Soil Profile Research Articles

Geospatial digital mapping of soil organic carbon using machine learning and geostatistical methods in different land uses

Improper management of soil resources leads to the destruction of soil organic carbon (SOC) stock and, as a result, the reduction of soil quality, as well as accelerating the process of climate change through the release of SOC into the atmosphere. This study was conducted to evaluate potential of different simulation models to map the spatial variability of SOC as affected by land use in a study area in Qarasu watershed in Kermanshah province, west of Iran. Map of sampling points was prepared using the Latin hypercube sampling method. A total of 168 observation points were selected and the soil profile was dug and described in these points. The soil samples were taken in different horizon to determine the SOC content in laboratory. SOC was mapped using kriging geostatistical method in the study area. The SOC changes were simulated using multivariate analysis and machine learning methods including generalized linear model (GLM), linear additive model (LAM), cubist, random forest (RF), and support vector machine (SVM) models. Comprehensive measurement data is utilized to develop and validate the predictive models. Predictor variables included 16 topographic variables as well as two vegetation, six parent material, and four climatic variables. In-depth statistical analyses are proposed to evaluate the proposed models performance. The results showed that the SOC content ranged from 0.19 to 8.44 percent in different land uses. The spherical variogram model with MAE = 0.41 best fits to interpolate and map SOC using ordinary kriging in different land uses. The LAM method was estimated wider range of the SOC change (SOC = 0.18–4.82%) among different simulation model. However, the RF model (R2 = 0.64 and RMSE = 0.58%) was the most accurate in predicting SOC quantity comparing the other simulation models. It can be used as a reliable simulation model to predict SOC variability in the study area and other similar semiarid regions of West Asia in different land uses. Among the different predictor variables, the parent material’s intrinsic soil properties and topography variables had the greatest effect in predicting soil organic carbon variability.

УДЕЛЬНАЯ АКТИВНОСТЬ И ОСОБЕННОСТИ ВЕРТИКАЛЬНОГО РАСПРЕДЕЛЕНИЯ 137CS В ПОЧВАХ АГРАРНЫХ ЛАНДШАФТОВ ЦЕНТРАЛЬНЫХ РАЙОНОВ КРАСНОЯРСКОГО КРАЯ

The purpose of the study is to determine the migration activity of 137Cs according to the soil profile in agricultural landscapes with additional radioactive contamination. An extensive literature review is provided, reflecting technogenic radioactive contamination of territories, features of 137Cs migration activity on various types of soils and the depth of 137Cs migration along the profile of soils of agrobiocenoses contaminated as a result of radiation accidents on the territory of the Russian Federation. The paper is devoted to assessing the specific activity and determining the vertical migration of 137Cs in soils and agricultural landscapes of the central regions of the Krasnoyarsk Region. Based on a radioecological survey of the territory of the central regions of the region, the author identified agricultural landscapes with additional technogenic pollution. It has been established that the average value of ambient dose equivalent rate (ADR) in the agricultural landscapes of the region corresponds to the range of values characteristic of the territory of the Krasnoyarsk Region. In an agricultural landscape without radiation load, the density of soil contamination with 137Cs s was 0.04 Ku/km2, in landscapes with additional technogenic pollution – 0.78; 1.84 Ku/km2. The value of the specific activity of 137Cs in the soils of hay-pasture agrobiocenoses of agricultural landscapes with technogenic pollution exceeds the average for the Krasnoyarsk Region, according to regional standards “Permissible values of radiation pollution of the natural environment in the Krasnoyarsk Region”, corresponds to the “registration” level. The vertical distribution of 137Cs in soils of agricultural landscapes with anthropogenic load indicates the predominant accumulation of technogenic radionuclides in the 10–20 cm layer. In the observation zone of the Federal State Unitary Enterprise Mining and Chemical Combine, the depth of migration of 137Cs in the soils of agrobiocenoses with additional technogenic load is 40 cm, which confirms the assumption that some areas have been contaminated as a result of the previous activities of the enterprise.

Probabilistic stratigraphic modeling from sparse boreholes based on deep learning

The safety and efficiency of geotechnical design and construction heavily rely on the stratigraphic model from site investigation. However, inherent intricate stratigraphic variations and sparse borehole data introduce uncertainty and pose challenges for subsurface stratigraphy modeling. This paper proposes a hybrid neural network of Pixel Bi-directional Long Short-Term Memory (Bi-LSTM) with dense conditional random field (CRF) for probabilistic stratigraphic modeling using limited site-specific boreholes. The proposed method provides a powerful and useful tool for effectively capturing complex spatial dependencies and probabilistic evaluation of subsurface stratigraphic uncertainty. Given the hierarchical and heterogeneous characteristics of layered soils, a novel soft-boundary label relaxation (Soft-BLR) technique is developed to vectorize stratigraphic variables. Within the framework of the proposed hybrid neural network, the Pixel Bi-LSTM is combined with the Monte Carlo dropout to efficiently approximate the complex stratigraphic distribution. By defining a linear combination of Gaussian kernels, the dense conditional random field is established in the predicted soil profile to further minimize uncertainty around stratigraphic boundaries. Furthermore, this model is illustrated by the synthetic case and applied to two real cases from Hong Kong. The proposed method can not only derive a more reasonable stratigraphic model but also map the spatial uncertainty.

ВЛИЯНИЕ ОБРАБОТКИ ТОРФЯНИСТО-ГЛЕЕВОЙ ПОЧВЫ НА ВОДНО-ТЕПЛОВОЙ РЕЖИМ И УРОЖАЙНОСТЬ КАРТОФЕЛЯ В УСЛОВИЯХ СЕВЕРНОГО ЗАУРАЛЬЯ

The purpose of the study is to establish the influence of the depth of plowing of peaty-gley soil on the water and temperature regime, and potato yield. A study of the influence of the depth of cultivation of peaty-gley soil on the water-thermal regime and potato yield was carried out in 2014–2016 in the Tarmanskoye lowland swamp in the forest-steppe zone of the Northern Trans-Urals. As a result of the study, a decrease in moisture capacity in a 0.2-meter layer of peaty-gley soil was established by 17.2–34.7 %. This was facilitated by the enrichment of mineral soil during plowing to a depth of 0.27–0.37 m. At a depth of 0.2–0.4 m, moisture capacity increases by 5.5–13.4 % due to the organic matter of peat. Deep plowing (0.37 m) ensured an increase in moisture reserves in the 0.5 m layer from 0.6 HB at the control (0.22 m) to the upper limit of the optimum (0.9 HB). In the lower part of the soil profile (0.6–1.0 m), moisture reserves did not depend on the plowing depth. The maximum changes in soil temperature were established in plots with plowing of 0.15 m of mineral soil, where it increased on average by 0.6–0.7 °C over the years of study. The most significant differences in soil warming were noted in the first half of the growing season (1.1–1.2 °C). Potato yield on peaty-gley soil depends on the plowing depth: 0.22 m – 26.69 t; 0.27 m – 29.15 t (9.2 %); 0.32 m – 30.11 (12.8); 0.37 m – 32.45 t/ha (21.6 %). The starch content in potato tubers of the Nevsky variety increases compared to the control at a plowing depth of 0.37 m from 11.3 to 13.4 %.

Pedological Approach for Soil Carbon Stock Estimating in Gayo Highland Coffee Plantations, Aceh-Indonesia

Background: Soil carbon stocks (SCS) play a key role in regulating soil fertility and global climate. Determining the amount of SCS through a pedological approach is still limited, while the amount of SCS in highland areas based on elevation is still debated, also the role of elevation-slope combinations on SCS is not well known. This research aims to determine the amount of SCS in each soil horizon, elevation, slope position and also the effect of elevation and slope position on SCS. Methods: A total of 46 undisturbed and disturbed soil samples were collected in each pedogenic horizon from 12 soil profiles at four elevation levels ie 700-715; 1000-1060; 1300-1351; 1600-1616 meter above sea levael (m.a.s.l.) and three slope positions (foot, middle, and upper of slope) in Gayo highland Arabica coffee plantation fields. Result: The results showed that SCS of soil horizons in Arabica coffee plantations in the Gayo highlands varied from 5.97 to 84.56 MgC.ha-1, with SCS of the upper horizons being higher than those of the lower horizons. The amount of solum SCS from the soil profile also varied from 73.91 to 218.25 MgC.ha-1. Based on the elevation, the highest mean amount of SCS of the solum was 157.35 MgC.ha-1 which was found at the elevation of 1600-1616 m.a.s.l, whereas the mean amount of solum according to the slope position was 167.34 MgC.ha-1 which was found on the foot of slope. Elevation and slope position significantly increased the SCS with the highest value found in the combination of 1000-1060 m.a.s.l, and foot of slope.

Depth dependence of soil organic carbon additional storage capacity in different soil types by the 2050 target for carbon neutrality

Abstract. Land planning projects aiming to maximize soil organic carbon (SOC) stocks are increasing in number and scope, often in line with the objective to reach carbon neutrality by 2050. In response, a rising number of studies assesses where additional SOC could be stored over regional to global spatial scales. In order to provide realistic values transferrable beyond the scientific community, studies providing targets of SOC accrual should consider the timescales needed to reach them, taking into consideration the effects of C inputs, soil type, and depth on soil C dynamics. This research was conducted in a 320 km2 territory in north-eastern France, where eight contrasted soil types have been identified, characterized, and mapped thanks to a high density of fully described soil profiles. Continuous profiles of SOC stocks were interpolated for each soil type and land use (cropland, grassland, or forest). We defined potential targets for SOC accrual using percentile boundary lines and used a linear model of depth-dependent C dynamics to explore the C inputs necessary to reach those targets within 25 years. We also used values from the literature to model C input scenarios and provided maps of SOC stocks, maximum SOC accrual, and realistic SOC accrual over 25 years. SOC stocks and maximum SOC accrual are highly heterogenous over the region of study. Median SOC stocks range from 78–333 tC ha−1. Maximum SOC accrual varies from 19 tC ha−1 in forested Leptosols to 197 tC ha−1 in grassland Gleysols. The simulated realistic SOC accrual over 25 years in the whole region of study was one-fifth of the the maximum SOC accrual. Further consideration of depth-dependent SOC dynamics in different soil types is therefore needed to provide targets of SOC storage over timescales relevant to public policies aiming to approach carbon neutrality by 2050.

Pedogenic carbonate as a transient soil component in a humid, temperate forest (Michigan, USA)

Abstract In humid, continental Michigan, we identified pedogenic carbonate in a soil profile developed on glacial drift sediments, as rinds, rhizoliths, and filaments (at depths >50 cm). Given that the climate setting is unusual for pedogenic carbonate, we investigated its formation with environmental monitoring and isotope analyses of carbonate (δ13C, δ18O, Δ47, and 14C) and waters (δ18O and δ2H). We found covariation in δ13C and Δ47 amongst the carbonate types (rhizoliths, rinds, filaments, bulk soil, and detrital clasts), and 14C ages of rinds that predate plausible formation ages. The δ13C and Δ47 values of the bulk carbonate and some of the pedogenic morphologies are not fully compatible with pedogenic formation in the modern environment. The δ18O data from precipitation and river waters and from carbonates are not uniquely identifying; they are compatible with the soil carbonate being pedogenic, detrital, or a mix. We conclude that the soil carbonate is likely a physical mix of pedogenic and detrital carbonate. Pedogenic carbonate is forming in this humid setting, likely because seasonal cycles in soil respiration and temperature cause cycles of dissolution and re-precipitation of detrital and pedogenic carbonate. The pedogenic carbonate may be a transient feature as carbonate-rich till undergoes post-glacial chemical weathering.

Monitoring nutrient and beneficial elements in the topsoil: the function of weathered background and later surficial process on their distribution.

Monitoring the distribution of nutrient and beneficial elements (NBEs) in topsoils is important for assessing agricultural and ecological risks and for promoting human health. In order to understand their distribution effectively, it is critical to clarify their sources and main influence factors. In this study, a total of 272 topsoils and 46 soil parent material samples and some samples along 4 vertical profiles were collected in the Mentougou area of Beijing. Then, 12 NBEs were determined for each sample, including elements of N, P, S, Se, Zn, Mn, V, Ge, K, F, Ca, Mg. The mean content of 12 NBEs was statistically calculated and their spatial distributions were mapped. NBEs in topsoils were mainly influenced by the background of parent materials and the subsequent surficial processes. To address the weathered background, the study area was divided into 4 units, including igneous rocks, clastic rocks, carbonate, and loess units. For each unit, cluster analysis was performed to identify the relationship between 12 NBEs in topsoils. Furthermore, the changes in characteristics of 12 NBEs along vertical soil profiles of 4 units were individually analyzed by comparison with the weathered background. Therefore, the main factors influencing the distribution of 12 NBEs in topsoils were identified respectively. According to each element's main influencing factors, 12 NBEs were divided into 5 groups. The main influencing factors were same for elements in each group but different each other for 5 groups. Besides the weathered background, the distribution of NBEs in topsoils was significantly influenced by subsequent surficial processes, such as organic enrichment, leaching, and calcification. In addition to these natural surficial processes, the influence of human activities, a special surficial process, was also observed on the distribution of N, P, S, and Zn in topsoils in farming areas by interpreting normalized difference vegetation index (NDVI). This study provides a semi-quantitative method to determine the role of weathered background and subsequent surficial processes in the distribution of NBEs in topsoils, which helps to understand the current situation and evolution trend.

Maintaining Silage Corn Production Under Sodic Irrigation Water Conditions in a Semi-Arid Environment

The Zayandeh-Rud watershed of Iran has had water scarcity for decades, giving rise to pressures toward limiting water allocation for the agriculture sector. Marginal waters can be an alternative source for irrigated agriculture in water-scarce regions if adequately managed. One of the critical hazards for sustainable agriculture and the environment is the accumulated salinity–sodicity problem as a consequence of irrigating with unconventional waters. Applying additional water beyond the crop water requirement, known as leaching application, has been suggested as a solution to this problem. A physical model was built to investigate the effects of the severe sodicity and salinity conditions of irrigation water by creating 250 mm diameter soil columns (27 columns) filled with sandy clay loam soil. The severity of the irrigation water’s sodicity (sodium adsorption ratios (SAR): 5.27, 16.56, and 28.57) and its interactions with various leaching fractions (0%, 15%, and 30%) on critical soil chemical characteristics and corn yield were studied. Implementing a 30% leaching fraction reduced the SAR and salinity in the soil’s first layer (0–10 cm) when irrigating with saline–hyper-sodic water (SAR = 28.57 and ECiw = 9 dS/m). However, an elevated level of sodicity accumulation in the soil profile was observed, emphasizing the importance of adding calcium and magnesium amendments during the irrigation season. A noticeable increase in the efficiency of leaching applications in reducing accumulated salts and the sodicity level in the corn rootzone was detected with higher levels of irrigation water sodicity. The reduction in the accumulated salinity and sodium in the first soil layer due to implementing a 30% leaching fraction resulted in a 223.3% increase in the total biomass of silage corn. Applying a 30% leaching fraction also increased the corn biomass by 58% and 114.56% when irrigating with waters with 5.57 and 16.56 SAR values. The effectiveness of a 15% leaching fraction for enhancing the soil and crop conditions was significantly lower than that of the 30% leaching fraction. Nevertheless, in case of unavailability of sufficient water supply for irrigation purposes, applying a 15% leaching fraction could mitigate the consequences of sodic water irrigation. The results demonstrate that in the absence of the proper calcium amendments, the implementation of leaching management could still be effective in enhancing corn production under sodic water irrigation conditions.

Simulation of pesticide transport in 70-m-thick soil profiles in response to large water applications

Simulation of pesticide transport in 70-m-thick soil profiles in response to large water applications

Soil Organic Carbon and Nitrogen Storage and Distribution in the Agricultural Soils as Affected by Soil Depths and Inundation Land Types

A study was initiated on soil organic carbon (SOC) and total nitrogen (TN) storage and their distribution as affected by soil depths and inundation land types selecting ideal two catena across eight soil profiles up to the depth of 120 cm in the Brahmaputra and the Ganges alluviums. Soil organic carbon and TN storage is higher in the surface soil depth than the other soil depths. The contents and distribution of SOC and TN in all the soil depths varies significantly. Moreover, inundation land types and soil depths exhibited a significant effect (p<0.001) on SOC and TN storage. Soil organic carbon and TN storage were higher in the lowland (LL) and medium lowland (MLL) sites than that in the highland (HL) and medium highland (MHL) sites across the alluviums, which indicates that the topographic variability as well as their water recession conditions which ultimately focuses on SOC loss or sequestration. The Brahmaputra alluvium possesses higher SOC and TN storage than the Ganges alluvium which may be due to the variability of their land use and local management practices. Proper emphasis should be given on sub soil depths and inundation levels in formulating any agricultural policy planning. J. Asiat. Soc. Bangladesh, Sci. 50(1-2): 137-152, June-December 2024

Effects of digestate application, winter crop species and development on dissolved organic matter composition along the soil profile

Effects of digestate application, winter crop species and development on dissolved organic matter composition along the soil profile

Molecular mechanisms and biomineralization processes of ferromanganese nodule formation: Insights its effect on nutrient imbalance and heavy metal immobilization in native soil profiles

Molecular mechanisms and biomineralization processes of ferromanganese nodule formation: Insights its effect on nutrient imbalance and heavy metal immobilization in native soil profiles

Ecological and hygienic assessment of natural hydrocarbons content in arctic and subarctic soils of the European North-East of the Russian Federation

Introduction. The study of natural levels of hydrocarbons (HCs) content in soils is an urgent task, the solution of which will help to objectively assess the level of anthropogenic contamination of soils and timely limit the processes of extraction, processing, and transport of petroleum HCs. The analysis of HCs content in background soils will make it possible to reveal the regularities of their accumulation in the Arctic and Subarctic regions, taking into account the landscape and geochemistry of the areas. Materials and methods. Representative samples of the main soil types were selected using the route method, taking into account the peculiarities of soil cover formation in different landscapes. The concentration of HCs in the samples was determined in hexane extracts based on their fluorescence intensity. Results. The studies have shown that HCs accumulation and distribution in soil profiles are influenced by various factors such as soil genesis, relief, organic matter content, and physical clay. The highest HCs concentrations were observed in soils of accumulation landscapes on loamy sediments (Retisols), and the lowest in soils of eluvial landscapes on sands (Podzols). HCs profile differentiation is also more pronounced on loamy soils and less so on sandy soils. The results obtained allowed updating the existing database and mapping the HCs distribution in the background soils of the European Arctic and Subarctic. Limitations. The limitation of the study is related to the fact that only background soils at a distance of at least 1 km from railways and motorways, 5 km from settlements and 10 km from industrial plants were sampled. In this paper, only natural HCs were analysed, without considering other classes of organic and inorganic compounds. Conclusion. The data on the concentration of natural HCs in different background soils of the European North-East of Russia with respect to landscape-geochemical peculiarities have been obtained. The results provide an opportunity to assess the possible level of contamination of soils of the European Arctic and Subarctic. The HC content in organogenic horizons is shown to be characterised by a high accumulation capacity and act as an integral indicator of the aerotechnogenic load on the soil cover. Threshold values of HCs concentration are proposed for the studied soils, which are in a wide range from 3.4 to 40 mg/kg and can be used for ecological and hygienic assessment of high latitude soils.

Computer simulation of the soil water regime under an apple orchard in a mountainous area (using the example of the leached chernozem of the experimental agricultural station Gorno-Altaiskoe)

Relevance. Progressive degradation of farmland soils – erosion, salinization, desertification. Aim. To establish features of water-physical properties of leached chernozem under an apple orchard and associated patterns of soil profile moisture distribution in summer period when precipitation deficiency observed. Methods. Moisture content in soil horizons was determined by the gravimetric method. To determine the granulometric composition of soils, the pipette method was used. The soil bulk density was determined by the cutting ring method. For solid phase density determination the pycnometric method was used. The method of graphic interpolation was used for transition the soil texture classification from Russian to international one. Water infiltration modeling into the soil profile was carried out using the HYDRUS-1D program. The parameters of approximating of the water retention curve of soils by the Van Genuchten equation were obtained by the calculation method of pedotransfer functions «Rosetta Lite» of the RETC program, using data on soil density and soil texture. Results. It has been established that the upper well-structured horizons of leached chernozem under an apple orchard have a greater water-holding capacity; their water-retention curves are more flattened. The water retention curve of the more structureless B2k horizon, the soil texture of which is dominated by sandy fractions, is shifted towards lower humidity. During hot and dry summer period the moisture deficiency in the soil was noted only in the upper twenty-centimeter soil column (14 mm). The moisture of the lower horizons, where the bulk of tree roots are concentrated, is satisfactory. The model demonstrates the smallest discrepancies with the moisture values measured during the soil reclamation experiment one day after the start. The downward moisture penetration into the lower soil layers is prevented by low pressure in the clayey A and AB horizons. Selection of input parameters and debugging of the model based on experimental data allows it to be used to simulate further processes occurring in the soil. It was revealed that the formation of positive (upward) water flows, which ensure the “pull-up” of salts and substances from the lower part of the profile to the upper layers during dry periods of the year, has a significant impact on moisture distribution in the chernozem under the apple orchard.

Maize monoculture supported pre-Columbian urbanism in southwestern Amazonia.

The Casarabe culture (500-1400 CE), spreading over roughly 4,500 km2 of the monumental mounds region of the Llanos de Moxos, Bolivia, is one of the clearest examples of urbanism in pre-Columbian (pre-1492 CE) Amazonia. It exhibits a four-tier hierarchical settlement pattern, with hundreds of monumental mounds interconnected by canals and causeways1,2. Despite archaeological evidence indicating that maize was cultivated by this society3, it is unknown whether it was the staple crop and which type of agricultural farming system was used to support this urban-scale society. Here, we address this issue by integration of remote sensing, field survey and microbotanical analyses, which shows that the Casarabe culture invested heavily in landscape engineering, constructing a complex system of drainage canals (to drain excess water during the rainy season) and newly documented savannah farm ponds (to retain water in the dry season). Phytolith analyses of 178 samples from 18 soil profiles in drained fields, farm ponds and forested settings record the singular and ubiquitous presence of maize (Zea mays) in pre-Columbian fields and farm ponds, and an absence of evidence for agricultural practices in the forest. Collectively, our findings show how the Casarabe culture managed the savannah landscape for intensive year-round maize monoculture that probably sustained its relatively large population. Our results have implications for how we conceive agricultural systems in Amazonia, and show an example of a Neolithic-like, grain-based agrarian economy in the Amazon.

Distribution Characteristics and Ecological Risk Assessment of Pharmaceutical and Personal Care Products (PPCPs) in Different Water Sources, Soil Profiles and Rice Crops Under Rural Domestic Reclaimed Water Irrigations

Pharmaceutical and personal care products (PPCPs) have the characteristics of environmental persistence, bioaccumulation, and high toxicity, and their environmental behavior has attracted the attention in the process of sewage resource utilization in recent years. In this study, four kinds of irrigation water sources (the primary treated water of rural domestic sewage (RDS) R1, the secondary treated water of RDS R2, the ecological pond purified water R3 and river water (CK) and three kinds of water level regulations (low-, medium- and high-water level regulation of W1, W2, and W3) were set to study the migration law of 22 kinds of PPCPs in rural domestic reclaimed water (RDRW), paddy soil and rice plants. Five rice plant and soil samples were, respectively, taken from each treatment using the five-point sampling method in this study. The samples were pretreated using the solid-phase extraction (SPE) method. After pretreatment, PPCPs were quantitatively analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The objective of the research was to explore the distribution patterns in soil-crop system, further evaluating the ecological risks of PPCPs in soil and rice plants under the regulation of RDRW irrigation. The results showed that 21 kinds of PPCPs were detected in RDRW and CK, among which the concentration of ofloxacin (OFL) was the highest. Fifteen kinds of PPCPs were detected in paddy soil and rice grain, among which atenolol (ATE) content was relatively higher. Compared with CK, the total content of PPCPs in the soil surface layer (0–20 cm) was the highest under RDRW irrigation. The impacts of different water level regulations on the PPCPs content between soil profile and rice grain were not significant. In addition, the reduction rate of 15 PPCPs in soil under RDRW irrigation was greater than 85%, and the bio-concentration factor (BCF) of PPCPs in rice grain was less than 0.1. The ecological risk assessment showed that ibuprofen (IBU) was a high-risk substance pollutant, triclocarban (TRIC) was a medium-risk pollutant, ofloxacin (OFL) was a low-risk pollutant, while the other PPCPs were all risk-free pollutants under RDRW irrigation. Therefore, R3 water sources can be selected for direct agricultural irrigation, while direct irrigation of R1 and R2 water sources should be avoided.

SURFACE EROSION AND INFLUENCE THEM ON THE PROPERTIES AND PRODUCTIVE CAPACITY ON THE SLOPING LANDS IN THE SOUTH-WESTERN AREA OF OLTENIA

Within the south-west zone of Oltenia there are large surfaces occupied by soils affected by surface erosion. Among them, there are antrosol erodic encountered on the sloppy slopes with 3- 35% declination, in which conditions the accelerated erosion led to the removal of the most part of the soil profile in such a way that the remaining profile does not identify the former soil profile.The present researches have been taken into consideration an erodic arch anthrosol and erodic cambic anthrosol , both with a low humus content and mineral nutrients and a low natural fertility.

Shifts in fungal communities drive soil profile nutrient cycling during grassland restoration.

Soil microbial diversity and community life strategies are crucial for nutrient cycling during vegetation restoration. Although the changes in topsoil microbial communities during restoration have been extensively studied, the structure, life strategies, and function of microbial communities in the subsoil remain poorly understood, especially regarding their role in nutrient cycling during vegetation restoration. In this study, we conducted a comprehensive investigation of the changes in the soil microbial community, assembly process, life strategies, and nutrient cycling functional genes in soil profiles (0-100 cm) across a 36 year chronosequence (5, 15, 28, and 36 years) of fenced grassland and one grazing grassland on the Loess Plateau of China. Our results revealed that soil organic carbon increased by 76.0% in topsoil and 91.6% in subsoil after 36 years of restoration. The bacterial communities were influenced primarily by soil depth, while the fungal communities were highly sensitive to the years of restoration. Microbes in the subsoil recovered faster, and the microbial community structure and functional genes in the soil profiles gradually became more consistent following restoration. In addition, we observed a transition in microbial life history strategies from a persistent K-strategy to a rapid r-strategy during restoration. Notably, the fungal community assembly process played an important role in changes in nutrient cycling genes, which were accompanied by increased carbon fixation and nitrogen mineralization function. Overall, our findings provide several novel insights into the impact of changes in the fungal community on soil nutrient cycling in the soil profile during vegetation restoration.IMPORTANCEOur study revealed that microbes in the subsoil recovered faster than those in the topsoil, which contributed to the reduction in differences in microbial community structure and the distribution of functional genes throughout the soil profile during the restoration process. Importantly, the assembly of fungal communities plays a pivotal role in driving changes in nutrient cycling genes, such as increased carbon fixation and nitrogen mineralization, alongside a reduction in carbon degradation gene abundance. These alterations increase soil organic carbon and nutrient availability during restoration. Our results increase the understanding of the critical role of fungal communities in soil nutrient cycling genes, which facilitate nutrient accumulation in soil profiles during grassland restoration. This insight can guide the development of strategies for manipulating fungal communities to increase soil nutrients in grasslands.

Deep soil contributions to global nitrogen budgets

Previous estimates of deep soil inorganic nitrogen (N) reservoirs have been mainly limited to desert soils, however, recent evidence suggests that deep soil pools are far more ubiquitous across biomes and therefore may be important for global N budgets. Here, we used observations from 280 deep soil profiles (2-205 m) across a wide array of ecosystem and land cover types to seek insight into the full geospatial variation of deep soil nitrate. Using a random forest machine learning approach we estimate a total deep soil nitrate pool of 15.2 ( ± 1.1 SD) Pg of N. When included in the global soil N pool, our estimates of deep soil N increase the global N storage budget by 16%. Estimating these deep soil N pools continues to add to our understanding of soils as a fate for anthropogenically fixed N, and the critical role that deep soils play in our biosphere.