Parent Material Properties Research Articles

Physicochemical properties of selected soils formed on cretaceous sediments, shales and quaternary alluvium in Edo State, Nigeria

Physicochemical properties of some selected soils formed on three varied parent materials in Edo State, Nigeria, were evaluated for their physicochemical properties. Soil samples were collected from profile pits sunk on each parent material type. The collected soil samples were air-dried and analyzed for physicochemical properties and analyzed in the laboratory using standard methods. Results showed that the soils were low in plant nutrient elements, as revealed by their estimated levels of availability. Organic carbon, phosphorus and nitrogen were deficient in the soils. Soils formed on the three-parent materials were sufficient in Mg (1.11, 1.54, 0.88 cmol kg-1), Na (1.32, 1.39, 1.35 cmol kg-1) and K (0.20, 0.37, 0.28 cmol kg-1) while Ca was higher in soils formed on cretaceous sediment (3.08 cmol kg-1) and shale (5.22 cmol kg-1) than in quaternary alluvium (2.05 cmol kg-1). There was a significant positive correlation among the various soil properties of the different parent materials. In order to improve the productive capacity of these soils to obtain high crop yields; it is recommended that the soils be limed to increase pH levels to near neutral and optimum fertilization (organic and inorganic) for nitrogen, phosphorus and basic cations in the different parent materials.

Bedrock and climate jointly control the phosphorus status of subtropical forests along two elevational gradients

Terrestrial carbon sequestration is constrained by the supply of soil phosphorus (P). Climate and bedrock are two key independent drivers of soil P supply. Their potential interactions with soil P supply remains poorly understood. To address this issue, we examined the P status of subtropical forests in southern China along two adjacent elevational gradients with contrasting bedrock types (granite vs. slate). The results show that the P concentration of granite was significantly lower than that of slate. Accordingly, the P concentration of mineral soil, litter, and fine-root P on the granite was significantly lower than that on the slate. In contrast, their ratios to the bedrock P concentration were higher in the granite transect than in the slate transect. Moreover, we found a stronger nutrient uplift effect on P in the P-poor transects. Although bedrock P concentrations were constant along elevation, topsoil total P, soil labile inorganic P (Pi), soil labile organic P (Po), and soil moderately labile Pi concentrations showed a significant increasing trend with elevation on both transects. Multivariate linear regression models revealed that bedrock P explained more variation of plant and soil P than did climate. Soil moderately labile Po concentration showed contrasting elevational patterns on different bedrock types, which indicated an interactive effect between bedrock P concentration and climate on the soil moderately labile Po concentration. The Pearson correlation analysis indicated that plant and soil P measures were more tightly coupled in the P-poor transect than in the P-rich transect. These results indicate that the P status of subtropical forests is determined predominantly by the bedrock P concentration and by its interaction with climate. Our results suggest that predictions of ecosystem P status and its responses to climate change can be improved significantly by incorporating local-scale parent material properties into the modeling frameworks.

Influence of Material Properties on Interfacial Morphology during Magnetic Pulse Welding of Al1100 to Copper Alloys and Commercially Pure Titanium

During magnetic pulsed welding (MPW), a wavy interface pattern can be observed. However, this depends on the specific material combination being joined. Some combinations, e.g., steel to aluminum, simply provide undulating waves, while others, e.g., titanium to copper, provide elegant vortices. These physical features can affect the strength of the joint produced, and thus a more comprehensive understanding of the material combination effects during MPW is required. To investigate the interfacial morphology and parent material properties dependency during MPW, tubular Al1100 and various copper alloy joints were fabricated. The influence of two material properties, i.e., yield strength and density, were studied, and the interface morphology features were visually investigated. Results showed that both material properties affected the interface morphology. Explicitly, decreasing yield strength (Cu101 and Cu110) led to a wavy interface, and decreasing density (Cu110 and CP-Ti) resulted in a wave interface with a larger wavelength. Numerical analyses were also conducted in LS-DYNA and validated the interface morphologies observed experimentally. These simulations show that the effect on shear stresses in the material is the cause of the interface morphology variations obtained. The results from this research provide a better fundamental understanding of MPW phenomena with respect to the effect of material properties and thus how to design an effective MPW application.

Physiochemical characterization of agricultural waste biochars for partial cement replacement

PurposeThe purpose of this study is to explore the feasibility of utilizing agricultural (almond shell, rice husk and wood) waste biochars for partial cement replacement by evaluating the relationships between the physiochemical properties of biochars and the early-age characteristics of cement pastes.Design/methodology/approachBiochars are prepared through the thermal decomposition of biomass in an inert atmosphere. Using varying percentages, biochars are used to replace ordinary Portland cement (OPC) in cement pastes at a water/binder ratio of 0.35. Characterization methods include XPS, FTIR, SEM, TGA, BET, Raman, loss-on-ignition, setting, compression and water absorption tests.FindingsAccelerated setting in biochar-modified cement pastes is attributed to chemical interactions between surface functional groups of biochars and calcium cations from OPC, leading to the early development of metal carboxylate and alkyne salts, alongside the typical calcium-silicate-hydrate (C-S-H). Also, metal chlorides such as calcium chlorides in biochars contribute to the accelerate setting in pastes. Lower compression strength and higher water absorption result from weakened microstructure due to poor C-S-H development as the high carbon content in biochars reduces water available for optimum C-S-H hydration. Amorphous silica contributes to strength development in pastes through pozzolanic interactions. With its optimal physiochemical properties, rice-husk biochars are best suited for cement replacement.Research limitations/implicationsWhile biochar parent material properties have an impact on biochar properties, these are not investigated in this study. Additional investigations will be conducted in the future.Practical implicationsCarbon/silicon ratio, oxygen/carbon ratio, alkali and alkaline metal content, chlorine content, carboxylic and alkyne surface functional groups and surface areas of biochars may be used to estimate biochar suitability for cement replacement. Biochars with chlorides and reactive functional groups such as C=C and COOH demonstrate potential for concrete accelerator applications. Such applications will speed up the construction of concrete structures and reduce overall construction time and related costs.Social implicationsReductions in OPC production and agricultural waste deterioration will slow down the progression of negative environmental and human health impacts. Also, agricultural, manufacturing and construction employment opportunities will improve the quality of life in agricultural communities.Originality/valueEmpirical findings advance research and practice toward optimum utilization of biomass in cement-based materials.

Mapping Distribution Approach in Various Types of Use Sub-Optimal Dry Land in Aceh Besar District

Sub-optimal land can be defined as land that naturally has low productivity due to internal (intrinsic) factors such as parent material, physical, chemical, and biological properties of soil, and external factors such as rainfall and extreme temperatures. For that reason, it is necessary to map foreknow the various types of sub-optimal dry land uses and their size in the district Aceh Besar. Administration maps, land use maps, slope maps, and soil type maps would later be overlaid and digitized on the screen to obtain the map and the area of research to be carried out. The slope gradient was limited to only 25% due to looking conditions that allow it to be used in the management business agriculture. The forest area was 19,136.65 ha, the dry land agricultural area was 89,472.15 ha, area open land of 1,070.75 ha, and scrub area of 58,840.87 ha. It can be observed that land use in the Aceh Besar district is dominated by Dryland farming.

Parameters optimization for microcrack width in laser trepanned hole

Abstract Ceramic composite like Zirconia Toughened Alumina (ZTA) acquire with excellent toughness, high hardness and temperature resistance. These characteristics demand applications in manufacturing of ballistic body parts, cutting tool inserts, turbine blades and combustion chambers. Conventional machining methods are unsuitable to drill/cut holes in ZTA plate due to its improved mechanical properties. Researchers have found that laser beam machining has capability to drill or cut holes in structural ceramics. Formation of microcracks is inherent in laser drilled hole due to adhered layer of resolidified material and development of thermal stresses. The chances of formation of microcracks are more in laser drilling or cutting of hard and brittle material like ZTA. Sometimes, widening of microcrack propagates underneath recast layer and demolishes the hole surface quality and changes parent material properties, as well. Therefore, selection of optimum level of control factors or input process parameters became essential during laser drilling of ZTA to overcome the intensity of microcracks. In this research paper, the microcrack width of laser trepan drilled hole has been optimized using Artificial Intelligence tool such as Genetic Algorithm. Optimum result shows that microcrack width has been reduced by 17.66%. The comparative improvement has also been confirmed in SEM image.

Building a quality index for soils impacted by proximity to an industrial complex using statistical and data-mining methods

Differences in soil quality indices, in terms of the inherent properties of loess parent material and the potential for Zn, Pb and Cd contamination from the emissions of an adjacent large industrial complex, were determined. A set of independent variables was established for the soils, using principal component analysis (PCA) and a random forest (RF) method. The quality indices of 140 topsoil samples from the environs of an industrial complex were compared with those of reference soils taken from around the borders of the study area. Potential driving factors for the Zn, Pb and Cd concentrations were dehydrogenase activity (DHA), urease (Ure) activity and invertase activity (IA), C, N, K2O, MgO, P2O5 and soil clay content. Maps were generated to show the spatial distributions of the Zn, Pb and Cd contamination. Enrichment factors and potential ecological risks were calculated. We established that, in general, concentrations of Zn, Pb and Cd in the topsoil decreased with increasing distance from the industrial complex, and the levels of Zn and Cd exceeded established intervention values, even in some soils on arable land. The arable land was enriched in P2O5, while the highest values for K2O and MgO were found in wasteland soils. The mean C content of all the soils was about 2%, with N (about 0.2%), C/N ratio (about 12) and pH (about 6.9) in the order: arable land<meadow<wasteland. The highest DHA and Ure activity was determined in the reference (unpolluted) soils, while much higher IA was present in the wasteland soils. PCA model focused on factors connected with different soil uses, while RF model emphasised the natural resistance of the studied soils to degradation. Our results indicate that the driving factors of the soil quality index were controlled by the inherent properties of the loess parent material, rather than soil pollution.

Designing of a thin Mo diffusion barrier towards strong and reliable Ti/Cu dissimilar brazing

The dissimilar brazing of Ti and Cu has been recognized to be challenging owing to the affinity of forming brittle intermetallic compounds at joint interface. In the current investigation, it was demonstrated that such detrimental interfacial reaction products can be readily circumvented by employing a Mo diffusion barrier deposited on Ti substrate. Combining Mo interlayer and a Ag–Cu–Ti active filler alloy, intermetallic compounds free Ti/Cu brazed joints consisting of Ti–Mo solid solution, Mo interlayer and remnant braze can be obtained. As a result of the eradication of brittle phases, the resultant joints exhibit excellent structural integrity with bonding strength comparable to the parent material properties. Additionally, as a consequence of sluggish solid state diffusion at the Ti/Mo interface and limited dissolution of the Mo interlayer by filler alloy during brazing, the desirable joint microstructure can be reproduced within a wide range of bonding duration. Such results indicate that strong and reliable Ti/Cu dissimilar brazing can be achieved by the combination of a Mo diffusion barrier and Ag–Cu–Ti active filler alloy.

Investigation of spectral properties of different Quaternary paleosols and parent materials

Diffuse Reflectance Spectroscopy (DRS) is a rapid, relatively new method in Quaternary research to analyse sediments and paleosols. This method takes into account clay mineral content, amount of Fe-bearing minerals and grain size composition of samples, simultaneously. Different Quaternary sediment samples were chosen forcharacterization and comparison their reflectance curves to detect the essential spectral properties of differentpaleosols and parent materials. Samples of different sediment types and paleosol variants were investigatedfrom a loess-paleosol sequence from Malá nad Hronom (Slovakia) and from a fluvial-aeolian sediment complex from Pilismarót (Hungary). Five investigated curve sections were separated as the best indicators of reflectance properties of DRS curves. Spectral properties of samples were compared by using the length of investigated curve sections. This investigation showed quantifiable differences between the units of Pleistocene sediment successions, based on the reflectance properties. The influence of pedogenic processes was properly detectable. Significant discrepancies were observed between reflectance curves of well-developed paleosols and parent material samples in the visible and near-infrared range. Differences between the weak developed paleosol layers and their parent materials were only observed in the visible range. Fine sand, sandy silt and loess materials could be separated from each other based on the intensity of entire reflectance curves.

Testing of Welded Joints between Pipes for Pressure Vessels Made of Hot Rolled Fine-Grained Steel P460NL1

This paper contains results of tests performed in order to determine mechanical properties of steel P460NL1, used as filler material during the execution of welded joints. Arc welding of samples from which the specimens were taken was carried out through the application of welding process 111, because it is one of the processes for the execution of pipelines for pressure equipment. Microspecimens with diameter of Ø1,5 mm were tested in order to determine tensile properties of material taken from the heat-affected zone and weld metal, while specimens with diameter of Ø6 mm were tested in order to determine tensile properties of parent material. Standard Charpy V-notch specimens were used in order to determine impact energy. Results of metallographic tests which refer to the structure of a pipe welded joint are also presented.

Investigation on the temperature dependent out-of-plane quasi-static compressive behavior of metallic honeycombs

Abstract This study investigates the effect of temperature on the out-of-plane quasi-static compressive behavior of metallic honeycombs by numerical and theoretical methods. Adopting a temperature dependent elastic-perfectly plastic constitutive relation, the temperature dependent out-of-plane quasi-static compressive mechanical performance of Al5052 honeycomb is studied with the finite element method. The results show that the plateau stress, peak stress and specific energy absorption (SEA) of Al5052 honeycomb decrease gradually with increasing temperature, while the crush load efficiency (CLE) and deformation pattern are temperature insensitive. Then, based on the numerical results in this study and super folding element theory, the temperature dependent theoretical models without fitting parameters for the plateau stress and SEA of metallic honeycombs are developed, respectively. These theoretical models are successfully verified against numerical simulations and experiments. Based on these theoretical models, the effects of parent material properties on the plateau stress and SEA at different temperatures are discussed. The results in this study provide useful guidelines in optimizing the choice of parent materials to fabricate metallic honeycombs with better energy absorption efficiency at different temperatures.

Physical-chemical and mineralogical properties of parent materials and their relationship with the morphology of badlands

Badlands are present throughout the world, but not everywhere do they have the same morphology. The main objective of this study is to try to understand why these different morphologies occur by analysing the physical-chemical and mineralogical characteristics of the parental material in which badlands have developed. The study was carried out in three areas of the Region of Murcia (south-east Spain): Abanilla, Mula and Gebas.Several analyses were carried out: (i) field analysis (orientation, slope, length and shape of the slope, presence and characteristics of the rills, vegetation, vegetation pedestals, exposed roots, stoniness, physical and biological crusts, saline efflorescence, cracks, popcorn, piping processes, sedimentation areas and mass movements); (ii) physical-chemical analysis of the soils (colour, texture, aggregate stability, bulk density, organic matter, pH, electrical conductivity, cations and cation exchange capacity, total or equivalent calcium carbonate, sodium absorption ratio and exchangeable sodium percentage); and (iii) mineralogical analysis.The results of the analyses reveal how the rounded shapes in the badlands that appear in Abanilla have significant differences with respect to the angled shapes of Mula and Gebas, which could explain the different morphologies. In general, Abanilla has very small amount of sand, higher bulk density, small amount of organic matter, lower cation exchange capacity, and very high salinity, as shown in the values of electrical conductivity, sodio, SAR and ESP.On the other hand, similarities were found between the badlands of the Region of Murcia with the calanchi (angled shapes) and biancane (rounded shapes) of Italy.

Post welding heat treatment improving mechanical properties on Ti-6Al-4V

Ti-6Al-4V can be easily welded by tungsten inert gas (TIG) welding process. However, the parent material properties tend to worsen because of microstructural changes and residual stresses. Post welding heat treatments (PWHT) are used to restore the mechanical properties of the joints. In this work, automotive components made out of Ti-6Al-4V are welded by TIG process. Although the as-welded joints showed e reasonable static strength, the strain at failure resulted quite low so that a toughness improvement via post welding heat treatment was required. This contribution summarizes the preliminary results obtained by PWHT on both butt- and overlap-welded joints made out of titanium alloy (grade 5). Different heat treatment (HT) recipes were tested and results were showed in terms of stress-strains curves as well as microstructure and microhardness profiles. It is found that, with reference to overlap joints, a stress-relieving HT optimizes both the mechanical properties and toughness. A partial solution HT followed by ageing is required to increase significantly the static strength of butt-welded joints, unfortunately without toughness improvement.

Composition of clay minerals and their pedogenetic and taxonomic implications for Stagnic Anthrosols derived from different parent materials in Hunan Province, China

The aims of this study were to investigate the composition of clay minerals in soils derived from different parent materials and to elucidate how parent materials and pedogenic environment affect the distribution of clay minerals and reveal the implications for pedogenetics and taxonomy in Stagnic Anthrosols. Clay mineralogy and physicochemical properties of the Hydragric horizon of Stagnic Anthrosols derived from granite (GR), plate shale (PS), quaternary red clays (QRC), limestone (LS), purple sandy shale (PSS) and fluvial-lacustrine deposit (FLD) located in Hunan Province of China were analysed to explore the relationships between the conditions influencing the formation of the soil and the composition of clay minerals. Results indicated that the composition of clay minerals is closely related to both parent material and type of Stagnic Anthrosols: the soils derived from GR, PS and QRC, which are mostly classified as Fe-accumulic-Stagnic Anthrosols, are dominantly 1:1 type kaolinite and vermiculite and illite/vermiculite mixed layer minerals of widespread distribution. However, soils derived from LS, PSS and FLD were mainly classified as Hapli-Stagnic Anthrosols and are mainly composed of 2:1 type illite/smectite mixed layer minerals, where chlorite is commonly found. Illite is widely distributed and its content varies the least among different parent materials. An extremely significant relationship between pH and kaolinite, chlorite and mixed layer minerals was noted, and the two kinds of mixed layer minerals showed highly significant negative correlation. This study revealed that the types and quantities of clay minerals in the soil are closely related to the types of parent material. This reflected better direction and degree of development in Stagnic Anthrosols, which is related to the physicochemical properties of parent material and can be used as one of the bases for the classification of soil groups and subgroups within the soil family for Stagnic Anthrosols in Chinese Soil Taxonomy.

Ultrasound-assisted 3D printing of continuous fiber-reinforced thermoplastic (FRTP) composites

Investigation of manufacturing continuous fiber reinforced thermoplastic polymer composites (CFRTPCs) through 3D printing technologies has attracted great attention in the past few years due to excellent properties of CFRTPCs, such as high strength-to-weight ratio and stiffness. It is found that the properties of CFRTPCs are affected not only by the properties of the individual parent materials but also by interfacial characteristics. Modification of the interface is a great method to improve the wettability between fiber and polymer and hence the mechanical properties of CFRTPCs. In this work, an ultrasound-assisted 3D printing device for CFRTPCs is developed. The changes of surface profile and chemical structure of carbon fiber and carbon fiber prepreg after ultrasonic treatment are studied. The effects of ultrasonic processing parameters on the microstructure and mechanical properties of CFRTPCs are provided. It is found that the tensile and flexural strength of composite materials are improved by 34% and 29%, respectively, compared with untreated material by using the ultrasonic amplitude of 40 μm, resin solution mass fraction of 10%, processing speed of 15 mm/s.

Statistical characterisation of expanded metal mesh strand, to propose a correlation between properties of parent material and finish product, EMM

The use of steel plate shear walls (SPSW) for the design of structures under low seismic intensity results in very thin infill SPSW panels. Construction of such structures is infeasible, mainly due to the difficulty in connecting the infill to the boundary members. Thus, a designer is compelled to use a thicker infill section which in turn leads to heavier boundary elements. In order to overcome this constraint of design, a new type of infill panel using Expanded Metal Mesh (EMM) is studied as an alternative in place of a solid infill SPSW panel. Available codes on expanded metal mesh specify requirements of workmanship, quality control, etc. but neither recommend the strength of expanded metal mesh as a whole nor the strength of its components. Thus, it is necessary to perform extensive tests to extract the strength of expanded metal mesh as a whole in terms of the strength of its components and to come out with a correlation between the strength of the parent material (material from which EMM is manufactured) and that of the finished product (EMM). This paper a) presents the statistical characterization of EMM strands, b) recommends nominal design values for basic mechanical properties and c) proposes the correlation between the strength of the parent material and that of EMM strand.

Clay and climate are poor predictors of regional-scale soil carbon storage in the US Caribbean

Soils of the tropics play an important role in the global carbon (C) cycle as substrates for the most productive terrestrial ecosystems and as large C reservoirs. The amount of C stored in a soil is affected by soil properties such as texture, pH, and mineralogy, as well as climate, vegetation and land management, yet, uncertainty remains regarding the relative importance of these variables at different spatial scales. The goal of this study was to explore the factors influencing regional patterns in soil C storage. Soils were collected from 36 sites under four land cover types (forests, pastures, croplands and wetlands) and on 30 soil series in seven soil orders, representing the diversity in soil forming factors and major non-urban landscapes in Puerto Rico and the US Virgin Islands. Soils were analyzed at three depths, 0–30 cm, 30–100 cm, and 0–100 cm, for total carbon (TC), soil organic carbon (SOC), and total nitrogen (N). Traditional predictors of soil C storage such as clay content and climate were not sufficient to accurately capture regional soil C trends. The combination of clay plus fine silt was positively correlated with SOC stocks but explained a relatively small amount of the variation. Site temperature and mean annual precipitation were not correlated with SOC stocks. Soil order and land cover were weak predictors of SOC for a subset of data where forests and pastures were found on three of the same soil orders, allowing for a two-way ANOVA. Soil N showed similar trends as SOC. Patterns observed depended on the soil depth studied, reflecting relative differences in the strength of top-down and bottom-up factors influencing SOC and N storage. These findings suggest that mechanisms not described by the distribution of soil particle sizes need to be considered for better predictions of SOC dynamics. In a geologically diverse region, soil properties were better predictors of SOC than climate or land cover. Tropical regions represent a diversity of soil types yet parent material and soil physical properties other than texture are not currently included in most biogeochemical models attempting to predict the response of tropical soil C pools to environmental change. Recognition of the heterogeneity of geologic substrates and weathering gradients in tropical regions and incorporation of a more mechanistic understanding can improve soil C modeling and land management decisions.

Proposal of the correlation between cartographic units on the agricultural soil map and types and subtypes of Polish Soil Classification (6th edition, 2019)

Abstract Agricultural soil maps (ASM), prepared since mid-1960s until 1980s and digitalised recently, are important source of information on the quality and spatial variability of arable soils in Poland. Basic standard information in each map contour includes the indication of a (genetic) soil type (often also the subtype or variety related to parent material or other specific properties), soil texture classes throughout the profile, and the category of soil agricultural suitability, which covers the complex information about the soil conditions, land morphology, climate and moisture regime. Unfortunately, the genetic classification on ASM is simplified compared to soil classifications in Poland and does not reflect numerous modernisations of the classification systems, including the modifications of existing units and newly introduced soil types and subtypes. Thus, the reinterpretation of ASM is necessary to simplify the further use of ASM by various users, to allow the creation of modern soil maps based on archival databases, and to correlate the soil data with other modern national and international classifications. This paper includes a proposal of equivalents for the soil units indicated in agricultural soil map (using all soil data available in a map contour), correlated with a recent, the 6th edition of Polish Soil Classification.

Generation, sink, and emission of greenhouse gases by urban soils at different stages of the floodplain development in Moscow

The purpose of this research was to study the generation, sink, and emission of greenhouse gases by soils on technogenic parent materials, created at different stages of the Moskva River floodplain development (1—construction and 2—landscaping of residential areas). Field surveys revealed the spatial trends of concentration and emission of the greenhouse gases in following groups of soils: Retisols (RT-ab-ct) and Fluvisols (FL-hu, FL-hi.gl) before land engineering preparation for the construction, Urbic Technosols Transportic (TC-ub-ar.tn and TC-ub-hu.tn) at stage 1 and Urbic Technosols Folic (TC-ub-fo) at stage 2. CO2 and CH4 concentration in soils and their emission were determined using subsurface soil air equilibration tubes and the closed chamber method, respectively. Bacterial methane generation rate (MGR) and methane oxidation rate (MOR) were measured by kinetic methods. In natural soils MOR is caused only by intra-aggregate methanogenesis. The imbalance of methane generation and oxidation was observed in FL-hi.gl. It caused CH4 accumulation in the profile (7.5 ppm) and its emission to the atmosphere (0.11 mg CH4 m−2 h−1). RT-ab-ct acted as the sink of atmospheric methane. CO2 emission was 265.1 ± 24.0 and 151.9 ± 37.2 mg CO2 m−2 h−1 from RT-ab-ct and FL-hi.gl, respectively. In Technosols CH4 concentration was predominantly low (median was 2.7, 2.9, and 3.0 ppm, in TC-ub-ar.tn, TC-ub-hu.tn, and TC-ub-fo, respectively), but due to the occurrence of peat sediments under technogenic material, it increased to 1–2%. Methane emission was not observed due to functioning of biogeochemical barriers with high MOR. In TC-ub-ar.tn and TC-ub-hu.tn, the barriers were formed at 60-cm depth. In TC-ub-fo, the system of barriers was formed in Folic and Technic horizons (at 10- and 60-cm depth). CO2 emission was 2 times lower from TC-ub-ar.tn and TC-ub-hu.tn and 1.5 times higher from TC-ub-fo than from natural soils. Greenhouse gas generation, sink, and emission by natural soils and Technosols in floodplain were estimated. CO2 and CH4 content in Technosols varied depending on the properties of parent materials. Technosols at stage 1 did not emit CH4 due to formation of biogeochemical barriers—soil layers of high CH4 utilization rates. Urbic Technosols (Folic) at stage 2 performed as a source of significant CO2 emission.

Influence of shifts over an 80-year period in forest composition on soil properties

Forest composition in North America has undergone important changes since the European settlement. The effects of such alterations on soil properties remain largely unknown. This study aims to understand the long-term effects of shifts in forest composition on soil properties. Using data from 130 plots measured over an eighty-year period, the relationships between stand composition (both current and past), parent material and current soil chemical properties were studied with redundancy analyses. Results indicated that the parent material remained the dominant factor explaining soil properties, followed by current tree species composition. No legacy effect of past forest composition was found, but shifts in forest composition explained part of the current soil properties. Specifically, an increase in balsam fir was related to higher C/N ratio in the O-horizon, while an increase in maple species was related to higher net nitrification in both the O and B-horizons, and higher extractable P in the B-horizon. Our results suggest that increasing the maple component at the expense of conifers over several decades may enhance nutrient availability in the O-horizon.