Silt Content Research Articles

Assessment of Soil Physical and Chemical Properties among Urban and Peri-Urban Forests: A Case Study from Metropolitan Area of Brasov

Cities are affected by the impact of rapid urbanization on changes to soil properties. The aim of this study was to assess the physical and chemical properties of the soil of urban and peri-urban forests and to define which soil property is more significant for these two types of forests. The research took place in urban and peri-urban forests in the metropolitan area of Brasov, Romania. Among the properties determined were: particle size distribution, reaction, soil organic matter content, and the base saturation degree. As supplementary data, for plots from urban forests, the heavy metal content was determined. The results revealed that soils from urban forests had an alkaline reaction and the ones from peri-urban forests had a moderately acid reaction. The soil from the peri-urban plots was sandier and the other ones were more clayey. Testing the differences between the forests led to significant differences in the case of seven properties of which we mentioned pH and sand and clay content. Using PCA, the most significant and important soil properties for urban forests were the sum of basic exchangeable cations, cation exchange capacity, soil organic matter, and silt and clay contents. This study is more relevant in light of the EU Soil Strategy, which sets out a framework and concrete measures to protect and restore soils.

Effect of Aeolian Sand Powder Addition on Frost Resistance of Concrete Pavement.

In order to solve the problem of exploring the freeze-thaw characteristics of modified aeolian sand mixed with cement and silt, the authors propose a freeze-thaw cycle test of modified aeolian sand under the condition of mixing 5% cement and silt with different contents. In this experiment, under freeze-thaw conditions, its intensity decay and mass volume change law and the changes of freeze-thaw characteristics were comprehensively characterized by multiple indicators. The result shows that, after two freeze-thaw cycles, the compressive strength and peak strain of the improved aeolian sand were positively correlated with the silt content. With the increase of the number of freeze-thaw cycles, the compressive and antidestruction capacity of the improved aeolian sand with high silt content and low silt content decreased significantly. 15% silt content improves the structural stability of aeolian sand. It is proved that the authors' experiment can intuitively and effectively reflect the change law of soil strength after freezing and thawing of such improved aeolian sandy soil, which has displayed significance.

Mechanical properties and microstructure evolution of Malan loess

At the top of the Pleistocene Loess-Paleogene sequence, Malan loess is the main substrate for industrial production, daily life, and construction activities. The Malan loess at different depths from the Chinese Loess Plateau was used as a test material to gain insights into its mechanical properties and microstructure evolution. The direct shear test and, collapse test were conducted to study the mechanical properties of the original loess. The microstructure evolution was displayed by the scanning electron microscopy (SEM) imaging and particle size distribution. Meanwhile, The microscopic properties of the loess pores were quantified by an Image-Pro Plus (IPP) software. Pearson's correlation was used to analyze the mechanical properties of the loess at different depths by selecting basic physical properties and microstructural parameters. The results show that with increasing depth, the Malan loess gradually becomes denser, the pore area ratio and the proportion of macropore area decrease, and the pore shape tends to be flat. However, the particle size varies slightly. Furthermore, the cohesion of the Malan loess is positively correlated with the dry density, liquid limit, and clay content, while negatively correlated with the silt content and macropore area ratio. There are positive correlations between the internal friction angle and the silt content and macropore area ratio, and a negative correlation between the clay content and water content. The silt content and macropore area ratio play a positive role in the collapse coefficient, while the dry density, liquid limit and clay content exhibit a negative impact on the collapse coefficient. Finally, a schematic diagram of the basic physical properties and microstructure evolution of the original loess at different depths was established. These findings provide a guidance for construction and conservation of related loess engineerings.

Assessment of Hydrobiological and Soil Characteristics of Non-Fertilized, Earthen Fish Ponds in Sindh (Pakistan), Supplied with Seawater from Tidal Creeks

In this study, the suitability of four earthen, seawater ponds located in the Thatta district of Sindh province (Pakistan) was evaluated for the purpose of semi-intensive mariculture, which remains to be a severely underdeveloped branch of the agricultural industry of this populous Asian country. Initial pond soil probes were promising, as they showed a high clay and silt content. Monthly water samples were obtained in the year 2019 (from January to December), which allowed for the monitoring of water parameters, as well as the identification and relative quantification of planktic populations. As a result, the monthly variations of basic water parameters were found within optimal ranges for planktic growth (water temperature, salinity, pH, transparency, and dissolved oxygen). Bacillariophyta was the largest phytoplanktic group, with the most dominant species being Sundstroemia setigera, followed by the cyanobacteria Oscillatoria limosa. Copepoda was the most numerous group of identified zooplankton, followed by tintinnids and foraminiferans. Total suspended solids (TSS) calculations indicated up to nine-fold month-to-month reductions of planktic biomass, observed in the form of diminishing Bacillariophyta (December) and Copepoda (June and December). In conclusion, the studied ponds appear to be suitable for semi-intensive mariculture activity due to the abundance of diverse planktic forms (mainly Copepoda—preferable natural food for commercially important fish species), which was achieved even without the use of fertilizers. However, significant drops of planktic biomass may still occur, which implies the need for regular water monitoring procedures, which would in turn allow fish producers to implement periodical adjustments to the administered feeding rates with artificial diets.

Variability of soil quality indicators along with the different landscape positions of Choke Mountain agroecosystem, upper Blue Nile Basin, Ethiopia

Understanding the variability of soil quality indicators across topographic positions and agroecosystems (AES) is critical for improving soil fertility, productivity, and environmental sustainability. This study evaluates the variability of soil quality indicators along with the different landscape positions (upper, middle, and lower slopes) among the five AES of the Choke Mountain watershed in the upper Blue Nile Basin. A total of forty soil samples were gathered from Choke Mountain's five AES, upper, middle, and lower landscape positions. Principal component analysis (PCA) was used to determine the minimum datasets (MDS) from fourteen soil quality indicators. Using multivariate analysis of variance (MANOVA), the variability of soil quality indices among AES of the Choke, as well as variation with landscape positions, was investigated. The interaction effect of AES and topo-sequence (AES∗topo-sequence) has a substantial effect on three soil quality indicators, including soil silt content, soil pH, and available phosphorus. The highest mean value of silt content was found in the upper position of the hilly and mountainous highlands (AES 5), while the lowest was found in the lower part of the midland plain with black soil (AES 2). The highest mean pH of the soil was found in the lower part of the lowland and valley fragments (AES 1), and the lowest was in the lower position of the midland plain with brown soil (AES 3). The highest record of available P was found in AES 1's middle position and the lowest in AES 3's upper positions. AES had a significant impact on cation exchange capacity (CEC), and both AES and topography had a significant and distinct impact on organic matter (OM). Thus, the study suggests site-specific solutions to improve agricultural productivity and ease the constraints associated with each soil in each topo-sequence and AES.

Effects of biological crusts on soil organic carbon in sandlands under a precipitation gradient

Biological crusts (Biocrusts) are important surface active coverings in arid and semi-arid regions, which affect the content of soil organic carbon (SOC), SOC labile fractions and stability of SOC through photosynthetic carbon fixation. At present, studies on the variation characteristics of SOC, SOC labile fractions and the stability of SOC in biocrusts are rather limited. In this study, two types of typical biocrusts (moss crusts and algae crusts) were selected along a precipitation gradient from northwest to southeast in the Mu Us Sandland (straight line distance 188 km) by measuring soil organic carbon (SOC), soil microbial biomass carbon (MBC), water soluble carbon (DOC), particulate carbon (POC), easily oxidizable carbon (ROC). We aimed to explore the effects of biocrusts on the stability of SOC and carbon decomposition across the precipitation gradient. Results showed that:1) Two types of biocrusts significantly increased the contents of SOC, MBC, DOC, POC, ROC and stability of SOC. Moss crusts increased SOC contents by 1.6 to 2.6 times as that of algae crusts. 2) The lowest SOC contents of the two types of biocrusts were 6.43 g·kg-1 and 14.50 g·kg-1 respectively, which showed an increasing trend with increasing precipitation along the gradient. 3) With the increases of precipitation, the decomposition time of moss litters gradually decreased. The decomposition coefficient of moss litters during the study period (From July to Feb-ruary of the next year) ranged from 0.010 to 0.014, which was significantly lower than that of vascular plants. The carbon release of moss litters from northwest to southeast was 8.09, 10.89, 12.88 g·kg-1, respectively. 4) Results of canonical correspondence analysis showed that water vapor partial pressure, actual evapotranspiration, annual average temperature, subsurface short-wave radiation, potential evapotranspiration and vapor pressure difference were the key climate factors affecting the content of SOC and its active components. Silt content was the main soil factor affecting the content of SOC and its active components.

Landslide susceptibility modelling in Nyahode and Buzi sub-catchments of Zimbabwe

Abstract Landslides are natural hazards that have different susceptibility across landsurface terrains and are mostly triggered by high rainfall intensity. Cyclone Idai, which affected the Eastern Highlands of Zimbabwe in 2019, resulted in at least 634 deaths, and over 300 missing people due to landslides and floods, necessitating investigations to understand hydrometeorological hazards in the area. This study aimed at modelling landslide susceptibility using field and remote sensing data in Nyahode and Buzi sub-catchments. The mapped landslide inventory was used in the building and validation of the landslide susceptibility model. A geostatistical approach was used for landslide susceptibility model building with 11 landslide conditioning factors: slope degree, slope aspect, altitude, lithology, land use/land cover, distance from the river, Normalized Difference Vegetation Index, topographic wetness Index, and soil clay content, soil sand content, and soil silt content. The landslide susceptibility map was categorized into four classes, namely low, moderate, high, and very high. The Receiver Operating Characteristic curve used to validate obtained landslide susceptibility. Results show a frequency success rate of 0.85 and a frequency predictive rate of 0.82 indicating a very good accuracy in the identification of landslide susceptibility areas. The utilized method provides affordable, faster, practical, and more reliable results useful in land use planning, water resources, and disaster risk management as well as catchment protection actions to reduce the impact of landslide hazards.

Environmental Changes and Geomorphological Factors Influencing the Sediment Flux to a Coastal Lake Spanning the Deglacial- Early Holocene Period in East Antarctica

Abstract The geomorphological settings of the lakes in the coastal oases of East Antarctica play a significant role in the lake's response to the local and regional environment. A 63-cm radiocarbon-dated sediment core spanning between 18.7 and 7.2 cal ka BP was retrieved from Discussion Lake, Larsemann Hills of East Antarctica in order to understand the pathways of sediment transport and deposition and the mechanisms involved in response to changing environmental settings. This was achieved by analyzing the sedimentary sequence of this coastal lake for its grain size (sand-silt-clay) and organic matter content variations. Two cluster zones were identified viz., LZ1 (18.7 to 8.2 cal ka BP) and LZ2 (8.2 to 7.7 cal ka BP). LZ1 was dominated by fine-grained sediments (clay-silt), indicating wind and low meltwater influx influenced deposition of higher silt content. In addition, the lake during this period was in a moated or partially ice-free phases. On the other hand, coarser grains (sand) were predominant in LZ2 suggesting increased flux of the meltwater to the ice-free lake. Thus, the distinct shift in the sedimentary grains fractions (finer-to-coarser), indicated a change in environmental conditions of the lacustrine system, i.e., from an ice-covered lake to an ice-free lake in response to the regional warming trends and local geomorphological features. Furthermore, the environmental conditions, proximity of the lakes to coast or the ice-sheet, elevation and area, defines the sedimentological characteristics of the lake.

Assessment of physico-chemical parameters of primaeval forest soil in Thanh Chuong District of Nghe An Province, Vietnam

The physicochemical features of soil (PFOS) play an important role in the growth process of flora and vegetative diversity of the primaeval forests. The PFS in the primaeval forest belonging to Thanh Chuong District in Nghe An Province, Vietnam was investigated during 2016–2019 to assess the fertility and productivity status of the soils. To deploy this work, ninety-six soil samples at eight random locations from twenty-four sampling plots represented the upper, middle, and lower of the study area were analyzed for soil texture (ST), bulk density (BD), pH, total nitrogen (TN), total phosphorus (TP), and exchangeable cations (ECs) (K+, Ca2+ and Mg2+). Texturally, the soils were clay loam to sandy clay with average percentages of sands around 41%, silts 19%, and clay 40% while the bulk density of the soils was 0.83–1.41%. The acidic to slightly acidic soil pH (4.014.82) and high TN (0.95 -2.66 g/kg) and TP varies from 0.06 and 0.18 g/kg. Correlation analysis of the physicochemical parameters was conducted using the Pearson correlation test in R programming. Analysis showed that the variation in the texture of silt content among the soil depth was minimal.

The Impact of Salinization and Wind Erosion on the Texture of Surface Soils: An Investigation of Paired Samples from Soils with and without Salt Crust

Wind erosion removes fine soil particles and thus affects surface soil properties, but the existence of a salt crust could prevent wind erosion and protect fine soil particles. Such results referring to wind erosion affecting soil surface textural properties have been reported by many studies. However, it is still not clear whether soil properties differ between salt-crusted soils and adjacent soils without a salt crust in areas experiencing serious wind erosion. Therefore, the objective of this study was to investigate paired samples from salt-crusted and non-crusted surface soils at 23 sites in the Tarim River Basin. The particle size distribution, salt content and composition, and crust thickness and strength were determined. The results of the pooled t-test reveal that, compared with soils without a salt crust, the salt-crusted soils had finer particles (silt + clay), but this difference only occurred in paired soils from the same site, and the silt content showed the largest difference between the paired soils. The salt content and salt crust strength showed great variability, from 88.52 to 603 g·kg−1 and from 0.30 to 5.96 kg·cm−1, respectively, at all sites, but only a weak relationship (R2 = 0.396) between the salt content and crust strength was found, indicating that the salt content was not the only factor affecting crust strength. Our results suggest that wind erosion and salinization cause great soil texture spatial heterogeneity, especially for silt particles in the Tarim River Basin. Variation in salt crust strength can influence dust emissions and must be considered in future management.

Effect of Soil Management and Its Texture on Aggregate Stability Parameters and Wetting Rate

The present study was carried out to evaluate the soil management and soil texture on the structure parameters and soil water wetting rate. Six soil samples of 0-30 cm depth were selected from three different sites in the texture of Clay, loam and Sandy loam in Basra Governorate (Abi Al-Khasib, Madinah and Zubair). Three samples represented the treatment of soil management (soil cultivated with alfalfa crop for 7 years respectively). The other three samples were from the same sites for uncultivated soil (bare soil), with three replicates for each sample. Soil organic matter content, bulk density, mean weight diameter, aggregate stability percentage and water wetting rate were measured. The results showed that the soil management factor had a highly significant effect in raising the values ​​of OM, MWD and WSA%. It was as a general average of 56.337 gm.Kg-1, 0.893 mm,71.33%, respectively, and on the other hand, soil management led to a decrease in the values ​​of 𝛒𝐛 (1.38 Mgm.Kg-1) and WR (0.2522 cm33gm-1 min-1), and its rise in uncultivated soil of 1.51 Mgm.Kg-1, 0.3989 cm33gm-1 min-1, respectively. While the soil texture factor effect that the clay texture had the highest values ​​as the average of OM (34.71 gm.Kg-1), MWD (0.8 mm) and WSA (62.67%), followed by loam and sandy loam, respectively. While a decrease in the values ​​of 𝛒𝐛 (1.325 Mgm.Kg-1 ) and WR (0.265 cm33gm-1 min-1) in Clay soil with a significant difference compared to loam and sandy loam soil, and the interaction between the soil management factor and the increase in its content of silt and clay led to an improvement the soil properties.

Fine Soil Texture Is Conducive to Crop Productivity and Nitrogen Retention in Irrigated Cropland in a Desert-Oasis Ecotone, Northwest China

Agricultural production in oases requires extensive irrigation and nitrogen (N) inputs, which result in a high incidence of non-point-source pollution. Information on how soil texture affects crop productivity and water and N use efficiency is needed to improve N management in oases. A two-year field study with six free-draining leaching pits was set up to quantify soil water content (SWC), drainage, yield, N uptake, soil residual N, N leaching, water-use efficiency (WUE), and N fertilizer-use efficiency (NFUE) on sandy-textured soils in a young oasis field (24 years, YOF) and loam-textured soils in an old oasis field (>60 years; OOF) within an intensive oasis agricultural zone in Northwest China. The results showed that sand content in the YOF was significantly higher than that in the OOF (p < 0.01), while both clay and silt contents in the YOF were significantly lower than those in the OOF (p < 0.01). Soil water storage (SW) in the 0–100 cm soil layer, evapotranspiration water-use efficiency (WUEET) and irrigation water-use efficiency (WUEIrrig) in the OOF were, respectively, 87.1, 23.5, and 24.1% higher than those in the YOF (p < 0.05), and deep drainage in the YOF was 6.2 times higher than that in the OOF (p < 0.01). Maize N uptake and soil N accumulation in the OOF in the 0–100 cm soil layer were, respectively, 33.4 and 10.3% higher than those in the YOF (p < 0.05), and N leaching loss in the YOF was 1.65 times higher than that in the OOF (p > 0.01). Crop yield and NFUE in the OOF were, respectively, 23.9 and 27.2% higher than those in the YOF (p < 0.05). These results indicated that sandy-textured soils with high sand content were not conducive to water and N retention, resulting in lower crop yields and water- and fertilizer-use efficiency in YOF. Therefore, it is imperative that management practices in sandy-textured land promote improvements in soil structure and maintain the long-term productivity of the young cultivated fields.

Evaluation of Pedotransfer Functions for Estimating Soil Water Retention Curve of Ap Horizon Soils for Various Soil Series of Reclaimed Tidal Flat Soil

This investigation was to evaluate the applicability and prediction accuracy of pedotransfer function (PTF) to estimate the water retention curves of Ap horizon soils for five soil series which cannot be directly used to cultivate upland crops other than rice because of their high salinity. Soil water retention curves (SWRCs) were obtained from 150 undisturbed soil samples collected from the Ap horizons of which soil textures were grouped into sandy loam with high contents of sand (>60%) and low clay contents (<10%) and silt loam with relatively high silt content (>60%) and low sand content (<10%). Soil-water retention characteristics between 0 to −50 kPa and −50 to −1500 kPa were measured using the sandbox, kaolin-plate, and pressure chamber methods, respectively. The SWRCs were also estimated by Rawls and Brakensiek PTF (RB-PTF). The measured SWRCs of sandy loam and silt loam were compared against those obtained from RB-PTF. The SWRCs estimated with the modeled data closely fit the measured data of sandy loam and silt loam although saturated volume water content (θs) and residual volume water content (θr) of RB-PTF were higher than those of the measured mean for both soil textures. The air entry point (α) and the steepness of the water-retention curve (n) were higher in sandy loam than those of silt loam. SWRCS estimated by the RB-PTF yielded the best fit of all soil samples from the five series, whereas the MBE values less than zero indicate that θv measured at the water potentials is under-predicted. The r2 values greater than 0.9 for sandy loam and silt loam represent RB-PTF and are suitable for predicting SWRCs in RTFS because the measured data points do not vary around the estimated regression line.

Soil texture and pH exhibit important effects on biological nitrogen fixation in paddy soil

Biological nitrogen fixation (BNF) is an important source of soil nitrogen. However, for dry-wet alternative paddy soil, the combined effects of multiple driving factors, including soil physicochemical properties and the soil microbiome, on BNF are not fully understood. In this study, three types of paddy soil were collected to determine the BNF amount by field-based 15N2 labeling experiments. Soil nitrogen fixing microbiome was analyzed using high-throughput sequencing based on the nifH gene. Random forest analysis, co-occurrence network analysis and hierarchical partitioning were performed to screen the key diazotrophic community and critical soil properties. The results revealed that rice nitrogen acquisition from BNF ranged from 1.62 % to 7.80 %. Three key diazotrophic genera, Rubrivivax, Frankia and Azospirillum, significantly affected BNF. The BNF amount in the 0–1 cm soil layer was significantly higher than that in the 1–15 cm soil layer, which was consistent with the relative abundance of Cyanobacteria. The soil silt content and pH were positively correlated with the BNF amount by mediating the key diazotrophic microbiome. These results indicated that the BNF amount plays an important role in rice nitrogen acquisition and paddy soil nitrogen sources, which might be regulated by soil texture and soil pH.

Transport and targeted binding of Pluronic-coated nanoparticles in unsaturated porous media

The effectiveness of most in situ remedial technologies, including nanoremediation, lies on successful delivery of reagents to a subsurface target treatment zone. Targeted delivery of engineered nanoparticles (NPs) to treat petroleum hydrocarbons present in the unsaturated zone requires an understanding of their transport behaviour in these systems. A series of column experiments explored the effect of initial water saturation, flowrate, input dosage, and porous medium texture on the transport of iron oxide or cobalt ferrite NPs coated with an amphiphilic co-polymer, as well as their targeted attachment to a crude oil zone. As the initial water content increased with a concomitant reduction in air saturation, the degree of tailing present in the NP breakthrough curves (BTCs) reduced, and the mass of NPs recovered increased. Air saturation is positively correlated with the magnitude of air-water interfaces, which provide additional NP retention sites. At a lower injection flow rate, NP retention increased due to a longer residence time and comparatively high air saturation. NP transport behaviour was not sensitive to NP injection dose over the range tested. Increased retention and retardation of the NP BTC was observed in sediments with a higher clay and silt content. NPs coated with a lower concentration of a Pluronic block co-polymer to promote binding were preferentially retained within the crude oil zone. To simulate the asymmetrical NP breakthrough curves observed from the unsaturated systems required the use of a model that accounted for both mobile and immobile flow regions as well as NP attachment and detachment with nonlinear Langmuirian blocking. This model allowed examination of attachment and detachment rate coefficients which captured NP interaction with the porous medium and/or crude oil. It was found that the initial water saturation and flow rate did not have an appreciable impact on the NP attachment rate coefficient, while it increased by ~10× with increasing clay and silt content, and by ~100× in the presence of crude oil, indicating preferential NP attachment within the crude oil zone. As a result of the lower NP polymer concentration coating used to promote increased attachment to crude oil, higher retention was observed near the column inlet and was captured quantitatively by adding a depth-dependent straining term to the model. This retention behaviour represents a combination of irreversible attachment at the air-water interfaces and straining near the column inlet enhanced by the formation of NP aggregates. The detachment rate coefficient decreased with a lower initial water saturation and flowrate, but increased with higher clay and silt content. The findings from this study contribute to our understanding of the transport and binding behaviour of Pluronic-coated NPs in unsaturated conditions and, in particular, the role of initial water content, flowrate and porous medium texture. Demonstrated delivery of NPs to a target zone is an important step towards expanding the utility of NPs as treatment reagents.

Effects of habitat gradient and agro-climatic variation on selected soil physical and chemical properties in the Bale Mountains national park, south-eastern Ethiopia

BackgroundIncreasing evidence suggests that anthropogenic effects are responsible for drastic changes in landscape patterns and ecosystem services. This study aims to assess the effects of landscape change and agro-climatic variation on selected soil physical and chemical properties in the Bale Mountains national park. A combination of stratified and systematic sampling techniques was employed to draw representative soil samples. A total of 72 soil samples (3 agro-climatic zones × 3 land cover types × 2 habitat gradients × 4 replications = 72) at a depth of 0–20 cm were collected for the soil physical and chemical property analysis. A two-way analysis of variance was conducted to determine the level of variation in soil parameters. Tukey’s honest significance difference (HSD) test was used to compare treatment means at a 0.05 level of significance.ResultsThe results suggest that soil parameters differed significantly (p < 0.05) among agro-climatic zones, land cover, and habitat gradients. The soil pH, SOC, TN, AP, CEC and clay content were significantly higher in the lower altitude, natural vegetation and interior habitat, whereas the soil sand and silt content as well as the soil bulk density were significantly higher in the farmland and edge habitat.ConclusionsConservation and restoration priority should be given to those vegetation types and ecosystems that are highly affected by human interferences such as the grassland in the middle altitude, ericaceous land in the higher altitude, and moist forest in the lower altitudes.

Spatial-temporal heterogeneity of environmental factors and ecosystem functions in farmland shelterbelt systems in desert oasis ecotones

Farmland shelterbelt system (FSS) in oasis desert ecotones can effectively improve ecosystem services, especially in fragile agricultural areas. However, the spatial-temporal heterogeneity of its ecological effects still needs further clarity, because the interactions are complex and multiple. Understanding this allows us to know the key practical significance of ecological construction and agricultural management. In this study, four typical patterns of FSS (i.e. two lines pattern, TWLP; four lines pattern, FOLP; five lines pattern, FILP; eight lines pattern, EILP) were selected in a desert oasis ecotone in northern China to assess the distributions at vertical (0–100 cm), horizontal (0–3 H) and temporal (May- October) scales of soil properties, vegetation attributes, microclimates and variations of soil moisture storage (SMS) and soil salt contents (C) during the three growing seasons. The results showed that the major difference in soil properties and vegetation attributes of FSSs are the soil particle composition and canopy size, respectively. In FOLP and EILP, the silt contents were 51.6% and 41.5% respectively. The canopy size ranked from the highest to lowest values as follows: FOLP (8.70 m2) > EILP (6.91 m2) > TWLP (4.64 m2) > FILP (4.47 m2). Compared to the control, all patterns of FSSs registered significant effects on microclimate improvement. The FOLP and FILP achieved the same effects as well as EILP, with less spatial costs. Moreover, the variations of SMS and C were mainly different at the vertical scale. As indicated by the Redundancy (RDA) and variation partitioning (VP) analyses, soil properties played a more important role in reserving soil water and controlling soil salinity than vegetation attributes and microclimates, which the independent influence can explain 48.5% of total influence among all factors. Our results provide an efficient theoretical basis for FSS construction and agricultural water management practices.

Erosion intensity and check dam size affect the horizontal and vertical distribution of soil particles, carbon and nitrogen: Evidence from China’s Loess Plateau

Check dams are effective soil and water conservation structures worldwide that play an important role in preserving sediments containing carbon (C) and nitrogen (N). However, in terms of the depositional characteristics of C and N in check dams, research on the relative effects of erosion intensity and depositional area is limited, hindering our understanding of the fates of eroded C and N. This study compared the horizontal and vertical distributions of soil particles, organic C (OC), and total N (TN) in check dams of various sizes and erosion intensities in the Loess Plateau. The results showed greater variations in the horizontal and vertical patterns of soil particles of smaller check dams and highly serious erosion (erosion modulus = 15040 t km-2 a-1) than those that of larger check dams and strong erosion regions (erosion modulus = 5151 t km-2 a-1). Soil OC and TN contents decreased from the dam body to the gully head, especially in the highly serious erosion region. Notably, the effect of smaller check dam on the vertical distributions of soil OC and TN was more intense than that of the larger check dam in the strong erosion region. In contrast, a minor effect of check dam size was observed in the highly serious erosion region. Moreover, a closer relationship between the distribution of OC and TN with silt content rather than with clay content in check dams was observed, and this relationship was enhanced by an increase in erosion intensity. Overall, the synergistic effects of erosion intensity and check dam size affected the spatial patterns of OC and TN in sediments on the Loess Plateau. Careful consideration of these two factors is beneficial for accurately assessing the C and N fates in depositional areas.

Spectral analysis of soils in the lower course of the Acaraú River, Northeastern Brazil

The objective of this research was to analyze the spectral response of alluvial soils, representative of the coastal plain in the lower course of the Acaraú River, Ceará, Brazil, and to correlate with the granulometry and soil organic matter (SOM) contents, seeking to identify the best method to predict the attributes studied. In four soil profiles (n = 23 soil samples) the sand, silt, and clay and SOM contents were determined and was carried out the mineralogical characterization. Soil samples were submitted to spectral analysis using a spectroradiometer, with spectral range from visible to shortwave to near infrared (350 - 2,500 nm). It was possible to relate the soil attributes such as color, SOM contents, variation in granulometry and even mineralogy aspects, such as types of minerals in the clay fraction, with the spectral reflectance curves. Some spectral interpretations were useful in understanding aspects associated with the genesis of these soils, especially with regard to the formation environment and mineralogy. For the SOM contents, the best estimates were obtained by simple linear regression and higher correlation for the 564 nm spectrum range. Regression methods were efficient in estimating soil attributes, but the study is limited to the small sample size.

Terrain Variables Based Spatial Mapping of Soil Properties in a Watershed of Himalayan Landscape Using Random Forest Model

Soil information, including their spatial variability is vital for devising various soil and land management policies and strategies as well as assessing the environmental impact of different land use changes. Among the various soil forming factors, terrain plays a vital role in determining the spatial distribution of soil properties especially in hilly terrains due to its impact on soil processes as well as the redistribution of soil materials. The study was carried out for assessing the applicability and efficiency of various terrain parameters for prediction as well as spatial mapping of different soil properties using Random Forest (RF) modeling approach, in a mid-Himalayan watershed located in Tehri Garhwal district, Uttarakhand. Field data collection was done by collecting soil samples from 0-15cm depth (surface layer) at 68 different locations in the study area, following a transect survey method. Collected samples were pre-processed and analyzed in the laboratory for estimating various soil properties such as sand, silt and clay contents as well as soil nutrients such as Soil Organic Carbon (SOC) and nitrogen (N). Fifteen terrain parameters derived by digital terrain analysis of CartoDEM of 10m spatial resolution were used as predictor variables during RF modeling. Pearson correlation analysis revealed poor linear relationship of soil properties with various terrain parameters. Variable importance ranking revealed that compound topographic index, elevation, heat load index, integrated moisture index and mean curvature are the most important variables, explaining maximum variability in different properties. The performance of RF models for predicting various soil properties were evaluated based on the coefficient of determination (R2), Root Mean Square Error (RMSE) as well as Lin’s Concordance Correlation Coefficient (CCC). The models were found to perform well with R2 and CCC values of 0.47 and 0.50 for sand, 0.52 and 0.55 for silt, 0.44 and 0.57 for clay, 0.41 and 0.36 for organic carbon and 0.55 and 0.34 for nitrogen, respectively. The validated models were further employed for generating the spatial distribution maps of various soil properties. Such attempts combining various environmental variables with machine learning based models may aid us in mapping the spatial distribution of various soil properties in the hilly mountainous terrains with considerable accuracies.