High Sand Content Research Articles

Influence of climatic variables on biome transitions in the COLOMBIAN and PANAMANIAN Caribbean region

Disentangling the environmental determinants of tropical biomes is crucial for understanding their response to climate change. This study investigated the effect of climate and soil-related variables on biome transitions in the Caribbean region of Colombia and Panama, focusing on xerophytic forest (XF), tropical dry forest (TDF), and tropical rainforest (TRF). We analyzed the climatic variables at different time scales (daily, seasonal, and annual) and their interaction with soil properties. We performed an ordinal logistic regression to assess the combined effect of the most important variables in biome transitions. Our results showed that climate variables are major discriminators in our study region, particularly precipitation at a seasonal and annual scale. The ordinal logistic regression highlighted the significance of annual precipitation and dry-season length in biome transitions, with maximum temperature impacting TDF-TRF transitions. Soil differences, although present (e.g., higher sand content in XF), played a marginal role. Overall, our findings emphasize the dominance of climate over soil in shaping tropical biome distributions in the northern Caribbean part of South America. These findings contribute to a deeper understanding of tropical biome responses to climate change.

Simulation of sand and mud transport processes in currents and waves by time-dependent 2DV model

This paper presents a time-dependent, two-dimensional vertical model for the simulation of sand and mud concentrations, transport and bed level changes in tidal conditions with or without surface waves. The model solves the advection-diffusion equation for suspended sediment. The horizontal velocities and the sediment mixing coefficients are modelled as function of x, z and t. The settling velocity is constant or modelled as function of the sediment concentration. The sediment mixing coefficient over the water depth is described by flexible expressions based on current and wave parameters which can be modified easily in the input file. To represent mud flocculation and hindered settling processes, the settling velocity can be set as constant or concentration-dependent (input). The bed boundary condition is modelled as a bed concentration as function of the bed-shear stress. The model is valid for low and high sand and mud concentrations including fluid mud concentrations. The numerical SUSTIM2V-model is herein used to simulate sand and mud transport as measured in tidal waters. The model is also successfully used for simulation of high mud concentrations in the near-bed region as measured in the mouth of the Amazon River. The model has also been used to simulate scour along an offshore caisson-type foundation structure.

Review of Analytical Studies on The Failure of Granular Anchor Piles in Expansive Soil

Abstract: Soft ground, characterized by a high content of clay, silt, peat, and loose sand, is generally unsuitable for constructing large structures due to insufficient stability. Ground improvement techniques, such as the use of stone columns (or granular piles), are often implemented in these areas to enhance load-bearing capacity and minimize settlement. The Granular Anchor Pile (GAP) is an advanced version of the stone column that includes an anchor to boost its tensile load-bearing or pullout capacity. In this study, formulations from various authors regarding the pullout capacity of anchors embedded in clayey soils are analyzed to assess the contributions of pile failure and anchor failure to overall GAP failure. The results indicate that GAP failure occurs due to two main factors: 50%–65% of the anchor length failing, and 35%–50% of the pile length failing. This breakdown helps in understanding the role of each component in the overall pullout capacity of GAP

CHARACTERIZATION OF CLAYS FROM “MINES MARITSA IZTOK” AS RAW MATERIALS FOR CERAMIC INDUSTRY

The chemical and phase compositions of the clays from coal mining were evaluated by XRF and powder XRD method, respectively. Hot Stage Microscope was used to estimate the thermal behaviour. In addition, the thermal losses of the clays after 1 h thermal treatment at different temperatures were measured. This preliminary analysis elucidates potential prospects for using some of clays as raw materials for ceramic industry. It seems that samples which are montmorillonite type are more plastic, while the others, where higher sand content is observed, and the drying shrinkage is negligible could be characterized as less plastic. The initial results for the thermal behaviour and the structure of a brick sample (obtained by mixing two types of clays) and a foamed geopolymer are also reported. The first sample shows a beginning of the firing shrinkage at about 1000°C, while the second demonstrates intensive bloating after 950°C, leading to specimen with about 56 % closed porosity. Finally, X - ray Computed Tomography and SEM was used to highlight the structure of some test samples.

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 > 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.

Revealing the optimal strategy for tree plantations on controlling soil erosion in China: A meta-analysis

Tree plantation has increased globally, driven by a desire to supply multiple ecosystem services including soil erosion control. However, how to plant trees can more effectively mitigate soil erosion still lacks systematic investigation. Therefore, we conducted a meta-analysis consisting of 412 paired observations from 80 studies to rigorously compare the effects of tree plantations on soil erosion control across different plantation approaches in China. The results showed that plantation age and ground cover type were the primary factors influencing the efficiency of tree plantations on runoff and sediment reduction. Mature plantations (>20 years) showed more efficiency in runoff (80.9 %) and sediment (97.2 %) reduction than young plantations (<10 years). The benefit of tree plantations with grass cover on runoff reduction was 70 %, while the capacity of plantations without ground cover was not significant. In addition, tree plantations in areas with steep slope, low mean annual precipitation, high soil sand content, and low soil organic carbon had better benefits on soil erosion control. Loess Plateau and Karst areas suffer the most severe water erosion in China, with distinct environmental conditions. This paper further revealed the targeted plantation strategy for these two regions: tree plantations in Karst areas should focus on the lithophyticity and drought tolerance of tree species, in the Loess Plateau should consider the trade-off between water consumption and soil erosion control.

Effect of sand content on adhesion and cohesion of municipal sludge during drying practices: The characteristics and modification

Stickiness is a phenomenon observed widely in sludge drying practices, which negatively impacts the sludge drying efficiency. This paper was aimed at evaluating the stickiness characteristics of sludge when the sand content of sludge increases during the rainy season, and carrying out stickiness modification experiments on high sand content sludge. The results indicated that the sand content was significantly positively correlated with the stickiness of sludge. During drying process, the adhesion force and cohesion force of sludge decreased with the increase of drying temperature, and the adhesion force was consistently greater than the cohesion force in every group. The sludge stickiness was reduced after ultrasonic treatment and calcium oxide modification, but the reduction effect of sodium dodecyl sulfate on sludge stickiness was not good. This study confirmed the effect of sand content on sludge stickiness, and the stickiness of sludge with high sand content can be reduced by modifier. These findings contribute to our understanding of the stickiness of sludge with high sand content in the rainy season and provide valuable insights for the optimization of sludge drying process.

Plant growth promoting bacteria promote rice growth cultivated in two different sandy soils subjected distinct climates conditions.

Sandy soils contain around 70% sand in their composition, making them highly fragile and susceptible to land degradation. Practices such as no-tillage cultivation, the use of bioinoculants, and the application of organic amendments can restore the organic matter in these soils, ensuring sustainable production. In this context, this work aimed to study the microbiological aspects of two sandy soil areas (Brazilian Northeast and South) under contrasting climatic conditions (tropical and temperate). With this purpose, prokaryotic communities were evaluated, and the plant growth-promoting potential of isolated bacteria was assessed by rice inoculation in sandy soil. Despite the high sand content in both soils, soil from the NE was related to the highest phosphorous, calcium, potassium, copper, sodium, zinc, magnesium, and manganese contents, organic matter percentage, and pH. The Shannon diversity index indicated that prokaryotic communities in NE were more diverse than in SU, and PCA revealed that microbial composition exhibited distinct patterns. The rice inoculation experiments were executed to verify if the bacterial isolates displayed a similar growth promotion potential when inoculated in sandy soil areas subjected to different climatic conditions. When all PGP characteristics evaluated were pooled in a PCA, a similar pattern was observed for SU and NE. Burkholderia sp. SU94 was related to highest PGP characteristics evaluated. Paraburkholderia sp. NE32 showed similar results to those of the non-inoculated control. This similar effect of rice growth in the Northeast and South of Brazil suggests that isolate SU94 adapts to different environmental conditions.

Pore Structures in Detritusphere of Soils Under Switchgrass and Restored Prairie Vegetation Community

ABSTRACTRoot detritusphere, that is, the soil in the vicinity of decomposing root residues, plays an important role in soil microbial activity and C sequestration. Pore structure (size distributions and connectivity of soil pores) in the detritusphere serves as a major driver for these processes and, in turn, is influenced by the physical characteristics of both soil and roots. This study compared pore structure characteristics in the root detritusphere of soils of contrasting texture and mineralogy subjected to &gt; 6 years of contrasting vegetation: monoculture switchgrass and polyculture prairie systems. Soil samples were collected from five experimental sites in the US Midwest representing three soil types. Soil texture and mineralogy were measured using a hydrometer and x‐ray powder diffraction, respectively. The intact cores were scanned with x‐ray computed micro‐tomography to identify visible soil pores, biopores, and particulate organic matter (POM). We specifically focused on pore structure within the detritusphere around the POM of root origin. Results showed that the detritusphere of coarser textured soils, characterized by high sand and quartz contents, had lower porosity in the vicinity of POM compared with finer textured soils. POM vicinities in finer textured soils had high proportions of large (&gt; 300 μm diameter) pores, and their pores were better connected than in the coarser soils. Lower porosity in the outer (&gt; 1 mm) parts of the detritusphere of switchgrass than of prairie suggested soil compaction by roots, with the effect especially pronounced in the coarser soils. The results demonstrated that soil texture and mineralogy played a major, while vegetation played a more modest, role in defining the pore structure in the root detritusphere.

Effectiveness of Anaerobic Soil Disinfestation for Weed and Nematode Management in Organic Sweetpotato Production

Weeds and nematodes are particularly problematic in organic sweetpotato production due to a lack of effective pesticides. Anaerobic soil disinfestation (ASD) has the potential to fit into current pest management practices as an alternative to pesticide application. Greenhouse studies were conducted at the Clemson Coastal Research and Education Center (CREC) in Charleston, SC, to investigate the impact of carbon source amendment and a no carbon source treatment, and soil type on cumulative anaerobicity, weed control, nematode population, and sweetpotato vigor. Microcosms were filled with one of three different soil types (Charleston—loamy/native; Blackville—high coarse sand content; and Clemson—high clay content) and were mixed with cottonseed meal (CSM) or no carbon amendment. The pots were then sealed with plastic totally impenetrable film (Tif) for 6 weeks, followed by the transplanting of sweetpotato (cv Bayou Belle) slips. The results suggested that the CSM-treated microcosms spent more time under anaerobic conditions than those treated with the no carbon amendment. The microcosms that experienced a longer duration of anaerobicity had a lower percent weed cover (49%), fewer nematode egg masses, and a lower gall index when compared to microcosms which experienced a shorter duration of anaerobicity. Significantly higher instances of leaf necrosis were observed in the sweetpotato slips sown in the CSM-treated microcosms. The addition of CSM as a carbon source to facilitate ASD resulted in similar above-ground biomasses of the sweetpotato plants compared to the treatments containing no carbon amendment. However, a significantly lower below-ground biomass of the sweetpotato plants was observed in the CSM-treated microcosms.

Diversity of Seedlings in the Kerangas Forest Kersik Luway Nature Reserve

The Extreme Kerangas Forest is an edapic type of kerangas forest dominated by a much higher quartz sand content than the soil. However, the vegetation in this area is still abundant and the species have their own criteria that are very distinctive and different from other forest types. This paper describes in detail the investigation of seedling variety in the extreme Kerangas Forest of the Kersik Luway Nature Reserve. The research focuses on sapling vegetation in a 1-hectare area of this unique forest type, which is distinguished by high quartz sand content in the soil. The study methodologies are thoroughly described, including the application of the sensus method. The investigation found 38,225 unique saplings representing 16 species from 13 different groups. The most common species were Tristania obovata, Ilex hypoglauca Laec, Podocarpus neriifolius D.Don, Ficus sp. and Calophyllum glaucum. These species thrive in the Kerangas forest's nutrient-poor, acidic soils. According to the report, conservation efforts should prioritize the preservation of these unique ecosystems as well as the rehabilitation of barren areas containing rare species. The severe Kerangas forest in the Nature Reserve is home to a broad assortment of species that have evolved to thrive in harsh environments.

Physical and geochemical responses to bottom trawling on naturally disturbed sediments in the eastern Bering Sea

Abstract Recent concerns that commercial bottom trawling can contribute to a significant release of sequestered marine carbon have highlighted a need for research in this area. Here, a Before-After Control-Impact (BACI) experimental design was utilized in a previously untrawled area of the eastern Bering Sea. Six pairs of experimental and control corridors were sampled before, after, and 1 year after a trawl disturbance. Each experimental corridor was fished four consecutive times over ∼12 h with a commercial otter trawl. Results were contextualized with minimum detectable effects (MDE), and showed no evidence of a trawl effect on total organic carbon (P = .999, MDE ± 0.05% TOC), total nitrogen (P = .999, MDE ± 0.02% TN), δ13C, and δ15N isotope ratios and sediment size classes. Interannual changes observed in δ15N, sand, silt, and clay are attributed to natural variation. The study suggests that the characteristics of the study site, such as storm disturbances, high sand content, and low carbon content, limited the bottom-trawl effect on sediment composition following this initial trawl disturbance. The findings highlight the importance of site-specific studies that account for local conditions to support best management practices for commercial bottom trawling.

Sorghum landraces perform better than a commonly used cultivar under terminal drought, especially on sandy soil

Landraces of sorghum [Sorghum bicolor (L.) Moench] have a high potential for drought adaptations to increasingly extreme climates. We investigated the performance of five sorghum genotypes (four landraces and one commonly grown elite line) under water-limited conditions. Plants were grown until maturity in field-like columns on soils of four textures (silty clay, sandy loam, loamy sand, sand), which were dried during flowering stage down to 30 % usable field capacity. Plant transpiration, physiological characteristics, and yield were measured. For most of the measured parameters, the interaction between genotypes and soils was statistically significant. Alongside the gradient in available water between soils, plants had the highest total transpiration, transpiration efficiency (TE), harvest index (HI), and nutrient uptake in silty clay, steadily reduced towards soils with higher sand content. Especially in sandy soil, all measured plant performance parameters were significantly reduced compared to the other soils. There was a significant negative relationship between later flowering time and HI. While the elite cultivar M35–1 showed the highest TE, it suffered from late flowering and yield loss on all soils, especially when growing on sandy soil. The landraces IS 29914 and IS 8348 had a stable HI irrespective of their lowest TE. The shorter the plant, the better it coped with water and nutrient limitation and high transpiration efficiency was not connected to water conservation. The study overall emphasizes the high potential of sorghum landraces to overcome more extreme droughts as imposed by climate change. It also underlines the importance and strong interaction effect of soil texture on plant performance and transpiration efficiency, which is crucial to be considered in crop production. This outlines that specifically regions with sandy soils, characterized by low water-holding capacities, need genotypes that efficiently utilize the limited available water and nutrient resources – a genetic potential hidden in many landraces.

Effects of Muddy Water Infiltration on the Hydraulic Conductivity of Soils

Despite the high sand content of Yellow River water in arid Northwest China, locals in the region opt to use muddy water to meet the demand for agricultural irrigation. Muddy water irrigation is a complex process and is still poorly understood. In this study, six sets of saturated soil column infiltration tests were designed, considering soil texture (silt loam, sandy loam, and sand) and muddy water sand content (3%, 6%, 9%, and 12%) as the influencing factors, with two sets of validation tests. Change in hydraulic conductivity (Kh), the average change rate of hydraulic conductivity (ΔK), and cumulative infiltration volume (I) were experimentally studied in the context of muddy water infiltration to respectively establish the separate functional models and developed to fit their relationship with time. The study results indicated that the hydraulic conductivity (Kh) decreased with increasing muddy water infiltration time. For silt loam and sandy loam, Kh stabilized at 0.0030 and 0.0109 cm/min, respectively, after 70 min of infiltration. In contrast, Kh in the saturated sandy soil column significantly declined throughout the muddy water infiltration, showing a 90.84% reduction after 90 min compared to the saturated hydraulic conductivity of the sandy soil. As the sand content of the muddy water increased from 3% to 12%, Kh decreased by 83.99%, 90.90%, 91.92%, and 92.21% for 3%, 6%, 9%, and 12% sand content, respectively, in the saturated sandy soil columns at the end of the infiltration period. The I values were 21.20, 9.29, 7.90, and 6.25 cm for 3%, 6%, 9%, and 12% sand content, respectively. The ΔK values were 0.0037, 0.0041, 0.0043, and 0.0044 cm/min2 for the respective sand contents, at an infiltration time of 80 min. The validation test demonstrated that the segmented function model accurately emulated the changes in hydraulic conductivity of sandy soil textures throughout the infiltration period. Results from this study provide a significant basis for understanding the mechanisms to hinder muddy water infiltration and to efficiently utilize muddy water for irrigation.

Characterization of Soil and Growth Response of Rice on Different Positions along the Toposequence in Awka, Anambra State

This study examined soil characteristics and the growth response of Rice along different positions of a toposequence in Awka, Anambra State, Nigeria. The soils were delineated using the Geomorphon algorithm in the Geographic Resources Analysis Support System (GRASS) Geographic Information System (GIS) environments. This was then readapted to reflect the Uplands, midslopes, and Lowlands. The results show that in the uplands, bulk density increased down the profile, silt decreased down the profile, and clay fluctuated with increasing soil depth. In the lowlands, sand and silt content decreased down the profile, while clay content increased down the profile. The clay content had an inverse relationship with saturated hydraulic conductivity, decreasing the profile. In the midslope, sand content increased, and silt content decreased, while clay content was high in the topsoil, fluctuating with increasing depth. This result shows that physiographic positions critically influence the nature, properties, and variation of soils across the landscape. The soil properties, in turn, influenced the growth response of the rice plants, with particular reference to varietal variations (FARO 44, 52, 58, 59). Due to its high sand content, high runoff rate, and saturated hydraulic conductivity, the upland yielded rice plants with a lower number of tillers and height, while the reverse was the case in the lowlands. This may be attributed to Rice thriving best under swampy conditions, which are prevalent in lowland areas. The relatively low hydraulic conductivity, and higher organic matter, clay content, and water accumulation in the lowlands consequently ensure a higher yield. Generally, the swamp rice varieties (FARO 44 and 52) performed best in the lowlands, while the upland varieties (FARO 58 and 59) performed best in the midslopes.

Study on the working characteristics of a double jet pump used for high sand content extraction in the oil and gas production

In order to fulfill the present need for downhole lifting pumps in various cutting-edge drilling techniques, a double jet pump is ingeniously devised. The internal three-dimensional characteristics of this pump are utilized to optimize its structural parameters through the flow field simulation method. Extensive evaluations are conducted to assess the alterations in jet performance under different parameters, including area ratios, throat lengths, nozzle exit positions, and nozzle area ratios. The pivotal structural parameters of the double jet pump are optimized as follows: area ratio ma=0.22, throat length Lh=84.5 mm, nozzle exit position Lc=6.76 mm, and nozzle area ratio mb=0.3. Furthermore, an experimental platform is meticulously erected to validate the principles of the double jet pump and to analyze its jet performance. This ascertains the feasibility of the double jet pump and validates the accuracy of the simulation and analysis results. This device can be effectively employed in the oil and gas production characterized by a high sand content extraction.

Investigating soil properties on the north and south slopes at different elevations in Al-Jabal Al-Akhdar, Libya

This scholarly study investigated the physicochemical characteristics of soil in the Al-Jabal Al-Akhdar forest, Libya, with a specific focus on the influence of elevation and slope aspects. Fifty-six sample plots were established across varying elevations, each subdivided into four subplots, totaling 224. Soil samples were collected from each subplot at 0-15 cm depth. Results demonstrate significant variations in clay, silt, and sand content with elevation, indicating lower clay and higher sand content at higher elevations. Available water capacity (AWC) increased with altitude on the northern slope, while consistently lower values were observed on the southern slope. Bulk density (BD) decreased with increasing altitude, suggesting less compacted soils at higher elevations. Available phosphorus (Pav), available potassium (Kav), and pH values decreased with increasing altitude on both slopes. Cation exchange capacity (CEC) values varied at altitudes on the northern slope, with higher values observed at mid to high altitudes. Calcium carbonate (CaCO3) decreased with increasing altitude on the northern slope while showing inconsistent trends on the southern slope. Soil organic matter (SOM) content increased with altitude on both slopes. Pearson's correlation and Principal Component Analysis (PCA) examined relationships among soil properties, elevations, and aspects. Elevation positively correlated with AWC and SOM and negatively correlated with clay content, Kav, BD, and pH. PCA identified elevation, aspect, silt content, CaCO3, and electrical conductivity (EC) as primary influencers. SOM exhibited positive correlations with AWC and negative correlations with BD. Soil pH showed a negative correlation with SOM and a positive correlation with CaCO3. Additionally, CaCO3 content was positively correlated with the cation exchange capacity (CEC). These findings contribute to understanding soil property relationships, elevation, and aspect, emphasizing their role in shaping soil ecosystems and nutrient dynamics. Further research is warranted to explore additional factors influencing soil properties and to develop effective nutrient management strategies.

Anchor Shear Strength Damage under Varying Sand Content, Freeze-Thaw Cycles, and Axial Pressure Conditions

Sandy soil in the north of Hebei region of China is widely distributed, the temperature difference between day and night is large, the phenomenon of freezing and thawing is obvious, and the soil body before and after the freezing and thawing cycle of sandy soil slopes is affected by the changes. This paper takes the stability of a sandy soil anchorage interface under a freeze-thaw cycle as the research background and, based on the self-developed anchor-soil interface shear device, analyses the influence of changing sand rate, confining pressure, and the number of freeze-thaw cycles on the shear characteristics of an anchor-soil interface in anchorage specimens. The research findings indicate that, at 50–60% sand contents, the shear strength increases with a higher sand content and is positively correlated with confining pressure within a higher range. A higher sand content stabilises the anchoring body, but an excessively high sand content can lead to failure. Increasing the sand content, confining pressure, and freeze-thaw cycle number all result in a reduction in the shear displacement at the peak strength. After 11 freeze-thaw cycles, the shear strength of the anchoring body stabilises, with a reduction in strength of approximately 32%, and a higher sand content effectively reduces the reduction in strength.

Large and non-spherical seeds are less likely to form a persistent soil seed bank.

There is some evidence that seed traits can affect the long-term persistence of seeds in the soil. However, findings on this topic have differed between systems. Here, we brought together a worldwide database of seed persistence data for 1474 species to test the generality of seed mass-shape-persistence relationships. We found a significant trend for low seed persistence to be associated with larger and less spherical seeds. However, the relationship varied across different clades, growth forms and species ecological preferences. Specifically, relationships of seed mass-shape-persistence were more pronounced in Poales than in other order clades. Herbaceous species that tend to be found in sites with low soil sand content and precipitation have stronger relationships between seed shape and persistence than in sites with higher soil sand content and precipitation. For the woody plants, the relationship between persistence and seed morphology was stronger in sites with high soil sand content and low precipitation than in sites with low soil sand content and higher precipitation. Improving the ability to predict the soil seed bank formation process, including burial and persistence, could benefit the utilization of seed morphology-persistence relationships in management strategies for vegetation restoration and controlling species invasion across diverse vegetation types and environments.

Vegetation degradation alters soil physicochemical properties and potentially affects ecosystem services in green spaces of a tropical megacity (Lubumbashi, DR Congo)

Urban soils are degraded by various human pressures, including vegetation degradation, leading to changes in physical and chemical characteristics and affecting important ecosystem services. Soil physical properties are an important fertility control parameter, providing the basis for sustainable soil use in urban conditions; however, they do not receive sufficient attention in work on tropical cities. We assessed the impact of vegetation degradation in six urban green spaces (bare soils versus vegetated soils) on the physical (texture, soil bulk density and structure) and chemical (pH, cation exchange capacity (CEC), organic carbon (OC), nitrogen (N), phosphorus (P), potassium (K), copper (Cu) and manganese (Mn)) qualities of soils in a tropical megacity (Lubumbashi, DR Congo). Vegetated soils presented better physical and chemical qualities than bare soils. Vegetated soils were characterized by a high clay and silt content and a good consistency (soil structure), while bare soils were characterized by a high sand content and high bulk density. Vegetated soils were characterized by higher pH, OC, N, C/N ratio, CEC, P, and K. There was no significant difference in Mn or Cu between bare and vegetated soils. Cu was highly variable between sites (from 99 ± 61 mg.kg−1 in VS to 8559 ± 151 mg.kg−1 in BS). Our results demonstrate that the destruction of vegetation, leading to bare soil, negatively affects soil properties and may interfere with ecosystem services provided by urban soils in tropical climates. The physical properties observed in bare soils in this study, including silt, clay, and sand content, soil structure, and soil bulk density, along with chemical properties such as soil pH, cation exchange capacity, and soil organic carbon, can influence the ecosystem services provided by urban soils. These services include regulating water flow and nutrient cycling, enhancing nutrient availability, and supporting ecosystem functions through the cycling of water and nutrients.