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Unregulated trampling in natural and urban forests compacts the soil, and the plants suffer. In an urban forest in Moscow, soil bulk density in heavily trampled sites increases significantly: 1.6–1.8 g/cm3 compared with 0.6–0.7 g/cm3 on sites under negligible human pressure. As soil density increases, heavy metals and their mobile fractions accumulate in the soil and roots. Amongst forest species capable of loosening soil and thereby improving its physicochemical properties, larch has the lowest soil density (0.42–0.57 g/cm−3) and appears to reduce the toxicity of heavy metals in forest and forest park landscapes. [ABSTRACT FROM AUTHOR]

Exogenous nitrogen addition can alter plant growth and community structure, thereby influencing soil carbon and nitrogen storage and ultimately impacting ecosystem services and functions. Previous studies have primarily focused on the effects of biological or abiotic factors on soil carbon and nitrogen storage in alpine meadows, but there is a lack of research investigating changes in soil organic carbon and total nitrogen storage as well as their controlling factors under nitrogen addition. Therefore, this study examined soil organic carbon and nitrogen storage across four levels of nitrogen addition. The results showed that nitrogen input significantly increased soil organic carbon and total nitrogen storage. Soil total nitrogen storage was positively influenced by soil total nitrogen, graminoid importance value, soil available nitrogen, and plant belowground biomass, while it was negatively affected by soil bulk density. Soil carbon storage was positively affected by soil organic carbon and soil nitrate nitrogen, and negatively affected by soil bulk density and forb importance value. This study emphasizes the positive effects of nitrogen addition on the accumulation of soil organic carbon and total nitrogen storage and highlights the combined effects of plant traits and soil physicochemical properties on soil total nitrogen storage. [ABSTRACT FROM AUTHOR]

In semi-arid savanna grasslands, the sparse distribution of trees often forms what are commonly known as fertile islands. However, the effect of these trees on soil organic carbon (SOC), microbial biomass carbon (MBC), and dissolved organic carbon (DOC), remains poorly understood. In this study, the spatial distribution patterns of SOC, MBC, and DOC were investigated across soil profiles (0–5, 5–10, 10–30, 30–50, and 50–100 cm) at three distances from the tree trunk in an elm-dominated savanna ecosystem in Northeast China. Our results suggest that SOC, MBC, and DOC were significantly influenced by both the distance from the tree and the soil depth. The research provides evidence that elm trees can form fertile island effects, thereby enhancing the contents of SOC and labile organic carbon fractions. [ABSTRACT FROM AUTHOR]

The critical bed-shear stress (cbs) for erosion of mud–sand bed mixtures was studied in laboratory and field conditions with currents, waves, and combined currents and waves. Three types of erosion were distinguished: particle/floc erosion, surface erosion, and mass erosion. Important influencing parameters were found to be sediment composition (percentage clay, silt, and sand), presence of organic and carbonate materials, type of bed (homogeneous, remolded, layered by depositional processes), and the dry bulk density (consolidation stage). The laboratory and field results reveal that the critical bed-shear stress is not much influenced by cohesive effects if the percentage of fines (<63 μm) is smaller than approximately 15%. For pfines>15% up to approximately 50%, the critical bed-shear stress increases for increasing values of pfines but decreases again for pfines>50%. The fine fraction includes the clay fraction (pclay≅0.2 to 0.4 pfines), which contributes primarily to the cohesive effects. In addition, the bulk density depending on the soil composition (clay, silt, sand content, and consolidation stage) has a strong effect on the cbs for surface erosion. Small bed irregularities (local disturbances) also play an important role by creating local accelerations and decelerations with enhanced turbulence and initiating particle movements. A new empirical relation is suggested to predict the critical bed-shear stress for erosion based on the dry bulk density of the sediment samples. This relation is successfully applied in a morphodynamic model of a schematized tidal basin to represent spatial variations in the erodibility of fines between sandy channels and (relatively) muddy shoals. [ABSTRACT FROM AUTHOR]

Microarthropods such as mites (Acari) and springtails (Collembola) play a key role in the functioning of nutrient‐poor ecosystems. They contribute to the comminution of organic matter and they are likely to affect the structure and function of soil microbial communities through grazing and by changing substrate availability. However, the precise effects of their interactions with microbiota remain poorly understood. In the present study, we conducted a mesocosm field experiment to determine the effects of soil microarthropod density on community composition of soil fungi. We manipulated microarthropod densities in 100 defaunated and soil‐filled meshed mesocosms by inoculating half of the units with microarthropods (i.e. high‐density treatment), while the other half of the units only contained few specimens possibly hatching from recalcitrant eggs that survived defaunation (i.e. low‐density treatment). All mesocosms were then inserted in the top soil of a range of nutrient‐poor grasslands and heathlands in Belgium for the duration of three months. The entire mesocosms were composed of mesh (30 μm mesh size) to allow for a rapid (re‐)colonization by microbes from the surrounding soils, while migration of microarthropods in or out of the mesocosms was precluded. Litter bags (30 μm mesh size) containing two types of organic matter were also buried within each mesocosm, and organic matter mass loss over time was used as a proxy to assess effects of microarthropod density on microbe‐regulated decomposition rates. We found that fungal community composition differed strongly between the two microarthropod density treatments, regardless of habitat type. The mesocosms with higher microarthropod densities were characterized by a higher number of fungal OTUs and a higher number of fungal indicator species associated to this treatment. Microarthropod density, however, did not affect microbe‐regulated organic matter decomposition rates, nor did it affect relative abundances of putative fungal functional groups, thus suggesting considerable levels of fungal functional overlap. Synthesis. The lack of measurable changes in organic matter decomposition or shifts in fungal functional group representation suggest that effects of microarthropods on the functioning of fungal communities may be lower than originally thought. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

This study investigates the effects of physical and chemical soil degradation on crop productivity in the Korekore Watershed. The watershed was categorized into level, sloping, and steep slope gradients. Within each slope gradient, one cultivated land managed with soil and water conservation and one cultivated land without soil and water conservation were selected. Selected soil physicochemical analyses were performed on 18 disturbed and undisturbed soil samples and were taken from the top 0–20 cm depths from each cultivated land with three replications. The soil degradation index (SDI) was evaluated based on the percent changes in soil properties of cultivated land without soil and water conservation to that of the cultivated land managed with soil and water conservation. The crop productivity index was determined by analyzing the percentage growth rate and its standard deviation. Soil bulk density and moisture content improved undercultivated land managed with SWC practices. Significantly higher (p ≤ 0.05) soil organic carbon (SOC) content (2.02%), total N (0.12%), available P (4.69 ppm), and exchangeable K (1.33 cmolc/kg) were observed in cultivated land managed with SWC as compared to cultivated land without SWC measures. The value of the SDI (+243.9%) for the watershed has demonstrated that soil degradation has improved and soil and water conservation measures had a significant impact on crop yields. The average crop yield rate (CYR) (30%) was found to be lower than the estimate provided by the central statistics agency in Ethiopia. A higher CYR was observed in cultivated land managed with soil and water conservation practices. It can be concluded that physical and chemical soil degradation significantly impacts crops unless counterbalanced by soil and water conservation measures. Therefore, it is recommended to implement well‐integrated watershed management practices to improve soil quality and enhance crop productivity. [ABSTRACT FROM AUTHOR]

ABSTRACT During the process of treating soft soil foundations with prefabricated drainage drains (PVD), “soil columns” form around the PVD, and a “weak zone” forms outside the range of the “soil columns.” The difference in properties between the two forms a distinct interface, leading to a gradual decrease in drainage efficiency and obstruction of vertical drainage channels, which in turn causes cracks and lateral displacement in the soil during consolidation. The interfaces between adjacent soil layers are incomplete contact, and the water within the interstices impedes the transfer of heat, manifesting a thermal resistance effect. To address this phenomenon, a synchronous measurement system for the thermal gradient and the heat flux density between the soil interfaces has been developed. Applying Fourier's law of heat conduction, the thermal resistance coefficient has been determined. Based on the theory of thermo‐hydro‐mechanical coupling, a multi‐zone axisymmetric model for saturated soils that considers thermal resistance effect has been proposed. Semi‐analytical solutions were derived and validated through comparison with the custom FEM model and field experiments. The thermal consolidation characteristics of the multi‐zone soils under various thermal contact models have also been discussed, with a comprehensive analysis of the influence of different parameters. Outcomes show that: the generalized incomplete thermal contact model provides a better description of the thermal resistance phenomenon between multi‐zone soils interfaces; ignoring the thermal resistance effect leads to an overestimation of the deformation during the thermal consolidation, and, the thermal resistance effect decreases the influence of the thermo‐osmosis effect on the consolidation characteristics. [ABSTRACT FROM AUTHOR]

Girdling is a crucial technique for promoting the close-to-nature transformation of plantation forests in Hainan Tropical Rainforest National Park (HNNP). It has shown effectiveness in aspects such as community structure and biodiversity restoration. However, its impacts on ecological functions like eco-hydrology still require further in-depth investigation. This study analyzes the impact of girdling on the eco-hydrological indices of three plantations—Acacia mangium, Pinus caribaea, and Cunninghamia lanceolata—through field investigations and laboratory tests. The data was evaluated using a game theory combination weighting-cloud model. The results show that the eco-hydrological indicators of leaf litter in A. mangium increased by 5.77% while those of P. caribaea and C. lanceolata decreased by 11.86% and 5.29%, respectively. Soil bulk density decreased slightly across all plantations while total porosity increased, with A. mangium showing the highest increase of 20.31%. Organic carbon content increased by 76.81% in A. mangium and 7.24% in C. lanceolata, whereas it decreased in P. caribaea. Saturated hydraulic conductivity increased by 33.32% in P. caribaea and 20.91% in A. mangium but decreased in C. lanceolata. Based on the cloud model, the eco-hydrological function of A. mangium improved from 'medium' to 'good', while that of P. caribaea and C. lanceolata declined towards the 'poor' level. In summary, during the process of close-to-nature transformation of tropical rainforests, girdling is an effective method to enhance the ecohydrological functions of broadleaf planted forests. However, for coniferous species, the ecohydrological functions of the planted forests weaken in the short term following the transformation. [ABSTRACT FROM AUTHOR]

This study conducted an in-depth analysis of the landslide problem in the loess hill and gully area in northern Shaanxi Province, selecting the loess landslide site in Quchaigou, Ganquan County, Yan'an City, as the object to assess the stability of loess slopes under the conditions of different plant root densities and soil moisture contents through field investigation, physical mechanics experiments and numerical simulation of the GeoStudio model. Periploca sepium, a dominant species in the plant community, was selected to simulate the stability of loess slope soils under different root densities and soil water contents. The analysis showed that the stability coefficient of Periploca sepium natural soil root density was 1.263, which was a stable condition, but the stability of the stabilized slopes decreased with the increase in soil root density. Under the condition of 10% soil moisture content, the stability coefficient of the slope body is 1.136, which is a basic stable state, but with the increase in soil moisture content, the stability of the stable slope body decreases clearly. The results show that rainfall and human activities are the main triggering factors for loess landslides, and the vegetation root system has a dual role in landslide stability: on the one hand, it increases the soil shear strength, and on the other hand, it may promote water infiltration and reduce the shear strength. In addition, the high water-holding capacity and permeability anisotropy of loess may lead to a rapid increase in soil deadweight under rainfall conditions, increasing the risk of landslides. The results of this study are of great significance for disaster prevention and mitigation and regional planning and construction, and they also provide a reference for landslide studies in similar geological environments. [ABSTRACT FROM AUTHOR]

Overseeing the relative density of soils in all types of earth structures during both construction and operation is crucial to ensure that these structures attain the necessary density and strength. Especially in linear structures that extend over significant lengths, geotechnical investigations should include planning tests that allow for determining the maximum number of geotechnical parameters, such as cone penetration tests (CPTU) or Marchetti dilatometer tests (DMT). The article presents the in situ tests aimed at assessing the relative density of sandy soils. Empirical formulas available in the literature for determining the relative density Dr from DMT gave inconsistent results compared to those obtained from dynamic soundings, especially in the near-surface zone, where high KD readings significantly overestimate relative density values. Assuming the results of DPL probe tests as reference values, a formula for the compaction index based on DMT soundings has been proposed. In contrast to the formulas commonly used in the literature, the proposed formula for the relative density depends not only on the horizontal stress index KD, but also on the dilatometer modulus ED. [ABSTRACT FROM AUTHOR]

Shallow foundations supporting high-rise structures are often subjected to extreme lateral loading from wind and seismic activities. Nonlinear soil–foundation system behaviors, such as foundation uplift or bearing capacity mobilization (i.e., rocking behavior), can act as energy dissipation mechanisms, potentially reducing structural demands. However, such merits may be achieved at the expense of large residual deformations and settlements, which are influenced by various factors. One key factor which is highly influential on soil deformation mechanisms during rocking is the foundation embedment depth. This aspect of rocking foundations is investigated in this study under varying subgrade densities and initial vertical factors of safety (FSv), using the PIV technique and appropriate instrumentation. A series of reduced-scale slow cyclic tests were performed using a single-degree-of-freedom (SDOF) structure model. This study first examines the deformation mechanisms of strip foundations with depth-to-width (D/B) ratios of 0, 0.25, and 1, and then explores the effects of embedment depth on the performance of square foundations, evaluating moment capacity, settlement, recentering capability, rotational stiffness, and damping characteristics. The results demonstrate that the predominant deformation mechanism of the soil mass transitions from a wedge mechanism in surface foundations to a scoop mechanism in embedded foundations. Increasing the embedment depth enhances recentering capabilities, reduces damping, decreases settlement, increases rotational stiffness, and improves the moment capacity of the foundations. This comprehensive exploration of foundation performance and soil deformation mechanisms, considering varying embedment depths, FSv values, and soil relative densities, offers insights for optimizing the performance of rocking foundations under lateral loading conditions. [ABSTRACT FROM AUTHOR]

Wildfires and post-fire restoration methods significantly impact soil physicochemical properties and microbial characteristics in forest ecosystems. Understanding post-fire soil recovery and the impacts of various post-fire restoration methods is essential for developing effective restoration strategies. This study aimed to investigate how fire and soil depth influence soil physicochemical properties, enzymatic activities, and the structure of microbial communities, as well as how these factors change under different post-fire management practices. We sampled 0–10 cm (topsoil) and 10–20 cm (subsoil) in unburned plots, naturally restored plots, and two afforestation plots in southern China. The results showed that fire reduced topsoil soil moisture, nutrient levels, and microbial biomass. The variations in soil physicochemical properties significantly influenced microbial processes. Soil bulk density, nitrate, ammonium, carbon-to-nitrogen ratio, and availability of nitrogen, phosphorus, and potassium availability influenced soil enzyme activities. Soil pH, ammonium nitrogen, and the availability of nitrogen, phosphorus, and potassium were key factors shaping microbial composition. Fire altered the soil microbial communities by reducing the availability of nitrogen. Soil depth alleviated the impact of fire on the soil to some degree. Although artificial interventions reduced soil organic carbon, total nitrogen, and phosphorus, planting nitrogen-fixing species, such as Acacia mangium, promoted microbial recovery. [ABSTRACT FROM AUTHOR]

A field study was conducted to investigate the effects of selected climate-smart agriculture practices on soil bulk density (ρ), porosity (β), hydraulic conductivity (Ksat), and nutrient dynamics in southeast Texas. Treatment combinations of two types of organic manure (chicken and dairy) with three rates (0, 224, and 448 kg N ha−1) and two levels of biochar (2500 and 5000 kg ha−1) were used in a factorial randomized block design. Bulk density and porosity measurements were conducted on undisturbed soil core samples collected from the topsoil (0–10 cm) of a field cultivated with sweet corn. Ksat was calculated from the steady-state infiltration measured using the Tension Infiltrometer (TI). The ANOVA results indicated that the manure application rates, and biochar levels significantly affected the soil properties. Compared to the control, β increased by 15% and 29% for the recommended and double recommended manure rates. Similarly, hydraulic conductivity increased by 25% in the double-recommended rate plots compared to the control. Also, we applied the concept of non-parametric elasticity to understand the sensitivity of soil physical and chemical properties to Ksat. ρ and β are critical physical properties that are highly sensitive to Ksat. Among soil nutrients, Boron showed the highest sensitivity to Ksat. Hydraulic conductivity can be enhanced by employing selected climate-smart practices and improving water management. Future directions for this study focus on scaling these findings to diverse cropping systems and soil types while integrating long-term assessments to evaluate the cumulative effects of climate-smart practices on soil health, crop productivity, and ecosystem sustainability. [ABSTRACT FROM AUTHOR]

The current soil carbon paradigm puts particulate organic carbon (POC) as one of the major components of soil organic carbon worldwide, highlighting its pivotal role in carbon mitigation. In this study, we compiled a global dataset of 3418 data points of POC concentration in soils and applied empirical modeling and machine learning algorithms to investigate the spatial variation in POC concentration and its controls. The global POC concentration in topsoil (0–30 cm) is estimated as 3.02 g C/kg dry soil, exhibiting a declining trend from polar regions to the equator. Boreal forests contain the highest POC concentration, averaging at 4.58 g C/kg dry soil, whereas savannas exhibit the lowest at 1.41 g C/kg dry soil. We developed a global map of soil POC density in soil profiles of 0‐30 cm and 0–100 cm with an empirical model. The global stock of POC is 158.15 Pg C for 0–30 cm and 222.75 Pg C for 0–100 cm soil profiles with a substantial spatial variation. Analysis with a machine learning algorithm concluded the predominate controls of edaphic factors (i.e., bulk density and soil C content) on POC concentration across biomes. However, the secondary controls vary among biomes, with solid climate controls in grassland, pasture, and shrubland, while strong vegetation controls in forests. The biome‐level estimates and maps of POC density provide a benchmark for modeling C fractions in soils; the various controls on POC suggest incorporating biological and physiochemical mechanisms in soil C models to assess and forecast the soil POC dynamics in response to global change. [ABSTRACT FROM AUTHOR]

In order to investigate the characteristics and driving factors of keystone species change in vegetation communities, we conducted a network analysis to analyze the complexity of grassland plant communities and keystone species. We conducted a study with six plots of degraded grassland, intact grassland, and various ages of artificial grassland. We systematically analyzed the characteristics of vegetation community and soil physical–chemical properties under different treatments. Our findings revealed that the 5-year-old artificial grassland exhibited lower biodiversity, as indicated by a Shannon–Weiner index of 1.70 and a Pielou's evenness index of 0.72. In comparison to the degraded grassland, soil organic carbon and nitrate nitrogen levels in the 5-year-old artificial grassland increased by 22% and 13%, respectively, while soil density decreased by 9%. However, despite the relatively stable plant community in the 21-year-old artificial grassland, it had not fully recovered to the level of natural grassland due to the complexity of the plant community and the shift in keystone species. Therefore, it is crucial to consider the impact of soil bulk density and nutrient levels on the complexity of the plant community when restoring degraded alpine meadows through the establishment of artificial grassland. [ABSTRACT FROM AUTHOR]

The results of baseline evaluation of soil organic carbon (SOC) contents and stocks, soil bulk density, and their spatial variability and vertical distribution patterns within the upper 40-cm-thick layer of agrosoddy-podzolic soils developed from glacial till (Albic Gleyic Retisols (Episiltic, Anoloamic, Aric, Ochric)) and agrosoddy podzols developed from sands (Albic Podzols (Arenic, Aric, Ochric)) are considered. Thirteen monitoring plots (30 × 30 m) have been established on drained (closed drainage) arable land, hayfield, and unmanaged fallow land of the experimental site of the All-Russia Research Institute of Reclaimed Lands (VNIIMZ) in Tver oblast, European Russia. The spatial variability of the SOC content within the plots exceeds the reproducibility of SOC determination by the dry combustion method by 5–10 times. The standard deviation of the SOC stocks nonlinearly increases with increasing thickness of the assessed layer from 1–5 t/ha for a layer of 0–5 cm to 10–20 t/ha for a layer of 0–40 cm. Differentiated soil sampling from thin layers within the upper 40-cm-thick layer demonstrated a uniform vertical distribution of SOC in the plow layer of the arable land; differences between SOC stocks in the layers of 0–10 and 10–20 cm are statistically insignificant. In the Retisols of the five-year-old hayfield with perennial grasses and of the 5- to 20-year-old unmanages fallow lands, a sod layer of 3–10 cm in thickness is formed, and the SOC content displays an accumulative distribution with a maximum in the surface layer. However, the SOC stocks in the upper and lower parts of the former plow horizon do not display statistically significant differences. Similar regularities have been found for the sandy Podzols against the background of generally lower contents and stocks of SOC. [ABSTRACT FROM AUTHOR]

Two-dimensional discrete-element modelling was adopted to study the engineering and fundamental aspects of shear band formation in reverse faulting through sandy soils of varying densities. The employed discrete-element methodology was verified with experimental centrifuge results. From an engineering perspective, the results showed that the shear bands formed due to a reverse fault consisted of multiple ruptures formed at the different fault throws. These ruptures may deviate towards the hanging or footing wall depending on the faulting angle. The distortion zone outcropping location was captured by the W/H ratio at the 1% normalised fault throw (h/H) step. Various micro and macro aspects of shear banding, such as porosity, coordination number and strong contact forces within the localised areas along the shear bands, were studied. Moreover, a link was established between the micro and macro events occurring inside the shear bands. The results showed that the wedge pressure formed between the shear band and back-thrust rupture in a fault with a dip angle smaller than 45° significantly affected the back-thrust formation and micro–macro parameters in the shearing region. [ABSTRACT FROM AUTHOR]

Verticillium wilt of pistachio (Pistacia vera), caused by Verticillium dahliae, is one of the most important diseases in this crop. The most effective and economical control measure is the use of resistant rootstocks. The main objective of this work was to evaluate the resistance of five rootstocks commonly used in pistachio against the disease under field conditions. Pistachio plants (cv. Kerman) grafted on the rootstocks Pistacia atlantica, Pistacia integerrima, Pistacia terebinthus and cv. Platinum and UCBI hybrids, were planted in a field with high inoculum density of V. dahliae in the soil. Plants grafted on P. terebinthus, followed by P. integerrima, showed significantly higher disease severity values than the rest of the rootstocks almost 53 months after planting; also, plants grafted on P. atlantica were more resistant than those grafted on P. integerrima. These results highlighted the intraspecific variability in resistance to the disease. In addition, the disease was monitored in pistachios grafted onto P. terebinthus or UCBI in an established commercial field with three different zones of V. dahliae inoculum density in the soil (none, low or high). In the high‐density zone, the percentage of diseased plants was significantly lower for plants grafted on UCBI than for those grafted on P. terebinthus. The results indicate the importance of rootstock species and specific genotype or seed population used, concentration of V. dahliae inoculum in the soil, and previous history of crops on the plot, on the development of the disease under natural conditions. [ABSTRACT FROM AUTHOR]

Coastal wetlands are one of the most productive ecosystems on Earth with the capacity to sequester large amounts of carbon dioxide (CO2). Wetland loss due to anthropogenic and natural causes reduces the carbon (C) storage capacity and potentially releases previously fixed C in biomass and soil to the water column and atmosphere through decomposition. Coastal wetland restoration has the potential to mitigate some of the C losses depending on the balance of C fluxes. However, the role of vegetation and environmental conditions in governing rates of C accumulation in restoration sites is not well resolved. The purpose of this study was to examine seasonal C fluxes, specifically, gross ecosystem productivity (GEP), ecosystem respiration (ER), and net ecosystem exchange (NEE) of CO2 in unvegetated and vegetated (Spartina alterniflora) areas of a 2‐year old created marsh, and S. alterniflora and Spartina patens communities in a "natural" reference brackish marsh. S. alterniflora‐dominated areas were sinks for CO2 in both the newly created and reference marsh with an average CO2 uptake rate of 7.0 ± 1.0 μmol m−2 s−1. The unvegetated areas in the newly created marsh and S. patens areas in the reference marsh had approximately net neutral CO2 fluxes. S. alterniflora areas of the created marsh had similar carbon fluxes to that in the reference marsh, despite a much lower soil organic matter content. Because vegetation develops much faster than soil properties, restored marshes can be a C sink equivalent to natural marshes as soon as the marsh is vegetated. Ecosystem productivity and C assimilation in S. alterniflora areas of the reference marsh were enhanced by lower elevations (up to 6 cm) and higher soil bulk density (up to 0.28 g cm−3). At similar elevations, S. alterniflora in both the created and reference marshes was a greater C sink than S. patens areas of the reference marsh. Our findings illustrate that establishment of vegetation is critical to promoting C sink functions in created marshes and, notably, species do matter. [ABSTRACT FROM AUTHOR]

This study investigated the effects of film hole diameter and soil bulk density on the unidirectional intersection infiltration laws of muddy water fertilization film hole irrigation. Indoor soil box infiltration experiments were conducted. The thickness of the sediment layer, cumulative infiltration amount per unit area, vertical wetting front transport distance, moisture distribution in the wetting body, and nitrate and ammonium nitrogen transport laws were observed and analyzed. The results indicated that both the thickness of the sediment layer and the cumulative infiltration per unit area are inversely correlated with film hole diameter and soil bulk density. Conversely, the vertical wetting front transport distance and nitrogen content are positively correlated with film hole diameter, while exhibiting a negative correlation with soil bulk density. Notably, the initial point of intersection for the moist body was located below the soil surface, with the peak vertical soil moisture content at the intersection approximately 1.5 cm beneath the surface. The distribution pattern of soil nitrate nitrogen at the conclusion of infiltration mirrored that of water content, characterized by a sharp decline near the wetting front. In contrast, soil ammonium nitrogen content decreased significantly in the shallow soil layer as soil depth increased, without a corresponding abrupt decrease near the wetting front. These findings may provide a theoretical foundation for future research on the intersection infiltration laws of muddy water fertilization through film hole irrigation. [ABSTRACT FROM AUTHOR]

The impact of various crop rotation systems on the potential for soil carbon sequestration and stoichiometric characteristics is not yet fully understood, which poses challenges for effective land management and utilization. This study selected three typical crop rotation methods in the Longzhong Loess Plateau: maize–alfalfa rotation (MA), maize–sainfoin rotation (MS), and maize–wheat rotation (MW). Soil physical and chemical indices were measured, and the soil carbon density and soil stoichiometry were calculated and analyzed. The results show that the soil C/N of the surface soils was low across the rotation methods, indicating a rapid rate of organic matter decomposition and mineralization, which may hinder soil nutrient accumulation. The soil N/P was found to be lower than the national average of 8.0, indicating that nitrogen is a limited nutrient in the soil under the three crop rotation systems in this region. The soil total nitrogen content can be increased by rotation with leguminous forage. Sainfoin rotation can enhance the soil total carbon and organic carbon content, thereby improving the soil's carbon sequestration potential. The research findings provide a theoretical foundation for the selection of appropriate rotation methods and the maintenance of the stability of agricultural ecosystems in semi-arid regions. [ABSTRACT FROM AUTHOR]

Geographic patterns determine geogenic radon factors that, changing over the territory, form spatial structures of different scales associated with regional and local variations. The study of these structures is important for assessing the possibility of using limited data to predict geogenic radon potential. Our research focuses on the study of the physical properties of soils (moisture, soil density, porosity and void ratio) in the Kuznetsk coal basin. Their variations are studied using statistical methods, a variogram cloud and spatial autocorrelation of data. Soil moisture and porosity have the greatest variability in space and with depth. We conclude that the assessment of geogenic radon predictors requires consideration of the variation coefficient and autocorrelation indices at different scales. Based on the variability of humidity and the fairly homogeneous nature of the studied soils (loams), to assess the radon hazard, it is necessary to study the influence of climatic conditions, since the permeability of the environment for radon will be determined by soil moisture. With the predominance of substantially clayey soils, it is necessary to study the content of 226Ra in the upper horizons, since it is assumed that radon is predominantly diffusely transferred, in which its role is dominant. [ABSTRACT FROM AUTHOR]

Spectral induced polarization (SIP) exhibits potential to be a nonintrusive approach to monitor bacterial activity in biological hotspots associated with the critical zone of the earth. The polarization of bacteria in a low‐frequency electrical field is related to the polarization of their electrical double layer coating their surface. However, few studies have quantified the induced polarization responses on both gram‐negative (GN) and gram‐positive (GP) bacteria in soil column experiments. To address this gap, 17 experiments using two strains, Pseudomonas aeruginosa O1 (PAO1, GN) and Brevibacillus centrosporus (L3, GP) are conducted. Complex conductivity spectra are collected in the frequency range 10 mHz–10 kHz during bacterial growth and decay phases in soils. The complex conductivity spectra are fitted using a double Cole‐Cole model to remove the effect of Maxwell‐Wagner polarization. The change in the magnitude of the polarization (quadrature conductivity or normalized chargeability of the low‐frequency contribution) is linearly related to the bacterial density, regardless of the type of bacteria. The changes in the normalized chargeability and Cole‐Cole relaxation time are directly proportional to the density of bacteria. Furthermore, it is inferred that the thickness of microcolonies plays a critical role in the relaxation time rather than the diameter of individual bacteria. This study expands the potential of SIP for in situ monitoring of microbial activity in soils. Plain Language Summary: Microorganisms are ubiquitous in the environment. Understanding their impact on the critical zone is crucial in the context of climate change. Spectral induced polarization is a geophysical method that has been proven to be sensitive to the presence of bacteria in porous media, but no specific works have been done for both gram‐negative and gram‐positive bacteria in soils. Column reactor experiments are conducted using the same soil, inoculated with either gram‐negative or gram‐positive strains. Experimental results indicate a direct proportionality between the magnitude of the low‐frequency electrical polarization of the soil and the density of bacteria. It is inferred that the size of microcolonies plays a critical role in the value of the relaxation time. This study provides new quantitative insights into the relationship between the electrical properties and bacterial activity in soils with applications to the nonintrusive monitoring of biological hotspots in the critical zone of the earth. Key Points: The growth and decay of gram‐positive and gram‐negative bacteria in soils exhibit a clear signature on their complex conductivity spectra.The spectra are fitted by a double Cole‐Cole model, and the Maxwell‐Wagner polarization is removed.The normalized chargeability and the Cole‐Cole relaxation time vary linearly with the density of bacteria in the soil. [ABSTRACT FROM AUTHOR]

Soil erosion by wind poses a significant threat to various regions across the globe, such as drylands in the Middle East and Iran. Wind erosion hazard maps can assist in identifying the regions of highest wind erosion risk and are a valuable tool for the mitigation of its destructive consequences. This study aims to map wind erosion hazards by developing an interpretable (explainable) model based on machine learning (ML) and Shapley additive exPlanation (SHAP) interpretation techniques. Four ML models, namely random forest (RF), support vector machine (SVM), extreme gradient boosting (XGB), and quadratic discriminant analysis (QDA) were used. Thirteen features associated with wind erosion were mapped spatially and then subjected to a multivariate adaptive regression spline (MARS) feature selection algorithm, and then, tolerance coefficient (TC) and variance inflation factor (VIF) statistical tests were used to explore multicollinearity among the variables. MARS analysis shows that eight features consisting of elevation (or DEM), soil bulk density, precipitation, aspect, slope, soil sand content, vegetation cover (or NDVI), and lithology were the most effective for wind erosion, while no collinearity existed among these variables. The ML models were used for ranking the effective features, and the research introduces the application of an interpretable ML model for the interpretation of predictive model's output. The ranking of effective features by RF—as the most typical ML model—revealed that elevation and soil bulk density were the two most important features. According to the area under the receiver operating characteristic curve (AUROC) (with a value > 90%) and precision-recall (PR) (with a value > 90%) curves, all four ML models performed with great accuracy. According to the PR curve, the SVM model performed slightly better than others, and its results revealed that 20.9%, 23%, and 16.6% of the total area in Hormozgan Province is characterized by moderate, high, and very high hazard classes to wind erosion, respectively. SHAP revealed that soil sand content and elevation are the most important variables contributing to the predictive model output. Overall, our research is one of the pioneering applications of interpretable ML models in mapping wind erosion hazards in Southern Iran. We recommend that future research should address the aspect of interpretability in order to better understand predictive model outputs. [ABSTRACT FROM AUTHOR]

The aims of this study are capability assessment of the SWAT model and SWAT-CUP software in hydrological simulation and evaluation of uncertainty of SWAT model in estimating runoff. In the modeling process, the basin was divided into 12 sub-basins and 294 hydrological units (HRUs). Model calibration and uncertainty analysis were performed using the sequential uncertainty fitting (SUFI2) algorithm for 2000–2006 and 2007–2010, respectively. Based on the sensitivity analysis results, the parameters are the USLE_P soil protection factor, wet soil density (SOL_BD), and CN among the most important parameters in determining the amount of output runoff. Among these factors, SCS-CN was recognized as the most sensitive parameter. Based on the results, the coefficients R2, bR2, and Nash–Sutcliffe index (NS) were 0.75, 0.59, and 0.67 for calibration period and 0.46, 0.24, and 0.42 for validation period. The results of the model showed the model performance is weak in the stage of calibration. This is due to the lack of accuracy and precision in the statistics available in the region, the lack of statistics on the amount of water collected from the upstream gardens of the area, as well as the lack of statistics on the existing springs. The model is therefore recommended for applications in arid and semiarid catchments within Iran with similar data. Due to the limited availability of hydrological data in Iran, this study has not assessed and compared the uncertainty related to the SWAT model of future runoff. [ABSTRACT FROM AUTHOR]

Silicon (Si) and calcium (Ca), as elements abundant in the Earth's crust, are closely related to plant growth and stress resistance and have similar roles. Understanding the stoichiometry of Si and Ca can provide more insight into the mechanical and stress resistance of plants, as well as their preferences for the absorption and use of Si and Ca. Here, we measured the content of Si and Ca in the leaves of the dominant tree species located in the Mount Wuyi National Park, with an elevation ranging from 800 m to 1700 m, in an attempt to reveal changes in the Si and Ca content and ratio in the leaves along the altitude, as well as their possible relationships with environmental factors and phylogeny. The results indicated that the leaf Si and the leaf Si/Ca decreased, while the leaf Ca increased significantly with the increase in elevation. Changes in environmental factors induced by variations in elevation affected the silicon and calcium stoichiometry characteristics of the leaves, either directly or indirectly. Specifically, the mean annual precipitation, soil available silicon, soil organic matter, and soil bulk density accounted for most of the variations in leaf silicon and calcium. The leaf silicon and calcium stoichiometry was phylogenetically conservative, suggesting more similar characteristics among closely related tree species. Structural equation modeling and variation partitioning indicated that phylogeny might be more important than environmental factors in influencing leaf Si and Ca stoichiometry. Additionally, the shared effects of environmental factors and taxonomic levels indicated changes in the forest community, and the differential responses of different functional types due to elevation variation also affected the altitudinal patterns of leaf Si and Ca stoichiometry. [ABSTRACT FROM AUTHOR]

Mixed broad-leaved trees are particularly effective in addressing ecological issues such as soil degradation and biodiversity loss caused by the dense planting of Chinese fir. Understanding the changes in soil bacterial communities in fir–broadleaf mixed forests as a function of fir retention density may offer new insights for optimizing management practices and enhancing the ecological functions of the underground components of forest ecosystems. In this study, the diversity and composition of soil bacterial communities in mixed Cunninghamia lanceolata and Betula luminifera forests (CFBFs) with diverse retention densities of Chinese fir (1250, 1560, and 1690 trees/hm2) were analyzed. The results suggested that the soil characteristics and microbial communities' diversity and structure are significantly influenced by the retention densities of Chinese fir in CFBFs. At the aggregate scale, the CFBFs with a retention density of 1560 trees/hm2 presented the greatest soil bacterial community diversity (based on the Chao 1 (3562.75) and Shannon indices (6.58)), and the diversity and richness of soil bacteria initially increase and then decrease as the retention density decreases. In CFBFs, regardless of the retention density, bacterial communities in soil were mainly composed of Acidobacteria, Proteobacteria, and Planctomycetes. The relative abundance of soil Acidobacteria first elevated and afterwards decreased as the retention density decreased, with the highest levels (47.15%) observed in the stand with 1560 trees/hm2 of Chinese fir. The Principal Coordinates Analysis (PCoA) showed that the soil microbial community structure in CFBEs with a retention density of 1560 trees/hm2 is significantly different from CFBEs with a retention density of 1260, and 1690 trees/hm2. Moreover, with different retention densities of Chinese fir, soil organic C, total N concentrations, and soil pH also significantly affected the diversity and composition of CFBF soil bacterial communities. Our results show that the choice of retention densities significantly influences soil microbial diversity and composition in CFBFs. Optimal retention densities (1560 trees/hm2) of Chinese fir in CFBFs can maximize bacterial diversity and stability, providing management guidance for thinning for sustainable management of the soil microenvironment of CFBFs. [ABSTRACT FROM AUTHOR]

Compared with long-term and continuous application of large amounts of chemical fertilizers, fertilizers with microbial organic nutrient sources can improve soil environment, increase soil fertility and increase crop yield. In view of the current low soil fertility and poor soil environment leading to low crop yield and instability in the arid regions of northwest China, the effects of organic fertilizer with microbial nutrient sources on soil nutrients and pumpkin yield were studied in 2022 and 2023 in this region. The fertilizer application level was used as control factor, with four treatments of low level (L), medium level (M), high level (H), and a conventional fertilizer control (CK). The results showed that the high application level of organic fertilizer was more beneficial to the growth of pumpkin, and the stem diameter, vine length, and leaf area of pumpkin under H treatment were the highest from 2022 to 2023. Compared to CK, the average soil bulk density was significantly decreased by 8.27–18.51% (P< 0.05); the soil organic carbon, available phosphorus, available potassium, and nitrate nitrogen under H treatment were increased by an average of 32.37%, 21.85%, 18.70%, and 36.97%, respectively. Under different organic fertilizer treatments, the pumpkin yield under M treatment was the highest, reaching 30926.18 kg·ha-1, followed by H treatment. compared to CK, M and H treatments increased the yield by 25.26% and 7.01%, respectively, and improved water use efficiency by 14.18% and 2.21%, respectively. Redundancy analysis (RDA) of soil nutrients, pumpkin growth dynamics and yield in 2022 and 2023 showed that soil organic carbon, available phosphorus, available potassium, nitrate nitrogen, and water use efficiency were significantly positively correlated with pumpkin yield (P<0.01). In conclusion, H and M treatments can improve soil fertility promote pumpkin growth and development, and ultimately increase pumpkin yield. In summary, medium organic fertilizer level (M=5700 kg·ha-1) is recommended as the fertilization scheme for local pumpkin cultivation. [ABSTRACT FROM AUTHOR]

Green soybean (edamame), an early-harvested soybean, is a popular vegetable in Asia and is recognised as a healthy vegetable in the other parts of the world. In Japan, edamame yield has gradually decreased over the last 30 years, despite similar cultivation areas. Damage caused by the soybean cyst nematode (SCN), Heterodera glycines, is one of the main causes. We surveyed the distribution of SCN in different locations and found a wide distribution of SCN across Japan. Different control measures are available, such as chemical control using fumigants or a granular type of nematicide, solarisation, and rotation with non-host crops. We are developing a new type of biological control method, which comprises short-term field cultivation and soil incorporation of mung bean. This method not only decreases the SCN density in soil but also mitigates soil erosion and nitrate leaching. For future SCN control it is essential to establish an environmentally friendly management strategy. [ABSTRACT FROM AUTHOR]

Determining total organic carbon and its stock and quantifying the chemical fractions of soil organic matter can be used as indicators of the quality of the soil management used in a cropping area. This study aimed to quantify soil organic matter's carbon stock and chemical fractions in different soil management systems used in the western Bahian Cerrado, Brazil, and compare them to a native Cerrado area. Ten microregions (Alto Horizonte, Anel da Soja, Bela Vista, Cascudeiro, Coaceral, Novo Paraná, Panambi, Placas, Roda Velha, Roda Velha de Baixo), three soil management systems [tillage system (TS), no-tillage systems (nTS), native Cerrado (NC)], and two soil layers (0–0.1 and 0.1–0.2 m) were studied. Soil bulk density (Sd), soil organic matter (SOM), total organic carbon (TOC), SOM quantification (qSOM), equivalent carbon stock (EqCs), humin (HF), humic acid (HAF) and fulvic acid (FAF) fractions from SOM were evaluated. The results indicated that Sd in all evaluated microregions was below the critical upper limit that would restrict plant root development. SOM, TOC, EqCs, and qSOM revealed increasing results following the TS, nTS, and NC order. The NC area presented the highest soil organic fraction contents (HF, HAF, and FAF). The microregions with better soil quality for all evaluated parameters were Coaceral and Cascudeiro; the lowest soil quality was observed in Alto Horizonte. The present study indicates that conservation agricultural management, such as the no-tillage system, improves the structure and composition of SOM parameters over time. [ABSTRACT FROM AUTHOR]

The additive mass method (AMM) is applied to test the compaction density of soil–rock mixtures (S–RMs) due to its high efficiency, nondestructiveness and accuracy. However, there is no systematic research on influence factor of AMM. In this study, AMM test parameters were systematically calibrated first, and a calculation model for the compaction density of S–RM was established in the test area. After that, the AMM was applied in the on‐site detection of the compaction density of an earth–rockfill dam. After calibration test, the main geophone frequency was 40 Hz, the drop distance and offset distance were 20 and 70 cm, respectively, and set the ∆m of five levels as 38, 88, 138, 213, and 288 kg. The detection error of K–K/ρ model had a better precision than the ω−2−ω−2/ρ model through on‐site testing and verification. A new calculation model with lower accuracy based on vibration stiffness–vibration stiffness/density K−K/ρ) model was proposed according to the test error distribution. It was found that the test error of the K−K/ρ model was reduced to 0.9%. The results demonstrated that the AMM could accurately detect the compaction density of S–RM after the test parameters were reasonably determined. [ABSTRACT FROM AUTHOR]

Altitude and ecological factors significantly influence plant growth and the accumulation of secondary metabolites. However, current research on the impact of altitude and ecological factors on the yield and medicinal quality of Artemisia argyi (A. argyi) is limited. This study established sampling sites in wild populations of A. argyi across seven altitude ranges on Funiu Mountain. We quantified the yield, output rate of moxa, and key medicinal ingredients. Additionally, we analyzed the response of yield and medicinal quality of wild A. argyi populations to various ecological factors at different altitudes. The results showed that wild populations of A. argyi exhibited higher yields and medicinal quality at altitudes below 500 m. Yield was positively correlated with higher soil total nitrogen (TN) content and lower soil total phosphorus (TP) content, while the improvements in medicinal quality were positively associated with higher population density and lower contents of both soil TN and TP. The variation in soil C/N, C/P, and N/P ratios across different altitudes was substantial, affecting soil mineralization and subsequently influencing the absorption of mineral elements by A. argyi. Notably, the phosphorus content in leaves and stems was negatively correlated with yield and medicinal quality, respectively. In contrast, the accumulation of nitrogen, phosphorus, and potassium in leaves was positively correlated with yield. The differences in the primary medicinal ingredients between the leaves and stems of A. argyi were maximum at altitudes below 500 m. The contents of neochlorogenic acid and cryptochlorogenic acid in both leaves and stems showed a significant positive correlation. In the principal component analysis, the primary medicinal ingredients from the leaves contributed more significantly to the overall quality than those from stems. These results suggest that A. argyi is best suited for cultivation at altitudes below 500 m. Population density and the soil's TN and TP contents play a crucial role in determining the yield and medicinal quality of A. argyi. Futhermore, the medicinal quality of A. argyi is more indicative of the main medicinal ingredients found in the leaves, while the stems also serve as a key organ for accumulating flavonoids and phenolic acids. [ABSTRACT FROM AUTHOR]

The effects of reseeded native Gramineae and Leguminosae species on the multifunctionality of desert steppe have remained unclear. Therefore, we examined a semiarid desert steppe that was reseeded 5 years earlier with a dominant native Gramineae species, Agropyron mongolicum; a dominant native Leguminosae species, Lespedeza potaninii; and a 1:1 reseeded mixture of A. mongolicum × L. potaninii. We evaluated the changes in plant communities and soil properties and then quantified aboveground ecosystem multifunctionality (AEMF), belowground ecosystem multifunctionality (BEMF), and overall ecosystem multifunctionality (EMF) using an averaging approach. Compared with the native steppe without reseeding, both reseeded A. mongolicum and A. mongolicum × L. potaninii increased fine root volume, plant height, plant cover, aboveground biomass (AGB), belowground biomass (BGB), soil water storage (SWS), soil organic carbon, light fraction organic carbon, labile organic carbon, total nitrogen (TN), nitrate nitrogen, and total phosphorus (P), but decreased soil bulk density. However, reseeded L. potaninii increased coarse root volume, plant height, plant cover, AGB, BGB, and SWS but decreased plant richness, plant diversity, TN, and total P. In addition, reseeded A. mongolicum and A. mongolicum × L. potaninii increased AEMF, BEMF, and overall EMF, but reseeded L. potaninii only increased AEMF. Further analysis indicated that the fine roots played a crucial role in improving individual ecosystem functions and eventually in determining EMF. Therefore, the reseeding of a desert steppe with Gramineae species has greater potential than with Leguminosae species for improving EMF, since Gramineae species have greater fine roots volume than Leguminosae species. [ABSTRACT FROM AUTHOR]

Aims: This study examines the effects of land-use types and slope position on selected soil physico-chemical properties in the Ageza Watershed, Northwestern Ethiopia, focusing on soil fertility depletion and its impact on agricultural productivity. Materials and methods: The experiment utilized a randomized complete block design (RCBD) with three replications, involving three land-use types and slope positions. A total of 27 soil samples (both disturbed and undisturbed) were collected, prepared, and analyzed for selected physico-chemical properties following standard laboratory procedures. Data were analyzed using two-way ANOVA with SAS software. Results: Significant variations in most soil physico-chemical properties were observed across land-use types and slope positions. Soil bulk density, organic carbon (OC), total nitrogen (TN), available phosphorus (Av. P), cation exchange capacity (CEC), and exchangeable bases significantly (P ≤ 0.001) differed among the land-use types and slope positions. The main effects showed significant (P ≤ 0.05) differences in sand, silt, and clay contents across the land-use types. However, pH did not show significant differences (P > 0.05). Soil bulk density, silt content, Av. P, exchangeable bases, and CEC all showed significant (P ≤ 0.01) differences among the slope positions. Forest land had the highest values for clay (46.11%), OC (6.08%), Av. P (20.60 mg/kg), CEC (33.89 cmol (+) kg-¹), and exchangeable cations: Ca²+ (23.72 cmol (+) kg-¹), Mg²+ (4.40 cmol (+) kg-¹), K+ (1.18 cmol (+) kg-¹), and Na+ (0.77 cmol (+) kg-¹). Grazing land exhibited higher silt and bulk density, while cultivated land had higher sand content. Lower slope positions recorded the highest values for clay (47.33%), silt (20.77%), pH (4.90), Av. P (16.61 mg/kg), Ca²+ (20.10 cmol (+) kg-¹), Mg²+ (3.73 cmol (+) kg-¹), K+ (1.00 cmol (+) kg-¹), Na+ (0.66 cmol (+) kg-¹), and CEC (28.71 cmol (+) kg-¹), while bulk density was higher in the upper slope position. Conclusion: Land-use types and slope positions significantly influence variations in soil physico-chemical properties and overall soil fertility status. Forest preservation and management are essential to improve the soil fertility in this region. [ABSTRACT FROM AUTHOR]

A study was conducted in the mountains of Magoebaskloof, Limpopo Province, where oak trees grow along the banks of the Broederstroom River. This study revealed that 22 nematode genera were associated with oak trees (Quercus robur). The most frequently occurring nematodes were Aphelenchus sp. (100%) and Plectus sp. (100%), followed by Helicotylenchus sp. (90%). This study examined the relationship between nematodes and the physicochemical properties of the soil using Pearson correlation. It uncovered that the organic matter content (OMC) had a negative correlation with the number of Panagrolaimus sp. (r = −0.770) and Hemicycliophora sp. (r = −0.674). Conversely, the sand percentage positively correlated (r = 0.695) with the number of Hemicycliophora sp. The clay content of the soil showed a positive correlation (r = 0.617) with the number of Ditylenchus. Soil pH demonstrated a significant negative correlation with Acrobeloides sp. (r = −0.877). The canonical correspondence analysis (CCA) explained 63.3% of the relationship between nematodes and soil physicochemical properties. The CCA results indicated that Ditylenchus exhibited a positive correlation with OMC, while the Panagrolaimus and Hemicycliophora species showed a negative correlation with OMC. The results indicated that none of the soil sample sites were under stress. The soil food web analysis revealed that most soil samples were nutrient-enriched with a low C/N ratio. In conclusion, this study revealed that oak trees harbor a high diversity of plant-parasitic and free-living nematodes. The results suggest that soil nematodes, particularly free-living bacterivores, such as Panagrolaimus, can indicate organic matter content in the soil. [ABSTRACT FROM AUTHOR]

Sowing depth is a critical factor in crop growth and is determined by both the soil conditions and the force of the opener. The trend for the future is to control sowing depth based on soil dynamic parameters. Therefore, this paper developed a downforce measurement and control system based on the 'T'-shaped furrow opener and investigated the influence of soil dynamic parameters and opener downforce on sowing depth. A test-rig was constructed and the accuracy of the system in measuring downforce and controlling downforce and sowing depth was verified. The study shows that at different sowing depths, soil moisture, bulk density and their interaction have a significant effect on downforce (P < 0.01). As the moisture content decreases and the bulk density increases, the required downforce increases for the same sowing depth. A mathematical model of downforce-sowing depth-soil bulk density-soil moisture content was established using experimental data, with an R2 of 0.916, VIF <5 and a Durbin-Watson value of 1.628. Field experiments show that, at an operating speed of 6 km h−1, the control strategy based on the soil dynamic parameters predicted by downforce theory significantly outperformed the strategy of adjusting the downforce in response to perceived changes in downforce. This indicates that after dynamic and rapid measurement of soil bulk density and moisture content during field operations, sowing depth can be accurately controlled based on the directed downforce of the opener. The mathematical model provides a theoretical basis for sowing depth control based on soil dynamic parameters. • Proposing a sowing depth control strategy based on soil dynamic parameters. • System developed under static conditions and validated through dynamic experiments. • A mathematical model for the precise control of sowing depth was established. [ABSTRACT FROM AUTHOR]

Numerous studies have highlighted the role of X-ray computed tomography (X-ray CT) in understanding root architecture. Nevertheless, setting definitive scanning parameters for diverse soils in varied container sizes remains challenging. This study investigates the influence of X-ray CT system voltage on the penetration capability in diverse soils and container sizes, focusing on two key parameters: (1) gray values, which indicate X-ray attenuation and contribute to image contrast, and (2) signal-to-noise ratio, a measure of image clarity. Five soil samples were collected from various depths within a soil profile to encompass bulk density values ranging from 1.34 to 1.84 g·cm-3 to conduct the experiment. Containers with dimensions of 6×6×6 cm³, 8×8×6 cm³, 10×10×6 cm³,12×12×6cm³,14×14×6cm³, and 16×16×6cm³ were used. Voltage levels spanning 75 to 225 kV, in 25-kV increments, were applied to each sample. The observed gray values of the X-ray images were fitted using a logistic model of three parameters. Results showed that increasing voltage leads to enhanced penetration up to a plateau point, irrespective of soil density or container size. This plateau could potentially yield higher quality scans, given that lower voltages result in subdued gray values and reduced image contrast. Notably, it was observed that soil properties, including mineral composition, directly affect image gray values. This study established optimal voltage settings for specific soil types at fixed densities, offering valuable insights for researchers investigating soil-root interactions. Although the current findings are based on five soils, a more extensive sampling encompassing diverse soil textures and densities is necessary for a comprehensive understanding of X-ray penetration behavior across various soil types. [ABSTRACT FROM AUTHOR]

Understanding the underlying temporal dynamics influencing invasive plant control outcomes is essential to achieve restoration and land management goals. Within grasslands, herbicides are commonly used as the main method for invasive plant control, but the efficacy of management may be dependent on seasonal dynamics, as well as the number of applications. Additionally, assessments to quantify invasive plant control are often limited to aboveground plant composition, overlooking the potential repository of propagules stored in the soil seedbank, and additional impacts on nontarget species. To ensure that an herbicide method is effectively controlling invader populations, while limiting impacts on the resident plant communities, both above‐ and belowground species responses must be assessed. We established an herbicide field experiment across different sites and years in Riverside, CA, U.S.A., to assess the control of a global annual invasive forb, Oncosiphon pilulifer. We investigated how seasonal herbicide management (early‐season vs. late‐season) and repeated annual herbicide applications (1 vs. 2 years) influenced cover and seedbank density of our focal invader and the resident plant community 1 year after treatment. We found that although late‐ and early‐season‐applied herbicides reduced invader cover, early‐season applications were the only strategy to reduce invader seedbank density, indicating potential longer term management control. Lastly, native cover was limited in post‐treated areas, suggesting that additional management strategies may be needed to overcome native establishment limitations in invaded grasslands. [ABSTRACT FROM AUTHOR]

The importance of fine‐root diameter for ecosystem functioning is increasingly recognized, yet much remains to be learned about the variation in fine‐root diameter at large scales. We conducted an analysis of fine‐root diameter for five root orders for 1163 plant species to detect patterns in relation to resource availability (e.g. carbon, nitrogen, water and net primary production (NPP)), stress intensity (e.g. plant/soil biodiversity and soil bulk density) and temperature. First‐ to fourth‐order root diameters showed non‐linear relationships with mean annual temperature (except for first‐order root diameter) and/or with latitude. The diameters of the five root orders decreased with increasing mean annual precipitation, but increased with greater NPP, which was the strongest determinant of fine‐root diameter. Increasing soil biodiversity was associated with decreasing diameters of fourth‐ and fifth‐order roots, while greater plant biodiversity was associated with decreasing diameters of first‐ to third‐order roots. Soil total nitrogen concentration had a positive effect on first‐order root diameter but a negative effect on fourth‐ and fifth‐order root diameters. The patterns reversed for soil total phosphorus concentration. First‐ to third‐order and fifth‐order root diameters increased with greater soil bulk density. Second‐ to fourth‐order root diameters increased with higher soil pH. Overall, the variables related to climatic, biological and edaphic factors explained 44–63% of the total variance in the diameters of the different root orders. The unique patterns of plasticity observed in fine‐root diameter across root orders in response to varying environmental conditions contributes to a diversification of plant strategies for nutrient/water acquisition and transport under climate change. [ABSTRACT FROM AUTHOR]

The vertical bearing capacity of the suction caissons is vital to the safety of marine jacket foundations. The sand friction angle is a key parameter for calculating the vertical bearing capacity. The sand friction angle is state-dependent, which is affected by the compact state and stress state. However, this effect is neglected in the current study, resulting in deviations in the calculation results of the vertical bearing capacity. Therefore, a novel method is preliminarily proposed to account for this impact while evaluating the vertical bearing capacity of suction foundations. First, a new friction angle is expressed as a function of relative density and soil depth, which differs significantly from the commonly used constant friction angle. The state-dependent sand friction angle is available. Then, the general and simplified vertical bearing capacity formulas are clarified. Four key parameters in the former and a new first-order coefficient in the latter are identified. The calculation procedure based on the new friction angle is also specified. Finally, combined with model tests, a comparison study is carried out. The results show that the calculation results using the new friction angle are more accurate and practical. This study can provide a reference for the foundation design. [ABSTRACT FROM AUTHOR]

Stone column installation is commonly employed to prevent liquefaction. Stone columns mitigate liquefaction by means of mainly three mechanisms which are drainage, stiffening and densification. A factor of safety against liquefaction $FS$ FS is used to quantify liquefaction potential. The aim of this study was to assess the efficiency of stone columns as a liquefaction remediation based on twenty four case studies. In these cases, SPT and CPT tests were recorded before and after stone columns installation. It was found that the installation of stone columns considerably increased soil density mainly in clean to slightly silty sand. The average rate of increase in the penetration resistance ${N_{1,60,cs}}$ N 1 , 60 , cs and ${q_{c1Ncs}}$ q c 1 Ncs were about 31.13% to 69.29% and 57.10% to 318.28%, respectively. Furthermore, the cyclic shear stress ratio of reinforced soil can be reduced by 13.5% to 77.5% due to the stiffening improvement of stone columns. Densification and stiffening mechanisms have been investigated through several approaches. Their individual and combined effects have been analysed. Comparative results indicate that considering the densification and stiffening effects in liquefaction analyses improved considerably the performance of stone columns. [ABSTRACT FROM AUTHOR]

The slope safety factor is a crucial indicator for assessing slope stability. However, the current methods for calculating safety factors are predominantly based on the search of limit equilibrium theory and the iteration of finite element methods, leading to overly intricate computational procedures. Considering classical mechanics theory and the definition of slope safety factors, there inevitably exists a certain functional relationship between various slope parameters and their safety factors. Thus, we propose an approach utilizing response surface surrogate functions to express this relationship.We studied two types of slopes: soil slopes and rock slopes. For soil slopes, assumed to be single-layer saturated clay, we considered five parameters: soil density, cohesion, friction angle, slope height, and slope angle. For rock slopes, we considered six parameters: rock density, uniaxial compressive strength of the rock, GSI, mi, slope height, and slope angle.we introduce a data sampling technique based on genetic algorithms to enhance the quality of training data. This approach reduces the uncertainty in fitting outcomes while minimizing the volume of sample data, while still meeting precision requirements and generalizability.To address the demands of this study, we establish a convolutional neural network to approximate the response surface. A comparison is made with response surfaces approximated using FCNN and polynomial methods, revealing superior performance of the convolutional neural network. Following training, the surrogate function derived enables rapid and accurate computation of the slope safety factor. [ABSTRACT FROM AUTHOR]

The main challenge of the no-tillage system (NTS) is to reconcile productivity, the maintenance of surface residues, and the stabilization of soil organic matter (SOM). To address this challenge, particularly in tropical regions, various cover crops have been tested. The objective of this study was to test the effects of agricultural crop succession systems on the stock and stability of soil organic carbon in different surface layers of the soils. The research was carried out in the state of Goiás, Brazil, in an experiment set up in 2016, designed in randomized blocks with a split-plot scheme (treatments and soil layers), comprising four repetitions (blocks). The treatments (plots) consisted of crops grown in succession to soybean, which were as follows: T1—soybean/corn (Zea mays); T2—soybean/pearl millet (Pennisetum glaucum); T3—soybean/Urochloa ruziziensis (brachiaria); and T4—corn + Urochloa ruziziensis. The subplots represented the following soil layers: 0–5, 5–10, 10–20, and 20–40 cm. We evaluated the biomass dry mass and the soil parameters such as soil density, total porosity, and light organic matter across all layers. The organic carbon, grain size fractionation (mineral-associated organic carbon—MOC; sand-sized carbon—POC), and isotopic composition (δ13C) were determined in the 0–5 and 5–10 cm layers. The highest biomass dry production was observed in the soybean/pearl millet succession, which reduced the soil density and increased the total porosity in the surface layer. The soybean/pearl millet treatment produced high amounts of light organic matter, particularly in the 0–5 cm layer, a result also found for the soybean/brachiaria and soybean/corn + brachiaria systems. The crop successions did not alter the soil carbon stock or stability; however, the surface layer stored the highest amount of carbon, with elevated total organic carbon values and carbon stocks and stability (MOC and POC). Overall, in this study, replacing corn with other crops in succession with soybean did not affect the stock or stability of soil organic carbon. The species grown in succession with soybean contributed to the higher surface carbon stock and stability, promoting the formation of more stable and recalcitrant carbon. [ABSTRACT FROM AUTHOR]

Conservation soil management, such as no-tillage and Rip Strip®, can be developed as an alternative to degradation processes such as compaction. This study aimed to compare conventional and conservation soil tillage regarding their soil physical attributes, root system, and stalk yield for two years. The experiment was conducted on the premises of Fazenda Cresciúma in an area of Typic Eutrudox in the municipality of Jardinópolis, state of São Paulo, Brazil, with an experimental design in random blocks. The treatments evaluated for the transplanted sugarcane were as follows: CT—conventional tillage with disk harrow; CTS—conventional tillage with disk harrow and subsoiling; MT—minimum tillage with Rip Strip®; NT—no-tillage. The variables evaluated were dry root mass, soil bulk density (Bd), total porosity (TP), and stalk yield for sugarcane plant and first ratoon harvest. The results allowed us to observe that CT was the system that most reduced the TP (varying 0.44–0.47 m3 m−3), while MT was the one that presented fewer changes (TP varying 0.47–0.51 m3 m−3). NT obtained the highest stalk yield (123 Mg ha−1) in the sugarcane plant cycle and greater amounts of roots in depths below 0.80 m. Conservation tillage by Rip Strip® proved to be a viable system for use in sugarcane because it provides greater dry root mass on the surface and maintenance of physical attributes compared to conventional tillage. [ABSTRACT FROM AUTHOR]

Brazil's Fundão dam collapse is one of the world's largest disasters of tailing dam failures. Previous research has evaluated toxic metals and non-metals (Cd, Cr, Ni, Pb, As, Hg) in the same soil samples used in this study, and results have indicated that only Fe and Mn concentrations increased above the original baseline (Melo et al., 2023). Consequently, the present study's focus has shifted towards assessing and integrating changes in soil quality regarding chemical fertility and morphological, physical, and mineralogical attributes in the floodplains post-dam collapse. Soil samples from 0 to 0.2 and 0.2–0.4 m depths, and samples of Urochloa sp. were collected along ten transects, spanning 100 km perpendicular to the Doce River channel. This sampling strategy targeted specific landscape positions including areas affected by deposited iron tailings (DIT), soil tailing mixture (STM), and control soil (CS) devoid of iron tailing interference. Results showed no discernible alterations in Ca, Mg, K, and P concentrations in Urochloa sp., and the most severe negative impacts observed regarded the replacement of kaolinitic pre-disaster matrix for hematitic matrix, reduction in organic carbon, and the prevalence of sand and silt particles. These factors collectively contributed to triggering: (i) decrease in chemical fertility and cation exchange capacity and (ii) significant decline in physical quality, evidenced by increased density and reduced total porosity and macroporosity. Addressing these adverse effects would require the augment of organic matter levels and offset the dominance of the hematitic matrix in the DIT. Furthermore, it is imperative to decompact the DIT by mechanized or plant cultivation means. [ABSTRACT FROM AUTHOR]

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The main objective of the current study was to use seven lots in Hartford, CT that are planned for community reuse to determine the optimal sampling density that allows for the detection of hotspots of lead pollution while limiting the labor of the sampling process. The sampling density was investigated using soil Pb measured by in situ X-ray Fluorescence as the indicator to evaluate soil health, with a new threshold of 200-mg/kg proposed by the USEPA in January of 2024. Even though this study takes place in an urban setting, where the new USEPA policy requires the use of a 100-mg/kg threshold for Pb due to the fact that there are other identifiable sources of the contaminant, only the 200-mg/kg threshold is discussed because it is evident from the analysis that compliance of a 100 mg/kg threshold in urban plots is highly unlikely (five out of seven sites would require complete site excavation prior to reuse). Using the inverse distance weighted geospatial interpolation of in situ pXRF determined lead measurements, grid sampling resolutions of 3-m, 4-m, 5-m, 6-m, 8-m, 10-m, and 12-m were compared. Ultimately, the case study finds that the largest grid resolution that can be implemented for soil screening to maintain hotspots of pollution to properly inform soil management decisions is a 6-m grid, or a density of approximately 1/36-m2. [ABSTRACT FROM AUTHOR]