Soil Profile Research Articles

Pedogenetic analysis of xerometamorphic horizons of chestnut soils of the Northern Caspian Sea plain

The paper characterizes the profiles of virgin chestnut soils and solonetz in the north of the Caspian lowland adjacent to the Djanibek reserve. The objective of the study was to analyze the morphology, physical properties and chemical and mineralogical composition of the so-called xerometamorphic horizons of chestnut soils in the research area. The initial hypothesis was the general genetic similarity of xerometamorphic horizons with natric horizons in the corresponding conjugate soils. With the general similarity of morphological features, mineralogical and chemical composition of these horizons, there was a significant difference in the content of exchangeable sodium and in the presence of signs of clay illuviation in the natric horizons. It is suggested that xerometamorphic horizons reflect the initial stages of formation of alkaline soils, further diluted by divergent pedogenesis. The proposal of a number of specialists on the allocation of the BMK horizon in soils used in agriculture and, accordingly, the type of agro-soils is supported.

Predominant Cropping Systems affect Soil Organic Carbon Content in the Soil Profile of North–West India

Predominant Cropping Systems affect Soil Organic Carbon Content in the Soil Profile of North–West India

Influence of Foundation–Soil–Foundation Interaction on the Dynamic Response of Offshore Wind Turbine Jackets Founded on Buckets

This study investigates the impact of soil–structure interaction (SSI) and foundation–soil–foundation interaction (FSFI) on the dynamic behaviour of jacket substructures founded on buckets for offshore wind turbines. A parametric analysis was conducted, focusing on critical load cases for conservative foundation design. Different load configurations were examined: collinear wind and wave (fluid–structure interaction) loads, along with misaligned configurations at 45° and 90°, to assess the impact of different loading directions. The dynamic response was evaluated through key structural parameters, including axial forces, shear forces, bending moments, and stresses on the jacket. Simulations employed the National Renewable Energy Laboratory (NREL) 5MW offshore wind turbine mounted on the OC4 project jacket founded on suction buckets. An additional optimised jacket design was also studied for comparison. An OpenFAST model incorporating SSI and FSFI considering a homogeneous soil profile was employed for the dynamic analysis. The results highlight the significant role of the FSFI on the dynamic behaviour of multi-supported jacket substructure, affecting the natural frequency, acceleration responses, and internal forces.

Digital modeling of lateral water flows and caesium-137 at the microlandscape level in semi-hydromorphic soils of the Bryansk region

A significant role in the movement of water in the soil profile belongs to the preferential vertical water flows, while less attention is paid to the study of lateral flows. We propose a method for studying lateral moisture flows at the microlandscape level using 137Cs of “Chernobyl” origin. For GIS modeling of lateral transport, the hydrological attributes of the microrelief were used, based on a digital relief model (DEM) at a scale of 1:200 with a horizontal section of 20 cm. The Catchment Areas, the Overland Flow Distance, the ephemeral Tricle Network (Strahler Order), as well as the topographic humidity index (TWI) qualitatively characterize the intensity of soil moisture, as well as lateral flows at the microlandscape level. The idea of “preferential lateral flows” introduced by analogy with vertical “preferential moisture flows”. Due to the spatial features of the structure of the nano- and microrelief, lateral transfer forms ephemeral patterns with different humidification modes: “finger-like”, filamentous, and others. A weak level of lateral migration of 137Cs was revealed depending on DEM derivatives.

Landscape–Geochemical Assessment of Content of Potentially Toxic Trace Elements in Arctic Soils

The importance of research to assess the impact of potentially toxic trace elements (PTEs) on the environment and the importance of environmental monitoring, taking into account the natural variability of soil properties, shaped the aim of our study: to determine the background concentrations of PTEs in different soil profiles in the European Northeast, specifically in the Republic of Komi in Russia, taking into account the landscape and geochemical characteristics of the area. We analysed 173 soil samples from five main soil subtypes. The acid soluble forms of PTEs (Cu, Pb, Zn, Ni, Cd and Mn) were measured using an atomic emission spectrometer. We developed a database of PTE contents and created distribution maps for the Komi Republic using GIS technologies. The study found that PTE levels in soils from accumulative landscapes (such as depressions and floodplains) were generally higher than those in soils from eluvial landscapes (interfluves). We identified correlations between the levels of different PTEs and certain soil properties, providing insights into the biogeochemical migration patterns of these elements. The differentiation of PTEs in soil profiles was more pronounced in loamy automorphic soils and less so in sandy semi-hydromorphic and hydromorphic soils. Most soils, except floodplain soils, showed a clear eluvial–illuvial pattern of PTE distribution within the mineral soil profile, whereas floodplain soils showed a more uniform PTE distribution. The results of this study are useful for assessing the contamination levels of these soil types in high-latitude regions.

Soil organic matter of Cambisols in Vitosha mountain, Bulgaria

A complex of soil carbon properties was studied and a research was made about the content of soil organic matter and organic C. The surface A and Bw horizon of Cambisols were studied in order understand relations of soil organic content and composition. Sample soil profiles in the middle part of Vitosha Nature Park were taken under different type of trees. Higher amount of total carbon and free low-molecular humic acids were determined in the surface and in the cambic horizons. The amount of soil organic carbon is high – from 2.08 % to 5.44 % in the surface horizon. The fulvic-humic type of soil organic matter predominates in studied soil horizons. Similar to this most of the soil samples have ration C/N > 15 which is Mull humus. This type is commonly associated with temperate forest ecosystems, where deciduous trees shed their leaves annually, and contributing organic matter to the soil.

Phosphorus leaching in high-P soils under maize silage and interseeding cover crop system

Managing soil phosphorus (P) in agroecosystems with high P levels is crucial to mitigate P loss in water sources without compromising yields. The objective of this study was to assess maize silage (Zea mays L.) + interseeding cover crop of annual ryegrass (Lolium multiforum) or using a relay cover crop and starter P (P0, P10, and P20) on (i) P leaching, (ii) changes in soil P status, and (iii) maize yield, cover crop biomass and P uptake. A six-year study was conducted between 2018 and 2023 in two sites. Leachate samples were collected every two weeks between 2021and 2023. The concentration of P in leachate exceeded 0.5 mg L–1 indicating a high risk of P leaching at the current levels of soil P. High concentration of P in leachate with a peak at 0.9 mg L–1 in August and 1.45 mg L–1 in October during 2021 and 2022 was pronounced under interseeded compared to relay cover crop system due to improve water infiltration contributing to the downward movement of P. In contrast, the concentration of P in leachate was high under relay cover crops in February and March particularly in 2023, which could be attributed to the delay in cover crops establishment and growth in early spring. The concentration of P extracted using anion exchange membranes (PO4AEMs) increased with increasing starter P rate during the first weeks after planting maize silage. There were spikes of PO4AEMs, reaching 1.18 and 1.73 µg cm–2 d–1 during the 4th, 7th, and 8th weeks after planting maize which coincided with high soil moisture content occurring after irrigation or rainfall events. The lack of dry matter yield response to starter P at harvest was due to high initial soil P. The soil P status remained significantly high averaging 196.6 mg kg–1 as Mehlich-3 P, despite negative cumulative P budgets. A close observation of the relationships among soil P indicators shows a trend of rapidly decreasing water extractable P under interseeding compared with relay cover crops. It is possible that the production of high biomass under interseeding cover crops increased the amount of P taken up from the soil. We conclude that interseeding cover crops within cash crops in high P soils could be effective at decreasing soil P, but could enhance P leached in the first years of cropping due to high water infiltration along the soil profile.

Highly Efficient JR Optimization Technique for Solving Prediction Problem of Soil Organic Carbon on Large Scale.

We utilized remote sensing and ground cover data to predict soil organic carbon (SOC) content across a vast geographic region. Employing a combination of machine learning and deep learning techniques, we developed a novel data fusion approach that integrated Digital Elevation Model (DEM) data, MODIS satellite imagery, WOSIS soil profile data, and CHELSA environmental data. This combined dataset, named GeoBlendMDWC, was specifically designed for SOC prediction. The primary aim of this research is to develop and evaluate a novel optimization algorithm for accurate SOC prediction by leveraging multi-source environmental data. Specifically, this study aims to (1) create an integrated dataset combining remote sensing and ground data for comprehensive SOC analysis, (2) develop a new optimization technique that enhances both machine learning and deep learning model performance, and (3) evaluate the algorithm's efficiency and accuracy against established optimization methods like Jaya and GridSearchCV. This study focused on India, Australia, and South Africa, countries known for their significant agricultural activities. We introduced a novel optimization technique for both machine learning and deep neural networks, comparing its performance to established methods like the Jaya optimization technique and GridSearchCV. The models evaluated included XGBoost Regression, LightGBM, Gradient Boosting Regression (GBR), Random Forest Regression, Decision Tree Regression, and a Multilayer Perceptron (MLP) model. Our research demonstrated that the proposed optimization algorithm consistently outperformed existing methods in terms of execution time and performance. It achieved results comparable to GridSearchCV, reaching an R2 of 90.16, which was a significant improvement over the base XGBoost model's R2 of 79.08. In deep learning optimization, it significantly outperformed the Jaya algorithm, achieving an R2 of 61.34 compared to Jaya's 30.04. Moreover, it was 20-30 times faster than GridSearchCV. Given its speed and accuracy, this algorithm can be applied to real-time data processing in remote sensing satellites. This advanced methodology will greatly benefit the agriculture and farming sectors by providing precise SOC predictions.

Validation of Double Constant and Falling Head Permeameter for Determination of Hydraulic Conductivity of Soils in the Laboratory

The objective of this research was to validate alternative equipment for determining the hydraulic conductivity of saturated soil (Ksat) in laboratory settings. The aim was to develop a single piece of equipment that could be used to carry out tests using both the constant-head permeameter (CHP) and the falling-head permeameter (FHP) methods with minimal disturbance to the samples. To this end, undisturbed soil samples were collected (in volumetric cylinders with 100 and 250 cm3) from three soil profiles with different textures to evaluate the sensitivity of the double permeameter (DP) in determining Ksat, considering the method, the sample size, and the textural class of the soils. To assess the efficacy of the DP in estimating Ksat, the coefficient of variation (CV) was determined for the two methods (CHP and FHP), the sample size (100 and 250 cm3), and the applied hydraulic head (cwc) (constant: 1.5 and 2.5 cwc; falling: Δhi, upper limit, h1 = 67.6 and h2 = 57.6 cwc; Δhii, medium limit, h1 = 49.3 and h2 = 39.3 cwc; and Δhiii, lower limit, h1 = 31.3 and h2 = 21.3 cwc). The results indicate that the DP may be employed as an alternative permeameter for Ksat tests employing the CHP and FHP methods. The most favorable statistical coefficients were observed in tests conducted with samples of a sandy texture (Profile 3, Ap horizon), particularly those with a larger volume (250 cm3), for both the CHP and FHP methods, irrespective of the applied hydraulic head. The equipment can be utilized within the full range of methodological limits employed in this study, and the appropriate limit must be selected according to the physical properties of the soil to be employed in the tests.

Effects of foundation conditions on failure modes of jacket type offshore platforms using incremental irregular wave dynamic analysis

Quantitative assessment of environmental conditions and their loading effects is crucial for the optimal design of marine structures, especially offshore platforms subject to extreme environmental conditions. Wave load, particularly irregular wave load, significantly influences the structural response and ultimate strength of jacket-type offshore platforms (JTOPs) throughout their operational life. The dynamic nature of these irregular wave loads necessitates the use of advanced time history analysis to accurately capture their impact. This study aims to enhance the understanding of how foundation conditions impact failure modes and the structural response of JTOPs through an innovative incremental irregular wave dynamic analysis procedure. By focusing on an existing steel jacket-type platform in the Persian Gulf, this research evaluates six models with varying soil profiles and pile conditions to assess their effects on structural performance. The application of incremental irregular wave dynamic analysis provides a more precise and realistic modeling of wave impacts compared to traditional methods. The findings demonstrate that stronger soil profiles and improved pile conditions significantly enhance structural integrity, particularly under extreme loading conditions. Specifically, optimizing pile configurations is critical for enabling the structure to endure larger waves, whereas variations in the yield stress of steel material have a lesser impact on the platform's response. Additionally, the dynamic results are compared with pushover analysis, which serves as a benchmark to evaluate the accuracy and effectiveness of the pushover analysis compared to incremental irregular wave analysis method used in this study.

Risk for nitrogen leaching after application of solid manure in autumn differs between manure types

Manure application performed in autumn requires regulation due to the risk of nitrogen (N) leaching during winter. On the other hand, application of manure in spring can pose some practical problems depending on the risk for N immobilization and the difficulty in ploughing heavy clay soils during this time of year. The risk for leaching is likely to differ between different soil texture and manure characteristics. In this study, we sought to estimate the risk for nitrogen leaching depending on the carbon/nitrogen ratio (C/N) of the manure, time for manure application, and soil type. We combined 3-year lysimeter experiments with 2-year field plot experiments and laboratory soil incubations and compared results with those from an empirical model. We compared effects of manure application on two soils (silty clay and loamy sand) and solid manures with different representing C/N ratios. In incubations, only manure with a C/N-ratio below 14 contributed with significant amounts of leachable N during the first months after application. In the lysimeter study, N leaching was unaffected by the timing of the application of the manure with C/N-ratio 18. However, regarding manure with C/N-ratio 10, N leaching was elevated with 10–15 kg N per ha after manure application in October compared to November and March on both soil types. The mineral N analyses from soil profiles in the field experiments showed a similar pattern, however, the increase was higher on the loamy sand compared to the silty clay. The ammonia emissions did not differ between manure types, but were on average 24% of applied NH4-N after application in October when air temperature was on average 12°C compared to only 3% of applied NH4-N in November and March when air temperature was on average 5°C. Similar to lysimeter results, the modelled N leaching was higher the earlier the manure application occurred in autumn. However, the model also predicted increased leaching for the manure with a high C/N-ratio, and a smaller effect on leaching on clay soil. Considering this, the model calculations overestimated the leaching effects from manure with a high C/N-ratio and underestimated the leaching effects on clay soil.

Hysteresis in seasonal land-atmospheric interactions over India and its characteristics across croplands and forests

Abstract Satellite-derived vegetation optical depth and soil moisture (SM) data reveal the critical role of the soil-vegetation continuum in storing rainwater during the Indian Summer Monsoon and supporting evapotranspiration (ET) during the dry non-monsoon season. During the non-monsoon drier period, the climatologically estimated spatial mean of ET exceeds precipitation input, a phenomenon known as the soil–vegetation capacitor effect, which is pivotal in maintaining ecosystem productivity. Notably, our analysis reveals significant variations in the capacitor period between croplands and forests, with croplands exhibiting a ∼77 d longer due to dual crop seasons influenced by regional precipitation. The well-recognized hysteresis curves, observed in magnetization and soil–water characteristic curves, highlight phenomena where a system’s state is influenced by its historical inputs or states and are integral to our findings. We report a previously undocumented seasonal hysteresis in the relationship between the evaporative fraction (EVF) and SM for Indian croplands and forests. We further found that the croplands SM-EVF relation exhibits a reversal in hysteresis in the case of root-zone SM. The surface SM-EVF hysteresis is not present in forests with large root depths and reduced soil evaporation due to high canopy shading, and yet it is present for the root-zone SM. With its reversal for croplands, the newly found hysteresis must be addressed in redefining the critical SM threshold to demarcate the energy and water-limiting regimes. It should be incorporated in the land surface modeling parameterization. Additionally, we observed hysteresis in the SM-gross primary productivity relationship across both land covers and soil profiles (surface and root-zone), underscoring the need to investigate such processes to consider their dynamics in future ecological and hydrological models.

Integrated Assessment of Metal Contamination of Soils, Sediments, and Runoff Water in a Dry Riverbed from a Mining Area Under Torrential Rain Events

Dry riverbeds can transport mining waste during torrential rain events, disseminating pollutants from mining areas to natural ecosystems. This study evaluates the impact of these mine wastes on soils, sediments, and runoff/pore water in the La Carrasquilla dry riverbed (southeastern Spain). An integrated approach utilizing geochemical and mineralogical techniques was employed, analyzing water, soil, and sediment samples from both the headwater and mouth of the riverbed. Soil profiles and pore water were collected at 30 cm, 60 cm, and 90 cm deep, alongside sediment and runoff water samples. The assessment of metal(loid) contamination focused on arsenic, cadmium, chromium, copper, iron, nickel, manganese, zinc, and lead, utilizing sequential extraction to evaluate metal partitioning across soil phases. Various pollution indices, including the contamination factor (Cf), pollution load index (PLI), potential ecological risk index (RI), and metal(loid) evaluation index (MEI), were employed to classify contamination levels. The highest level of contamination was reported in the headwater, which suggested anthropogenic activities linked to the presence of mining residues as the major source of metal(loid)s. However, an active deposition of As, Cd, Cu, Fe, Mn, and Zn was reported in the topsoil at the mouth. In the headwater, a quartz and muscovite-rich zone exhibited the highest Cf for Pb (1022), primarily bound to the soil residual fraction (62.8%). At the headwater and mouth, pore water showed higher concentrations of sulfate, Ca, Na, Cl, Mg, and Mn and higher salinity than acceptable limits for drinking water or irrigation established by the World Health Organization. Runoff-water metal concentrations surpassed established guidelines, with MEI values indicating significant contamination by cadmium (36.1) and manganese (19.0). These findings highlight the considerable ecological risk of Pb and underscore the need for targeted remediation strategies to mitigate environmental impacts in the Mar Menor coastal lagoon.

Factory-Related Environmental Pollution: A Study Of The Impact Of Cement Dust On Soil Quality Around Dangote Cement Plant, Tse-Kutcha, Gboko Local Government Area, Benue State

Environmental pollution has been a close embodiment of the human society since man’s first appearance on the planet earth some few hundreds of thousand years ago. This paper examines the impact of dust emission from the exploitation and processing of limestone by the Dangote Cement Factory on the soils of Tse-kucha community. Soil profile at the depth of 0 – 80 cm were dug at distances of 0.5 km (Tse-Kucha), 1.0 km (Amua) and 1.5 km (Amua) and soil samples were collected from each horizon of the soil profile. Soil samples were also collected from another profile dug at Gaando, a nearby community to Tse-kucha where there are no cement dusts in soils for comparison. The soil samples were analysed for some physical and chemical properties related to soil fertility such as pH, organic carbon, exchangeable bases; Ca, Mg, Na and K, exchangeable acidity, infiltration capacities, available phosphorous, total nitrogen, cation exchange capacity and percentage base saturation using standard analytical procedures. Additionally, structured questionnaire was designed and administered on the respondents of the study area to complement information needed on the impact of Dangote cement plant on soil quality of the study area. The results revealed a predominantly sandy-loamy composition with significant (p < 0.05) difference in the soil parameters tested. Furthermore, the result revealed that cement dust emissions from the factory significantly affect the yield of crops in study area. area.

Combined measurement of roots, δ18O and δ2H, and a Bayesian mixed model capture the soil profiles of wheat water uptake in a deep loamy soil

The profile of crop water uptake from the soil depends on rainfall regime (amount, seasonality, frequency distribution of rainfall event size), soil, crop, and management. This study, with a focus on winter wheat in a wheat-fallow system, combines measurements of hydrogen (δD) and oxygen (δ18O) isotopes with a Bayesian mixing model (MixSIAR), and measurements of root length density to (i) quantify crop water uptake from soil down to 3 m depth, (ii) to assess the influence of soil water at sowing, soil mulching, seasonal conditions and their interaction on the profiles of soil water uptake, and (iii) to probe for relations between yield and the profiles of soil water uptake. Across treatments and seasons, water uptake at jointing featured a ratio 2.1: 1.0: 1.8: 2.2 in four soil layers, top 0.2 m, 0.20.4 m, 0.41.2 m, and 1.2–3.0 m. At anthesis, the ratios shifted to 5.2: 1.0: 1.7: 2.0. Water uptake at jointing was higher from top-soil in dry (∼60 %) than in wet condition (∼30 %), and the opposite was true in deeper layers; water supply had a smaller effect on the profiles of water uptake at anthesis. Compared to bare ground, mulch favored root proliferation and water uptake in 0.42.0 m soil layer. For a given soil layer, soil moisture correlated negatively with root length density. Yield correlated positively and linearly with water uptake from 0.43.0 m soil at jointing, indicating that faster root development at early stages favors water uptake from deep soil in the critical period of grain yield formation. We discuss the implications of our findings for agronomic management and breeding.

Vertical variations in enzymatic activity and C:N:P stoichiometry in forest soils under the influence of different tree species

Abstract Tree species play a crucial role in shaping soil properties, significantly influencing nutrient cycling and ecological dynamics within forest ecosystems. In this comprehensive study, we examined the influence of tree species on soil chemistry especially on C/N/P stoichiometry and enzymatic activities across soil profiles. We analyzed soil samples beneath eight distinct tree species at three vertical horizons of soil: organic (O), humus mineral (A), and mineral enrichment (B) horizons. Our study involved detailed assessment of soil carbon, nitrogen, and phosphorus contents, along with the activities of key enzymes: β-glucosidase, N-acetyl-β-glucosaminidase, and phosphatase. The study revealed pronounced vertical stratification in soil properties, significantly influenced by the tree species. General linear models (GLMs) highlighted differences in C: N:P stoichiometry and enzymatic activity across different soil horizons and among tree species. Enzymatic activity was strongly correlated with C, N and P content. The conducted research confirms the distinctiveness of coniferous and deciduous species in terms of C, N and P stoichiometry and the activity of the tested enzymes involved in the C, N and P circulation. These variations are indicative of the intricate interactions between tree species and soil processes. Our findings underscore the role of diversity of trees in modulating soil nutrient dynamics and enzyme-driven processes, which are crucial for understanding soil ecosystem functions and nutrient cycling. This study provides new insights into the role of tree species in shaping the soil environment, offering implications for forest management and conservation strategies. Taking into account the impact of individual tree species covered by the research on the soil, it is worth considering the cultivation of mixed stands.

An innovative Time Domain Reflectometry (TDR) sensor to monitor earthquake induced void redistribution in layered soils

Liquefaction induced soil void redistribution, i.e., the formation of thin water film between soil layers, has been identified as an important trigger of ground liquefaction occurring in stratified soils with embedded low permeability layer. Conventional liquefaction assessment of soils are conducted on uniform soil samples, which do not capture the liquefaction due to void redistribution and therefore, potentially underestimate the liquefaction occurring in the field conditions. The void redistribution, however, has not been directly validated due to lack of experimental tools for such measurements. This paper presents an innovative high resolution Time Domain Reflectometry (TDR) sensing system to directly quantify the development of thin water film in layered soils. A new spiral TDR sensor is designed and fabricated with the assistance of 3-D printing technology. A spiral sensor design is proposed to achieves high spatial resolution and sensitivity in detecting thin water film. The new spiral sensor is applied to monitor the dynamic evolvement of water film under static and dynamic conditions. In the static tests, water films with different thickness are generated between two saturated sand layers using special experimental setup. The testing results indicate that the spiral TDR waveguide has capability to detect water film as thin as 1 mm. In the dynamic experiments, the onset and evolution of interlayer water film is produced in stratified soil profile with shaking table excitation. It includes TDR system with fast signal acquisition. An algorithm is developed to analyze TDR signals to determine the thickness of water film based on the dielectric mixing model for soil-water mixture. The thickness of interlayer water film by analyzing recorded TDR signal agree reasonably well with the results of direct physical measurements. Overall, this study demonstrates the potential of an innovative TDR sensor to provide real time monitoring of water film developed in layered soils subjected to seismic ground shaking, and therefore provide a tool to generate important insight on ground liquefaction triggered by void redistribution along low permeability layers.

Microbial necromass in soil profiles increases less efficiently than root biomass in long-term fenced grassland: Effects of microbial nitrogen limitation and soil depth

Grassland fencing is acknowledged as a crucial initiative to enhance biodiversity and to increase soil organic carbon (SOC) content in ecologically fragile regions or barren systems. Theoretical perspectives propose that fencing induced an increase in root biomass, and its penetration into the soil profile introduced organic matter that facilitated SOC formation through microbial necromass and root residues. It is hypothesized that long-term grassland fencing increases root biomass, thereby enhancing SOC formation within the soil profile through microbial residues in badland ecosystems. To test this hypothesis, we selected grasslands subjected to varying durations of fencing post-grazing (i.e., 10, 15, 20, 30, and 40 y). Our investigation aimed to clarify microbial necromass dynamics in 0–100 cm soil profiles after fencing and to identify the influencing factors. Long-term grassland fencing (i.e., >30 y) increased root biomass by 160 %, SOC by 69 %, and necromass by 41 % compared to grazed grassland within the 0–40 cm horizon; in contrast, increased root biomass by 870 %, SOC by 111 %, and necromass by 46 % in the 40–100 cm horizon. Necromass in deep soil (40–100 cm) accounted for about 50 % of total residues in the 0–100 cm profile. Increased root and living microbial biomass stimulated the necromass accumulation, with a more pronounced increase in fungal residues compared with bacterial residues. Nonetheless, microbial nutrient limitation increases C or N-acquisition enzyme coefficients, which subsequently reduced fungal and bacterial residues and stimulated their recycling. Despite substantial increases in root biomass within the soil profile after fencing, limitation of microbial N and depth reduced the effectiveness of enhancing SOC and necromass. In conclusion, although microbial residues were the important source of SOC in grasslands of the Loess Plateau, microbial N limitation impeded necromass accumulation, and the interplay of root biomass, soil depth, and nutrient limitation regulated the dynamics of necromass following grassland fencing.

Migration mechanisms of soil carbon and nitrogen element during the natural restoration process in coal mining subsidence areas

ABSTRACT Understanding the movement and alteration of carbon and nitrogen elements in soil is crucial for addressing ecological restoration in coal mining subsidence areas. However, the migration process and mechanisms of these elements during the natural restoration process remain unclear. This study analysed the fluctuating variations and formation mechanisms of TC and TN content in soil profiles at different restoration times in coal mining subsidence areas. Initially, both TC and TN contents decreased followed by an increase during the natural restoration process. Soil compaction effects, variation of C/N ratio, and soil enzyme activity were considered as predominant factors controlling carbon and nitrogen element cycles in collapsed soil profiles. This study will provide valuable insights into understanding the mechanisms behind carbon and nitrogen cycles during natural recovery while establishing a scientific basis for ecological restoration in coal mining subsidence areas.

Integrating downhole seismic testing into dynamic probing light (DPL): first results

Dynamic probing light (DPL) is available among a wide range of dynamic penetrometers. This equipment can be used in locations where conventional sounding equipment may have limited access. Here, the shear wave velocity (Vs) determination by the downhole seismic technique is incorporated to the DPL to develop a hybrid test, the seismic DPL test, for the preliminary characterization of tropical soils. The corresponding equipment, test procedure and data interpretation of the seismic DPL (S-DPL) test are presented and discussed. S-DPL test campaigns were carried out at two experimental research sites where crosshole seismic tests were conducted to provide reference Vs profiles. The Vs profiles determined with the S-DPL test are in accordance with those determined with the crosshole test for both sites. The proposed hybrid test (S-DPL) has the potential to serve applications in preliminary site characterization, particularly at sites including unsaturated tropical soil profiles.