Soil Layer Research Articles

Quercus acutissima exhibits more adaptable water uptake patterns in response to seasonal changes compared to Pinus massoniana

BackgroundSeasonal precipitation variability significantly affects water use in forests; however, whether water uptake is adapted to changes in precipitation, particularly whether it could affect the coexistence of tree species, has rarely been quantified in forest systems. MethodIn this study, dual stable isotopes and the Li-6400 portable photosynthesis system were used to determine the water sources of a mixed conifer (Pinus massoniana) and broadleaf (Quercus acutissima) forest and changes in hydraulic characteristics during the dry and wet seasons in a southern hilly region of China. ResultsAlthough the hydraulic characteristics of P. massoniana were lower than those of Q. acutissima, it maintained a stable water source from the deep soil layer and a higher stomatal conductance (Gs), leading to a higher transpiration rate (Tr) during the growing seasons. Q. acutissima mainly absorbed water from deeper soil layers in the dry season and took up from shallow soil layers in the wet season. Its Gs values exhibited sensitivity to precipitation, while it maintained a lower Tr value during the growing seasons. The excessive water-use strategy observed in P. massoniana may confer weak drought-tolerance during higher frequency and more intense extreme precipitation events, whereas Q. acutissima may exhibit better ecological adaption to precipitation changes. ConclusionsThe overlap of water niches in mixed forests did not appear to affect the coexistence of tree species. The present study provides insights into reforestation and water management in the southern hilly regions of China.

The Cycles agroecosystem model: Fundamentals, testing, and applications

Models of the soil–plant-atmosphere continuum are repositories of knowledge and gears in analytical and decision support tools applied to agroecosystems. In this paper, we present the Cycles agroecosystem model theory along with test cases and applications. Cycles combines innovations for simulating soil hydrology and biogeochemistry, including carbon and nitrogen saturation theory, with a modular software architecture. These elements enable simulating monoculture or polyculture crop sequences and associated management practices, containerizing for applications that require high-performance computing, and data assimilation at runtime. A comparison of simulated and measured daily evapotranspiration (ET) obtained with the eddy covariance method for maize (Zea mays L.) and shrub willow (Salix spp.) shows that Cycles represents well meteorological and vegetation controls of ET (root mean square error or RMSE = 0.75 mm d-1). Cycles accurately simulated differences of 150 mm in growing season ET between these two plant communities. Comparisons of modeled versus measured soil water content under soybean (Glycine max [L.] Merr.) in southeastern Pennsylvania for six soil layers at 0.1-m increments show accurate representation of water depletion and recharge (RMSE of 0.027–0.011 m3 m−3). Simulations of growth and nitrogen uptake of wheat (Triticum aestivum L.) in eastern Washington also highlight the model’s skill simulating processes that affect water and nutrient fluxes simultaneously. To highlight Cycles’ suitability for incorporation in high performance computing applications, we present a coupling of Cycles with an autonomous crop sequence builder (Cycles-A) in the Chesapeake Bay watershed. This system automatically identified areas for double cropping and selected the optimum combination of annual crops across the watershed. The Cycles model innovations and agroecosystem framing continue advancing the premise of making models not only dynamic knowledge repositories but useful tools for research and landscape management.

Integrating Deficit Irrigation Strategies and Soil-Management Systems in Almond Orchards for Resilient Agriculture

This work was conducted over three-year monitoring seasons of three almond cultivars (Guara, Marta, and Lauranne) subjected to deficit irrigation in combination with cover crops in a Mediterranean semiarid area (SW, Spain). Four water–soil treatments were evaluated based on the conjunction of two irrigation strategies: fully irrigated (FI), covering 100% of the ETC, and regulated deficit irrigation (RDI), with two soil-management systems: bare soil (BS) and cover crop based on a mixture of vetch (Vicia sativa L.) and oat (Avena sativa L.) (CC). Throughout the study period in trees, the yield, the stem water potential (Ψstem), leaf nutrient content (N, P, K, Ca, Mg, Na, Fe, Zn, Mn, and Cu) in soils, organic carbon, microbial biomass, fluoresceine diacetate, and enzymatic activities (dehydrogenase, protease, β-glucosidase, and alkaline phosphatase) were determined. In addition, the dry matter and carbon fixation by plant covers were evaluated. For Guara and Lauranne, yield reductions (22 and 26%, respectively) were found for water-stressed (RDI-CC) plots with respect to non-stressed combination (FI-CC) plots, contrasting with cv. Marta, without a significant impact on productivity in all combinations. That is, the RDI (~3.000 m3 ha−1) strategy enabled acceptable productivity, offering promising possibilities for cultivation performance under water-scarcity scenarios. Important differences in Ψstem could be observed and ascribed to irrigation strategies, especially for Guara and Lauranne, but without significant effects due to the soil-management systems applied. No differences were observed in the tree nutritional status due to the presence or absence of CC; however, its presence increased the fixation of atmospheric carbon, which was not the case under BS conditions. Additionally, CC significantly fostered the microbial processes and enzymatic activities, particularly in upper soil layers (0–10 cm) and with plenty of water supply in FI-CC plots and to a lesser extent in RDI-CC plots, which could encourage prominent aspects for soil quality and health restoration. Thus, the cover crop is congruent with RDI to facilitate soil functionality and water savings in a changing climate, contributing to resilient farming systems in the Mediterranean environment.

Spatiotemporal coupling dynamics and factors influencing soil organic carbon and crop yield in Chinese farmlands

Clarifying the correlation between soil organic carbon (SOC) and crop yield is key to achieving carbon neutrality and ensuring food security. However, owing to the lack of analysis based on large-scale farmland monitoring data and research on deep soil, relevant research has not yet reached a consensus. Here, we based on the monitoring data of 118 sample plots from 21 typical farmland and farmland compound ecosystem stations of the China Ecosystem Research Network (CERN) between 2004 and 2020, the temporal and spatial coupling associations between SOC content and crop yield in 0–20 cm and 0–100 cm soil layers and its factors influencing were determined. The findings revealed that between 2004 and 2020, SOC content in 0–20 cm soil layer, SOC content in 0–100 cm soil layer, and crop yield in typical farmland in China showed a fluctuating upward trend, the average annual growth rates were 0.59 %, 0.27 % and 1.07 %, respectively. The coupling relationship between SOC content and crop yield was not always good in different periods, which varies largely in different geographical divisions. Among the anthropogenic factors, exogenous carbon input can improve the coupling relationship between them by increasing the soil organic carbon content and crop yield, while the effect of less tillage and no tillage is limited. Among the natural factors, temperature, soil bulk density, and farmland type all have an impact on farmland SOC content and crop yield at different significance levels. Each variable had different effects on SOC content and crop yield in typical farmlands in different geographical regions. With deepening soil layer, influence of anthropogenic factors such as exogenous carbon input on SOC content decreases, but it still cannot be ignored. Based on these findings, the study recommends that exogenous carbon input play an important role in soil carbon sequestration and improving crop yield.

Holocene paleoenvironment of the Nihewan Basin, China, inferred from high-resolution luminescence dating and a multiproxy analysis of gully sediments

As a pivotal region for studying early human occupation in East Asia, the Nihewan Basin has witnessed numerous studies on Paleolithic sites and associated paleoenvironmental records. However, little attention has been given to the Holocene period, despite the basin being a crossroads for the exchange of NE China Neolithic cultures. In the central part of the Nihewan Basin, we found a gully sediment section with a thickness of ∼9 m, which exhibits clear parallel bedding throughout. The section is composed of ten sediment layers (Layers 10–1 from bottom to top), from which three distinct dark-colored soil layers (Layers 8, 4 and 2) and two erosion surfaces (between Layers 10 and 9, and Layers 2 and 1) were identified. Forty-four sediment samples from the section were optically dated, and the obtained ages were refined using Bayesian statistical modeling. The age-depth relationship and sedimentary characteristics suggest that the sedimentation process of Layers 9–2 was continuous. To reconstruct the paleoenvironment, the grain-size distribution, magnetic susceptibility, and pollen content of the sediments were analyzed. The three soil layers exhibit high magnetic susceptibility values. Based on these climatic proxies, five climate stages were recognized. From ∼12.7 to ∼6.8 ka, the climate in the basin region was cold and dry. The period between ∼6.8 and ∼5.4 ka was marked by optimal climate conditions that led to soil formation. Subsequently, the climate was colder and drier during the period of ∼5.4 – ∼4.0 ka, and transitioned to warm and wet conditions again from ∼4.0 to ∼2.7 ka. Another stage of soil formation occurred between ∼2.7 and ∼1.7 ka, during which the climate was predominantly warm and humid, albeit punctuated by a brief interval of colder and drier conditions. These climate variations coincided with cultural evolution stages within the basin, highlighting a close relationship between environmental change and human adaptation.

Carbon Sequestration and Soil Fertility Management in Sandy and Clayey Soils Revealed by Over Four Decades of Long‐Term Field Experiments in Thailand

ABSTRACTWe investigated the impact of organic matter (OM) application on soil organic carbon (SOC) sequestration and cassava yield in sandy (sand content > 72% and > 62%) and clayey (sand content > 47%) soils through three long‐term experiments conducted from 1975 to 1976 in Thailand. Eight treatments—nitrogen (N), phosphorus (P), and potassium (K) fertilization, cassava residue (CR), and compost application (COM)—were assigned to the control (CT), N, NP, NK, NPK, CR, NPK + CR, and NPK + COM groups. Changes in SOC, cassava yield, and soil chemical properties, were recorded. Interactions of these parameters were visualized using structural equation modeling (SEM). SOC concentrations were determined at five different depths in 2021. A significant treatment effect was observed in the initial stage of the experiment in sandy soils. Conversely, in clayey soil, a significant effect was observed only in the later stage. SOC sequestration rates (mean ± SD of the three sites, Mg C ha−1 0.2 m−1) were in the order of NPK + COM (10.1 ± 6.5), NPK + CR (5.6 ± 3.1), CR (2.8 ± 2.0), NPK (2.0 ± 2.1), NK (1.9 ± 1.3), NP (1.8 ± 2.0), and N (1.2 ± 1.1). SEM highlighted the effect of OM application on SOC sequestration across the three sites. Furthermore, SOC increases positively influenced cassava yield in sandy but not in clayey soils. Vertical distribution of SOC showed consistent treatment effects in deeper soil layers, especially in sandy soils, underscoring the importance of considering deep soil layers for carbon sequestration.

Effects of long-term biodegradable film mulching on yield and water productivity of maize in North China Plain

Biodegradable films are considered ideal alternatives to polyethylene films because of their advantages in increasing crop yield and controlling soil pollution. However, the influences of biodegradable film mulching on soil physicochemical environments and water productivity after long-term mulching remain poorly understood. Therefore, a field experiment after long-term mulching (since 2016) was conducted to explore the effects of black biodegradable film (BB), transparent biodegradable film (TB), and traditional polyethylene film (PE) on soil physicochemical environments, aboveground biomass accumulation, grain yield, evapotranspiration, and water productivity (WP) of maize in the 2021 and 2022 in the North China Plain. The results showed that polyethylene films and biodegradable films had a similar ability to preserve soil moisture, promote maize growth, reduce evapotranspiration, and increase WP. Moreover, the performances of BB were more equivalent to PE, and there was no significant difference on WP and yield under BB and PE. Compared with traditional flat planting without mulching (CK), BB and PE significantly increased yield (9.5 % and 12.7 % in 2021; 5.25 % and 6.37 % in 2022) and WP (11.54 % and 21.47 % in 2021; 24.28 % and 23.42 % in 2022). Film mulching treatments increased the soil organic carbon sequestration rate, and the content of soil organic carbon, microbial activity, and urease activity in the 0–20 cm soil layer compared with CK. According to structural equation modeling, the increasing soil water storage because of films mulching positively influenced yield by enhancing enzyme activities which were related to soil nutrients. Over all, these results showed that black biodegradable film is an ideal replacement for polyethylene films under long-term mulching conditions because of its comparable agronomic performance and influence on soil physicochemical environments in the North China Plain.

Содержание валовых форм цинка, свинца и кадмия в дерново-подзолистых супесчаных почвах земель сельскохозяйственного назначения

Abstract. Purpose and objectives. The research is aimed at studying the peculiarities of the distribution of gross forms of zinc, mumps, cadmium according to the soil profile of sod-podzolic sandy loam soils of agricultural lands of the Ryazan region and determining the current regional background. Methodology and methods. To solve the tasks set, pits with a depth of 1.5 m were laid in different regions of the region, the depth and structural features of the soil layer and the effect on the migration conditions of the studied elements were analyzed. Based on the results of determining the content of the studied elements in the soil at intervals of 0.1–0.2 m to the maternal, the calculation of background concentrations was performed. A comparative analysis of the proposed background values with well-known values of world and domestic researchers has been carried out. The scientific novelty of the conducted research lies in the fact that the proposed background values are modern and calculated directly for the sod-podzolic sandy loam soil of the Ryazan region. Results. The structure of soil profiles of sod-podzolic sandy loam soil at a depth of 110–120 cm has the following form: O – A – EL – ELBt – Bt – BtC – C. At the same time, noticeable geochemical barriers delaying the migration of heavy metals are noted in the horizon A and Bt. The obtained values of the studied elements were in the concentration ranges for Zn (5.4–12.8 mg/kg), Pb (2.1–7.4 mg/kg), Cd (0.031-0.081 mg/kg). Background concentrations are proposed: Zn – 8.3 mg/kg, Pb – 4.2 mg/kg, Cd – 0.053 mg/kg, which differ from the well-known values of world and domestic researchers presented in a comparative analysis and give a modern idea of the regional background content of gross forms of zinc, lead and cadmium in sod-podzolic sandy loam soils Ryazan region.

Simulation algorithm of greenhouse soil water movement based on cellular automata

Soil moisture movement reveals the hydrological environment and irrigation characteristics of plants, which is very important and basic hydrological problem. A soil moisture movement algorithm based on cellular automata suitable for greenhouse was proposed to simulate the lateral flow and vertical penetration of soil water in different soil layers. Artemisia annua was used as an experimental plant, and two numerical simulations were set up to determine the minimum water replenishment and the degree of upward soil modification. To verify the performance of the model, corn was used as an experimental plant for application simulation. The numerical simulation results show that the effect of only water for plant cells is superior to soil cells, and the disturbance behavior of the underlying soil layer should be minimized during the cultivation process. The average MAE/RMSE of all soil layers is 0.86/1.06 and in deep layer (50 cm and 60 cm) is 0.53/0.64. It shows the model has a certain prediction and simulation ability, especially in deep soil layers. The proposed algorithm can simply calculate soil flow, set the minimum water replenishment, and evaluate the water replenishment efficiency, which can provide a theoretical reference for the water replenishment and soil replacement scheme.

Improvement Effect of Straw Interlayer Thickness on Saline-Alkali Soil

In order to evaluate and optimize the application effect of straw interlayer technology in improving soil quality and crop production in saline-alkali soil, and to understand the synergistic relationship between soil water and nutrient distribution, crop roots and above-ground growth in saline-alkali soil, the improvement effect of straw interlayer thickness on saline-alkali soil was studied. Through the indoor root box control experiment combined with the field micro-zone verification experiment, four corn straw interlayer thickens were set (CK: no straw interlayer; S3: Straw layer thickness is 3 cm; S5: The straw layer thickness is 5 cm; S7: straw interlayer thickness is 7 cm), and the effects of straw interlayer thickness on soil water and salt transport and nutrient distribution are simulated. The results showed that straw interlayer could enhance the water retention and salt leaching capacity of 0–40 cm soil layer after irrigation, and S5 treatment had the best effect, with soil water content increased by 11.0% and salt content decreased by 4.0% compared with CK (P < A0.05). Compared with CK, straw separation treatment decreased the soil nutrient content in 0–40 cm soil layer (except alkali-hydrolyzed nitrogen and available potassium), and increased the soil nutrient content in 40–60 cm soil layer, and S5 treatment had the largest increase, in which available potassium was significantly increased by 15.0% compared with CK (P <0.05). Therefore, it shows that the straw interlayer can play a role in preventing water and reducing permeability, and can reduce the salt content of the soil above the interlayer, and has a good effect on the improvement of saline-alkali soil.

Characteristics of deep soil layer water deficit under different artificial vegetation types of the Loess Plateau, China

AbstractSoil water is a crucial factor for the growth of vegetation and sustainable development in water‐limited areas. After large‐scale vegetation restoration on the Chinese Loess Plateau, understanding the relationship between vegetation and deep soil moisture has become a crucial focus in current research. In this study, artificial forest (Pinus tabulaeformis [PT], Robinia pseudoacacia [RP] and Platycladus orientalis [PO]), apple orchard (AO), secondary forest (SF) and farmland (FL) were selected as the research objects, and grassland (GL) as the control, using soil‐drilling techniques. We systematically monitored the soil water content of 0–10 m soil layer over two hydrological years, and explored the effects of different vegetation types on soil water deficiency. The results showed that: (1) The deep soil water various significantly among different vegetation types. Compared with GL, the soil water content in all forest land was generally lower, and this difference became more pronounced in deeper soil layer (>7 m), which indicating the depth of the influence of vegetation on soil water has reached 10 m. (2) The mean soil water deficit size (SWDS) values of PT (0.14), RP (0.17), PO (0.07), AO (0.15), SF (0.10) and FL (0.27) in 0–1 m were all positive, indicating that surface soil water had accumulated during more than half of the sampling periods. In the 2–10 m soil layer, mean SWDS was negative in all vegetation types except in FL, leading to soil desiccation. SWDS was found to fluctuate with soil depth. (3) SWDS was affected by a combination of soil properties and vegetation growth. Our results indicate that the current afforestation model could lead to the deficiency of deep soil water. Therefore, it is imperative to make reasonable vegetation structure according to the available local soil and water resources in future vegetation allocation and management.

Field investigations on the thermo-mechanical behavior of a partially activated energy pile in Miocene sediments

The City of Vienna, as one of the largest public clients in Austria, initiated a research project to determine the load-bearing behavior of various foundation elements in typical Viennese soils. Numerous large-scale tests were carried out on bored piles, micro piles, anchors, and jet grouted columns. In addition, two energy piles were installed in different soil layers to investigate their behavior under mechanical and thermal loading in each soil layer separately. This paper discusses the energy pile in the Miocene sediments, which consist mainly of silty fine sand and some sandy silt. The energy pile – fully instrumented with strain gauges, extensometers, heat gauges and optical fiber sensors – was loaded for two and a half months. The mechanical load was kept constant throughout the thermal cycles to determine the response of the pile to thermal loads. The measured temperature data were used in numerical back-calculations to determine the thermal parameters of the soil layers and the concrete. Based on the measured strain and deformation data, the deformation behavior of the energy pile due to the thermal load was investigated. Finally, a static pile load test was carried out on the energy pile and the results are compared with those of the conventional reference piles installed in the vicinity, which have not been subjected to thermal loading. The test demonstrated that, after several weeks of cyclic thermal loading, the energy pile exhibited more favorable load-deformation behavior compared to conventional reference piles.

Effects of Tillage Depth and Lime Application on Acidification Reduction and Nutrient Availability in Vertisol Soil

Cropland acidification seriously restricts sustainable agricultural development. The main purpose of this study was to determine whether deeper tilling could alleviate topsoil acidification to improve the quality of arable land. A soil column incubation experiment simulating tillage depths (10 cm, 30 cm and 50 cm) and lime addition was conducted to determine their effects on soil acidification improvement. The changes in soil pH, exchangeable acidity, ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3−-N), available phosphorus (AP), and microbial phospholipid fatty acids (PLFA) were analyzed. Tillage depth, lime application, and their interaction all had significant impacts on soil pH. T50 (simulated tillage depth of 50 cm) and T50+Lime (simulated tillage depth of 50 cm plus lime) treatments significantly increased the topsoil pH from 5.41 to 6.35 and 7.12, respectively. T50 treatment significantly reduced the soil exchangeable acid content compared to the T10 treatment. The nutrient accumulation along soil column indicated that the T50 and T50+Lime treatments significantly increased NO3−-N and AP content in the >30–50 cm soil layer. Compared with T30, NO3−-N accumulation in the >30–50 cm soil layers of T50 and T50+Lime treatments was 6.62 and 7.93 times higher, respectively. The accumulation of AP in the >30–50 cm soil layers of the T50 and T50+Lime treatments was 1.33 and 1.54 times higher than in the T30 treatment, respectively. These findings imply tillage up to 50 cm without exogenous materials could be a potential measure to reduce topsoil acidification and increase nutrition availability of >30–50 cm soil layers. Tillage of up to 30 cm combined with lime application confers greater benefits, which would particularly impact crops with shallow root systems. Subsequent field experiments will be conducted to further investigate the efficacy of these strategies in enhancing crop yield.

Assessing the compression properties of Gravel-bearing forest soil in northeast China’s seasonally frozen regions under Freeze-thaw cycles and varying gravel content

Due to climate change, human activities and natural disturbances in high-latitude permafrost and seasonally frozen areas are gradually increasing, attracting more attention from scholars. However, research primarily focuses on soil biology and chemistry in these regions, with limited exploration of their mechanical properties, especially compression properties. This study aims to evaluate the effects of gravel content and freeze–thaw (F-T) cycles on the compression properties of coarse-grained layered forest soil from northeast China’s seasonally frozen regions, with the goal of predicting the soil’s compressive changes under heavy mechanical loads. Specifically, using uniaxial confined compression tests (UCCT) on 252 disturbed soil samples (including two soil layers: AB and Bhs; six gravel contents; and seven F-T cycles), three characteristic compression coefficients—precompression stress (σpc), compression index (Cc), and swelling index (Cs)—were measured. Additionally, scanning electron microscopy (SEM) was used to analyze the mesostructure evolution of coarse-grained gravel-bearing soil. Volume changes of samples were measured after 15F-T cycles with varying gravel contents. Results indicate non-linear effects of gravel content and F-T cycles on σpc. Gravel content below 50% positively influences σpc, while content above 50% increases soil pore content, decreasing σpc. Cc and Cs exhibit an approximately negative correlation with gravel content and initially increase followed by a decrease with more F-T cycles. Moreover, the σpc and Cc of the AB layer are higher than those in the Bhs layer, likely due to differences in clay and organic carbon contents. Notably, the observed trends differ from previous studies on other soil types such as farmland and paddy fields. This study fills a gap in understanding the compression characteristics of layered gravel-bearing forest soil in seasonally frozen regions, providing valuable insights for evaluating soil compression in both seasonally frozen and permafrost regions, and understanding mechanical vehicle-soil interactions. It also lays the theoretical groundwork and provides data support for constructing compression models of layered gravel-bearing forest soil.

Impact of textural layers in soils on irrigation infiltration processes in an oasis farmland, northwestern China

AbstractThe Hexi Corridor Oasis in China is an important agricultural area supported by extensive irrigation. The sandy soil in the area exhibits textural layering, which has marked effects on its properties. Textural layered soils play an important role in distributing and regulating water regimes in irrigated fields. However, little is known about the textural layering‐dependent variability in soil water infiltration characteristics following irrigation and the potential effects on soil hydrology and water regimes in these soils. The objective of this study was to determine water infiltration processes and their influencing factors for six soil profile types in an oasis farmland. Six in situ constant‐head infiltration measurements (with three replications in each of six sites) were conducted with a single‐ring infiltrometer in different soil texture configurations, and Hydrus‐2D model was applied to evaluate soil water distribution. The results showed that the wetting front depth for all treatments was in the following order: ST‐1 > ST‐5 > ST‐6 > ST‐3 > ST‐2 > ST‐4; the stable infiltration rate ranged from 1.2 to 3.3 cm/min during the investigation period in all treatments. The presence of a finer‐textured soil layer decreased water infiltration rates through the profiles, and the thickness and burial depth of textured layers had obvious effects on infiltration, compared with homogeneous sand profiles. Presence of a medium‐textured layer affected the infiltration characteristics and soil water spatial variability; driven by increased field capacity and the wilting point, hydraulic conductivity was correlated with soil variables that were related to soil structure, such as wilting point and field capacity, and less so with variables that were related to soil texture, such as the clay fractions (p < 0.001). These results suggested that textural layering altered the soil structure and caused heterogeneous infiltration of water, with implications for the distribution of irrigation water and prevention of deep percolation in this oasis farmland. The result of this study offers a new analysis of ponded single‐ring water infiltrometer data that the soil water infiltration is also influenced by the type of textural layered than just the irrigation system, which supports crop irrigation management in study area and other regions with similar soil regimes.

Machine‐Learning Based Multi‐Layer Soil Moisture Forecasts—An Application Case Study of the Montana 2017 Flash Drought

AbstractSoil moisture (SM) is an essential climate variable, governing land‐atmosphere interactions, runoff generation, and vegetation growth and productivity. Timely forecasts of SM spatial distribution and vertical profiles are needed for early detection and prediction of potential droughts. However, previous studies have primarily concentrated on historical or near real‐time soil moisture mapping, with less effort devoted to the development and integration of soil moisture forecast components within drought assessment systems. A satellite‐driven machine‐learning approach was developed in this study to build complex relationships between diversified predictor data sets and in situ multi‐layer SM measurements from the Montana Mesonet, a regionally dense environmental station network in the US upper Missouri and Columbia basins. The resulting 30‐m daily SM predictions showed strong performance against in situ SM measurements from 4‐, 8‐ and 20‐inch soil layers, and with 1‐ to 2‐week forecast lead times (R > 0.91; RMSE ≤ 0.047 cm3/cm3). The machine‐learning model was subsequently applied to the entire Montana region, and the SM deficit forecasts with both 1‐ and 2‐week lead times successfully depicted onset, progression, and termination phases of the 2017 Montana flash drought, which was not effectively identified from prevailing operational systems. The resulting system is capable of delineating local scale SM heterogeneity, and could be extended to predict other critical water cycle variables, potentially enhancing future drought forecasts through multivariate assessments and benefiting water resource management, agricultural practices, and the provision of ecosystem services.

Analysis of cement-stabilized soil on road embankment employing finite element analysis - a case study

Abstract The application of stabilized soil is fast expanding around the world, and it is delivering improvements to the construction industry. Stabilized soil is a popular choice for reinforcing road embankments around the world. A layer of cement-stabilized soil can reduce the settlement of the soil layer below the embankments. This study compares the long-term settlement of road embankments with and without cement-stabilized soil layers of the Chittagong Port Access Road located at Teknaf Bangladesh. The settlement analysis of the road embankment was performed using the Finite Element Analysis with Plaxis2D. In this study, two forms of sequence modeling were used. First, the settlement of a road embankment without reinforcement was examined. The second modeling step was to determine the settlement of an embankment reinforced with a cement-stabilized soil layer. Following the simulation, a comparison was performed. Additionally, the effect of cement content (4%, 8%, and 12%), compaction energy, and single, double, and triple layers of CSS on long-term settlement along with the factor of safety of the embankment have been addressed. The results demonstrated that using this specific cement-stabilized soil below the road embankment has decreased the long-term settlement of the soil while increasing the safety of the embankment compared to that without the cement-stabilized soil reinforcement.

Advancing microplastics remediation in bioretention systems using biochar/kaolin: Optimizing organics removal, plant health, and microbial community dynamics

Bioretention systems can efficiently eliminate microplastics (MPs) from stormwater and prevent their potential pollution in surface water. However, MPs dynamics in bioretention systems and their effects on microbes, plants, and organics removal are unknown. In this study, five lab-scale bioretention columns (i.e., control and four treatments) were established and filled with soil and fillers (zeolite and ceramsite). Various sorbents were utilized in columns, including biochar, kaolin and kaolin-biochar (KBC) composites for MPs adsorption. This study examines how biochar/kaolin amendment affects MPs and organics (COD and TOC) removal, plant health, and microbial community structure in bioretention systems. In the 60-day time-series column experiment, all amended columns removed over 90 % of MPs compared to the control. The biochar, kaolin and their combined composite eliminated MPs by 90 %, 94 %, and 97 %, respectively. Adding vegetation to the columns improved MPs removal. Moreover, bioretention systems were more effective in removing MPs ranging from 0.6 to 1 mm with a 71 % removal rate than MPs ranging from 0.3 to 0.6 mm, resulting in a 54 % removal. Organics were removed contrarily in the soil and filler layer of the bioretention system, with the soil layer removal higher due to increased microbial activity. The removal rate of total organic carbon was higher (90 %) than that of chemical oxygen demand (80 %). The most dominant phylum of the bacteria in the soil of the MPs-amended columns were Proteobacteria and Acidobacteriota, which constituted 16–27 % and 41–58 %, respectively. While the dominant phylum in that of fillers were Bacteroidota and Firmicutes, which constituted 18–42 % and 42–65 %, respectively. The maximum microbial enrichment was observed in the biochar and KBC vegetated columns. This work advances our understanding of the complex dynamics between microplastics and organic matter in stormwater and how, individually and in combination, vegetation, biochar, and kaolin vegetation, biochar, and kaolin, individually and in combination, enhance bioretention systems' effectiveness in managing multiple pollutants.

Microplastic accumulation and transport in agricultural soils with long-term sewage sludge amendments

Land application of sewage sludge brings microplastic contamination to soil. However, studies regarding the occurrence and mobility of sludge-borne microplastics in soil are insufficient. In the present study, based on an experimental field, the effects of sludge application amount on the accumulation and migration of microplastics in 0–20 (upper) and 20–40cm (lower) soil layers were evaluated. After 16 years of continuous sludge application (36 t/ha per year), the microplastic content and migration ratio in upper soil reached 6,811 particles/kg and 148%, which was about 5 and 20 times, respectively, higher than that of the control soil without sludge. The microplastics in upper and lower soil layers, were mainly 0.2–0.5mm in size, mostly fibrous in shape, primarily transparent in color, and predominantly rayon in composition. Microplastic surfaces may persistently adsorb clay minerals and iron/titanium oxides from soil, posing potential environmental risks. Sludge application had a significant positive correlation with soil microplastic abundance, resulting in a good fit of predictive model constructed for microplastic accumulation in sludge-amended soils. These findings help to improve the knowledge on environmental behavior of microplastics in sludge-amended soil, and can provide a scientific basis for the regulation of microplastic pollution during sludge land application.

Bacterial and fungal keystone taxa play different roles in maintaining community resistance and driving soil organic carbon dynamics in response to Solidago Canadensis invasion

The invasion of alien plants has significant implications for vegetation structure and diversity, which could lead to changes in the carbon (C) input from vegetation and change the transformation and decomposition processes of C, thereby altering the dynamics of soil organic carbon (SOC) within ecosystems. Whether alien plant invasion increases the SOC stock and changes SOC fractions consistently within regional scales, and the underlying mechanisms driving these SOC dynamics remain poorly understood. This study investigated SOC dynamics by comparing the plots that suffered invasion and non-invasion of Solidago Canadensis across five ecological function areas in Anhui Province, China, considering climate, edaphic factors, vegetation, and soil microbes. The results demonstrated that the impact of S. Canadensis invasion on SOC storage was not consistent at each site in the 0–20 cm soil layer, as indicated by the range of SOC content (5.94–12.45 g kg−1) observed at non-invaded plots. Stable SOC exhibited similar response patterns with SOC to plant invasion, whereas labile SOC did not. In addition, bacterial and fungal communities were shifted in structure at each site by plant invasion. Bacterial communities exhibited greater resistance to S. Canadensis invasion than did fungal communities, as evidenced by three aspects of the resistance indices—community resistance, phylogenetic conservation, and network complexity. The mechanisms driving SOC dynamics under S. Canadensis invasion were explored using structural equation models. This revealed that fungal keystone taxa responsible for community resistance controlled stable SOC fractions. In contrast, bacterial keystone taxa had the opposite effect on labile and stable SOC. Climatic and edaphic factors were also involved in the labile and stable SOC dynamics. Overall, this study provides novel insights into the dynamics of SOC under S. Canadensis invasion on a regional scale.