55 Document code A Article ID 1007-662X(2004)01-0011-08 Foundation item: This research was supported by Key Knowledge Innovation Project (KZCX3-SW-418) of Chinese Academy of Sciences.Biography: CHEN Guang-sheng (1978-), male, master candidate in Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, P. R. ChinaResponsible editor: Song Funan
基金This research was supported by Key Knowledge Innova-tion Project (SCXZD0102) of Institute of Applied Ecology Chinese Academy of Sciences and sponsored by the Science and Technology Department of Inner Mongolia Autonomic Region,P. R. China (2001010)
文摘The experiment was conducted at the Ganqika Sandy Land Ecological Station in Ke抏rqinzuoyihouqi County, Inner Mongolia, in a growing season from April 28 to October 28, 2001. Peat and weathered coal were added to the aeolian sandy soil in different ratios. Two-year-old Pinus sylvestris var. mongolica seedlings and plastic pots were used in the experiment. The experimental results indicated that: 1) the peat and weathered coal could significantly improve the physical and chemical prop-erties of aeolian sandy soil, and thus promoted the growth of seedlings; 2) the effect of peat on seedling growth, including height, base diameter, root length and biomass, presented an order of 8%>10%>5%>2%>0 in terms of peat contents, and the effect of weathered coal on seedling growth presented an order of 5%>8%>10%>2%>0 in terms of weathered coal contents for height and basal diameter, 5%>8%>2% >10%>0 for root length, and 5%>2%>8% >10%>0 for biomass; 3) the effects of peat were generally greater than that of weathered coal. Meanwhile, 8% peat was the best treatment to promote the growth of P. sylvestris var. mongolica seedlings.
文摘Calamagrostis epigejos (L.) Roth. is a perennial grass with slender and long rhizome segments between interconnected neighbor ramets. To investigate the phenotypic plasticity in response to the heterogeneous soil water supply, ramet pairs of the species were subjected to heterogeneous water supply by which either mother ramets or daughter ramets were in high or low soil water supply, respectively, in the Maowusu (Mu Us) Sandy Land of Nei Mongol. The results showed that the phenotypic characteristics of the individual ramets of C epigejos were greatly influenced by the heterogeneous water supply. The ramets treated with high water supply significantly produced more new rhizomes and more offspring (ramets), and accumulated more shoot biomass, and allocated more biomass to their shoots than those treated with low water supply. In comparison with the daughter ramets in homogeneous soil water supply, phenotypic characteristics, in terms of new rhizome growth, the production of new offspring, and the biomass allocation pattern, of the daughter ramets within the pairs of the species were not significantly changed, no matter that high or low soil water supply to mother ramets. The phenotypic responses of mother ramets to soil water supply were similar to those of daughter ramets. From these results, it is inferred that the interconnected ramets of C epigejos response phenotypically to their local soil water rather than to the soil water experienced by the interconnected ramets. The interconnected ramets of C epigejos might be independent of each other in water relationship, although they are physically interconnected with rhizome segments. The physiological independence of interconnected ramets might facilitate the risk spreading and thus enhance the genet survivorship under the frequent drought stresses in Mu Us Sandland.
基金Supported by National Key Technology Research and Development Program during the 12th Five-year Plan Period(2012BAD16B0202)Special Fund for Forest Scientific Research in the Public Interest(201004018)~~
文摘[Objective] This study aimed to investigate the artificial vegetations on soil physicochemical properties of sandy land. [Method] The soil physicochemical proper- ties in five representative lands respectively covered by Artemisia ordosica, Salix cheilophila, Hedysarum scoparium, Populus simonii and Amorpha fruticosa, all of which were planted artificially at the same year were measured in the present study, using a bare soil as the control. [Result] Artificial vegetation improved the soil physicochemical properties by different extents in the lands covered by different plants. The soil physicochemical properties such as bulk density under A. Fruticosa and H. Scoparium were improved greatly. The frequency distribution of soil particle size under artificial vegetations exhibited a bimodal curve. The average soil particle size under A. fruticosa was the smallest, and the soil was very poorly sorted. The soil nutrients in the sandy land were not significantly improved by artificial vegeta- tion. [Conclusion] Artificial vegetation has a certain impact on soil properties in sandy land, as it greatly improves the soil physical properties but not the chemical properties.
文摘A new species, Spirulina (Arthrospira) bayannurensis B. Sh. Li et C. Qiao sp. nov. was firstly collected from the Lake of Bayannur, Mu Us Sandy Land, Inner Mongolia Autonomous Region in China on April 30, 1996 The morphological characteristics of the new species are described and illustrated by light micrographs, scanning and transmission electron micrographs. The type specimen of this new species is kept in Herbarium of Inner Mongolia Agricultural University.
基金Under the auspices of Key Direction Program of Chinese Academy of Science(No.KZCX2-YW-Q06-03)MajorState Basic Research Development Program of China(No.2009CB421103)+1 种基金National Natural Science Foundation of China(No.41001050)Major Science and Technology Program for Water Pollution Control and Treatment(No.2012ZX07201004)
文摘This paper analyzed the water-retention mechanism of feldspathic sandstone （fine-（〈 1 mm diam.） and gravel-sized （2-3 cm diam.） in Mu Us Sandy Land, Northwest China. The objective of this study is to study the effect of feldspathic sandstone amendment on water retention in sandy land. The results showed that as the proportion of fine feldspathic sandstone in the sandy land soil increased, the soil texture changed from sand to silt loam, the capillary po- rosity gradually increased from 26.3% to 44.9%, and the soil saturated hydraulic conductivity decreased from 7.10 ram/rain to 0.07 mm/min. Feldspathic sandstone gravel formed micro-reservoirs in the sandy land soil, playing the role of a ＇water absorbent＇ and ＇water retaining agent＇ in sandy land. Amendment with feldspathic sandstone can increase water retention in the arable layer of sandy land by 67%. This study provides a theoretical basis for the amelioration of sandy land on a large scale. It can be concluded that amendment with feldspathic sandstone can improve the physical properties of sandy land soil and increase soil water retention.
