Silt Content Research Articles

Effects of different sand fixation plantations on soil properties in the Hunshandake Sandy Land, Eastern Inner Mongolia, China.

Planting forests is an effective way to improve desertification. In order to elucidate the impacts of different vegetation types on soil development and restoration of degraded lands, we compared the properties of soils at different depths in three plantation forests in the Hunsandak Sandy Land in the Chinese agro-pastoral ecotone (Ulmus pumila, Pinus sylvestris var. mongolica, and Populus simonii). The results show that all three plantation forests were able to significantly improve the soil properties, and they resulted in soil nutrient enrichment in the surface layer. As the soil depth increased, the soil became progressively poorer in nutrients, the fine particle content decreased, and the bulk density and water content increased. The orders of the fractal dimension characterization and soil improvement effects of the different tree species were as follows: U. pumila > P. sylvestris var. mongolica > P. simonii. Compared with the bare sand, the soil bulk density under the U. pumila plantation was 19% lower; the soil water content was 74% higher; the soil organic matter, total N, P, and K were 336%, 207%, 106%, and 31% higher; the available N, P, and K were 41%, 125%, and 21% higher; and the clay and silt contents were 498% and 387% higher, respectively. The ranges of the soil fractal dimension were 1.67-2.08 for the bare sandy land and 2.14-2.32 for the planted forests. The soil fractal dimension was strongly correlated with the soil physicochemical properties, especially with the soil nutrients and fine particle content, which exhibited highly significant correlations (p < 0.01), and the correlation coefficients were all greater than 0.8. Therefore, we believe that U. pumila is a suitable sand-fixing plant species in this area. In addition, the soil fractal dimension can be used as an important reference index for characterizing soil properties in sandy areas.

Pertubations of Physicochemical Properties and Heavy Metal in the Soil of Coastal Areas of Akwa Ibom State, Nigeria

This study aimed at assessing the concentrations and perturbations of the physicochemical properties and heavy metals in the soil of the coastal regions of Akwa Ibom State, Nigeria. Sampling was carried out across three mangrove locations (Iko Town, Okoroutip and Uta Ewa) in Eastern Obolo, Ibeno and Ikot Abasi Local Government Areas respectively. Four vegetation plots were randomly selected, and within each plot, three belt transects were established. Physicochemical properties [Sand, Clay, Silt, organic carbon (OC), total nitrogen, sulphate and chlorine content] and heavy metals (Arsenic, Silver, Chromium, Copper, Nickel, Lead, Mercury, Cadmium, Titanium, Vanadium and Zinc) were analyzed using standardized methods. Results from this study revealed considerable variations in the physicochemical properties of soil in the study area. The aforementioned heavy metals were present in both wet and dry seasons in considerable concentrations in the soil samples within the study areas. However, were within and below WHO limits. The variations in the physicochemical properties and the presence of these heavy metals in the samples are indicative of an impacted environment unsuitable for the growth and survival of the endemic flora and fauna species of this unique ecosystem. In view of the current knowledge of the role of mangrove ecosystems in blue-economy of the nation and mitigation of ongoing climate change, we advocate a tripartite alliance between the government, multinational companies operating within the area and the various impacted communities that leads to a concerted efforts of constant monitoring and remediation in the reduction of current and future pollutant levels.

Understanding the ecological versatility of Tetracladium species in temperate forest soils.

Although Tetracladium species have traditionally been studied as aquatic saprotrophs, the growing number of metagenomic and metabarcoding reports detecting them in soil environments raises important questions about their ecological adaptability and versatility. We investigated the factors associated with the relative abundance, diversity and ecological dynamics of Tetracladium in temperate forest soils. Through amplicon sequencing of soil samples collected from 54 stands in six forest sites across the eastern United States, we identified 29 distinct Amplicon Sequence Variants (ASVs) representing Tetracladium, with large differences in relative abundance and small changes in ASV community composition among sites. Tetracladium richness was positively related to soil pH, soil temperature, total sulphur and silt content, and negatively related to plant litter quality, such as the lignin-to-nitrogen ratio and the lignocellulose index. Co-occurrence network analysis indicated negative relationships between Tetracladium and other abundant fungal groups, including ectomycorrhizal and arbuscular mycorrhizal fungi. Collectively, our findings highlight the ecological significance of Tetracladium in temperate forest soils and emphasize the importance of site-specific factors and microbial interactions in shaping their distribution patterns and ecological dynamics.

Towards the mechanical stability of biocrusts in drylands: Insights from inorganic ions and organic compounds and their interactions

Biocrusts are an important component of dryland ecosystems as they perform crucial ecological functions like stabilizing soils, mediating the hydrological cycle, and improving nutrient availability. The high mechanical stability of biocrusts is understood to be linked to exopolymeric substances (EPS), which in turn, are responsible for the adsorption of various ions and chemical compounds. This study aimed to investigate the chemical composition of biocrusts and assess potential correlations between their chemical composition and mechanical stability. Samples of three types of biocrusts (cyanobacteria, cyanobacteria and moss mixed, and moss crusts) and bare soil (as control) were collected from the northern Loess Plateau of China. The inorganic ions and organic compounds present in biocrusts were quantified using inductively coupled plasma-optic emission spectrometry, ion chromatography, and gas chromatography-mass spectrometry. Biocrust mechanical stability was assessed by penetration resistance (PR) and the mean weight diameter (MWD) of aggregates. Finally, the contribution of inorganic ions and organic compounds to the stability of the biocrusts was elucidated. The results indicated that all three types of biocrusts were more stable than bare soil, with moss crusts being the most stable. Chemical analyses revealed an enrichment of inorganic ions such as K+, Ca2+, Na+, Mg2+, SO42–, and halogen ions within the biocrusts, while they showed a depletion of Fe2+, Al3+, and NO3–. Ten types of organic compounds were identified in biocrusts and bare soil, with medium-chain alkanes and long-chain acids being the dominant compounds. In some cases, acids accounted for more than 40 % of the total organic compound content of the biocrusts. Redundancy analysis showed that the content of inorganic ions, such as Ca2+ and Mg2+, and organic compounds such as acids, amides, and alkenes, exhibited the closest association with the biocrust stability. Partial least squares path modeling indicated that both inorganic ions and organic compounds indirectly affected biocrust stability by influencing electric conductivity, bulk density, EPS, and fine particle (clay and silt) content. A strong association was found between the inorganic ions and PR or MWD (0.658 and 0.744, respectively), whilst the total effect of organic compounds on PR and MWD was 0.814 and 0.801, respectively. It is suggested that both the magnitude and types of chemicals associated with EPS indicate their capability to grant mechanical stability of the biocrusts, which in turn is conducive to maintaining the critical functions of biocrusts in global drylands.

Subsurface drainage and nitrogen management affects soil properties in upstate Missouri U.S.

Enhanced efficiency nitrogen (N) fertilizer management may reduce environmental N losses and increase grain yields. The effect of N fertilizer management practices on soil properties is uncertain. In this 5-year study, we evaluated different N fertilizer management [non-treated control (NTC), fall applied anhydrous ammonia (AA) 190 kg N ha−1 with nitrapyrin (fall AA + NI), preplant AA at 190 kg N ha−1 (spring AA), top-dressed urea (TD urea) as 42 kg N ha−1 SuperU and 126 kg N ha−1 ESN as a 25:75 % granular blend] practices in free drained (FD) and non-drained (ND) soils for their impact on soil properties. In FD soils, N fertilization significantly (P > 0.05) increased soil pH, CEC, cations, and Bray I P compared to the NTC. Improved soil aeration and increased plant growth with TD urea and spring AA fertilizer treatments in FD soils increased soil organic matter (OM) 10–13 % and total organic carbon (TOC) 27–35 % compared to the NTC. Increased clay content and reduced silt content were observed in FD soils with N fertilizer treatments compared to NTC. However, fertilizer applications in ND soils had no effect on soil properties. Increased crop production with FD and 4R N fertilizer applications can improve soil properties with increased soil OM and TOC content. This suggests that a synergetic effect of N fertilization and soil drainage can improve soil health by increasing soil cation exchange capacity (CEC), OM, and TOC content.

Protective role of reactive aluminum phases to stabilize soil organic matter against long-term cultivation in the humid tropics under volcanic influence

ABSTRACT Cultivation can cause rapid depletion of soil organic matter (SOM), particularly in the humid tropics. Understanding the factors controlling SOM storage is a key step toward effective soil management for sustainable crop production. While clay + silt content is known to be an important factor for soil organic carbon (SOC) storage, recent studies have shown greater importance of oxalate-extracted Al (Alo; roughly corresponds to short-range-order aluminosilicate minerals and organo-Al complexes) and Fe (Feo). However, the extent to which these mineralogical factors control the response of SOM pool to land-use changes remains unclear, especially in the tropics. This study aimed to clarify the factors regulating SOM content in croplands compared to secondary forests or home gardens in Negros Occidental, Philippines. Along two line transects having a wide range of Alo contents, soil samples were collected at a depth of 0 − 10 cm from sugarcane sites (n = 33; long-term continuous cultivation of >70 years) that were paired with either secondary forests (n = 10) or home gardens (n = 20). Sugarcane sites had significantly lower SOC and total nitrogen (N) contents than secondary forest and home garden sites, whereas there was no clear difference between the latter two land uses. Both SOC and total N contents showed significant positive correlations with Alo content and, to a much less extent, with Feo content, but not with clay + silt content. The slope of the regression line between SOC and Alo was indifferent between sugarcane and the other two land uses, while the intercept was significantly lower in the sugarcane sites. These results suggest the protective role of Alo phases in both agricultural and forest soils and the presence of unprotected SOM (e.g. plant litter) in the latter sites. Furthermore, δ13C analysis suggested that the proportion of forest (C3 plant) derived carbon remaining in the sugarcane soils ranged between 10% and 50% and increased with Alo content. Together, our study showed indirect evidence of Alo-induced stabilization of SOM against long-term cultivation under the humid tropical environment.

SPATIAL VARIABILITY OF THE HEAT EMITTED FROM THE LAND SURFACE IN DETERMINING THE CHARACTERISTICS OF DESERT SOILS IN AL-SAMAWAH DESERT USING “GIS”

This study was aimed to reveal the variation land surface temperature "LST" with some characteristics of desert soils in the Samawa desert at Al-Muthanna province, and to adopt solutions and treatments by identifying factors and indicators that have a direct impact to desertification, by using geographic information systems mapping for spatial distribution Some physical and chemical properties were selected. . the result showed that there was a statistical relationship between LST and the physical characteristics, as it was revealed that the comparison of sand and silt content with the land surface temperature "LST" . There is a significant relationship with the determination coefficient of R2=0.6. The chemical properties, the results showed that there was a significant connection between the electrical conductivity with the land surface temperature with a coefficient of determination R2=0.5 and an It was also observed that there is a significant relationship between the land surface temperature and the temperature measured in the field with a determination coefficient R2=0.6.

Influence of land-use types and topographic slopes on the physico-chemical characteristics of soils in Northwestern Ethiopia

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

Integrating field surveys and remote sensing to optimize phosphorus resource management for rainfed rice production in the Central plateau of Burkina Faso.

Rice production in sub-Saharan Africa (SSA) is restricted by low water availability, soil fertility, and fertilizer input, and phosphate rock (PR) application is expected to increase production. Soil water conditions and soil types affect the efficacy of phosphorus fertilization in improving productivity. However, these factors are rarely discussed together. In this study, we aimed to investigate the soil types and soil water conditions in the fields, as well as their effects on rice productivity after phosphorus fertilization, and optimize the findings using remote sensing techniques. A soil profiling survey, followed by a field experiment in seven farmer fields, was performed in the Central plateau of Burkina Faso. The following treatments were applied: nitrogen and potassium fertilization without phosphorus (NK), PR application with NK (NK+PR), and triple super phosphate (TSP) application with NK (NK+TSP). Submergence duration and cumulative water depth were recorded manually. The inundation score, estimated using a digital elevation model, explained the distribution of soil types and soil water conditions and correlated negatively with sand content and positively with silt and clay content, indicating an illuvial accumulation of fine soil particles with nutrient transportation. The field experiment showed that although grain yield was significantly restricted by phosphorus deficiency, the increase in yield after phosphorus fertilization was higher in Lixisols and Luvisols than in Cambisols because of the low Bray-2-phosphorus content of Lixisols and Luvisols. The inundation score correlated positively with grain yields after NK+PR and NK+TSP treatments. In conclusion, soils with low inundation scores (mainly Lixisols and Luvisols) showed a drastic increase in grain yield after TSP application, whereas those with high inundation scores showed comparable yields after PR and TSP application despite the low phosphorus fertilization effect. Our findings would help optimize fertilization practices to increase rice productivity in SSA.

Influence of soil microplastic contamination on maize (Zea mays) development and microbial dynamics

BackgroundMicroplastics are contaminants in soil ecosystems that alter biophysical processes, affect plant growth, ecosystems and humans in the long run. This study was conducted to investigate the influence of soil microplastic contamination on the growth, development, and microbial dynamics of maize (Zea mays).Composite soil samples were collected from the farm from 0 to 10 cm depth. Physicochemical properties were assessed before maize seed sowing. Three soil weight categories were treated with 30 g, 20 g and 10 g microplastics. Soil physicochemical properties and heavy metal content in maize plants were analyzed. Morphological parameters, microbial counts, and microorganism identification were conducted. FTIR analysis was carried out in selected plant parts.ResultsThe study revealed a pH range of 5.00–6.70, electrical conductivity of 70–158 µS/cm, organic carbon and organic matter, total nitrogen, average phosphorus content, clay and silt content. The concentrations of heavy metals in plant parts were within WHO standard limits of 425.5 and 500 mg/kg for iron and manganese, but above the limits of 40, 60, and 350 mg/kg for copper, zinc and magnesium. The plant had various leaf sizes and heights, with chlorosis and necrotic activity ranging from 0.33 to 2.67, and a range of 1.33 to 6.33, respectively. Soil samples showed a total bacterial count (TBC) of 2.00 × 103 cfu/g to 7.60 × 104 cfu/g and a total fungal count (TFC) of 4.00 × 103 cfu/g to 2.20 × 104 cfu/g. Pseudomonas aeruginosa, Bacillus subtilis, Escherichia coli, Staphylococcus epidermidis, Proteus mirabilis and Bacillus cereus had percentage occurrences of 44.31, 21.17, 9.12, and 3.26%, respectively. Penicillium notatum was the most prevalent, while Fusarium spp. was the least prevalent. The FTIR analysis of maize seeds from soil samples A, B, and C revealed various organic compounds, with opium powder and streptomycin sulphate being the most abundant. The study revealed that pot B had the highest microplastic concentration at 1 WAS, while pot C had the lowest at 0.10 mg/kg, indicating a differential soil microplastic accumulation.ConclusionMicroplastics impact soil health, plant growth, and nutrient cycling, necessitating sustainable agriculture. Long-term research is needed to understand ecological and physiological impacts and explore remediation techniques.

Identification of dominant drivers of streamflow spatiotemporal variations in typical mountainous areas in the Hexi Corridor, China

Study regionTypical mountain areas in the Hexi Corridor, China. Study focusWater security and ecosystem sustainability of arid inland river basins are highly dependent on upstream streamflow. However, due to the complex geographical environment and limited observation data in the study region, the attribution of spatiotemporal variations in streamflow influenced by climate change and/or human activities remains unclear. Here, we used partial least squares regression (PLSR) and the Budyko framework to unravel the dominant drivers of spatiotemporal variation in streamflow over the past 30 yr. New hydrological insight for the regionPrecipitation, topographic wetness index, slope, forest land, gross primary productivity, hydrological connectivity, soil organic carbon content, silt content, relative relief, NDVI and gravel content dominated spatial variation in streamflow. Temporal variation of streamflow was sensitive to precipitation and land surface. Specifically, increased precipitation and land surface alteration dominated the increase in streamflow in 50 % of the watersheds and the decrease in streamflow in 33 % of them, respectively. Further, land surface alteration was dominated by expansion of agricultural and built-up areas, weakened hydrological connectivity, increased landscape aggregation and forest cover. Controlling agricultural and built-up areas and the scale of afforestation, and focusing on the dynamics of hydrological connectivity and landscape patterns in the upstream reaches are imperative to maintain the security and sustainability of water resources in the arid inland river basins.

Evaluation of Physical Properties of Aggregates: A Case Study on Aggregate Sources around Kathmandu Valley

Aggregates play a crucial role in construction works, and this research aims to characterize aggregates from different sources in the Kathmandu Valley, considering factors such as particle size, shape, water absorption, and toughness, resistance to abrasion, crushing value, and impact value. The study investigated identifying and testing aggregates from the sources around and within Kathmandu Valley. A preliminary survey identified nine quarries around Kathmandu Valley based on accessibility to the valley and the highest producers (regarding materials volume). Coarse aggregate samples were collected from Dukuchap (Lalitpur), kaldhunga (Kavre), Bogati Panauti (Kavre), Aagra Khola (Makwanpur) and Melamchi (Sindhupal Chowk. Fine aggregates were collected from Melamchi (Sindhupal Chowk), Belkhu (Dhading), and Sankhu (Kathmandu). Evaluation of physical properties of aggregates included fineness modulus test, water absorption test, crushing value test, Impact value test, silt content test, Flakiness and Elongation test, and abrasion resistance test. Upon meticulous evaluation of the collected samples, it was observed that Fineness Modulus, specific gravity, water absorption, materials finer than 75μm and silt content of the sources were found in between the respective range of (1.97 to3.49), (2.53 to2.62), (1.05 to1.96) % and (1.74 to 5)% and (1.21 to 11.04) respectively. Similarly, specific gravity, water absorption, flakiness index, abrasion value, impact value, and crushing value of coarse aggregates were found in the range of (2.65-2.72), (0.36-1.07)%,(15.03-18.41)%,(15.94-41.52)%,(15.23-34.31)% and(13.55-28.68)% respectively.

Assessment of Soil Fertility Status in Vegetable Growing Area of Daman-Palung, Nepal

Soil fertility assessment is essential for sustainable planning for a particular area. Considering this, a study was conducted in November 2018, to determine the soil fertility status of the vegetable growing area of Makwanpur district, Nepal. In total, 50 soil samples were collected randomly from a depth of 0-20 cm using a soil sampling auger. A standard analytical method was used to analyze the texture, soil pH, (Organic matter (OM), Nitrogen (N), Phosphorus (P2O5), and Potassium (K2O) status of samples at the National Soil Science Research Centre, Khumaltar. The sand, silt and clay content were 45.67±2.08, 35.6±51.37 and 18.49±0.93 respectively and were indicated as loam and sandy loam in texture. The soil was moderately acidic (pH 5.11±0.5) in nature. Soil organic matter ranged from low to medium but the medium (3.37±1.72 %) was prevalent. Total nitrogen content (0.22±0.01 %) and available phosphorus (230.58 ±85.61 ppm), were found to be high. Furthermore, available potassium (97.4±70.04 ppm) content was medium in the soil. The purpose of this soil fertility assessment is to help researchers and farmers in Daman, Palung know the soil fertility status of their area and to guide sustainable soil fertility practices. This soil fertility assessment aims to help researchers and farmers in Daman, Palung understand soil fertility status and determine the best soil fertility practices for their area.

Structures and properties of the late pleistocene paleosols of the loess-soil section of Obi-Mazar (Tajikistan)

The loess-soil series of Central Asia cover the history of subaerial sedimentation of the last 2–2.5 mln years. Significant thicknesses, a large number of paleosols, and an impressive chronology place the loess-soil series of the Afghan-Tajik depression on a par with the famous sections of the Loess Plateau of China. The study of the most significant sections located within the Khovaling Loess Plateau makes it possible to develop a regional chronostratigraphic chart, to study the structure and conditions of formation of the main stratigraphic benchmarks–buried paleosols. The present study is devoted to the clarification of the structural features of loess and paleosols of the Late Pleistocene in one of the sections of the Khovaling–Obi-Mazar Plateau. Based on the results of stratigraphic dissection, description of the macro- and micromorphological structure, magnetic susceptibility analysis, study of the chemical and granulometric composition, a comprehensive description of the structure and properties was carried out and the most probable conditions for the formation of paleosols and loess were established. In the Late Pleistocene part of the section, two loess layers and a pedocomplex PC1 with three welded paleosols, consisting of a total of 7 horizons, are distinguished. The deposits are characterized by high silt content, carbon content, and the presence of signs of pedogenesis and biological activity in all layers of the studied section. Available data indicate the presence of a poorly developed MIS 3 paleosol in the upper loess layer. The developed pedocomplex PC1 of Obi-Mazar, according to its stratigraphic position, structural features, and magnetic susceptibility data, belongs to the MIS 5. According to preliminary data, its formation occurred in semi-humid and humid conditions under forest vegetation, which contributed to the biogenic segregation of Fe-Mn compounds, as well as intra- and interhorizon redistribution of carbonates due to diagenetic processes. Towards the end of the Last Interglacial, gradual aridization occurred, due to which the upper paleosol to be the least developed.

Effect of Caragana microphylla Lam. on Desertified Grassland Restoration

Background: The restoration of the degraded sandy grasslands in Hulun Buir is crucial for maintaining the local ecological balance and sustainable development. Caragana microphylla Lam., a shrub species widely employed in the restoration of sandy vegetation. It is essential to understand its impact on the understory vegetation and soil properties during this process. Methods: This study employed ANOVA, Pearson correlation, and redundancy analysis to systematically analyze the impact of C. microphylla on the three critical stages of desertified grassland vegetation recovery: semi-fixed dunes, fixed dunes, and sandy grasslands. It provided strategies for the restoration of desertified grassland vegetation and offered additional theoretical evidence for the role of vegetation in promoting the recovery of sandy lands. Results: (1) As the degree of vegetation recovery in desertified grasslands increases, the species richness of understory vegetation, Shannon–Wiener index, community height, and biomass also increase. Both the community height and biomass within shrublands are higher than outside, with species richness within the shrublands being higher than outside during the semi-fixed and fixed-sand land stages. (2) In both the 0~10 cm and 10~20 cm soil layers, soil water content showed an increasing trend, peaking in the sandy grassland stage (1.2%), and was higher within the shrublands than outside. The soil water content at 10~20 cm was higher than in the 0~10 cm layer. In both layers, clay and silt content gradually increased with the degree of vegetation recovery in the sandy land, and higher within the shrublands than outside, while the opposite was true for sand content. (3) In both soil layers, soil organic carbon gradually increased with the degree of vegetation recovery, peaking in the sandy grassland stage (4.12 g·kg−1), and was higher within the shrublands than outside. Total nitrogen increased from the semi-fixed-sand land stage to the fixed-sand land stage, with higher levels within the shrublands than outside at all stages. Soil pH within the shrublands decreased as the degree of vegetation recovery increased. There was no significant change in the total phosphorus content. (4) In both soil layers, soil physicochemical characteristics accounted for 59.6% and 46.9% of the vegetation changes within and outside the shrublands, respectively, with the main influencing factors being the soil particle size, total nitrogen, soil water content, and soil organic carbon. Conclusions: In the process of sandy grassland restoration, C. microphylla facilitates the growth and development of vegetation by enhancing the underlying soil physicochemical properties, specifically regarding the soil particle size distribution, soil water content, soil organic carbon, and total nitrogen.

The Effects of Forest Gaps on the Physical and Ecological Stoichiometric Characteristics of Soil in Pinus densiflora Sieb. and Robinia pseudoacacia L. Forests

Forest gaps alter the environmental conditions of forest microclimates and significantly affect the biogeochemical cycle of forest ecosystems. This study examined how forest gaps and non-gap areas affect soil’s physical properties and eco-stoichiometric characteristics. Relevant theories and methods were employed to analyze the impact of forest gaps on nutrient cycling in Pinus densiflora Sieb. (PDS) and Robinia pseudoacacia L. (RPL) forests located in the Taishan Mountains. The results revealed that (1) forest gaps significantly enhanced the soil physical properties of PDS and RPL forests compared to non-gap areas (NPs). Notably, the bulk density of the soil decreased by 53%–12%, particularly in the surface layer (0–20 cm). Additionally, its non-capillary porosity increased by 44%–65%, while the clay and silt content rose by 39%–152% and 24%–130%, respectively. Conversely, the sand content decreased significantly, by 24%–32% (p &lt; 0.05). (2) The contents of C, N, and P in the gap soil of PDS forests showed a significant increase compared to those in non-gap soil, with increases of 56%–131% for carbon, 107%–1523% for nitrogen, and 100%–155% for phosphorus. There was a significant drop of 10%–33% and 39%–41% in their C:N and C:P ratios, respectively (p &lt; 0.05). The contents of C and P in the gap soil of the Robinia pseudo acacia L. Forest increased significantly, by 14%–22% and 34.4%–71%, respectively. Its C:P and N:P ratios significantly increased, by 14% to 404% and 11% to 41%, respectively (p &lt; 0.05). (3) Compared with NPs, the forest gap significantly reduced the soil electrical conductivity and increased the soil pH. Additionally, compared to the soil at the gap’s edge, the surface soil in the gap’s center had noticeably higher concentrations of C, N, and P. (4) Key variables affecting the soil pH, silt content, bulk density, and overall porosity in forest gaps include the concentrations of carbon (C), nitrogen (N), and phosphorus (P) present and their ecological stoichiometric ratios. The findings showed that forest gaps had a considerable impact on the soil’s physical characteristics and ecological stoichiometry. They also had a high potential for providing nutrients, which might aid in the establishment of plantation plants.

Assessing the ecological functioning and biodiversity of remnant native flat oyster (Ostrea angasi) reefs in temperate southeast Australia

Oyster reefs are critically endangered coastal habitats which provide valuable ecosystems services. Despite their importance, there remains a significant knowledge gap in our understanding of how oyster and sediment characteristics influence the ecological functioning and biodiversity of remnant Australian flat oyster (Ostrea angasi) reefs. To inform restoration efforts, we assessed relationships between community respiration rates (CR), inorganic nitrogen fluxes, filtration rates, biodiversity, and oyster morphometrics as well as sediment conditions for three remanent flat oyster reefs (Oyster Cove, Ralphs Bay, and Quarantine Bay) in southeast Tasmania. Additionally, we explored relationships between net denitrification, and flat oyster morphometrics and sediment conditions at one of the sites (Ralphs Bay) in southeast Tasmania. We observed positive relationships between CR, inorganic nitrogen fluxes, filtration rates, and live flat oyster biomass, as well as between the richness and biomass of associated taxa and total flat oyster biomass (both tissue and shell including dead shell), across all three locations. We also found an increase in net denitrification associated with live oyster biomass at one of the oyster reefs (Ralphs Bay). The CR, inorganic nitrogen fluxes, filtration rates, diversity of taxa and biomass of bivalves and flat oyster biomass was higher at Ralphs Bay, which has the most intact reef, compared to the other two locations. In contrast to other studies, the organic and silt content of the sediment showed limited influence on CR, inorganic nitrogen fluxes, filtration rates and net denitrification. CR, and inorganic nitrogen fluxes in these flat oyster reefs were like other restored and natural oyster reefs globally, but net denitrification, filtration rate and taxonomic richness exceeded those previously observed globally. These results highlight the important role of oyster biomass in enhancing water quality and biodiversity. Burgeoning flat oyster reef restoration initiatives should prioritise the enhancement of both live oyster populations and dead shells to recover their associated ecological functions and biological diversity.

Prediction of thermal conductivity of frozen soils from basic soil properties using ensemble learning methods

Thermal conductivity is one of the important properties required for understanding the frozen soils behavior. There are several models available in the literature for the prediction of thermal conductivity of frozen soils based on the proportions of unfrozen water, ice, gas, and soil particles. In this study, two ensemble learning methods-based models; namely, the Random Forest (RF) model and the Least Squares Boosting (LSB) model, are extended to estimate the thermal conductivity of frozen soils. These models utilize basic soil properties as input parameters that include water content, dry density, temperature, and fractions of gravel, sand, silt, and clay, can be measured easily, or determined. Additionally, seven widely used thermal conductivity models, referred to as the traditional models for frozen soils, were evaluated. Both the RF and LSB models, as well as the traditional models, were assessed using data of 823 tests derived from 43 soils with different textures that were gathered from the literature. The results highlight that the traditional models have their strengths and limitations in terms of their use for different types of soils. In contrast, the proposed ensemble learning methods-based models provide higher prediction accuracy compared to the traditional models and can be applied to all soil types and temperature ranges. Furthermore, estimation from the ensemble learning methods-based models can be used to provide probability of multi-dimensional analysis of frozen soils.

Spatiotemporal response of microplastics to natural and anthropogenic factors in estuarine waters

Riverine outflow is the primary pathway for transporting microplastics from terrestrial to marine environments, making estuaries hotspots for microplastics pollution. However, how and to what extent natural and anthropogenic factors affect the distribution of microplastics in estuarine waters remains largely unknown. A meta-analysis of 126 estuaries from 93 studies revealed a global median microplastics abundance of 196.9 items/m3, with a range from 0.007 ± 0.003 to 792,000 ± 138,000 items/m3. Microplastics were more abundant in estuaries in Asia and Oceania compared to Europe and South America. The microplastic abundance in estuarine waters was positively correlated with regional population density, per capita plastic waste, agricultural land proportion, and silt content, while the human development index (HDI) and mean annual precipitation displayed negative effects on microplastic abundance. Notably, HDI was the dominant factor influencing microplastic abundance in estuarine waters. In developing countries, microplastic abundance in estuarine waters showed positive changes, whereas it remained stable in developed countries over time. This study offers critical insights into the effects of natural and anthropogenic factors on the distribution patterns of microplastics in estuarine waters, providing important support for future management of microplastics pollution in estuaries.

Effects of initial soil moisture on rill erodibility and critical shear stress factors in the WEPP model across diverse soil types

Rill erosion, a significant issue in agricultural regions, is intricately linked to initial soil moisture conditions, affecting the development of concentrated flow erosion processes. However, understanding its dynamics amidst varying soil moisture conditions remain challenging. This study aimed to assess the impact of different soil moisture levels on rill erodibility parameters in the Water Erosion Prediction Project (WEPP) model and to evaluate soil cohesion across a spectrum of soils. Through laboratory experiments employing a small V-shaped rill channel, we investigated rill erodibility (Kr) and critical hydraulic shear stress (τcr), under three soil moisture scenarios: initially dry, saturated, and drainage, with incremental surface inflow rates. Additionally, we examined the efficiency of soil cohesion obtained from an Automated Soil Cohesion Measurement Apparatus in predicting Kr and τcr across various soil textures. Our analysis encompassed twenty soils representing nine texture classes, revealing significant correlations between basic soil properties, cohesion parameters, and WEPP model rill erodibility. Notably, initial soil moisture conditions exerted substantial influence on erodibility potentials. Soils with higher silt contents demonstrated better fits in terms of Nash-Sutcliffe model efficiency, particularly under initially dry and saturated conditions. However, predictions for initially drained soils yielded poor fits, emphasizing the intricate interplay between soil properties and hydrological conditions. In conclusion, our findings emphasize the critical role of topsoil water dynamics in rill erodibility. We propose that soil cohesion serves as a valuable predictor, complementing friction forces within the soil and enhancing simulations of rill erodibility under shallow flow conditions in rills, particularly in next-generation process-based modeling approaches.