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Journal articles on the topic 'Soils Soil structure'
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1
Rengasamy, P., and KA Olsson. "Sodicity and soil structure." Soil Research 29, no. 6 (1991): 935. http://dx.doi.org/10.1071/sr9910935.
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Sodic soils are widespread in Australia reflecting the predominance of sodium chloride in groundwaters and soil solutions. Sodic soils are subject to severe structural degradation and restrict plant performance through poor soil-water and soil-air relations. Sodicity is shown to be a latent problem in saline-sodic soils where deleterious effects are evident only after leaching profiles free of salts. A classification of sodic soils based on sodium adsorption ratio, pH and electrolyte conductivity is outlined. Current understanding of the processes and the component mechanisms of sodic soil behaviour are integrated to form the necessary bases for practical solutions in the long term and to define areas for research. The principles of organic and biological amelioration of sodicity, as alternatives to costly inorganic amendments, are discussed.
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Aliboeva, M. A. "Morphological Structure Of Mountain Soils." American Journal of Agriculture and Biomedical Engineering 03, no. 12 (December 30, 2021): 33–37. http://dx.doi.org/10.37547/tajabe/volume03issue12-08.
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This article discusses morphological structure of mountain soils. The mountainous regions of the Republic of Uzbekistan are located mainly in Tashkent, Surkhandarya, Samarkand, Jizzakh, Syrdarya, Fergana Valley and Navoi regions, and differ from each other in their greenery, charm and structure. Mountain soils are distributed sequentially according to the law of vertical zoning, depending on the altitude above sea level. The soil cover in these regions is characterized by their development (evolution), genesis, agrochemical, agrophysical properties and, most importantly, morphological structure. Each region has its own natural factors, which directly affect the development and morphological structure of the soil cover.
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JavidSharifi, Behtash, and Sedigheh Gheisari. "EFFECTS OF STRUCTURE HEIGHT ON SEISMIC DEMAND OF MOMENT-RESISTING REINFORCED CONCRETE FRAMES CONSIDERING SOIL-STRUCTURE INTERACTION." NED University Journal of Research XVIII, no. 1 (January 1, 2021): 15–32. http://dx.doi.org/10.35453/nedjr-stmech-2020-0006.
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Forces and displacements induced in a building due to structural responses to earthquake excitation are called seismic demands which depend upon the input motion, structural characteristics, site effects and the interaction of structure with soil. Structural response of three laterally non-controlled moment-resisting reinforced concrete frame structures with three different soil conditions are have been investigated in this paper. The soil conditions include loose soil, medium soil and rigid ground. The soil-structure interaction of low-, mid- and high-rise frame structures with the above mentioned soil types was analysed by performing nonlinear response history analyses. A set of eleven earthquake motions was employed in the analyses and maximum structural seismic demands for the frame structures were calculated. It was found that pressure-independent relatively loose sandy soils are not very critical for low-rise structures. On the other hand, pressure-independent relatively loose sandy soils and pressure-independent medium sandy soils are highly critical for mid-rise and high-rise structures, respectively. Categorisation of the soils is performed based on the value ranges of a series of constitutive parameters. Further, fixity of the base is most effective in controlling storey displacements until approximately one-third of the structure height. Medium soil leads to highest maximum base shears in low-rise structures while fixed-base and medium cases, and fixed base state control the behaviours of mid-rise and high-rise structures, respectively.
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Zhai, Zhanghui, Yaguo Zhang, Shuxiong Xiao, and Tonglu Li. "Undrained Elastoplastic Solution for Cylindrical Cavity Expansion in Structured Cam Clay Soil Considering the Destructuration Effects." Applied Sciences 12, no. 1 (January 3, 2022): 440. http://dx.doi.org/10.3390/app12010440.
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Soil structure has significant influences on the mechanical behaviors of natural soils, although it is rarely considered in previous cavity expansion analyses. This paper presents an undrained elastoplastic solution for cylindrical cavity expansion in structured soils, considering the destructuration effects. Firstly, a structural ratio was defined to denote the degree of the initial structure, and the Structured Cam Clay (SCC) model was employed to describe the subsequent stress-induced destructuration, including the structure degradation and crushing. Secondly, combined with the large strain theory, the considered problem was formulated as a system of first-order differential equations, which can be solved in a simplified procedure with the introduced auxiliary variable. Finally, the significance and efficiency of the present solution was demonstrated by comparing with the previous solutions, and parametric studies were also conducted to investigate the effects of soil structure and destructuration on the cavity expansion process. The results show that the soil structure has pronounced effects on the mechanical behavior of structured soils around the cavity. For structured soils, a cavity pressure that is larger than the corresponding reconstituted soils when the cavity expands to the same radius is required, and the effective stresses first increase to a peak value before decreasing rapidly with soil structure degradation and crushing. The same final critical state is reached for soils with different degrees of the initial structure, which indicates that the soil structure is completely destroyed during the cavity expansion. With the increase of the destructuring index, the soil structure was destroyed more rapidly, and the stress release during the plastic deformation became more significant. Moreover, the present solution was applied in the jacking of a casing during the sand compact pile installation and in situ self-boring pressuremeter (SBPM) tests, which indicates that the present solution provides an effective theoretical tool for predicting the behavior of natural structured soils around the cavity.
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Li, Wugang, Wenhua Liu, Zhijia Xue, and Xiuli Sun. "A Constitutive Model for Overconsolidated Structured Soils Using Structural Variable." Shock and Vibration 2021 (August 9, 2021): 1–14. http://dx.doi.org/10.1155/2021/5530038.
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Due to the influence of soil structure, structured soils exhibit significantly different mechanical behavior compared to the reconstituted soils having the same material. In this work, a theoretical analysis focusing on the mechanical behavior of structured soils is presented. Based on the mechanical behavior of the structured soil, a newly defined variable structural index was used as a measurement of the integrity of soil structure based on the concept of intrinsic compression line of intact structured soils. Furthermore, a novel correlation for the variation in volume of structured soils is established using effective stress and newly defined structural index as the constitutive variables. The novel correlation provided interpretation about the mechanism of compression behavior of the structured soils. Afterwards, the proposed correlation for the variation in volume was extended to triaxial stress state in the framework of subloading surface to include the effect of overconsolidation. Comparisons between the predictions and experimental results validated the proposed constitutive model for structured soils.
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Timofeeva, Yulia, Elena Sukhacheva, Boris Aparin, Vitaly Terleev, Aleksandr Nikonorov, and Luka Akimov. "Soil structure of sand quarries territory." E3S Web of Conferences 157 (2020): 02017. http://dx.doi.org/10.1051/e3sconf/202015702017.
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Anthropogenic activities are one of the leading factors of soil differentiation. Significant changes in the soil cover occur as a result of the construction of quarries. The mining industry causes the complete degradation of soils in large areas, the change of the natural soil cover and elevation around the quarries, the destruction of vegetation, disturbs biodiversity of the territory and the death of ecosystems. Soil cover structures of mining quarries have been considered on the example of the Leningrad region such as a natural conditions and environmental peculiarities typical for the whole Russian North-West area. Decoding and diagnostic signs of anthropogenic transformed soils were determined. The type and degree of transformation of the component composition, the contrast and heterogeneity of the soil cover, intercomponent connections, the shape and figure of the internal organization of the of soil cover structures have been identified. The complexity of the anthropogenic transformed soils cover is illustrated by “key site”.
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Cotching, W. E., and K. C. Belbin. "Assessment of the influence of soil structure on soil strength/soil wetness relationships on Red Ferrosols in north-west Tasmania." Soil Research 45, no. 2 (2007): 147. http://dx.doi.org/10.1071/sr06113.
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The relationship of soil wetness to soil strength in Red Ferrosols was compared between fields of well structured to degraded soil structure. Soil structure was assessed using a visual rating. Soil resistance measurements were taken over a range of soil wetness, using a recording penetrometer. Readings were taken as the soil dried by evapotranspiration after both irrigation and rainfall events. The influence of soil wetness on penetration resistance was greater on fields with degraded structure than on well-structured fields. In fields with degraded structure, the wetter the soil, the smaller were the penetration resistance values. Field soil structure score was negatively correlated with the slope of the line relating soil wetness and penetration resistance at 150–300 mm depth. The structurally degraded fields had a highly significant relationship between penetration resistance and soil wetness at 150–300 mm depth. In well-structured fields, variations in soil wetness had less effect on penetration resistance. These results indicate that visual assessment can be used with confidence to assess Ferrosol structure. The implications for soil management are that fields with degraded soil structure have greater resistance to root growth at drier moisture contents than well-structured fields. Consequently, farmers need to keep degraded soils wetter with more frequent irrigation than well-structured soils, to ensure optimum plant growth.
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Wilpert, Klaus von. "Forest Soils—What’s Their Peculiarity?" Soil Systems 6, no. 1 (January 6, 2022): 5. http://dx.doi.org/10.3390/soilsystems6010005.
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Mankind expects from forests and forest soils benefits like pure drinking water, space for recreation, habitats for nature-near biocenoses and the production of timber as unrivaled climate-friendly raw material. An overview over 208 recent articles revealed that ecosystem services are actually the main focus in the perception of forest soil functions. Studies on structures and processes that are the basis of forest soil functions and ecosystem services are widely lacking. Therefore, additional literature was included dealing with the distinct soil structure and high porosity and pore continuity of forest soils, as well as with their high biological activity and chemical soil reaction. Thus, the highly differentiated, hierarchical soil structure in combination with the ion exchange capacity and the acid buffering capacity could be described as the main characteristics of forest soils confounding the desired ecosystem services. However, some of these functions of forest soils are endangered under the influence of environmental change or even because of forest management, like mono-cultures or soil compaction through forest machines. In the face of the high vulnerability of forest soils and increased threads, e.g., through soil acidification, it is evident that active soil management strategies must be implemented with the aim to counteract the loss of soil functions or to recover them.
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Xu, Bin Bin. "Influence of Soil Structure on the Mechanical Response of Soft Soil." E3S Web of Conferences 38 (2018): 03027. http://dx.doi.org/10.1051/e3sconf/20183803027.
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Usually the natural sedimentary soils possess structure more or less, which makes their mechanical response much different from the fully remolded soils. In this paper, the influence of soil structure on the mechanical response such as compressibility, shear, permeability is literately reviewed. It is found that the compressibility and consolidation behavior of structured and remolded soils can be divided clearly before or after the structural yield stress. The stress-strain relationship can be divided into two segments before and after the structural yield stress. Before the yield stress, the curve is elevating and after the yield stress the curve is decreasing. The increasing rate of pore water pressure increases after the soil reached yield stress.
10
Saye, Steven R., Bryan P. Kumm, and Alan J. Lutenegger. "Estimating overconsolidation ratio (OCR) in structured and unstructured cohesive soil with field vane tests referencing soil index properties." Canadian Geotechnical Journal 58, no. 1 (January 2021): 125–41. http://dx.doi.org/10.1139/cgj-2019-0414.
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Estimation of the preconsolidation stress and overconsolidation ratio (OCR) in uniform cohesive soils using a field vane is variably impacted by the combined effects of soil type and plasticity, geologic history, structured vs. unstructured behavior, and the presence of sand or organic matter. Published empirical correlations for cohesive soils consider the effects of soil type and plasticity, but significant variability can occur with changes in soil structure and organic matter content for specific instances. The adaption of the “stress history and normalized soil engineering properties” (SHANSEP) format improves the characterization of overconsolidated soils using field vane tests by applying a proposed empirical approach to identify structured soils from unstructured soils and updating the SHANSEP-based approach to separately evaluate structured and unstructured soils. Validation of the correlation coefficients for individual projects will be needed as the approach is applied to new geologic materials and with potentially different field vane equipment and laboratory testing procedures used to characterize the soils. This additional testing provides an opportunity to improve the correlations for specific conditions and reduce the variability in the OCR assessments.
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Camacho, Antonio, César Mora, Antonio Picazo, Carlos Rochera, Alba Camacho-Santamans, Daniel Morant, Luis Roca-Pérez, José Joaquín Ramos-Miras, José A. Rodríguez-Martín, and Rafael Boluda. "Effects of Soil Quality on the Microbial Community Structure of Poorly Evolved Mediterranean Soils." Toxics 10, no. 1 (January 3, 2022): 14. http://dx.doi.org/10.3390/toxics10010014.
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Physical and chemical alterations may affect the microbiota of soils as much as the specific presence of toxic pollutants. The relationship between the microbial diversity patterns and the soil quality in a Mediterranean context is studied here to test the hypothesis that soil microbiota is strongly affected by the level of anthropogenic soil alteration. Our aim has been to determine the potential effect of organic matter loss and associated changes in soil microbiota of poorly evolved Mediterranean soils (Leptosols and Regosols) suffering anthropogenic stress (i.e., cropping and deforestation). The studied soils correspond to nine different sites which differed in some features, such as the parent material, vegetation cover, or soil use and types. A methodological approach has been used that combines the classical physical and chemical study of soils with molecular characterization of the microbial assemblages using specific primers for Bacteria, Archaea and ectomycorrhizal Fungi. In agreement with previous studies within the region, physical, chemical and biological characteristics of soils varied notably depending on these factors. Microbial biomass, soil organic matter, and moisture, decreased in soils as deforestation increased, even in those partially degraded to substitution shrubland. Major differences were observed in the microbial community structure between the mollic and rendzic Leptosols found in forest soils, and the skeletic and dolomitic Leptosols in substitute shrublands, as well as with the skeletic and dolomitic Leptosols and calcaric Regosols in dry croplands. Forest soils displayed a higher microbial richness (OTU’s number) and biomass, as well as more stable and connected ecological networks. Here, we point out how human activities such as agriculture and other effects of deforestation led to changes in soil properties, thus affecting its quality driving changes in their microbial diversity and biomass patterns. Our findings demonstrate the potential risk that the replacement of forest areas may have in the conservation of the soil’s microbiota pool, both active and passive, which are basic for the maintenance of biogeochemical processes.
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Yu, Zhi, Kunnan Liang, Guihua Huang, Xianbang Wang, Mingping Lin, Yinglong Chen, and Zaizhi Zhou. "Soil Bacterial Community Shifts Are Driven by Soil Nutrient Availability along a Teak Plantation Chronosequence in Tropical Forests in China." Biology 10, no. 12 (December 15, 2021): 1329. http://dx.doi.org/10.3390/biology10121329.
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Soil bacterial communities play crucial roles in ecosystem functions and biogeochemical cycles of fundamental elements and are sensitive to environmental changes. However, the response of soil bacterial communities to chronosequence in tropical ecosystems is still poorly understood. This study characterized the structures and co-occurrence patterns of soil bacterial communities in rhizosphere and bulk soils along a chronosequence of teak plantations and adjacent native grassland as control. Stand ages significantly shifted the structure of soil bacterial communities but had no significant impact on bacterial community diversity. Bacterial community diversity in bulk soils was significantly higher than that in rhizosphere soils. The number of nodes and edges in the bacterial co-occurrence network first increased and then decreased with the chronosequence. The number of strongly positive correlations per network was much higher than negative correlations. Available potassium, total potassium, and available phosphorus were significant factors influencing the structure of the bacterial community in bulk soils. In contrast, urease, total potassium, pH, and total phosphorus were significant factors affecting the structure of the bacterial community in the rhizosphere soils. These results indicate that available nutrients in the soil are the main drivers regulating soil bacterial community variation along a teak plantation chronosequence.
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Lopes, Bruna de Carvalho Faria Lima, Vinícius de Oliveira Kühn, Ângela Custódia Guimarães Queiroz, Bernardo Caicedo, and Manoel Porfírio Cordão Neto. "Structure evaluation of a tropical residual soil under wide range of compaction conditions." Géotechnique Letters 12, no. 2 (June 1, 2022): 1–8. http://dx.doi.org/10.1680/jgele.21.00101.
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Soil compaction is one of the most common techniques used to engineer the soil. It is especially appealing to developing countries for its cost-effective and sustainable attributes for improving the soil's geotechnical characteristics. The compaction process along with the complexity of residual soils, abundant in the tropics zone, can have an impact on the performance of geotechnical structures built with these soils. Therefore, it is important to understand the influence that certain compaction conditions have on the structure of these materials. To investigate that, mercury intrusion porosimetry tests were performed on compacted samples of a tropical residual soil from Brazil under different conditions of water content and compactive effort. Results show that the compacted soil under all studied conditions presents a bimodal pore-size distribution (PSD). It appears that the low availability of water within the macro-pores, hence suction, could have played a decisive role in maintaining the bimodal framework of the PSD. In this respect, this study contributes to a better understanding of the tropical residual soils’ structure when subjected to different compaction conditions, thus providing means to improve field applications.
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Shepherd, T. G., S. Saggar, R. H. Newman, C. W. Ross, and J. L. Dando. "Tillage-induced changes to soil structure and organic carbon fractions in New Zealand soils." Soil Research 39, no. 3 (2001): 465. http://dx.doi.org/10.1071/sr00018.
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The effects of increasing cropping and soil compaction on aggregate stability and dry-sieved aggregate-size distribution, and their relationship to total organic C (TOC) and the major functional groups of soil organic carbon, were investigated on 5 soils of contrasting mineralogy. All soils except the allophanic soil showed a significant decline in aggregate stability under medium- to long-term cropping. Mica-rich, fine-textured mineral and humic soils showed the greatest increase in the mean weight diameter (MWD) of dry aggregates, while the oxide-rich soils, and particularly the allophanic soils, showed only a slight increase in the MWD after long-term cropping. On conversion back to pasture, the aggregate stability of the mica-rich soils increased and the MWD of the aggregate-size distribution decreased, with the humic soil showing the greatest recovery. Aggregate stability and dry aggregate-size distribution patterns show that soil resistance to structural degradation and soil resilience increased from fine-textured to coarse-textured to humic mica-rich soils to oxide-rich soils to allophanic soils. Coarse- and fine-textured mica-rich and oxide-rich soils under pasture contained medium amounts of TOC, hot-water soluble carbohydrate (WSC), and acid hydrolysable carbohydrate (AHC), all of which declined significantly under cropping. The rate of decline varied with soil type in the initial years of cropping, but was similar under medium- and long-term cropping. TOC was high in the humic mica-rich and allophanic soils, and levels did not decline appreciably under medium- and long-term cropping. 13C-nuclear magnetic resonance evidence also indicates that all major functional groups of soil organic carbon declined under cropping, with O-alkyl C and alkyl C showing the fastest and slowest rate of decline, respectively. On conversion back to pasture, both WSC and AHC returned to levels originally present under long-term pasture. TOC recovered to original pasture levels in the humic soil, but recovered only to 60–70% of original levels in the coarse- and fine-textured soils. Aggregate stability was strongly correlated to TOC, WSC, and AHC (P < 0.001), while aggregate-size distribution was moderately correlated to aggregate stability (P < 0.01) and weakly correlated to AHC (P < 0.05). Scanning electron microscopy indicated a loss of the binding agents around aggregates under cropping. The effect of the loss of these binding agents on soil structure was more pronounced in mica-rich soils than in oxide-rich and allophanic soils. The very high aggregate stabilities of the humic soil under pasture was attributed to the presence of a protective water-repellent lattice of long-chain polymethylene compounds around the soil aggregates.
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TROFIMOV, V. Т., and V. A. KOROLEV. "ABOUT THE FUNDAMENTAL ASPECTS OF THE GENETIC APPROACH TO THE STUDY OF SOILS." Engineering Geology World 14, no. 1 (June 15, 2019): 8–19. http://dx.doi.org/10.25296/1993-5056-2019-14-1-8-19.
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The fundamental methodological and philosophical aspects of the genetic approach to the study of soil formation, the genesis of the composition, structure, state and properties, as well as the role of the spatial position of soils in the array and the role of anthropogenic impacts on soil massifs, including the formation of improved and degraded soils, are considered. In the genetic approach to the study of soils, which became the methodological basis of soil science, is that the composition, structure, condition and properties of soils are considered as the result of their genesis and subsequent postgenetic transformations at the stage of diagenesis, catagenesis, metamorphism and hypergenesis. The distinction of concepts of “soil genesis”, “genesis of soil composition”, “genesis of soil structure”, “genesis of soil condition” and “genesis of soil properties” is shown. When characterizing these concepts, it is necessary to take into account the syngenetic, epi-syngenetic, syn-epigenetic and epigenetic features of soils. In accordance with this, the composition, structure, condition, and properties of soils may be of four classes according to their origin: syngenetic, epi-syngenetic, syn-epigenetic, or epigenetic. The genetic approach plays a particularly important role in the study of anthropogenically-formed and man-made altered soils, as well as in the construction of new genetic classifications of natural and man-made soils. The genetic approach to the study of soils follows from the Priklonsky-SergeevLomtadze law: the composition, structure, condition and properties of soils are determined by their genesis, the nature of postgenetic processes and the modern spatial (coordinate) position. This fundamental approach should underlie the development of new general classifications of soils, which is especially important now, when work is underway to prepare the new GOST 25100 “Soils. General classification”.
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Pires, Luiz F., Klaus Reichardt, Miguel Cooper, Fabio A. M. Cássaro, Nivea M. P. Dias, and Osny O. S. Bacchi. "Pore system changes of damaged Brazilian oxisols and nitosols induced by wet-dry cycles as seen in 2-D micromorphologic image analysis." Anais da Academia Brasileira de Ciências 81, no. 1 (March 2009): 151–61. http://dx.doi.org/10.1590/s0001-37652009000100016.
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Soil pore structure characterization using 2-D image analysis constitutes a simple method to obtain essential information related to soil porosity and pore size distribution (PSD). Such information is important to infer on soil quality, which is related to soil structure and transport processes inside the soil. Most of the time soils are submitted to wetting and drying cycles (W-D), which can cause important changes in soils with damaged structures. This report uses 2-D image analysis to evaluate possible modifications induced by W-D cycles on the structure of damaged soil samples. Samples of three tropical soils (Geric Ferralsol, GF; Eutric Nitosol, EN; and Rhodic Ferralsol, RF) were submitted to three treatments: 0WD, the control treatment in which samples were not submitted to any W-D cycle; 3WD and 9WD with samples submitted to 3 and 9 consecutive W-D cycles, respectively. It was observed that W-D cycles produced significant changes in large irregular pores of the GF and RF soils, and in rounded pores of the EN soil. Nevertheless, important changes in smaller pores (35, 75, and 150 µm) were also observed for all soils. As an overall consideration, it can be said that the use of image analysis helped to explain important changes in soil pore systems (shape, number, and size distribution) as consequence of W-D cycles.
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SA, Wemedo. "Impact Assessment of Gas Flaring on Soil Bacterial Community Structure and Physicochemical Property in Nigeria." Open Access Journal of Microbiology & Biotechnology 5, no. 2 (2020): 1–9. http://dx.doi.org/10.23880/oajmb-16000165.
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Gas flaring is the wasteful emission of hydrocarbon gases into the atmosphere; it is routinely used to dispose flammable gas that either is assumed unusable or uneconomical to recover. The burning of the wasteful gas has been shown to have significant environmental consequences. Therefore, this study was designed to determine the impact of gas flaring on soil bacterial spectrum and its physicochemical property. Soil microbiological quality was investigated using culture techniques while physicochemical property of the soil was analyzed using standard analytical procedures. Results obtained showed that pH and Av. phosphorus decreased from 5.80 and 8.86mg/kg in control soil to 5.40 and 6.50mg/kg in flared soil respectively. Electrical conductivity and total organic carbon increased from 100μS/cm and 0.20% in control soil to 160μS/cm and 0.63% in flared soil respectively. Total nitrogen slightly increased from 0.01% in control soil to 0.02% in flared soil. Soil textural class was sandy-clay-loam for both control and flared soils. Mean counts of bacteria increased from 4x10 3 cfu/g in SD50m to 2.0x10 4 cfu/g in SD100m, 3.1x10 4 cfu/g in SD200m, 4.5x10 4 in SD300m to 4.8x10 5 cfu/g in control soil. All the bacterial species were isolated from control and SD300m soils except Acinetobacter and Microbacteriun species which did not occur in SD300m soil. Six (6) organisms: Bacillus, Corynebacterium , Pseudomonas , Paenibacillus, Pusillimonas and Salinicoccus species were isolated from SD50m soil. The number of bacterial genera isolated increased to eleven (11) in SD100m soil with Cronobacter , Enterobacter , Escherichia coli , Kluyvera , and Microbacterium species added to those of SD50m soil. Fifteen (15) organisms occurred in SD200m soil as Acinetobacter , Arthrobacter , Brevibacterium , Klebsiella , Rathayibacter and Staphylococcus species were added. This study revealed that gas flaring decreased bacterial population in soil in close proximity to the flare point; the effect being reduced as the sampling distance from the flare point increased. Some physicochemical parameters decreased in flared soils and others increased when compared with control soils. Gas flaring selectively inhibited soil bacteria with more species occurring in soils farther away from the flare and soil closest to the flare point having less numbers of bacteria. In conclusion, gas flaring had negative impact on soil bacteria and varied effect on physicochemical properties of the soil; in this way soil fertility could have been hampered. Oil and gas companies as well as government agency need to adopt measures that would curb unnecessary gas flaring in Nigeria by putting the flared gas into economic use.
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Alikonis, Antanas. "INFLUENCE OF CLAYEY SOIL STRUCTURE ON ITS MODULUS OF STIFFNESS." JOURNAL OF CIVIL ENGINEERING AND MANAGEMENT 5, no. 2 (April 30, 1999): 108–15. http://dx.doi.org/10.3846/13921525.1999.10531444.
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Disturbance of soil structure influences its density, strength and deformation properties. Among other cases soil structure could be disturbed by compacting it. It is possible to increase deformation properties of sand or gravel by compacting them. However, for clay soils deformation properties may increase if they are compacted. Differences of settlements of a building depends on the different deformation properties of the artificially placed and compacted soils beneath the foundations. Different values of stiffness modulus are used for the structural design of the buildings which are constructed on the soils with different compressibility. Coefficient of changeability of soil compression (1) was used. It may be calculated as a ratio of maximum and minimum values of deformation modulus, or according to the maximum and minimum values of coefficient of relative compressibility (3). Coefficient of the relative compressibility of soil can be calculated depending on the maximum and minimum values of tip resistence from CPT test (5). According to the coefficient of the relative compressibility we could estimate whether the soil is uniform, nonuniform or extremely non-uniform. It is important for the design of civil engineering structures. Mechanical properties of soils may be back-calculated using theoretical values of settlements and loads. Most frequently within the building layout area soils are natural and artificially compacted. For a compacted soil it is possible to draw compression curve in semi-logarithmic scale using compression curve of the same natural soil and the void ratio of the artificially placed and compacted soil. Thus we can determine compressibility of the soil with disturbed or undisturbed structure. Using parameters of soil compressibility, we can determine the coefficient of the relative compressibility, maximum and minimum values of settlement and modulus of stiffness.
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Bocuti, Edwaldo D., Ricardo S. S. Amorim, Kaynara F. L. Kavasaki, Marcelo R. V. Prado, Carlos L. R. Santos, and Luis A. Di L. Di Raimo. "Soil structure and its relationship with soybean yield." Revista Brasileira de Engenharia Agrícola e Ambiental 25, no. 3 (March 2021): 168–73. http://dx.doi.org/10.1590/1807-1929/agriambi.v25n3p168-173.
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ABSTRACT Soil structure conditions the interaction between the physical-hydraulic, chemical, and biological attributes and determines the potential of soil productivity. Therefore, the objective of this study was to evaluate the structure of soils of areas subjected to soybean production and the impacts of soil structure on crop yield. In total, 28 soybean production areas were selected in the State of Mato Grosso, Brazil, and analyzed for particle size, soil organic carbon and aggregates. Data of soil attributes were subjected to descriptive analysis, Pearson’s correlation and Kruskal-Wallis test at p ≤ 0.05. In general, considering the non-irrigated soybean production areas, it was found that soils with mean sand content between 100.00 and 800.10 g kg-1 and clay content between 120.00 and 627.80 g kg-1 showed average soybean yield of 3,536.36 kg ha-1. Soils that had aggregates with mean weight diameter and mean geometric diameter above 1.50 mm showed soybean yield equal to or greater than 3,370.67 kg ha-1. Soils of similar textural groups can define different levels of soybean yield, depending on characteristics such as the type of management adopted and production technology applied in the soybean production area.
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Tyszkiewicz, Zofia. "Quantitative-qualitative structures of the soil fungi communities in three profiles of peat-muck soils." Acta Agrobotanica 55, no. 1 (2013): 335–45. http://dx.doi.org/10.5586/aa.2002.032.
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The mycological investigations were performed on three soil profiles, which represent the slightly, moderately and strongly mucked peat-muck soils located in the Biebrza Valley. The aim of the study was the comparison of quantitative-qualitative structures of the fungi communities in the chosen peat-muck soils. The results indicate that soil fungi communities from compared soils reveal only small degree of similarity. The variety in quantitative and in qualitative structure increase with increasing mucking of organic deposits. These results may suggest that decreasing moisture of habitat stimulates the development of soil fungi. The most numerous soil fungi communities were observed in the turf layer and subturf layer of all soils.
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Grevers, M. C. J., and E. de Jong. "Soil structure and crop yield over a 5-year period following subsoiling Solonetzic and Chernozemic soils in Saskatchewan." Canadian Journal of Soil Science 73, no. 1 (February 1, 1993): 81–91. http://dx.doi.org/10.4141/cjss93-008.
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The effect of subsoiling of Solonetzic and of Chernozemic soils was studied over a 5-yr period under dryland conditions and under irrigation, involving 11 farm sites, and 2 soil zones. Subsoiling reduced soil density for up to 3 yr on most of the Solonetzic soils and on one of the Chernozemic soils. Overwinter soil-water recharge in subsoiled Solonetzic soils was increased for up to 3 yr, but not in subsoiled Chernozemic soils. Under irrigated conditions, subsoiling reduced soil salinity and sodicity at one site; however, under dryland conditions soil salinity and sodicity levels remained unaltered. Crop emergence on one of the Solonetzic soils was decreased in the first year after subsoiling because of poor seedbed conditions. Subsoiling increased crop production on Solonetzic soils in the 1st, 2nd, 3rd and in the 4th years, and at one site in the 5th year. Subsoiling did not affect crop production on Chernozemic soils. Increased crop production resulted from increased soil water depletion with depth, and also from greater crop water-use efficiency. Soil loosening by subsoiling, as indicated by decreased soil bulk density of the B horizon lasted up to 3 yr, during which the largest yield increases were measured. The results suggest that subsoiling may have to be repeated every 5 yr or more. Key words: Subsoiling, amelioration, soil water, crop growth
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Liu, M. D., and J. P. Carter. "A structured Cam Clay model." Canadian Geotechnical Journal 39, no. 6 (December 1, 2002): 1313–32. http://dx.doi.org/10.1139/t02-069.
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A theoretical study of the behaviour of structured soil is presented. A new model, referred to as the Structured Cam Clay model, is formulated by introducing the influence of soil structure into the Modified Cam Clay model. The proposed model is hierarchical, i.e., it is identical to the Modified Cam Clay soil model if a soil has no structure or if its structure is removed by loading. Three new parameters describing the effects of soil structure are introduced, and the results of a parametric study are also presented. The proposed model has been used to predict the behaviour of structured soils in both compression and shearing tests. By making comparisons of predictions with experimental data and by conducting the parametric study it is demonstrated that the new model provides satisfactory qualitative and quantitative modelling of many important features of the behaviour of structured soils.Key words: calcareous soils, clays, fabric, structure, constitutive relations, plasticity.
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Haskevych, Volodymyr, and Oksana Haskevych. "Description of structure of soil cover of Ranged Pobuzhya." Visnyk of the Lviv University. Series Geography, no. 44 (November 28, 2013): 62–70. http://dx.doi.org/10.30970/vgg.2013.44.1193.
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The basic units of structure of soil cover of Ranged Pobuzhya (basic soil habitats and microcatena) have been evaluated. Their content, features of geometric structure and conditions of formation have been analyzed. Average size ranges, partition coefficients and indices of branching and limits variability geometric characteristics elemental soil habitats and microcatena have been calculated. The impact of erosion on soils differentiation has been analyzed. Key words: soils structure, soil elemental area, microcatena, dismemberment, branching, erosion.
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Bezih, Kamel, Alaa Chateauneuf, and Rafik Demagh. "Effect of Long-Term Soil Deformations on RC Structures Including Soil-Structure Interaction." Civil Engineering Journal 6, no. 12 (November 30, 2020): 2290–311. http://dx.doi.org/10.28991/cej-2020-03091618.
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Lifetime service of Reinforced Concrete (RC) structures is of major interest. It depends on the action of the superstructure and the response of soil contact at the same time. Therefore, it is necessary to consider the soil-structure interaction in the safety analysis of the RC structures to ensure reliable and economical design. In this paper, a finite element model of soil-structure interaction is developed. This model addresses the effect of long-term soil deformations on the structural safety of RC structures. It is also applied to real RC structures where soil-structure interaction is considered in the function of time. The modeling of the mechanical analysis of the soil-structure system is implemented as a one-dimensional model of a spring element to simulate a real case of RC continuous beams. The finite element method is used in this model to address the nonlinear time behavior of the soil and to calculate the consolidation settlement at the support-sections and the bending moment of RC structures girders. Numerical simulation tests with different loading services were performed on three types of soft soils with several compressibility parameters. This is done for homogeneous and heterogeneous soils. The finite element model of soil-structure interaction provides a practical approach to show and to quantify; (1) the importance of the variability of the compressibility parameters, and (2) the heterogeneity soil behavior in the safety RC structures assessment. It also shows a significant impact of soil-structure interaction, especially with nonlinear soil behavior versus the time on the design rules of redundant RC structures. Doi: 10.28991/cej-2020-03091618 Full Text: PDF
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Chang, Tian, Shiau, Chen, and Chiu. "Influence of Thorny Bamboo Plantations on Soil Microbial Biomass and Community Structure in Subtropical Badland Soils." Forests 10, no. 10 (October 1, 2019): 854. http://dx.doi.org/10.3390/f10100854.
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Vegetation in southeastern Taiwan plays an important role in rehabilitating badland soils (high silt and clay content) and maintaining the soil microbial community. The establishment of thorny bamboo (Bambusa stenostachya Hackel) may have had a profound impact on the abundance and community structure of soil microorganisms. However, little is known regarding the influence of bamboo on soil biota in the badland ecosystem. The present study was conducted at three badland sites in southwestern Taiwan and focused on the measurement of phospholipid fatty acids (PLFA) together with soil microbial biomass C (Cmic) and N (Nmic) contents, enzyme activities, and denaturing gradient gel electrophoresis (DGGE) assessments. The abundances of whole soil microbes as well as bacterial and fungal groups—as evident by PLFA, Cmic and Nmic contents—were much higher in the bamboo plantation soils than the bare land soils. The increased soil organic matter in bamboo plantations relative to the control largely explained the enhancement, the abundance and diversity in the soil microbial community. Principal component analysis of individual PLFA peaks separated the bamboo plantation soil from the non-plantation bare land soil. DGGE analysis also revealed a difference in both bacterial and fungal community structures between soil types. Redundancy analysis of PLFA peak abundance and soil properties indicated that microbial community structure was positively correlated with soil organic C and total N and negatively correlated with pH. This differentiation could be attributed to bamboo in suitable habitats providing an essential nutrient source for soil microbes. The pH reduction in these alkaline soils also contributed to the increase in the size of the microbial community in bamboo-regenerated soils. Together, the results of this study indicate that bamboo plantations are beneficial for soil microbial activities and soil quality in badland areas.
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Sun, H. Y., S. P. Deng, and W. R. Raun. "Bacterial Community Structure and Diversity in a Century-Old Manure-Treated Agroecosystem." Applied and Environmental Microbiology 70, no. 10 (October 2004): 5868–74. http://dx.doi.org/10.1128/aem.70.10.5868-5874.2004.
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ABSTRACT Changes in soil microbial community structure and diversity may reflect environmental impact. We examined 16S rRNA gene fingerprints of bacterial communities in six agroecosystems by PCR amplification and denaturing gradient gel electrophoresis (PCR-DGGE) separation. These soils were treated with manure for over a century or different fertilizers for over 70 years. Bacterial community structure and diversity were affected by soil management practices, as evidenced by changes in the PCR-DGGE banding patterns. Bacterial community structure in the manure-treated soil was more closely related to the structure in the untreated soil than that in soils treated with inorganic fertilizers. Lime treatment had little effect on bacterial community structure. Soils treated with P and N-P had bacterial community structures more closely related to each other than to those of soils given other treatments. Among the soils tested, a significantly higher number of bacterial ribotypes and a more even distribution of the bacterial community existed in the manure-treated soil. Of the 99 clones obtained from the soil treated with manure for over a century, two (both Pseudomonas spp.) exhibited 100% similarity to sequences in the GenBank database. Two of the clones were possible chimeras. Based on similarity matching, the remaining 97 clones formed six major clusters. Fifty-six out of 97 were assigned taxonomic units which grouped into five major taxa: α-, β-, and γ-Proteobacteria (36 clones), Acidobacteria (16 clones), Bacteroidetes (2 clones), Nitrospirae (1 clone), and Firmicutes (1 clone). Forty-one clones remained unclassified. Results from this study suggested that bacterial community structure was closely related to agroecosystem management practices conducted for over 70 years.
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Morgunov, K. P., and M. A. Kolosov. "Soil Liquefaction Problems in the Foundations Hydraulic Structures." Science & Technique 21, no. 3 (June 1, 2022): 201–10. http://dx.doi.org/10.21122/2227-1031-2022-21-3-201-210.
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An analysis of the probability and conditions for the occurrence of soil liquefaction at the base and in the vicinity of hydraulic structures is presented in the paper. As a rule, hydraulic structures are erected in the valleys of watercourses, the structure of the soil in which contributes to the occurrence of liquefaction processes. These soils are fine-grained, non-cohesive, usually consisting of fine- and medium-grained or silty sands, sandy loams, interspersed with layers of loams. Massifs under pressure hydraulic structures are quite water-saturated. Soil liquefaction occurs as a result of the destruction of structural bonds between particles in water-saturated dispersed soils under the action of stresses of various types. An external dynamic or static load applied to a water-saturated massif composed of weak, finely dispersed soils can lead to a complete or partial loss of soil bearing capacity and its transition to a fluid state. The magnitude of soil resistance to shear is determined by the degree of its water saturation; at a moisture content of about 20 %, the angle of repose of sandy soils is significantly reduced. The restoration of the strength properties of soils is prevented by the pore water pressure, the process of compaction (consolidation) of the soil mass occurs after the water is squeezed out of the pores, the flow time of which depends on the filtration properties of the massif. Liquefaction of soils leads to a disruption in the normal functioning of a hydraulic structure, the creation of emergency situations. The paper provides examples of accidents at hydraulic structures in Russia caused by liquefaction phenomena. It is noted that the main directions of protecting the structures of hydraulic structures from dangerous liquefaction are to prevent the possibility of liquefaction and the reduction of its harmful effects. In this regard, several methods are considered – compaction and strengthening of soils at the base of structures; filtering surcharge device using geotextiles and geogrids; creation of an effective drainage system.
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Zhang, Miao Xin, Bao Dong Liu, Peng Fei Li, and Zhi Mao Feng. "Structure-Soil Interaction of Buried Corrugated Steel Arch Bridge." Advanced Materials Research 163-167 (December 2010): 2112–17. http://dx.doi.org/10.4028/www.scientific.net/amr.163-167.2112.
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Corrugated steel plate and surrounding soils are working together to share the load in buried corrugated steel structures. It is complicated to consider the structure-soil interaction, so the finite element method has already become the chief means of complicated structure analysis. Based on a practical project, considering structure-soil interaction, by using the finite element program of ANSYS, the paper set up a 2-D FE model and analyzed the soil pressure, the structural deformation and the internal force under different load conditions in detail. The analysis shows that structure-soil interaction has brought about stresses redistribution of surrounding soils, and adverse effects of soil pressure and displacement were limited. The variation range of soil pressure on the crown of arch increases with the load increases and the peak value of soil pressure approach to the code value and a rebound appears in the vehicle load range. The tendencies of vertical soil displacement are nearly the same to different load conditions, and the peak value of moments has an obvious change and can be influenced greatly by deflective load.
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Hu, Yuwei, Changqun Duan, Denggao Fu, Xiaoni Wu, Kai Yan, Eustace Fernando, Samantha C. Karunarathna, Itthayakorn Promputtha, Peter E. Mortimer, and Jianchu Xu. "Structure of Bacterial Communities in Phosphorus-Enriched Rhizosphere Soils." Applied Sciences 10, no. 18 (September 14, 2020): 6387. http://dx.doi.org/10.3390/app10186387.
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Although phytoremediation is the main method for P-removal and maintaining ecosystem balance in geological phosphorus-enriched soils (PES), little is known about the structure and function of microbial communities in PES. Interactions between plants and soil microorganisms mainly occur in the rhizosphere. The aim of this work was to investigate the composition and diversity of bacterial communities found in rhizosphere soils associated with the following three dominant plant species: Erianthus rufipilus, Coriaria nepalensis, and Pinus yunnanensis. In addition, we compared these rhizosphere bacterial communities with those derived from bulk soils and grassland plots in PES from the Dianchi Lake basin of southwestern China. The Illumina MiSeq platform for high-throughput sequencing of 16S rRNA was used for the taxonomy and the analysis of soil bacterial communities. The results showed higher bacterial diversity and nutrient content in rhizosphere soils as compared with bulk soils. Rhizosphere bacteria were predominantly comprised of Proteobacteria (24.43%) and Acidobacteria (21.09%), followed by Verrucomicrobia (19.48%) and Planctomycetes (9.20%). A comparison of rhizosphere soils of the selected plant species in our study and the grassland plots showed that Acidobacteria were the most abundant in the rhizosphere soil of E. rufipilus; Bradyrhizobiaceae and Rhizobiaceae in the order Rhizobiales from C. nepalensis were found to have the greatest abundance; and Verrucomicrobia and Planctomycetes were in higher abundance in P. yunnanensis rhizosphere soils and in grassland plots. A redundancy analysis revealed that bacterial abundance and diversity were mainly influenced by soil water content, soil organic matter, and total nitrogen.
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Bengough, A. Glyn, Roy Neilson, Bryan Griffiths, and David Trudgill. "The extent to which nematode communities are affected by soil factors-a pot experiment." Nematology 4, no. 8 (2002): 943–52. http://dx.doi.org/10.1163/156854102321122566.
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AbstractFour similar, agricultural soils with distinct nematode communities were used to determine the extent to which soil and inoculum factors affected nematode community structure. The soils all had a sandy loam texture from the same geographical area and had been in pasture or arable rotation for the last 10 years. Treatments were established in pots containing a middle layer of frozen defaunated soil, sandwiched between an inoculum that was either fresh soil from the same site ('self') or a mixture of soils to give a more diverse inoculum ('mixed'). Principal component analysis indicated that a single soil type given different inocula developed different community structures (i.e., the community under 'self' differed from that under 'mixed') suggesting an inoculum effect. It was also true that different soil types under a single inoculum soil also developed different community structures (i.e., community under 'mixed' differed with soil type), suggesting a soil effect. It is likely that the nematode community structure is influenced by a combination of antecedent land use, soil factors, species introductions and inter-species competition, which should be considered in any interpretation of nematode communities as a biotic indicator.
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Baxter, James W., Stewart TA Pickett, Margaret M. Carreiro, and John Dighton. "Ectomycorrhizal diversity and community structure in oak forest stands exposed to contrasting anthropogenic impacts." Canadian Journal of Botany 77, no. 6 (October 30, 1999): 771–82. http://dx.doi.org/10.1139/b99-039.
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We compared the ectomycorrhizal community structure of oak forest stands located in either an urban or a rural area. Urban stands had higher N deposition rates, soil heavy metal levels, and earthworm counts than rural stands. Ectomycorrhizal types were quantified on roots of mature oak (Quercus) in soil cores and on Quercus rubra L. seedlings grown in soil cores in the glasshouse. Twenty-six ectomycorrhizal types were distinguished on mature oak in rural soils versus 16 in urban soils. Nine ectomycorrhizal types were distinguished on Q. rubra seedlings grown in rural soils versus seven in urban soils. Despite fewer ectomycorrhizal types in urban soils, richness of ectomycorrhizal types per centimetre fine root of mature oak or Q. rubra seedlings did not differ between urban and rural soils. Ectomycorrhizal colonization (ectomycorrhizal tips/m fine root) was lower in urban than rural soil cores but higher on Q. rubra seedlings grown in urban versus rural soils. Fine root length per unit soil volume was higher in urban than rural stands. No difference in fine root length was observed between Q. rubra seedlings grown in urban and rural soils. These differences in ectomycorrhizal community structure between the urban and rural stands are likely due to anthropogenic impacts.Key words: air pollution, anthropogenic impacts, community structure, diversity, ectomycorrhiza, Quercus rubra.
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Valdés-Rodríguez, Ofelia Andrea, Odilón Sánchez-Sánchez, Arturo Pérez-Vázquez, Joshua S. Caplan, and Frédéric Danjon. "Jatropha curcasL. Root Structure and Growth in Diverse Soils." Scientific World Journal 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/827295.
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Unlike most biofuel species,Jatropha curcashas promise for use in marginal lands, but it may serve an additional role by stabilizing soils. We evaluated the growth and structural responsiveness of youngJ. curcasplants to diverse soil conditions. Soils included a sand, a sandy-loam, and a clay-loam from eastern Mexico. Growth and structural parameters were analyzed for shoots and roots, although the focus was the plasticity of the primary root system architecture (the taproot and four lateral roots). The sandy soil reduced the growth of both shoot and root systems significantly more than sandy-loam or clay-loam soils; there was particularly high plasticity in root and shoot thickness, as well as shoot length. However, the architecture of the primary root system did not vary with soil type; the departure of the primary root system from an index of perfect symmetry was14±5% (mean ± standard deviation). AlthoughJ. curcasdeveloped more extensively in the sandy-loam and clay-loam soils than in sandy soil, it maintained a consistent root to shoot ratio and root system architecture across all types of soil. This strong genetic determination would make the species useful for soil stabilization purposes, even while being cultivated primarily for seed oil.
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Nahirniak, S. V., T. A. Dontsova, A. V. Lapinsky, M. V. Tereshkov, and R. C. Singh. "Soil and soil breathing remote monitoring: A short review." Biosystems Diversity 28, no. 4 (November 14, 2020): 350–56. http://dx.doi.org/10.15421/012044.
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The efficiency of agricultural use of soils depends directly on their quality indicators, which include an extended set of characteristics: from data of the environmental situation to the component composition of the soil air. Therefore, for a more complete survey of agricultural land in order to determine their qualitative indicators and subsequent application, it is necessary to carry out comprehensive monitoring while simultaneously studying the characteristics of soils and their air composition. The article is devoted to the literature analysis on the remote monitoring of soils and soil air. Particular attention was paid to the relationship between soil type and soil air composition and it was found that the soil air composition (in the combination with pH and humidity parameters) can assess the type, quality and environmental condition of soils. Since when developing a remote monitoring system of soil air soil moisture and soil structure significantly affect the processes occurring in soils, and ultimately the quantitative composition of soil air, it is very important to know the dependence of the soil air composition on the type and quality of the soil itself, the influence of moisture, structure and other parameters on it. It was shown that the use of sensors is a promising direction for the development of the soils and soil air remote monitoring. It was indicated that soil and soil air remote monitoring in real time will provide reliable, timely information on the environmental status of soils and their quality. Commercial sensors that can be used to determine CO2, O2, NOx, CH4, CO, H2 and NH3 were considered and the technique for sensor signal processing was chosen. A remote monitoring system with the use of existing commercial sensors was proposed, the movement of which can be realized with the help of quadcopter, which will allow parallel scanning of the soils and the land terrain. Such a system will make it possible to correctly assess the readiness of soils for planting, determine their intended use, correctly apply fertilizers, and even predict the yield of certain crops. Thereby, this approach will create a modern on-line system for full monitoring of soil, land and rapid response in the case of its change for the agro-industrial sector.
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Al-Yasir, Abdullah Talib, and Abbas Jawad Al-Taie. "Geotechnical Review for Gypseous Soils: Properties and Stabilization." Jurnal Kejuruteraan 34, no. 5 (September 30, 2022): 785–99. http://dx.doi.org/10.17576/jkukm-2022-34(5)-04.
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In many arid and semi-arid regions, collapsible soils are well-known to be problematic in nature and negatively affect the performance of engineering structures. Gypseous soil considers one of the well-known types of collapsible soil. It represents a real challenge to engineers due to different problems encountered by engineering projects implemented in this soil. The mineralogy, composition, and fabric of gypseous soil affect its ability to deform when subjected to wetting (due to changing the whole structure soil particles). Numerous studies considered the problems of gypseous soils and their treatment with different additives and using different methods. In this paper, the properties of gypsum (physical appearances, hardness, density, chemical structure), gypsum effect on soil properties (specific gravity, compaction properties, shear strength), main geotechnical properties of gypseous soils, their problems, and different important additives (traditional and non-traditional) and methods used in gypseous soils problems mitigation have been discussed. Gypsum is one of unpredictable materials that have different forms, low hardness, and low density. Gypsum is the main occurring source of sulphate in soils, it affects their geotechnical properties to different degrees depending on its content, the presence of the other salts (than gypsum), soil gradation and type, and organic matters. There is a critical gypsum content beyond which gypsum negatively affects the shear strength of soils, this content is (10-20)%. Finally, although there are many additives used in the treatment of gypsum soil, the use of some additives should be done with caution to avoid destructive results, especially with clay gypseous soil.
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Leuther, Frederic, and Steffen Schlüter. "Impact of freeze–thaw cycles on soil structure and soil hydraulic properties." SOIL 7, no. 1 (June 11, 2021): 179–91. http://dx.doi.org/10.5194/soil-7-179-2021.
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Abstract. The ploughing of soils in autumn drastically loosens the soil structure and, at the same time, reduces its stability against external stresses. A fragmentation of these artificially produced soil clods during wintertime is often observed in areas with air temperatures fluctuating around the freezing point. From the pore perspective, it is still unclear (i) under which conditions frost action has a measurable effect on soil structure, (ii) what the impact on soil hydraulic properties is, and (iii) how many freeze–thaw cycles (FTCs) are necessary to induce soil structure changes. The aim of this study was to analyse the cumulative effects of multiple FTC on soil structure and soil hydraulic properties for two different textures and two different initial structures. A silt clay with a substantial amount of swelling clay minerals and a silty loam with fewer swell/shrink dynamics were either kept intact in undisturbed soil cores taken from the topsoil from a grassland or repacked with soil clods taken from a ploughed field nearby. FTCs were simulated under controlled conditions and changes in pore structure ≥ 48 µm were regularly recorded using X-ray µCT. After 19 FTCs, the impact on hydraulic properties were measured, and the resolution of structural characteristics were enhanced towards narrow macropores with subsamples scanned at 10 µm. The impact of FTC on soil structure was dependent on the initial structure, soil texture, and the number of FTCs. Frost action induced a consolidation of repacked soil clods, resulting in a systematic reduction in pore sizes and macropore connectivity. In contrast, the macropore systems of the undisturbed soils were only slightly affected. Independent of the initial structure, a fragmentation of soil clods and macro-aggregates larger than 0.8 to 1.2 mm increased the connectivity of pores smaller than 0.5 to 0.8 mm. The fragmentation increased the unsaturated hydraulic conductivity of all treatments by a factor of 3 in by a factor of 3 in a matrix potential range of −100 to −350 hPa, while water retention was only slightly affected for the silt clay soil. Already 2 to 5 FTCs enforced a well-connected pore system of narrow macropores in all treatments, but it was steadily improved by further FTCs. The implications of fewer FTCs during milder winters caused by global warming are twofold. In ploughed soils, the beneficial seedbed consolidation will be less intense. In grassland soils, which have reached a soil structure in dynamic equilibrium that has experienced many FTCs in the making, there is still a beneficial increase in water supply through increasing unsaturated hydraulic conductivity by continued FTCs that might also be less efficient in the future.
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Jha, Neha, Surinder Saggar, Donna Giltrap, Russ Tillman, and Julie Deslippe. "Soil properties impacting denitrifier community size, structure, and activity in New Zealand dairy-grazed pasture." Biogeosciences 14, no. 18 (September 22, 2017): 4243–53. http://dx.doi.org/10.5194/bg-14-4243-2017.
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Abstract. Denitrification is an anaerobic respiration process that is the primary contributor of the nitrous oxide (N2O) produced from grassland soils. Our objective was to gain insight into the relationships between denitrifier community size, structure, and activity for a range of pasture soils. We collected 10 dairy pasture soils with contrasting soil textures, drainage classes, management strategies (effluent irrigation or non-irrigation), and geographic locations in New Zealand, and measured their physicochemical characteristics. We measured denitrifier abundance by quantitative polymerase chain reaction (qPCR) and assessed denitrifier diversity and community structure by terminal restriction fragment length polymorphism (T-RFLP) of the nitrite reductase (nirS, nirK) and N2O reductase (nosZ) genes. We quantified denitrifier enzyme activity (DEA) using an acetylene inhibition technique. We investigated whether varied soil conditions lead to different denitrifier communities in soils, and if so, whether they are associated with different denitrification activities and are likely to generate different N2O emissions. Differences in the physicochemical characteristics of the soils were driven mainly by soil mineralogy and the management practices of the farms. We found that nirS and nirK communities were strongly structured along gradients of soil water and phosphorus (P) contents. By contrast, the size and structure of the nosZ community was unrelated to any of the measured soil characteristics. In soils with high water content, the richnesses and abundances of nirS, nirK, and nosZ genes were all significantly positively correlated with DEA. Our data suggest that management strategies to limit N2O emissions through denitrification are likely to be most important for dairy farms on fertile or allophanic soils during wetter periods. Finally, our data suggest that new techniques that would selectively target nirS denitrifiers may be the most effective for limiting N2O emissions through denitrification across a wide range of soil types.
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Sravya, G. Jyothi, and A. Manchalwar. "Comparison of Seismic isolation with isolator and Soil structure Interaction U-shaped metallic isolator and Soil structure Interaction." E3S Web of Conferences 184 (2020): 01097. http://dx.doi.org/10.1051/e3sconf/202018401097.
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Soil condition is an important research area in earthquake engineering. In this work we evaluated the impact of soil-structure interaction (SSI) and U-shaped steel damper on the isolated response of the building base. Different soils for a seismic performance of multistory buildings are systematically compared and discussed. The soil’s physical state is divided into; hard soil, medium soil, and soft soil. It was compared with the U-shaped steel damper and there is noticeable difference between them. This study concludes that the use of steel damper shaped and SSI has been effective in minimizing structural response. It was observed that interaction of the soil structure provides some flexibility to the structure by increasing the structure’s displacements. Modeling base isolation along with consideration of soil structure interaction therefore leads to better structural response prediction.
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Kozlovskii, V. E., E. V. Gorodnova, and S. S. Kolmogorova. "STRUCTURE SETTING ON COMPOSITE-BASED SOILS." Vestnik Tomskogo gosudarstvennogo arkhitekturno-stroitel'nogo universiteta. JOURNAL of Construction and Architecture 22, no. 1 (February 27, 2020): 164–70. http://dx.doi.org/10.31675/1607-1859-2020-22-1-164-170.
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The paper studies the interaction between the building construction and composite-based soil with a view to determine its elastic properties affecting the structure deformation and internal forces. The soil model is assumed to be elastic, according to the Winkler coefficient calculated from the Kolosov stress decay function. The Galerkin numerical method used in calculations utilizes basic functions corresponding to the type of fixing the discontinuous and continuous structures. Unknown coefficients in linear combinations of basic functions are obtained via linear algebra methods, solving the system of equations. The force functions of the structure are found by derivation of the deflection function. Geological parameters are accepted to be real and matching the construction conditions of a large industrial warehouse of agricultural designation in the Pskov region, Russia. The soil effect on the flexural strength, shearing forces, and bearing reaction is estimated under the discontinuous and continuous structures at the available geological soil parameters. The structure setting on composite-based soils under the operating load is predicted herein.
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de Jonge, L. W., P. Moldrup, and P. Schjønning. "Soil Infrastructure, Interfaces and Translocation Processes in Inner Space (''Soil-it-is''): towards a road map for the constraints and crossroads of soil architecture and biophysical processes." Hydrology and Earth System Sciences Discussions 6, no. 2 (March 25, 2009): 2633–78. http://dx.doi.org/10.5194/hessd-6-2633-2009.
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Abstract. Soil functions and their impact on health, economy and the environment are evident at the macro scale but determined at the micro scale, based on interactions between soil micro-architecture and the transport and transformation processes occurring in the pore and particle networks and at their interfaces. Soil structure formation and its resilience to disturbance are highly dynamic features affected by management (energy input), moisture (matric potential), and solids composition and complexation (organic carbon, OC, and clay interactions). In this paper we review and put into perspective preliminary results of the newly started research program ''Soil-it-is'' on functional soil architecture. To identify and quantify biophysical constraints on soil structure changes and resilience, we claim that new paradigms are needed to better interpret processes and parameters measured at the bulk soil scale and their links to the seemingly chaotic soil inner space behavior at the micro scale (soil self-organization). As a first step, we revisit the soil matrix (solids phase) and pore system (water and air phases), constituting the complementary and interactive networks of soil infrastructure. For a field-pair with contrasting soil management, we suggest new ways of data analysis on measured soil-gas transport parameters at different moisture conditions to evaluate controls of soil matrix and pore network formation. Results imply that some soils form sponge-like pore networks (mostly healthy soils in terms of environmental functions), while other soils form pipe-like structures (poorly functioning soils), with the difference related to both complexation of organic matter and degradation of soil structure. The recently presented Dexter threshold (ratio of clay to organic carbon of 10 g g−1) is found to be a promising constraint for a soil's ability to maintain or regenerate functional structure. Next, we show the Dexter threshold may also apply to hydrological and physical-chemical interface phenomena including soil-water repellency and sorption of volatile organic vapors (gas-water-solids interfaces) as well as polycyclic aromatic hydrocarbons (water-solids interfaces). However, data for differently-managed soils imply that energy input, soil-moisture status, and vegetation (quality of eluded organic matter) may be equally important constraints together with the complexation and degradation of organic carbon in deciding functional soil architecture and interface processes. Finally, we envision a road map to soil inner space where we search for the main controls of particle and pore network changes and structure build-up and resilience at each crossroad of biophysical parameters, where, for example, complexation between organic matter and clay, and moisture-induced changes from hydrophilic to hydrophobic surface conditions can play a role. We hypothesize that each crossroad (e.g. between OC/clay ratio and matric potential) may initiate breakdown or activation of soil self-organization at a given time as affected by gradients in energy and moisture from soil use and climate. The road map may serve as inspiration for renewed and multi-disciplinary focus on functional soil architecture.
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Holland, J. E., R. E. White, and R. Edis. "The relation between soil structure and solute transport under raised bed cropping and conventional cultivation in south-western Victoria." Soil Research 45, no. 8 (2007): 577. http://dx.doi.org/10.1071/sr07068.
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This study examined the relationship between soil structure and solute transport in a texture contrast soil under 2 different tillage treatments—raised beds and conventional cultivation—in south-western Victoria. Undisturbed soil samples were collected for resin-impregnation and image analysis. This enabled several descriptive parameters of macropore structure to be calculated. Large, undisturbed soil samples were also collected for a solute transport experiment using a KCl solution. A convective log-normal transfer function was used to model Cl– movement. The assessment of soil structure showed that the raised beds contained a better connected pore network than the conventionally cultivated soil. Solute transport was faster through the raised bed soil when close to saturation (at –5 mm tension). Under these conditions, the solute transport parameters showed a smaller ratio of transport volume to soil water volume in the raised bed than the conventionally cultivated soil. Together, these data strongly indicate that the raised beds had greater pore connectivity and were able to transmit solute faster and more efficiently than the conventionally cultivated soil. It is concluded that raised bed soils are better structured and provide less risk from waterlogging than conventionally cultivated soils. However, there is greater potential for preferential flow of pesticides and solutes in raised bed soils.
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McKEAGUE, J. A., and G. C. TOPP. "PITFALLS IN INTERPRETATION OF SOIL DRAINAGE FROM SOIL SURVEY INFORMATION." Canadian Journal of Soil Science 66, no. 1 (February 1, 1986): 37–44. http://dx.doi.org/10.4141/cjss86-004.
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Soil drainage groups assigned on the basis of soil survey information were evaluated against measured saturated hydraulic conductivity (Ksat) data for nine soils in Ontario. The drainage groups used in the drainage guide for Ontario, are based mainly on assumed relationships between soil texture and the capacity of the soil to transmit water.Measured Ksat values were incompatible with the drainage groups assigned to at least four of the nine soils. For the soils tested, there was very little relationship between texture and Ksat. Structure, including porosity, had a major influence on Ksat, and near-surface structure is influenced greatly by land use. Thus, general interpretations of the drainage characteristics of soil series have serious limitations. The usefulness of soil survey information for interpretation of soil drainage could be increased by improved description of soil morphology and by reliable estimates of Ksat during mapping. Such estimates can be based on morphology if they are regularly recalibrated by measurement. Key words: Hydraulic conductivity, tile drainage, texture, soil morphology
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Aislabie, J., J. J. Smith, R. Fraser, and M. McLeod. "Leaching of bacterial indicators of faecal contamination through four New Zealand soils." Soil Research 39, no. 6 (2001): 1397. http://dx.doi.org/10.1071/sr00086.
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Land application of animal waste can result in bacterial contamination of shallow groundwater and/or waterways. Using 500-mm-diameter barrel lysimeters, we investigated the potential for bacterial indicators to leach through 4 New Zealand soils treated with dairy shed effluent (DSE). DSE was applied to soil lysimeters containing poorly drained Gley Soils (Te Kowhai and Netherton) and well-drained Allophanic (Waihou) and Pumice Soils (Atiamuri) at 50 mm/h, a typical field application rate used by farmers. Simulated rainfall was applied continuously at a rate of 5–10 mm/h, and leachate collected at a depth of 700 or 750 mm was analysed for faecal coliforms, Escherichia coli, and faecal enterococci. Bacterial indicators of faecal contamination readily moved through the Te Kowhai and Netherton soils, but not the Waihou and Atiamuri soils. Differential microbial movement was attributed to differences in soil structure. The poorly drained soils have coarse subsoil structures with macropores, favouring bypass flow. In contrast, the welldrained soils have a finer, more uniformly porous soil structure that minimised bypass flow and allowed matrix flow.
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de Jonge, L. W., P. Moldrup, and P. Schjønning. "Soil Infrastructure, Interfaces & Translocation Processes in Inner Space ("Soil-it-is"): towards a road map for the constraints and crossroads of soil architecture and biophysical processes." Hydrology and Earth System Sciences 13, no. 8 (August 19, 2009): 1485–502. http://dx.doi.org/10.5194/hess-13-1485-2009.
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Abstract. Soil functions and their impact on health, economy, and the environment are evident at the macro scale but determined at the micro scale, based on interactions between soil micro-architecture and the transport and transformation processes occurring in the soil infrastructure comprising pore and particle networks and at their interfaces. Soil structure formation and its resilience to disturbance are highly dynamic features affected by management (energy input), moisture (matric potential), and solids composition and complexation (organic matter and clay interactions). In this paper we review and put into perspective preliminary results of the newly started research program "Soil-it-is" on functional soil architecture. To identify and quantify biophysical constraints on soil structure changes and resilience, we claim that new approaches are needed to better interpret processes and parameters measured at the bulk soil scale and their links to the seemingly chaotic soil inner space behavior at the micro scale. As a first step, we revisit the soil matrix (solids phase) and pore system (water and air phases), constituting the complementary and interactive networks of soil infrastructure. For a field-pair with contrasting soil management, we suggest new ways of data analysis on measured soil-gas transport parameters at different moisture conditions to evaluate controls of soil matrix and pore network formation. Results imply that some soils form sponge-like pore networks (mostly healthy soils in terms of agricultural and environmental functions), while other soils form pipe-like structures (agriculturally poorly functioning soils), with the difference related to both complexation of organic matter and degradation of soil structure. The recently presented Dexter et al. (2008) threshold (ratio of clay to organic carbon of 10 kg kg−1) is found to be a promising constraint for a soil's ability to maintain or regenerate functional structure. Next, we show the Dexter et al. (2008) threshold may also apply to hydrological and physical-chemical interface phenomena including soil-water repellency and sorption of volatile organic vapors (gas-water-solids interfaces) as well as polycyclic aromatic hydrocarbons (water-solids interfaces). However, data for differently-managed soils imply that energy input, soil-moisture status, and vegetation (quality of eluded organic matter) may be equally important constraints together with the complexation and degradation of organic carbon in deciding functional soil architecture and interface processes. Finally, we envision a road map to soil inner space where we search for the main controls of particle and pore network changes and structure build-up and resilience at each crossroad of biophysical parameters, where, for example, complexation between organic matter and clay, and moisture-induced changes from hydrophilic to hydrophobic surface conditions can play a role. We hypothesize that each crossroad (e.g. between organic carbon/clay ratio and matric potential) may control how soil self-organization will manifest itself at a given time as affected by gradients in energy and moisture from soil use and climate. The road map may serve as inspiration for renewed and multi-disciplinary focus on functional soil architecture.
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Lauber, Christian L., Micah Hamady, Rob Knight, and Noah Fierer. "Pyrosequencing-Based Assessment of Soil pH as a Predictor of Soil Bacterial Community Structure at the Continental Scale." Applied and Environmental Microbiology 75, no. 15 (June 5, 2009): 5111–20. http://dx.doi.org/10.1128/aem.00335-09.
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ABSTRACT Soils harbor enormously diverse bacterial populations, and soil bacterial communities can vary greatly in composition across space. However, our understanding of the specific changes in soil bacterial community structure that occur across larger spatial scales is limited because most previous work has focused on either surveying a relatively small number of soils in detail or analyzing a larger number of soils with techniques that provide little detail about the phylogenetic structure of the bacterial communities. Here we used a bar-coded pyrosequencing technique to characterize bacterial communities in 88 soils from across North and South America, obtaining an average of 1,501 sequences per soil. We found that overall bacterial community composition, as measured by pairwise UniFrac distances, was significantly correlated with differences in soil pH (r = 0.79), largely driven by changes in the relative abundances of Acidobacteria, Actinobacteria, and Bacteroidetes across the range of soil pHs. In addition, soil pH explains a significant portion of the variability associated with observed changes in the phylogenetic structure within each dominant lineage. The overall phylogenetic diversity of the bacterial communities was also correlated with soil pH (R2 = 0.50), with peak diversity in soils with near-neutral pHs. Together, these results suggest that the structure of soil bacterial communities is predictable, to some degree, across larger spatial scales, and the effect of soil pH on bacterial community composition is evident at even relatively coarse levels of taxonomic resolution.
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Maghsoodi, Soheib, Olivier Cuisinier, and Farimah Masrouri. "Thermo-mechanical behaviour of clay-structure interface." E3S Web of Conferences 92 (2019): 10002. http://dx.doi.org/10.1051/e3sconf/20199210002.
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The mechanical behaviour of the soil-structure interface plays a major role in the shear characteristics and bearing capacity of foundations. In thermo-active structures, due to non-isothermal conditions, the interface behaviour becomes more complex. The objective of this study is to investigate the effects of temperature variations on the mechanical behaviour of soils and soil-structure interface. Constant normal load (CNL) and constant normal stiffness (CNS) tests were performed on soil and soil-structure interface in a direct shear device at temperatures of 5, 22 and 60 °C. Kaolin clay was used as proxy for clayey soils. The results showed that, in clay samples the temperature increase, increased the cohesion and consequently the shear strength, due to thermal contraction during heating. The temperature rise had less impact on the shear strength in the case of the clay-structure interface than in the clay samples. The adhesion of the clay-structure interface, is less than the cohesion of the clay samples.
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Korolev, Vladimir A. "PROBLEMS AND TASKS OF THEORETICAL SOIL SCIENCE." Gruntovedenie 1, no. 17 (2022): 38–44. http://dx.doi.org/10.53278/2306-9139-2022-1-17-38-44.
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The article deals with the problems and tasks of a new section of Soil Science — Theoretical soil science. It is noted that Theoretical soil science is a section of soil science about the most general laws that mathematically describe the composition, structure, properties of soils and their formation, processes in them, as well as changes in soils under the influence of internal and external factors. It is shown that the main goal of Theoretical soil science is the study and mathematical description of the most general laws of the formation of the composition, structure and properties of soils, the laws of their change under the influence of internal factors and external influences, as well as the interaction between soils, represented in mathematical form. The main method of understanding Theoretical soil science is not empirical research methods, as in classical soil science, but the use of theoretical (primarily mathematical) models of phenomena in soil and their comparison with reality.
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Korolev, V. A. "PROBLEMS AND TASKS OF THEORETICAL SOIL SCIENCE." Gruntovedenie 2, no. 17 (2021): 38–44. http://dx.doi.org/10.53278/2306-9139-2021-2-17-38-44.
Full textAbstract:
The article deals with the problems and tasks of a new section of Soil Science — Theoretical soil science. It is noted that Theoretical soil science is a section of soil science about the most general laws that mathematically describe the composition, structure, properties of soils and their formation, processes in them, as well as changes in soils under the influence of internal and external factors. It is shown that the main goal of Theoretical soil science is the study and mathematical description of the most general laws of the formation of the composition, structure and properties of soils, the laws of their change under the influence of internal factors and external influences, as well as the interaction between soils, represented in mathematical form. The main method of understanding Theoretical soil science is not empirical research methods, as in classical soil science, but the use of theoretical (primarily mathematical) models of phenomena in soil and their comparison with reality.
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Tikhonovich, I. A., T. I. Chernov, A. D. Zhelezova, A. K. Tkhakakhova, E. E. Andronov, and O. V. Kutovaya. "TAXONOMIC STRUCTURE OF PROKARYOTIC COMMUNITIES IN SOILS OF DIFFERENT BIOCLIMATIC ZONES." Dokuchaev Soil Bulletin, no. 95 (November 1, 2018): 125–53. http://dx.doi.org/10.19047/0136-1694-2018-95-125-153.
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Using high-throughput sequencing, we performed a full-profile analysis of the taxonomic structure and diversity of prokaryotic communities of zonal soil series: sod-podzolic, dark gray, typical chernozem, brown soil, meadow-chestnut soil and solonets. Phyla Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Gemmatimonadetes, Planctomycetes, Proteobacteria and Verrucomicrobia formed up to 95% of prokaryotic communities in all studied soil horizons. Phyla Proteobacteria and Actinobacteria and archaeal phylum Thaumarchaeota dominated in all soils. We revealed the trends of changes in the representation of bacterial phyla in the soils of the zonal range from taiga to dry-steppe: a decrease of Acidobacteria and an increase of Actinobacteria in the upper horizons. The diversity indices of the prokaryotic communities of different genetic horizons of the studied soils were evaluated. In all soils, a decrease in diversity indices with the depth of the horizon was revealed. In all soils, a decrease in diversity indices with depth of the horizon was found, with a rare and slight increase in some lower horizons: structural metamorphic (BM), textural (BT) or accumulative carbonate (BCA) horizons. When examining the prokaryotic communities of soils with different genesis, no determining influence of pH and organic matter contents on the diversity indices was found. Differences in the taxonomic structure and diversity of prokaryotic communities of soils of different bioclimatic zones were presented due to a combination of factors: the difference in chemical and physical properties of soils, as well as in water and temperature conditions.
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Mamedov, Amrakh I., Atsushi Tsunekawa, Nigussie Haregeweyn, Mitsuru Tsubo, Haruyuki Fujimaki, Takayuki Kawai, Birhanu Kebede, et al. "Soil Structure Stability under Different Land Uses in Association with Polyacrylamide Effects." Sustainability 13, no. 3 (January 29, 2021): 1407. http://dx.doi.org/10.3390/su13031407.
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Soil structural stability is a vital aspect of soil quality and functions, and of maintaining sustainable land management. The objective of this study was to compare the contribution of four long-term land-use systems (crop, bush, grass, and forest) coupled with anionic polyacrylamide (PAM = 0, 25, and 200 mg L−1) application on the structural stability of soils in three watersheds of Ethiopia varying in elevation. Effect of treatments on soil structural stability indices were assessed using the high energy moisture characteristic (HEMC, 0–50 hPa) method, which provides (i) water retention model parameters α and n, and (ii) soil structure index (SI). Soil (watershed), land use and PAM treatments had significant effects on the shape of the water retention curves (α, n) and SI, with diverse changes in the macropore sizes (60–250; >250 μm). Soil organic carbon (SOC) content and SI were strongly related to soil pH, CaCO3 soil type-clay mineralogy, exchangeable Ca2+, and Na+ (negatively). The order of soil SI (0.013–0.064 hPa−1) and SOC (1.4–8.1%) by land use was similar (forest > grass > bush > cropland). PAM effect on increasing soil SI (1.2–2.0 times), was inversely related to SOC content, being also pronounced in soils from watersheds of low (Vertisol) and medium (Luvisol) elevation, and the cropland soil from high (Acrisol) elevation. Treating cropland soils with a high PAM rate yielded greater SI (0.028–0.042 hPa−1) than untreated bush- and grassland soils (0.021–0.033 hPa−1). For sustainable management and faster improvement in soil physical quality, soil properties, and land-use history should be considered together with PAM application.
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Haskevych, V., V. Blystiv, and H. Skilska. "Morphic characteristics of brown soils on Stryi-Sian Plateau." Visnyk of the Lviv University. Series Geography 1, no. 40 (December 12, 2012): 169–84. http://dx.doi.org/10.30970/vgg.2012.40.2041.
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The article considers the results of studies of morphology brown soils on Stryі-Sian Plateau. Described the structure of virgin soil profiles under forest vegetation, analyzed are the changes of morphological characteristics of brown soils due to their use in different agricultural areas. Key words: soil, brown soil, morphic characteristics, erosion, degradation, soils protection.