Methanotrophs,organisms that obtain oxygen by oxidizing methane,are recognized as the only known biological sink for atmospheric CH_4,and forest soil methanotrophs play crucial roles in mitigating global warming.The s...Methanotrophs,organisms that obtain oxygen by oxidizing methane,are recognized as the only known biological sink for atmospheric CH_4,and forest soil methanotrophs play crucial roles in mitigating global warming.The succession patterns of methanotrophic communities and functions in Wudalianchi volcano forest soils could provide a basis for the study of evolutionary mechanisms between soil microorganisms,the environment,and carbon cycling of temperate forest ecosystems under climate change.In this study,the characteristics and drivers of methanotrophic community structure and function of two volcanic soils at different stages of development are analyzed,including an old volcano and a new volcano,which most recently erupted 300 years and 17-19×10^(5)years ago,respectively,and a non-volcano hills as control,based on space for time substitution and Miseq sequencing and bioinformation technology.The results showed that CH_(4) fluxes were significantly higher in old-stage volcano forest soils than new-stage forest soils and non-volcano forest soils.There were significant differences in the community composition and diversity of soil methanotrophs from different volcano forest soils.Methylococcus was the dominant genus in all soil samples.Additionally,the relative abundance of Methylococcus,along with Clonothrix,Methyloglobulus,Methylomagum,Methylomonas and Methylosarcina,were the important genera responsible for the differences in methanotrophic community structure in different volcano forest soils.The relative abundance of methanotroph belonging toγ-proteobacteria was significantly higher than that belonging toα-proteobacteria(P<0.05).Chao1,Shannon and Simpson indices of soil methanotrophic community were significantly lower in new-stage volcanos and were significantly affected by bulk density,total porosity,p H,nitrate,dissolved organic carbon and dissolved organic nitrogen.There were significant differences in community structure between new-stage and old-stage volcanoes.Bulk density and p H are important soil properties contributing to the divergence of methanotrophs community structure,and changes in soil properties due to soil development time are important factors driving differences in methanotrophs communities in Wudalianchi volcanic soils.展开更多
Geotechnical engineering data are usually small-sample and high-dimensional,which brings a lot of challenges in predictive modeling.This paper uses a typical high-dimensional and small-sample swell pressure(P s)datase...Geotechnical engineering data are usually small-sample and high-dimensional,which brings a lot of challenges in predictive modeling.This paper uses a typical high-dimensional and small-sample swell pressure(P s)dataset to explore the possibility of using multi-algorithm hybrid ensemble and dimensionality reduction methods to mitigate the uncertainty of soil parameter prediction.Based on six machine learning(ML)algorithms,the base learner pool is constructed,and four ensemble methods,Stacking(SG),Blending(BG),Voting regression(VR),and Feature weight linear stacking(FWL),are used for the multi-algorithm ensemble.Furthermore,the importance of permutation is used for feature dimensionality reduction to mitigate the impact of weakly correlated variables on predictive modeling.The results show that the proposed methods are superior to traditional prediction models and base ML models,where FWL is more suitable for modeling with small-sample datasets,and dimensionality reduction can simplify the data structure and reduce the adverse impact of the small-sample effect,which points the way to feature selection for predictive modeling.Based on the ensemble methods,the feature importance of the five primary factors affecting P s is the maximum dry density(31.145%),clay fraction(15.876%),swell percent(15.289%),plasticity index(14%),and optimum moisture content(13.69%),the influence of input parameters on P s is also investigated,in line with the findings of the existing literature.展开更多
This study aimed to investigate the pollution characteristics, source apportionment, and health risks associated with trace metal(loid)s(TMs) in the major agricultural producing areas in Chongqing, China. We analyzed ...This study aimed to investigate the pollution characteristics, source apportionment, and health risks associated with trace metal(loid)s(TMs) in the major agricultural producing areas in Chongqing, China. We analyzed the source apportionment and assessed the health risk of TMs in agricultural soils by using positive matrix factorization(PMF) model and health risk assessment(HRA) model based on Monte Carlo simulation. Meanwhile, we combined PMF and HRA models to explore the health risks of TMs in agricultural soils by different pollution sources to determine the priority control factors. Results showed that the average contents of cadmium(Cd), arsenic (As), lead(Pb), chromium(Cr), copper(Cu), nickel(Ni), and zinc(Zn) in the soil were found to be 0.26, 5.93, 27.14, 61.32, 23.81, 32.45, and 78.65 mg/kg, respectively. Spatial analysis and source apportionment analysis revealed that urban and industrial sources, agricultural sources, and natural sources accounted for 33.0%, 27.7%, and 39.3% of TM accumulation in the soil, respectively. In the HRA model based on Monte Carlo simulation, noncarcinogenic risks were deemed negligible(hazard index <1), the carcinogenic risks were at acceptable level(10^(-6)<total carcinogenic risk ≤ 10^(-4)), with higher risks observed for children compared to adults. The relationship between TMs, their sources, and health risks indicated that urban and industrial sources were primarily associated with As, contributing to 75.1% of carcinogenic risks and 55.7% of non-carcinogenic risks, making them the primary control factors. Meanwhile, agricultural sources were primarily linked to Cd and Pb, contributing to 13.1% of carcinogenic risks and 21.8% of non-carcinogenic risks, designating them as secondary control factors.展开更多
The non-unique critical state of soils with time-dependent behaviors is a significant issue in geotechnical engineering problems.However,previous bounding surface plasticity models cannot predict accurately the non-un...The non-unique critical state of soils with time-dependent behaviors is a significant issue in geotechnical engineering problems.However,previous bounding surface plasticity models cannot predict accurately the non-unique critical state of soils,because the distance between the compression line and critical state line charged by strain-rate effect is basically neglected.To fill this gap,a generalized spacing ratio of soils is defined in the elasto-viscoplastic framework,and a bounding surface visco-plasticity model is formulated and verified,which can consider the generalized spacing ratio.Specifically,the generalized spacing ratio of soils reflects the distance between the compression line and the critical state line of soils with time-dependent behaviors.Then,the generalized spacing ratio is introduced into an improved anisotropic bounding surface.A new expression of the visco-plastic multiplier is derived by solving the consistency equation of an anisotropic bounding surface.In the expression,a strain rate index is proposed to account for the strain-rate effect on visco-plastic strain increment,and a visco-plastic hardening modulus is derived to predict the visco-plastic response of soils in overconsolidation conditions.The model is then verified through constant strain rate tests and creep tests.Notably,it can capture the non-unique critical states of soils with time-dependent behaviors due to the generalized spacing ratio and the creep rupture of soils due to the visco-plastic multiplier that considers the stress ratio and visco-plastic strain rate.展开更多
Afforestation has an important role in biodiversity conservation and ecosystem function improvement.A meta-analysis was carried out in China,which has the largest plantation area globally,to quantify the effects of pl...Afforestation has an important role in biodiversity conservation and ecosystem function improvement.A meta-analysis was carried out in China,which has the largest plantation area globally,to quantify the effects of plantings on soil microbial diversity.The results showed that the overall effect of afforestation on soil microbial diversity was positive across the country.Random forest algorithm suggested that soil carbon was the most important factor regulating microbial diversity and the positive response was only found with new plantings on low-carbon bare lands but not on high-carbon farmlands and grasslands.In addition,afforestation with broadleaved species increased microbial diversity,whereas planting with conifers had no effect on microbial diversity.This study clarified the effects of plantings on soil microbial diversity,which has an important implication for establishing appropriate policies and practices to improve the multiple functionalities(e.g.,biodiversity conservation and climate change mitigation)during plantation establishment.展开更多
The traditional standard wet sieving method uses steel sieves with aperture?0.063 mm and can only determine the particle size distribution(PSD)of gravel and sand in general soil.This paper extends the traditional meth...The traditional standard wet sieving method uses steel sieves with aperture?0.063 mm and can only determine the particle size distribution(PSD)of gravel and sand in general soil.This paper extends the traditional method and presents an extended wet sieving method.The extended method uses both the steel sieves and the nylon filter cloth sieves.The apertures of the cloth sieves are smaller than 0.063 mm and equal 0.048 mm,0.038 mm,0.014 mm,0.012 mm,0.0063 mm,0.004 mm,0.003 mm,0.002 mm,and 0.001 mm,respectively.The extended method uses five steps to separate the general soil into many material sub-groups of gravel,sand,silt and clay with known particle size ranges.The complete PSD of the general soil is then calculated from the dry masses of the individual material sub-groups.The extended method is demonstrated with a general soil of completely decomposed granite(CDG)in Hong Kong,China.The silt and clay materials with different particle size ranges are further examined,checked and verified using stereomicroscopic observation,physical and chemical property tests.The results further confirm the correctness of the extended wet sieving method.展开更多
Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions.Due to the unique marine depositional environment of coral sandy soils,the engineering characteristics and respons...Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions.Due to the unique marine depositional environment of coral sandy soils,the engineering characteristics and responses of these soils subjected to monotonic and cyclic loadings have been a subject of intense interest among the geotechnical and earthquake engineering communities.This paper critically reviews the progress of experimental investigations on the undrained behavior of coral sandy soils under monotonic and cyclic loadings over the last three decades.The focus of coverage includes the contractive-dilative behavior,the pattern of excess pore-water pressure(EPWP)generation and the liquefaction mechanism and liquefaction resistance,the small-strain shear modulus and strain-dependent shear modulus and damping,the cyclic softening feature,and the anisotropic characteristics of undrained responses of saturated coral sandy soils.In particular,the advances made in the past decades are reviewed from the following aspects:(1)the characterization of factors that impact the mechanism and patterns of EPWP build-up;(2)the identification of liquefaction triggering in terms of the apparent viscosity and the average flow coefficient;(3)the establishment of the invariable form of strain-based,stress-based,or energy-based EPWP ratio formulas and the unique relationship between the new proxy of liquefaction resistance and the number of cycles required to reach liquefaction;(4)the establishment of the invariable form of the predictive formulas of small strain modulus and strain-dependent shear modulus;and(5)the investigation on the effects of stress-induced anisotropy on liquefaction susceptibility and dynamic deformation characteristics.Insights gained through the critical review of these advances in the past decades offer a perspective for future research to further resolve the fundamental issues concerning the liquefaction mechanism and responses of coral sandy sites subjected to cyclic loadings associated with seismic events in marine environments.展开更多
In recent years,there has been growing interest in developing methods for mitigating greenhouse effect,as greenhouse gas emissions continue to contribute to global temperature rise.On the other hand,investigating geop...In recent years,there has been growing interest in developing methods for mitigating greenhouse effect,as greenhouse gas emissions continue to contribute to global temperature rise.On the other hand,investigating geopolymers as environmentally friendly binders to mitigate the greenhouse effect using soil stabilization has been widely conducted.However,the effect of CO_(2)exposure on the mechanical properties of geopolymer-stabilized soils is rarely reported.In this context,the effect of CO_(2)exposure on the mechanical and microstructural features of sandy soil stabilized with volcanic ash-based geopolymer was investigated.Several factors were concerned,for example the binder content,relative density,CO_(2)pressure,curing condition,curing time,and carbonate content.The results showed that the compressive strength of the stabilized sandy soil specimens with 20%volcanic ash increased from 3 MPa to 11 MPa.It was also observed that 100 kPa CO_(2)pressure was the optimal pressure for strength development among the other pressures.The mechanical strength showed a direct relationship with binder content and carbonate content.Additionally,in the ambient curing(AC)condition,the mechanical strength and carbonate content increased with the curing time.However,the required water for carbonation evaporated after 7 d of oven curing(OC)condition and as a result,the 14-d cured samples showed lower mechanical strength and carbonate content in comparison with 7-d cured samples.Moreover,the rate of strength development was higher in OC cured samples than AC cured samples until 7 d due to higher geopolymerization and carbonation rate.展开更多
Savanna regions in Nigeria face environmental degradation and barren land, negatively impacting food and agricultural productivity. Inter-rill erosion occurs due to raindrop impact and transport, particularly on hill ...Savanna regions in Nigeria face environmental degradation and barren land, negatively impacting food and agricultural productivity. Inter-rill erosion occurs due to raindrop impact and transport, particularly on hill slopes. A study was conducted using a sprinkler rainfall simulator and plot experiment to study soil erosion processes. Soil samples were collected from four farms in Gidan Kwanu, with varying moisture content. Sand content ranged from 46.0% to 76.20%, silt from 11.30% to 23.50%, and clay from 11.0% to 30.0%. Uncultivated and bare land had a higher average porosity (15.47% and 14.99%), while cultivated land had lower porosity (14.4%). The study found that most people in Gidan-Kwanu primarily practice farming, which is season-dependent and rain-fed. Soil type and texture significantly contribute to inter-rill erosion, with cultivated and uncultivated soil being more resistant to erosion than bare land soil. The study concluded that farming practices in Gidan-Kwanu are primarily season-dependent and rain-fed. Soil type and texture significantly contribute to inter-rill erosion, with cultivated and uncultivated soil being more resistant to erosion than bare land soil.展开更多
This research study explored the efficacy of leaf litter compost as a sustainable soil amendment with the objective of promoting soil health and mitigating the accumulation of potentially toxic elements. The investiga...This research study explored the efficacy of leaf litter compost as a sustainable soil amendment with the objective of promoting soil health and mitigating the accumulation of potentially toxic elements. The investigation encompassed the impact of various organic compost amendments, including leaf compost, cow dung manure, kitchen waste compost, municipal organic waste compost, and vermicompost. The study employed Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to evaluate soil nutrient levels and concentrations of Potentially Toxic Elements (PTEs) such as arsenic, chromium, cadmium, mercury, lead, nickel, and lithium. The fertilization and bioremediation potential of these compost amendments are quantified using an indexing method. Results indicated a substantial increase in overall nutrient levels (carbon, nitrogen, phosphorus, potassium, and sulfur) in soils treated with leaf compost and other organic composts. Fertility indices (FI) are notably higher in compost-amended soils (ranging from 2.667 to 3.938) compared to those amended with chemical fertilizers (ranging from 2.250 to 2.813) across all soil samples. Furthermore, the mean concentrations of PTEs were significantly lower in soils treated with leaf compost and other organic compost amendments compared to those treated with chemical fertilizers amendments. The assessment through the indexing method revealed a high clean index (CI) for leaf compost amendment (ranging from 3.407 to 3.58), whereas the chemical fertilizer amendment exhibits a relatively lower CI (ranging from 2.78 to 3.20). Consequently, leaf compost and other organic composts exhibit the potential to enhance sustainable productivity, promoting soil health and environmental safety by improving nutrient levels and remediating potentially toxic elements in the soil.展开更多
Assessing soil quality is essential for crop management and soil temporal changes. The present study aims to evaluate soil quality in the Ferralitic soils context countrywide. This assessment was done using multivaria...Assessing soil quality is essential for crop management and soil temporal changes. The present study aims to evaluate soil quality in the Ferralitic soils context countrywide. This assessment was done using multivariate soil quality indice (SQI) models, such as additive quality index (AQI), weighted quality indexes (WQI<sub>add</sub> and WQI<sub>com</sub>) and Nemoro quality index (NQI), applied to two approaches of indicator selection: total data set (TDS) and minimum data set (MDS). Physical and chemical soil indicators were extracted from the ORSTOM’s reports resulting from a sampling campaign in different provinces of Gabon. The TDS approach shows soil quality status according to eleven soil indicators extracted from the analysis of 1,059 samples from arable soil layer (0 - 30 cm depth). The results indicated that 87% of all provinces presented a very low soil quality (Q5) whatever the model. Among soil indicators, exchangeable K<sup>+</sup> and Mg<sup>2+</sup>, bulk density and C/N ratio were retained in MDS, using principal component analysis (PCA). In the MDS approach, 50 to 63% of provinces had low soil quality grades with AQI, WQI<sub>add</sub> and NQI, whereas the total was observed with WQI<sub>com</sub>. Only 25% of provinces had medium soil quality grades with AQI and NQI models, while 12.5% (NQI) and 25% (AQI) presented high quality grades. Robust statistical analyses confirmed the accuracy and validation (0.80 r P ≤ 0.016) of AQI, WQI<sub>add</sub> and NQI into the TDS and MDS approaches. The same sensitivity index value (1.53) was obtained with AQI and WQI<sub>add</sub>. However, WQI<sub>add</sub> was chosen as the best SQI model, according to its high linear regression value (R<sup>2</sup> = 0.82) between TDS and MDS. This study has important implications in decision-making on monitoring, evaluation and sustainable management of Gabonese soils in a pedoclimatic context unfavorable to plant growth.展开更多
The objective of this study was to establish a baseline for future studies that aim to determine possible contamination from human, agricultural and industrial activities. As well as the determination of the indices o...The objective of this study was to establish a baseline for future studies that aim to determine possible contamination from human, agricultural and industrial activities. As well as the determination of the indices of environmental or geological contamination and enrichment factors of heavy metals Cr, Ni, Cu, Zn, As, Cd, Hg and Pb in agricultural soils of Constanza, Jarabacoa, Rancho Arriba and San José de Ocoa (SJO), municipalities located in the valleys of the Central mountain range of the Dominican Republic. The determination of the concentrations of heavy metals was carried out using the X-ray Fluorescence technique. Just like in Azua, San Juan de la Maguana (SJM) y Barahona in the southwest. Producer municipalities of vegetables, rice, beans, corn, melon, watermelon, tomato, banana, avocado, sugar cane and fodder for cattle. The concentration of 160 mg·kg<sup>-1</sup> Probable Effect Level (PEL) of Cr according to the SQuiRTs table (USEPA-NOAA) for agricultural soils, were exceeded in 50% of the samples in SJM, SJO, Jarabacoa and Constanza;in Barahona and Azua by 20%. The PEL of 42.8 mg·kg-1</sup><sup></sup> of the Ni was higher in more than 50% of the samples from SJM, Azua, Barahona and Jarabacoa;in SJO and Constanza at 35%. In the case of Cu with a PEL of 108 mg·kg-1</sup><sup></sup> in SJO and Constanza, 5% of the samples exceeded its, in the other areas the concentrations were lower. Zn, As and Pb did not manage to exceed their respective PEL.展开更多
The burial of waste in developing countries, which is often carried out without respect for environmental standards, constitutes a risk of contamination of soils and even groundwater given the toxic elements they cont...The burial of waste in developing countries, which is often carried out without respect for environmental standards, constitutes a risk of contamination of soils and even groundwater given the toxic elements they contain. The objective of this work is to carry out a study of the retention of heavy metals through the contribution of cattle manure to soil samples from the final Agoè Nyivé landfill in Lomé, Togo. Soil samples from the final landfill were taken from the surface and depth at several locations to form a composite sample. The amendment of the composite sample was carried out with bovine manure on the mock-up in the Laboratory for six months. The determination of the total contents of heavy metals by the atomic absorption spectrophotometer (SAA) on the composite sample showed high contents exceeding the thresholds recommended by the AFNOR NF U 44-041 standard. Sequential extraction on these composite samples showed that the mobile portions of lead, cadmium, copper and zinc are respectively estimated at 78.06%, 50%, 28.89% and 91.59%. The bovine manure used to amend the landfill samples presents physicochemical parameters that can contribute to rendering heavy metals immobile in the soil matrix under natural conditions. The addition of manure initially made it possible to increase the values of pH, electrical conductivity, cation exchange capacity and organic matter, which promote the retention of heavy metals. Secondly, the addition of manure made it possible to reduce the mobile portion of the heavy metals studied;from 78.06% to 14.39% for lead, from 50% to 11.52% for cadmium, from 28.89% to almost 0% for copper and from 91.15% to 80.58% for zinc. The use of cattle manure as an amendment on the composite sample was decisive in reducing the mobility of heavy metals in the polluted soils of the final landfill.展开更多
The soils of Malta are calcareous and generally undeveloped. Organic matter (OM) in these soils is low and farmers are constantly urged to increase it. The objective of this study was to evaluate any temporal variatio...The soils of Malta are calcareous and generally undeveloped. Organic matter (OM) in these soils is low and farmers are constantly urged to increase it. The objective of this study was to evaluate any temporal variation in soil OM after 15 years of cultivation, and determine whether soil series, soil depth, and cultivation influence variation. OM was determined in the topsoil and subsoil of 7 agricultural and 4 non-agricultural sites. The sites represented 7 different soil series that are present on the island. In sampling periods 1 (t = 0 years) and 2 (t =15 years), the OM content in the collective (all soil series) bulk (topsoil and subsoil) uncultivated soil was 3.9 % and 3.8 % respectively. This was significantly greater than that of the collective bulk cultivated soil (2.4% and 2.3%). The OM in the collective uncultivated topsoil was 5.4% and 5.2% in periods 1 and 2 and was significantly higher than that of the cultivated topsoil (2.5% in both periods). The OM content in the collective uncultivated subsoil was 2.3% and 2.5% in periods 1 and 2 respectively but only that measured in period 2 was significantly higher than that of the cultivated subsoil (2.2% in both periods). On an individual soil series basis, the OM in the uncultivated topsoils was significantly higher than that of their cultivated counterparts. The differences in the subsoils were not significant. Across the uncultivated soil series, OM was significantly higher in the topsoil than in the subsoil but in the cultivated soil series the differences between topsoil and subsoil were not significant. There was no significant difference in OM between the uncultivated soils of different series, but in the cultivated the OM content was higher in soils that were more mature. After 15 years, no significant change in OM occurred in both the collective cultivated and uncultivated bulk soils, the collective topsoil and subsoil, and in most of the individual series. The OM content of each soil series was also similar to what was reported 60 and 50 years earlier by other researchers.展开更多
The main objective of our study has been to determine the role of deadwood in the shaping of the amount of soil organic matter fractions in mountain forest soils.For this purpose,a climosequence approach comprising no...The main objective of our study has been to determine the role of deadwood in the shaping of the amount of soil organic matter fractions in mountain forest soils.For this purpose,a climosequence approach comprising north(N)and south(S)exposure along the altitudinal gradient(600,800,1000 and 1200 m a.s.l.)was set up.By comparing the properties of decomposing deadwood and those of the soils located directly beneath the decaying wood we drew conclusions about the role of deadwood in the shaping of soil organic matter fractions and soil carbon storage in different climate conditions.The basic properties,enzymatic activity and fractions of soil organic matter(SOM)were determined in deadwood and affected directly by the components released from decaying wood.Heavily decomposed deadwood impacts soil organic matter stabilization more strongly than the less decayed deadwood and the light fraction of SOM is more sensitive to deadwood effects than the heavy fraction regardless of the location in the altitude gradient.Increase in SOM mineral-associated fraction C content is more pronounced in soils under the influence of deadwood located in lower locations of warmer exposure.Nutrients released from decaying wood stimulate the enzymatic activity of soils that are within the range of deadwood influence.展开更多
Fallout volcanic deposits of SommaVesuvius(Campania,southern Italy),characterized by the presence of layers with contrasting textural and hydraulic properties,are frequently affected by shallow landslides during rainw...Fallout volcanic deposits of SommaVesuvius(Campania,southern Italy),characterized by the presence of layers with contrasting textural and hydraulic properties,are frequently affected by shallow landslides during rainwater infiltration.The soils of the stratigraphic sequence present intraparticle pores,originated by the gases escaped during magma decompression in the volcanic conduit,thus are characterized by double porosity(i.e.,intraparticle and interparticle pores),which is expected to affect their hydraulic behaviour,and to play a key role in rainwater infiltration through layered deposits.To understand the effect of double porosity on the hydraulic behaviour of the involved soils,controlled experiments have been carried out in an infiltration column.The experimental apparatus is provided with newly designed non-invasive Time Domain Reflectometry(TDR)probes,not buried in the investigated soil layers so as to minimize disturbance to the flow,allowing water content measurement during vertical flow processes.Specifically,transient flow experiments are carried out through reconstituted specimens of black scoriae and grey pumices,both loose pyroclastic granular soils from fallout deposits of Somma-Vesuvius,featuring double porosity with different pore size distributions,that were estimated by X-ray tomography and Mercury Intrusion Porosimetry.The experimental results highlight the effects of the double porosity and clearly indicate the different behaviour of the two soils during wetting and drying processes,mainly related to the different dimensions of intraparticle pores.展开更多
Restoration of mining soils is important to the vegetation and environment.This study aimed to explore the variations in soil nutrient contents,microbial abundance,and biomass under different gradients of substrate am...Restoration of mining soils is important to the vegetation and environment.This study aimed to explore the variations in soil nutrient contents,microbial abundance,and biomass under different gradients of substrate amendments in mining soils to select effective measures.Soil samples were collected from the Bayan Obo mining region in Inner Mongolia Autonomous Region,China.Contents of soil organic matter(SOM),available nitrogen(AN),available phosphorus(AP),available potassium(AK),microbial biomass carbon/microbial biomass nitrogen(MBC/MBN)ratio,biomass,and bacteria,fungi,and actinomycetes abundance were assessed in Agropyron cristatum L.Gaertn.,Elymus dahuricus Turcz.,and Medicago sativa L.soils with artificial zeolite(AZ)and microbial fertilizer(MF)applied at T0(0 g/kg),T1(5 g/kg),T2(10 g/kg),and T3(20 g/kg).Redundancy analysis(RDA)and technique for order preference by similarity to ideal solution(TOPSIS)were used to identify the main factors controlling the variation of biomass.Results showed that chemical indices and microbial content of restored soils were far greater than those of control.The application of AZ significantly increases SOM,AN,and AP by 20.27%,23.61%,and 40.43%,respectively.AZ significantly increased bacteria,fungi,and actinomycetes abundance by 0.63,3.12,and 1.93 times of control,respectively.RDA indicated that AN,MBC/MBN ratio,and SOM were dominant predictors for biomass across samples with AZ application,explaining 87.6%of the biomass variance.SOM,MBC/MBN ratio,and AK were dominant predictors with MF application,explaining 82.9%of the biomass variance.TOPSIS indicated that T2 was the best dosage and the three plant species could all be used to repair mining soils.AZ and MF application at T2 concentration in the mining soils with M.sativa was found to be the most appropriate measure.展开更多
This paper presents an experimental and analytical investigation of the influence of variables related to soil weathering on the geomechanical performance of sand-silt mixtures containing lateritic soils,i.e.intensely...This paper presents an experimental and analytical investigation of the influence of variables related to soil weathering on the geomechanical performance of sand-silt mixtures containing lateritic soils,i.e.intensely weathered tropical soils with the influence of interparticle bonding.The sand-silt mixtures containing different relative proportions between uniform sand and lateritic soil were produced,and geomechanical soil characterization tests were performed.Based on the results,a transition from a primarily coarse-to a fine-grained prevailing soil structure was found to cause considerable impact on the geomechanical performance of these soils,as evidenced by design variables related to soil mineralogy and size distribution characteristics.Specifically,fines contents of both individual soil particles and soil aggregations were found to correlate with experimental results,while the relative proportion between sesquioxides(aluminum,and iron oxides),and silica,i.e.sesquioxide-silica ratios(SSR^(-1)),facilitated estimates concerning changes in geomechanical performance.Finally,the application of the sandsilt mixtures containing lateritic soil on soil walls reinforced with polymeric strips was also evaluated,further emphasizing the potential advantages of adopting variables related to soil weathering on design guidelines concerning tropical soils.展开更多
Acid soils occupy approximately 50% of potentially arable lands.Improving crop productivity in acid soils,therefore,will be crucial for ensuring food security and agricultural sustainability.High soil acidity often co...Acid soils occupy approximately 50% of potentially arable lands.Improving crop productivity in acid soils,therefore,will be crucial for ensuring food security and agricultural sustainability.High soil acidity often coexists with phosphorus(P) deficiency and aluminum(Al) toxicity,a combination that severely impedes crop growth and yield across wide areas.As roots explore soil for the nutrients and water required for plant growth and development,they also sense and respond to below-ground stresses.Within the terrestrial context of widespread P deficiency and Al toxicity pressures,plants,particularly roots,have evolved a variety of mechanisms for adapting to these stresses.As legumes,soybean(Glycine max) plants may acquire nitrogen(N) through symbiotic nitrogen fixation(SNF),an adaptation that can be useful for mitigating excessive N fertilizer use,either directly as leguminous crop participants in rotation and intercropping systems,or secondarily as green manure cover crops.In this review,we investigate legumes,especially soybean,for recent advances in our understanding of root-based mechanisms linked with root architecture modification,exudation and symbiosis,together with associated genetic and molecular strategies in adaptation to individual and/or interacting P and Al conditions in acid soils.We propose that breeding legume cultivars with superior nutrient efficiency and/or Al tolerance traits through genetic selection might become a potentially powerful strategy for producing crop varieties capable of maintaining or improving yields in more stressful soil conditions subjected to increasingly challenging environmental conditions.展开更多
This study aimed to investigate whether saline silt and sandy loam coastal soils could be reclaimed by micro-sprinkler irrigation.The experiments were run using moderately salt-tolerant tall fescue grass.Micro-sprinkl...This study aimed to investigate whether saline silt and sandy loam coastal soils could be reclaimed by micro-sprinkler irrigation.The experiments were run using moderately salt-tolerant tall fescue grass.Micro-sprinkler irrigation in three stages was used to regulate soil matric potential at a 20-cm soil depth.Continued regulation of soil water and salt through micro-sprinkler irrigation consistently resulted in an increasingly large low-salinity region.The application of the three stages of soil wateresalt regulation resulted in an absence of salt accumulation throughout the soil profile and the conversion of highly saline soils into moderately saline soils.There were increases in the plant height,leaf width,leaf length,and tiller numbers of tall fescue throughout the leaching process.The results showed that micro-sprinkler irrigation in three soil water and salt regulation stages can be used to successfully cultivate tall festuca in highly saline coastal soil.This approach achieved better effects in sandy loam soil than in silt soil.Tall fescue showed greater survival rates in sandy loam soil due to the rapid reclamation process,whereas plant growth was higher in silt soil because of effective water conservation.In sandy loam,soil moisture should be maintained during soil reclamation,and in silt soil,soil root-zone environments optimal for the emergence of plants should be quickly established.Micro-sprinkler irrigation can be successfully applied to the cultivation of tall fescue in coastal heavy saline soils under a three-stage soil wateresalt regulation regime.展开更多
基金the Special Projects for the Central Government to guide the development of local science and technology(ZY20B15)the Key Research&Development Program funding project of Heilongjiang Province(GA21C030)the Research Funds of Provincial Research Institutes of Heilongjiang Province(ZNBZ2022ZR07)。
文摘Methanotrophs,organisms that obtain oxygen by oxidizing methane,are recognized as the only known biological sink for atmospheric CH_4,and forest soil methanotrophs play crucial roles in mitigating global warming.The succession patterns of methanotrophic communities and functions in Wudalianchi volcano forest soils could provide a basis for the study of evolutionary mechanisms between soil microorganisms,the environment,and carbon cycling of temperate forest ecosystems under climate change.In this study,the characteristics and drivers of methanotrophic community structure and function of two volcanic soils at different stages of development are analyzed,including an old volcano and a new volcano,which most recently erupted 300 years and 17-19×10^(5)years ago,respectively,and a non-volcano hills as control,based on space for time substitution and Miseq sequencing and bioinformation technology.The results showed that CH_(4) fluxes were significantly higher in old-stage volcano forest soils than new-stage forest soils and non-volcano forest soils.There were significant differences in the community composition and diversity of soil methanotrophs from different volcano forest soils.Methylococcus was the dominant genus in all soil samples.Additionally,the relative abundance of Methylococcus,along with Clonothrix,Methyloglobulus,Methylomagum,Methylomonas and Methylosarcina,were the important genera responsible for the differences in methanotrophic community structure in different volcano forest soils.The relative abundance of methanotroph belonging toγ-proteobacteria was significantly higher than that belonging toα-proteobacteria(P<0.05).Chao1,Shannon and Simpson indices of soil methanotrophic community were significantly lower in new-stage volcanos and were significantly affected by bulk density,total porosity,p H,nitrate,dissolved organic carbon and dissolved organic nitrogen.There were significant differences in community structure between new-stage and old-stage volcanoes.Bulk density and p H are important soil properties contributing to the divergence of methanotrophs community structure,and changes in soil properties due to soil development time are important factors driving differences in methanotrophs communities in Wudalianchi volcanic soils.
基金great gratitude to National Key Research and Development Project(Grant No.2019YFC1509800)for their financial supportNational Nature Science Foundation of China(Grant No.12172211)for their financial support.
文摘Geotechnical engineering data are usually small-sample and high-dimensional,which brings a lot of challenges in predictive modeling.This paper uses a typical high-dimensional and small-sample swell pressure(P s)dataset to explore the possibility of using multi-algorithm hybrid ensemble and dimensionality reduction methods to mitigate the uncertainty of soil parameter prediction.Based on six machine learning(ML)algorithms,the base learner pool is constructed,and four ensemble methods,Stacking(SG),Blending(BG),Voting regression(VR),and Feature weight linear stacking(FWL),are used for the multi-algorithm ensemble.Furthermore,the importance of permutation is used for feature dimensionality reduction to mitigate the impact of weakly correlated variables on predictive modeling.The results show that the proposed methods are superior to traditional prediction models and base ML models,where FWL is more suitable for modeling with small-sample datasets,and dimensionality reduction can simplify the data structure and reduce the adverse impact of the small-sample effect,which points the way to feature selection for predictive modeling.Based on the ensemble methods,the feature importance of the five primary factors affecting P s is the maximum dry density(31.145%),clay fraction(15.876%),swell percent(15.289%),plasticity index(14%),and optimum moisture content(13.69%),the influence of input parameters on P s is also investigated,in line with the findings of the existing literature.
基金supported by Project of Chongqing Science and Technology Bureau (cstc2022jxjl0005)。
文摘This study aimed to investigate the pollution characteristics, source apportionment, and health risks associated with trace metal(loid)s(TMs) in the major agricultural producing areas in Chongqing, China. We analyzed the source apportionment and assessed the health risk of TMs in agricultural soils by using positive matrix factorization(PMF) model and health risk assessment(HRA) model based on Monte Carlo simulation. Meanwhile, we combined PMF and HRA models to explore the health risks of TMs in agricultural soils by different pollution sources to determine the priority control factors. Results showed that the average contents of cadmium(Cd), arsenic (As), lead(Pb), chromium(Cr), copper(Cu), nickel(Ni), and zinc(Zn) in the soil were found to be 0.26, 5.93, 27.14, 61.32, 23.81, 32.45, and 78.65 mg/kg, respectively. Spatial analysis and source apportionment analysis revealed that urban and industrial sources, agricultural sources, and natural sources accounted for 33.0%, 27.7%, and 39.3% of TM accumulation in the soil, respectively. In the HRA model based on Monte Carlo simulation, noncarcinogenic risks were deemed negligible(hazard index <1), the carcinogenic risks were at acceptable level(10^(-6)<total carcinogenic risk ≤ 10^(-4)), with higher risks observed for children compared to adults. The relationship between TMs, their sources, and health risks indicated that urban and industrial sources were primarily associated with As, contributing to 75.1% of carcinogenic risks and 55.7% of non-carcinogenic risks, making them the primary control factors. Meanwhile, agricultural sources were primarily linked to Cd and Pb, contributing to 13.1% of carcinogenic risks and 21.8% of non-carcinogenic risks, designating them as secondary control factors.
基金the financial support provided by the National Key R&D Program of China(Grant No.2023YFC3008400)National Natural Science Foundation of China(Grant No.42102317)Qin Chuangyuan“ScientisttEngineer”Team Construction Project of Shaanxi Province in China(Grant No.2023KXJ-178).
文摘The non-unique critical state of soils with time-dependent behaviors is a significant issue in geotechnical engineering problems.However,previous bounding surface plasticity models cannot predict accurately the non-unique critical state of soils,because the distance between the compression line and critical state line charged by strain-rate effect is basically neglected.To fill this gap,a generalized spacing ratio of soils is defined in the elasto-viscoplastic framework,and a bounding surface visco-plasticity model is formulated and verified,which can consider the generalized spacing ratio.Specifically,the generalized spacing ratio of soils reflects the distance between the compression line and the critical state line of soils with time-dependent behaviors.Then,the generalized spacing ratio is introduced into an improved anisotropic bounding surface.A new expression of the visco-plastic multiplier is derived by solving the consistency equation of an anisotropic bounding surface.In the expression,a strain rate index is proposed to account for the strain-rate effect on visco-plastic strain increment,and a visco-plastic hardening modulus is derived to predict the visco-plastic response of soils in overconsolidation conditions.The model is then verified through constant strain rate tests and creep tests.Notably,it can capture the non-unique critical states of soils with time-dependent behaviors due to the generalized spacing ratio and the creep rupture of soils due to the visco-plastic multiplier that considers the stress ratio and visco-plastic strain rate.
基金supported by the National Key Research and Development Program of China(2021YFD2200401)the National Natural Science Foundation of China(31901293)。
文摘Afforestation has an important role in biodiversity conservation and ecosystem function improvement.A meta-analysis was carried out in China,which has the largest plantation area globally,to quantify the effects of plantings on soil microbial diversity.The results showed that the overall effect of afforestation on soil microbial diversity was positive across the country.Random forest algorithm suggested that soil carbon was the most important factor regulating microbial diversity and the positive response was only found with new plantings on low-carbon bare lands but not on high-carbon farmlands and grasslands.In addition,afforestation with broadleaved species increased microbial diversity,whereas planting with conifers had no effect on microbial diversity.This study clarified the effects of plantings on soil microbial diversity,which has an important implication for establishing appropriate policies and practices to improve the multiple functionalities(e.g.,biodiversity conservation and climate change mitigation)during plantation establishment.
基金The work described in this paper was partially supported by grants from the Research Grant Council of the Hong Kong Special Administrative Region,China(Project Nos.HKU 17207518 and R5037-18).
文摘The traditional standard wet sieving method uses steel sieves with aperture?0.063 mm and can only determine the particle size distribution(PSD)of gravel and sand in general soil.This paper extends the traditional method and presents an extended wet sieving method.The extended method uses both the steel sieves and the nylon filter cloth sieves.The apertures of the cloth sieves are smaller than 0.063 mm and equal 0.048 mm,0.038 mm,0.014 mm,0.012 mm,0.0063 mm,0.004 mm,0.003 mm,0.002 mm,and 0.001 mm,respectively.The extended method uses five steps to separate the general soil into many material sub-groups of gravel,sand,silt and clay with known particle size ranges.The complete PSD of the general soil is then calculated from the dry masses of the individual material sub-groups.The extended method is demonstrated with a general soil of completely decomposed granite(CDG)in Hong Kong,China.The silt and clay materials with different particle size ranges are further examined,checked and verified using stereomicroscopic observation,physical and chemical property tests.The results further confirm the correctness of the extended wet sieving method.
基金National Natural Science Foundation of China under Grant No.52278503。
文摘Coral sandy soils widely exist in coral island reefs and seashores in tropical and subtropical regions.Due to the unique marine depositional environment of coral sandy soils,the engineering characteristics and responses of these soils subjected to monotonic and cyclic loadings have been a subject of intense interest among the geotechnical and earthquake engineering communities.This paper critically reviews the progress of experimental investigations on the undrained behavior of coral sandy soils under monotonic and cyclic loadings over the last three decades.The focus of coverage includes the contractive-dilative behavior,the pattern of excess pore-water pressure(EPWP)generation and the liquefaction mechanism and liquefaction resistance,the small-strain shear modulus and strain-dependent shear modulus and damping,the cyclic softening feature,and the anisotropic characteristics of undrained responses of saturated coral sandy soils.In particular,the advances made in the past decades are reviewed from the following aspects:(1)the characterization of factors that impact the mechanism and patterns of EPWP build-up;(2)the identification of liquefaction triggering in terms of the apparent viscosity and the average flow coefficient;(3)the establishment of the invariable form of strain-based,stress-based,or energy-based EPWP ratio formulas and the unique relationship between the new proxy of liquefaction resistance and the number of cycles required to reach liquefaction;(4)the establishment of the invariable form of the predictive formulas of small strain modulus and strain-dependent shear modulus;and(5)the investigation on the effects of stress-induced anisotropy on liquefaction susceptibility and dynamic deformation characteristics.Insights gained through the critical review of these advances in the past decades offer a perspective for future research to further resolve the fundamental issues concerning the liquefaction mechanism and responses of coral sandy sites subjected to cyclic loadings associated with seismic events in marine environments.
基金This study was supported by MatSoil Company(Grant No.04G/2022)This research was funded by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie(Grant No.778120).
文摘In recent years,there has been growing interest in developing methods for mitigating greenhouse effect,as greenhouse gas emissions continue to contribute to global temperature rise.On the other hand,investigating geopolymers as environmentally friendly binders to mitigate the greenhouse effect using soil stabilization has been widely conducted.However,the effect of CO_(2)exposure on the mechanical properties of geopolymer-stabilized soils is rarely reported.In this context,the effect of CO_(2)exposure on the mechanical and microstructural features of sandy soil stabilized with volcanic ash-based geopolymer was investigated.Several factors were concerned,for example the binder content,relative density,CO_(2)pressure,curing condition,curing time,and carbonate content.The results showed that the compressive strength of the stabilized sandy soil specimens with 20%volcanic ash increased from 3 MPa to 11 MPa.It was also observed that 100 kPa CO_(2)pressure was the optimal pressure for strength development among the other pressures.The mechanical strength showed a direct relationship with binder content and carbonate content.Additionally,in the ambient curing(AC)condition,the mechanical strength and carbonate content increased with the curing time.However,the required water for carbonation evaporated after 7 d of oven curing(OC)condition and as a result,the 14-d cured samples showed lower mechanical strength and carbonate content in comparison with 7-d cured samples.Moreover,the rate of strength development was higher in OC cured samples than AC cured samples until 7 d due to higher geopolymerization and carbonation rate.
文摘Savanna regions in Nigeria face environmental degradation and barren land, negatively impacting food and agricultural productivity. Inter-rill erosion occurs due to raindrop impact and transport, particularly on hill slopes. A study was conducted using a sprinkler rainfall simulator and plot experiment to study soil erosion processes. Soil samples were collected from four farms in Gidan Kwanu, with varying moisture content. Sand content ranged from 46.0% to 76.20%, silt from 11.30% to 23.50%, and clay from 11.0% to 30.0%. Uncultivated and bare land had a higher average porosity (15.47% and 14.99%), while cultivated land had lower porosity (14.4%). The study found that most people in Gidan-Kwanu primarily practice farming, which is season-dependent and rain-fed. Soil type and texture significantly contribute to inter-rill erosion, with cultivated and uncultivated soil being more resistant to erosion than bare land soil. The study concluded that farming practices in Gidan-Kwanu are primarily season-dependent and rain-fed. Soil type and texture significantly contribute to inter-rill erosion, with cultivated and uncultivated soil being more resistant to erosion than bare land soil.
文摘This research study explored the efficacy of leaf litter compost as a sustainable soil amendment with the objective of promoting soil health and mitigating the accumulation of potentially toxic elements. The investigation encompassed the impact of various organic compost amendments, including leaf compost, cow dung manure, kitchen waste compost, municipal organic waste compost, and vermicompost. The study employed Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to evaluate soil nutrient levels and concentrations of Potentially Toxic Elements (PTEs) such as arsenic, chromium, cadmium, mercury, lead, nickel, and lithium. The fertilization and bioremediation potential of these compost amendments are quantified using an indexing method. Results indicated a substantial increase in overall nutrient levels (carbon, nitrogen, phosphorus, potassium, and sulfur) in soils treated with leaf compost and other organic composts. Fertility indices (FI) are notably higher in compost-amended soils (ranging from 2.667 to 3.938) compared to those amended with chemical fertilizers (ranging from 2.250 to 2.813) across all soil samples. Furthermore, the mean concentrations of PTEs were significantly lower in soils treated with leaf compost and other organic compost amendments compared to those treated with chemical fertilizers amendments. The assessment through the indexing method revealed a high clean index (CI) for leaf compost amendment (ranging from 3.407 to 3.58), whereas the chemical fertilizer amendment exhibits a relatively lower CI (ranging from 2.78 to 3.20). Consequently, leaf compost and other organic composts exhibit the potential to enhance sustainable productivity, promoting soil health and environmental safety by improving nutrient levels and remediating potentially toxic elements in the soil.
文摘Assessing soil quality is essential for crop management and soil temporal changes. The present study aims to evaluate soil quality in the Ferralitic soils context countrywide. This assessment was done using multivariate soil quality indice (SQI) models, such as additive quality index (AQI), weighted quality indexes (WQI<sub>add</sub> and WQI<sub>com</sub>) and Nemoro quality index (NQI), applied to two approaches of indicator selection: total data set (TDS) and minimum data set (MDS). Physical and chemical soil indicators were extracted from the ORSTOM’s reports resulting from a sampling campaign in different provinces of Gabon. The TDS approach shows soil quality status according to eleven soil indicators extracted from the analysis of 1,059 samples from arable soil layer (0 - 30 cm depth). The results indicated that 87% of all provinces presented a very low soil quality (Q5) whatever the model. Among soil indicators, exchangeable K<sup>+</sup> and Mg<sup>2+</sup>, bulk density and C/N ratio were retained in MDS, using principal component analysis (PCA). In the MDS approach, 50 to 63% of provinces had low soil quality grades with AQI, WQI<sub>add</sub> and NQI, whereas the total was observed with WQI<sub>com</sub>. Only 25% of provinces had medium soil quality grades with AQI and NQI models, while 12.5% (NQI) and 25% (AQI) presented high quality grades. Robust statistical analyses confirmed the accuracy and validation (0.80 r P ≤ 0.016) of AQI, WQI<sub>add</sub> and NQI into the TDS and MDS approaches. The same sensitivity index value (1.53) was obtained with AQI and WQI<sub>add</sub>. However, WQI<sub>add</sub> was chosen as the best SQI model, according to its high linear regression value (R<sup>2</sup> = 0.82) between TDS and MDS. This study has important implications in decision-making on monitoring, evaluation and sustainable management of Gabonese soils in a pedoclimatic context unfavorable to plant growth.
文摘The objective of this study was to establish a baseline for future studies that aim to determine possible contamination from human, agricultural and industrial activities. As well as the determination of the indices of environmental or geological contamination and enrichment factors of heavy metals Cr, Ni, Cu, Zn, As, Cd, Hg and Pb in agricultural soils of Constanza, Jarabacoa, Rancho Arriba and San José de Ocoa (SJO), municipalities located in the valleys of the Central mountain range of the Dominican Republic. The determination of the concentrations of heavy metals was carried out using the X-ray Fluorescence technique. Just like in Azua, San Juan de la Maguana (SJM) y Barahona in the southwest. Producer municipalities of vegetables, rice, beans, corn, melon, watermelon, tomato, banana, avocado, sugar cane and fodder for cattle. The concentration of 160 mg·kg<sup>-1</sup> Probable Effect Level (PEL) of Cr according to the SQuiRTs table (USEPA-NOAA) for agricultural soils, were exceeded in 50% of the samples in SJM, SJO, Jarabacoa and Constanza;in Barahona and Azua by 20%. The PEL of 42.8 mg·kg-1</sup><sup></sup> of the Ni was higher in more than 50% of the samples from SJM, Azua, Barahona and Jarabacoa;in SJO and Constanza at 35%. In the case of Cu with a PEL of 108 mg·kg-1</sup><sup></sup> in SJO and Constanza, 5% of the samples exceeded its, in the other areas the concentrations were lower. Zn, As and Pb did not manage to exceed their respective PEL.
文摘The burial of waste in developing countries, which is often carried out without respect for environmental standards, constitutes a risk of contamination of soils and even groundwater given the toxic elements they contain. The objective of this work is to carry out a study of the retention of heavy metals through the contribution of cattle manure to soil samples from the final Agoè Nyivé landfill in Lomé, Togo. Soil samples from the final landfill were taken from the surface and depth at several locations to form a composite sample. The amendment of the composite sample was carried out with bovine manure on the mock-up in the Laboratory for six months. The determination of the total contents of heavy metals by the atomic absorption spectrophotometer (SAA) on the composite sample showed high contents exceeding the thresholds recommended by the AFNOR NF U 44-041 standard. Sequential extraction on these composite samples showed that the mobile portions of lead, cadmium, copper and zinc are respectively estimated at 78.06%, 50%, 28.89% and 91.59%. The bovine manure used to amend the landfill samples presents physicochemical parameters that can contribute to rendering heavy metals immobile in the soil matrix under natural conditions. The addition of manure initially made it possible to increase the values of pH, electrical conductivity, cation exchange capacity and organic matter, which promote the retention of heavy metals. Secondly, the addition of manure made it possible to reduce the mobile portion of the heavy metals studied;from 78.06% to 14.39% for lead, from 50% to 11.52% for cadmium, from 28.89% to almost 0% for copper and from 91.15% to 80.58% for zinc. The use of cattle manure as an amendment on the composite sample was decisive in reducing the mobility of heavy metals in the polluted soils of the final landfill.
文摘The soils of Malta are calcareous and generally undeveloped. Organic matter (OM) in these soils is low and farmers are constantly urged to increase it. The objective of this study was to evaluate any temporal variation in soil OM after 15 years of cultivation, and determine whether soil series, soil depth, and cultivation influence variation. OM was determined in the topsoil and subsoil of 7 agricultural and 4 non-agricultural sites. The sites represented 7 different soil series that are present on the island. In sampling periods 1 (t = 0 years) and 2 (t =15 years), the OM content in the collective (all soil series) bulk (topsoil and subsoil) uncultivated soil was 3.9 % and 3.8 % respectively. This was significantly greater than that of the collective bulk cultivated soil (2.4% and 2.3%). The OM in the collective uncultivated topsoil was 5.4% and 5.2% in periods 1 and 2 and was significantly higher than that of the cultivated topsoil (2.5% in both periods). The OM content in the collective uncultivated subsoil was 2.3% and 2.5% in periods 1 and 2 respectively but only that measured in period 2 was significantly higher than that of the cultivated subsoil (2.2% in both periods). On an individual soil series basis, the OM in the uncultivated topsoils was significantly higher than that of their cultivated counterparts. The differences in the subsoils were not significant. Across the uncultivated soil series, OM was significantly higher in the topsoil than in the subsoil but in the cultivated soil series the differences between topsoil and subsoil were not significant. There was no significant difference in OM between the uncultivated soils of different series, but in the cultivated the OM content was higher in soils that were more mature. After 15 years, no significant change in OM occurred in both the collective cultivated and uncultivated bulk soils, the collective topsoil and subsoil, and in most of the individual series. The OM content of each soil series was also similar to what was reported 60 and 50 years earlier by other researchers.
基金financed by the National Science Centre,Poland:decision no.DEC 2020/39/B/NZ9/00372
文摘The main objective of our study has been to determine the role of deadwood in the shaping of the amount of soil organic matter fractions in mountain forest soils.For this purpose,a climosequence approach comprising north(N)and south(S)exposure along the altitudinal gradient(600,800,1000 and 1200 m a.s.l.)was set up.By comparing the properties of decomposing deadwood and those of the soils located directly beneath the decaying wood we drew conclusions about the role of deadwood in the shaping of soil organic matter fractions and soil carbon storage in different climate conditions.The basic properties,enzymatic activity and fractions of soil organic matter(SOM)were determined in deadwood and affected directly by the components released from decaying wood.Heavily decomposed deadwood impacts soil organic matter stabilization more strongly than the less decayed deadwood and the light fraction of SOM is more sensitive to deadwood effects than the heavy fraction regardless of the location in the altitude gradient.Increase in SOM mineral-associated fraction C content is more pronounced in soils under the influence of deadwood located in lower locations of warmer exposure.Nutrients released from decaying wood stimulate the enzymatic activity of soils that are within the range of deadwood influence.
文摘Fallout volcanic deposits of SommaVesuvius(Campania,southern Italy),characterized by the presence of layers with contrasting textural and hydraulic properties,are frequently affected by shallow landslides during rainwater infiltration.The soils of the stratigraphic sequence present intraparticle pores,originated by the gases escaped during magma decompression in the volcanic conduit,thus are characterized by double porosity(i.e.,intraparticle and interparticle pores),which is expected to affect their hydraulic behaviour,and to play a key role in rainwater infiltration through layered deposits.To understand the effect of double porosity on the hydraulic behaviour of the involved soils,controlled experiments have been carried out in an infiltration column.The experimental apparatus is provided with newly designed non-invasive Time Domain Reflectometry(TDR)probes,not buried in the investigated soil layers so as to minimize disturbance to the flow,allowing water content measurement during vertical flow processes.Specifically,transient flow experiments are carried out through reconstituted specimens of black scoriae and grey pumices,both loose pyroclastic granular soils from fallout deposits of Somma-Vesuvius,featuring double porosity with different pore size distributions,that were estimated by X-ray tomography and Mercury Intrusion Porosimetry.The experimental results highlight the effects of the double porosity and clearly indicate the different behaviour of the two soils during wetting and drying processes,mainly related to the different dimensions of intraparticle pores.
基金supported by the Beijing Forestry University(BJFU),China。
文摘Restoration of mining soils is important to the vegetation and environment.This study aimed to explore the variations in soil nutrient contents,microbial abundance,and biomass under different gradients of substrate amendments in mining soils to select effective measures.Soil samples were collected from the Bayan Obo mining region in Inner Mongolia Autonomous Region,China.Contents of soil organic matter(SOM),available nitrogen(AN),available phosphorus(AP),available potassium(AK),microbial biomass carbon/microbial biomass nitrogen(MBC/MBN)ratio,biomass,and bacteria,fungi,and actinomycetes abundance were assessed in Agropyron cristatum L.Gaertn.,Elymus dahuricus Turcz.,and Medicago sativa L.soils with artificial zeolite(AZ)and microbial fertilizer(MF)applied at T0(0 g/kg),T1(5 g/kg),T2(10 g/kg),and T3(20 g/kg).Redundancy analysis(RDA)and technique for order preference by similarity to ideal solution(TOPSIS)were used to identify the main factors controlling the variation of biomass.Results showed that chemical indices and microbial content of restored soils were far greater than those of control.The application of AZ significantly increases SOM,AN,and AP by 20.27%,23.61%,and 40.43%,respectively.AZ significantly increased bacteria,fungi,and actinomycetes abundance by 0.63,3.12,and 1.93 times of control,respectively.RDA indicated that AN,MBC/MBN ratio,and SOM were dominant predictors for biomass across samples with AZ application,explaining 87.6%of the biomass variance.SOM,MBC/MBN ratio,and AK were dominant predictors with MF application,explaining 82.9%of the biomass variance.TOPSIS indicated that T2 was the best dosage and the three plant species could all be used to repair mining soils.AZ and MF application at T2 concentration in the mining soils with M.sativa was found to be the most appropriate measure.
文摘This paper presents an experimental and analytical investigation of the influence of variables related to soil weathering on the geomechanical performance of sand-silt mixtures containing lateritic soils,i.e.intensely weathered tropical soils with the influence of interparticle bonding.The sand-silt mixtures containing different relative proportions between uniform sand and lateritic soil were produced,and geomechanical soil characterization tests were performed.Based on the results,a transition from a primarily coarse-to a fine-grained prevailing soil structure was found to cause considerable impact on the geomechanical performance of these soils,as evidenced by design variables related to soil mineralogy and size distribution characteristics.Specifically,fines contents of both individual soil particles and soil aggregations were found to correlate with experimental results,while the relative proportion between sesquioxides(aluminum,and iron oxides),and silica,i.e.sesquioxide-silica ratios(SSR^(-1)),facilitated estimates concerning changes in geomechanical performance.Finally,the application of the sandsilt mixtures containing lateritic soil on soil walls reinforced with polymeric strips was also evaluated,further emphasizing the potential advantages of adopting variables related to soil weathering on design guidelines concerning tropical soils.
基金financially supported by the National Natural Science Foundation of China (32072661)the National Key Research and Development Program of China(2021YFF1000500)。
文摘Acid soils occupy approximately 50% of potentially arable lands.Improving crop productivity in acid soils,therefore,will be crucial for ensuring food security and agricultural sustainability.High soil acidity often coexists with phosphorus(P) deficiency and aluminum(Al) toxicity,a combination that severely impedes crop growth and yield across wide areas.As roots explore soil for the nutrients and water required for plant growth and development,they also sense and respond to below-ground stresses.Within the terrestrial context of widespread P deficiency and Al toxicity pressures,plants,particularly roots,have evolved a variety of mechanisms for adapting to these stresses.As legumes,soybean(Glycine max) plants may acquire nitrogen(N) through symbiotic nitrogen fixation(SNF),an adaptation that can be useful for mitigating excessive N fertilizer use,either directly as leguminous crop participants in rotation and intercropping systems,or secondarily as green manure cover crops.In this review,we investigate legumes,especially soybean,for recent advances in our understanding of root-based mechanisms linked with root architecture modification,exudation and symbiosis,together with associated genetic and molecular strategies in adaptation to individual and/or interacting P and Al conditions in acid soils.We propose that breeding legume cultivars with superior nutrient efficiency and/or Al tolerance traits through genetic selection might become a potentially powerful strategy for producing crop varieties capable of maintaining or improving yields in more stressful soil conditions subjected to increasingly challenging environmental conditions.
基金supported by the China Scholarship Council(Grant No.201906715015)the Priority Academic Development Program of Jiangsu Higher Education Institutions.
文摘This study aimed to investigate whether saline silt and sandy loam coastal soils could be reclaimed by micro-sprinkler irrigation.The experiments were run using moderately salt-tolerant tall fescue grass.Micro-sprinkler irrigation in three stages was used to regulate soil matric potential at a 20-cm soil depth.Continued regulation of soil water and salt through micro-sprinkler irrigation consistently resulted in an increasingly large low-salinity region.The application of the three stages of soil wateresalt regulation resulted in an absence of salt accumulation throughout the soil profile and the conversion of highly saline soils into moderately saline soils.There were increases in the plant height,leaf width,leaf length,and tiller numbers of tall fescue throughout the leaching process.The results showed that micro-sprinkler irrigation in three soil water and salt regulation stages can be used to successfully cultivate tall festuca in highly saline coastal soil.This approach achieved better effects in sandy loam soil than in silt soil.Tall fescue showed greater survival rates in sandy loam soil due to the rapid reclamation process,whereas plant growth was higher in silt soil because of effective water conservation.In sandy loam,soil moisture should be maintained during soil reclamation,and in silt soil,soil root-zone environments optimal for the emergence of plants should be quickly established.Micro-sprinkler irrigation can be successfully applied to the cultivation of tall fescue in coastal heavy saline soils under a three-stage soil wateresalt regulation regime.
