Surficial Soil Research Articles

Topographic Drivers of Soil Moisture Across a Large Sensor Network in the Southern Appalachian Mountains (USA)

AbstractUnderstanding the distribution of soil moisture is notoriously difficult in topographically complex regions that are subject to both large‐scale climate gradients and fine‐scale effects of terrain, vegetation, and soil structure. Remote sensing approaches capture large‐scale moisture patterns but are limited in spatial and temporal resolution, while commercial field sensors remain too expensive to deploy intensively over large spatial extents. Here, we demonstrate the use of low‐cost (<20 USD) custom sensors to create a large monitoring network of surficial (0–15 cm depth) volumetric soil moisture content (VMC) across Great Smoky Mountains National Park (GSMNP) (NC, TN, USA). In laboratory tests, temperature‐calibrated VMC values approached the accuracy of commercial probes. We deployed over 80 sensors across multiple watersheds, topographic positions, and a 1,800‐m elevation gradient, and created hierarchical models to understand associations of VMC with spatial (30‐m resolution) and temporal (daily) variables related to water supply and demand. Elevation had the strongest association with VMC, with a fivefold increase across the gradient reflecting 1.5‐fold changes in both (increased) precipitation and (decreased) evapotranspiration; slope angle was a strong mediating factor. Common proxies for moisture including topographic convergence index were not associated with VMC, likely due to limited contributions of surface drainage to local water balance. Our model predicted daily VMC of a set of validation sensors with a root mean square error of 4.8%, which may be improved by site‐specific field calibration. Our study indicates that spatially extensive, field‐based soil moisture networks are practical, accurate, and an important component of regional environmental monitoring.

Cadmium isotope fractionation during sorption to soil minerals: Lab evidence and field implication

Stable isotope is a potent geochemical tracer unveiling the dynamic sources of cadmium (Cd) in the environment. However, the sorption process of aqueous Cd onto solid surfaces (e.g., soil) fractionates isotopic signatures, which makes it difficult to interpret its sources and migration processes. Understanding how Cd fractionates during sorption to soil minerals, therefore, provides necessary data to open the isotope fractionation black box of liquid-solid phase partition of Cd. In this study, we explored isotopic fractionation characteristics during Cd sorption to typical soil minerals. Distinct Cd isotope fractionation was observed during sorption, including goethite (∆114/110Cdsolid−solution=−0.51∼−0.47‰), montmorillonite (−0.34∼−0.32‰), quartz (−0.34∼−0.30‰), gibbsite (−0.29∼−0.25‰), and kaolinite (−0.09∼−0.07‰), where lighter isotopes tended to be preferentially sorbed to the solid phase in a reversible manner. We've also conducted a field survey in a historical flooding-affected region to explore Cd isotopic compositions of soil samples adjacent to a polluted creek. Distinct isotopic signatures for surficial soils and deep soils were observed, which was depicted by a binary mixing mode. Leaching of Cd from mine tailings to the creek, as well as its re-adsorption to soil during historical flooding events both led to preferential enrichment of light isotopes in the solid phase, which was consistent with findings from lab sorption experiments. Mineralogical analyses including EPMA, TOF-SIMS, Mössbauer spectra, XRD, and chemical extraction tests, were applied to unveil how Cd was bound to soil minerals at field. Possible linkage between lab and field data were discussed on the basis of these findings. Results from this study are encouraging for future application of Cd isotopes for source tracing.

Distinct Depth-Discrete Profiles of Microbial Communities and Geochemical Insights in the Subsurface Critical Zone.

Microbial assembly and metabolic potential in the subsurface critical zone (SCZ) are substantially impacted by subsurface geochemistry and hydrogeology, selecting for microbes distinct from those in surficial soils. In this study, we integrated metagenomics and geochemistry to elucidate how microbial composition and metabolic potential are shaped and impacted by vertical variations in geochemistry and hydrogeology in terrestrial subsurface sediment. A sediment core from an uncontaminated, pristine well at Oak Ridge Field Research Center in Oak Ridge, Tennessee, including the shallow subsurface, vadose zone, capillary fringe, and saturated zone, was used in this study. Our results showed that subsurface microbes were highly localized and that communities were rarely interconnected. Microbial community composition as well as metabolic potential in carbon and nitrogen cycling varied even over short vertical distances. Further analyses indicated a strong depth-related covariation of community composition with a subset of 12 environmental variables. An analysis of dissolved organic carbon (DOC) quality via ultrahigh resolution mass spectrometry suggested that the SCZ was generally a low-carbon environment, with the relative portion of labile DOC decreasing and that of recalcitrant DOC increasing along the depth, selecting microbes from copiotrophs to oligotrophs and also impacting the microbial metabolic potential in the carbon cycle. Our study demonstrates that sediment geochemistry and hydrogeology are vital in the selection of distinct microbial populations and metabolism in the SCZ. IMPORTANCE In this study, we explored the links between geochemical parameters, microbial community structure and metabolic potential across the depth of sediment, including the shallow subsurface, vadose zone, capillary fringe, and saturated zone. Our results revealed that microbes in the terrestrial subsurface can be highly localized, with communities rarely being interconnected along the depth. Overall, our research demonstrates that sediment geochemistry and hydrogeology are vital in the selection of distinct microbial populations and metabolic potential in different depths of subsurface terrestrial sediment. Such studies correlating microbial community analyses and geochemistry analyses, including high resolution mass spectrometry analyses of natural organic carbon, will further the fundamental understanding of microbial ecology and biogeochemistry in subsurface terrestrial ecosystems and will benefit the future development of predictive models on nutrient turnover in these environments.

Impacts of cacao agroforestry systems on climate change, soil conservation, and water resources: a review

Abstract Agroforestry is crucial for improving water quality deteriorated by anthropogenic activities due to the use of chemical substances, including nitrogen (N) and phosphorous (P) in modern agricultural practices (MAPs). This state-of-the-art review aims to revise the influence of agroforestry systems (AFS) on climate change, soil conservation, and groundwater quality. The novelty of this review is that AFS can improve water quality, reduce nutrient loss, and support the biological, chemical, and physical properties of the soil. It is worth noting that the surficial geologic controls, slope gradient, soil types, and topographical conditions are factors that alter a watershed dominated by agroforestry areas. In addition, anthropic aspects, including agricultural practices, can also cause loss of water quality in basins dominated by an AFS area. This review is also novel in that it outlines how AFS can be used for the phytoremediation of contaminated soils to reduce aluminum (Al), mercury (Hg), and cadmium (Cd), among others. Therefore, AFS can be used for water decontamination, climate change mitigation, climate adaptation, and soil conservation. Further research is required to investigate the contribution of AFS to soil integrity.

Comparison of established and novel insecticides on survival and reproduction of Folsomia candida.

Neonicotinoid insecticides have been among the most widely and abundantly used insecticides for most of the current century. The effects of these substances on non-target terrestrial and aquatic organisms have resulted in a significant decrease in their use in many parts of the world. In response, the application of several novel classes of insecticides including diamides, ketoenols, pyridines, and butenolides has significantly increased. The hexapod subclass Collembola is an ecologically significant and widely distributed group of soil invertebrates often found in leaf litter and in surficial soils. In this study, the parthenogenic collembolan species Folsomia candida was exposed to six insecticides in a sandy loam soil for 28 days, including two neonicotinoids (thiamethoxam, clothianidin), a diamide (cyantraniliprole), a ketoenol (spirotetramat), a pyridine (flonicamid), and a butanolide (flupyradifurone) to assess the effect of each insecticide on survival and reproduction. Clothianidin, thiamethoxam, and cyantraniliprole (EC50s (reproduction): 0.19, 0.38, and 0.49 mg/kg soil, respectively) had a greater effect on survival and reproduction of F. candida than flupyradifurone, spirotetramat, and flonicamid (EC50s (reproduction): 0.73, >3.08, and 5.20 mg/kg soil, respectively). All significant impacts observed in this study were observed at concentrations below concentrations of the active ingredients that would be expected in agricultural soils. This article is protected by copyright. All rights reserved. Environ Toxicol Chem 2023;00:0-0. © 2023 SETAC.

Understanding the Spatial Variability of the Relationship between InSAR-Derived Deformation and Groundwater Level Using Machine Learning

The interferometric synthetic aperture radar (InSAR) technique was used in this study to derive the temporal and spatial information of ground deformation and explore its temporal correlation with groundwater dynamics. The random forest (RF) machine learning method was used to model the spatial variability of the temporal correlation and understand its influential contributors. The results showed that groundwater dynamics appeared to be an important factor in InSAR deformation at some bores where strong and positive correlations were observed. The RF model could explain up to 72% of spatial variances between InSAR deformation and groundwater dynamics. The spatial and temporal InSAR coherence (a proxy for the noise in InSAR results that is strongly related to vegetation) and soil moisture (difference, trend, and amplitude) were the most important factors explaining the spatial pattern of the temporal correlation between InSAR displacements and groundwater levels. This result confirms that noise sources (including deformation model fitting errors and radar signal decorrelation) and perturbation of the InSAR signal related to vegetation and surficial soils (clay content, moisture changes) should be accounted for when interpreting InSAR to support groundwater-related risk assessments and in groundwater resource management activities.

Partitioning and transformation behavior of Cd(II) and As(V) during As(V)-Cd(II)-Fe(III) coprecipitation: Effect of aging under aerobic conditions at pH 5 and 11 relevant to tailings and acid waste

Aerobic coprecipitation and subsequent aging of the As(V)-Cd(II)-Fe(III) system are ubiquitous processes in engineered settings, natural shallow water, surficial soils, and mine tailings. Herein, we have investigated the partitioning of As(V) and Cd(II) coupled with the solid evolution during As(V)-Cd(II)-Fe(III) coprecipitation and subsequent aging process under aerobic conditions at different pH (5 and 11) and Fe(III)/As(V) ratios (10 and 40) with various Cd(II) concentrations at 90 °C. X-ray diffraction and transmission electron microscopy results reveal that ferrihydrite is the dominant phase in the initial coprecipitates, regardless of pH and the coexisting As(V) and Cd(II). Low pH and high Fe(III)/As(V) ratios favor the transformation of initial ferrihydrite to hematite during the aging process, which can further promote the incorporation of ferrihydrite-bound As(V) and Cd(II) into stable hematite. Chemical analyses indicate that the partitioning fractions of adsorbed/extractable and solid-incorporated As(V) and Cd(II) are controlled by pH, Fe(III)/As(V) ratio, and aging time during ferrihydrite transformation. High Fe(III)/As(V) ratios facilitate the incorporation of the extractable Cd(II) into the aging intermediates, whereas the As(V) partitioning is less affected by the initial Cd(II) concentration. The crystallization rates of ferrihydrite at high Fe(III)/As(V) ratios or low pH are higher than those at low Fe(III)/As(V) ratios or high pH. Furthermore, increased Cd(II) concentrations significantly reduce the crystallization rates of the initial ferrihydrite. These findings have shed new light on the mobility and transformation behavior of toxic As(V) and Cd(II) in the As(V)-Cd(II)-Fe(III) coexisting environment under aerobic conditions and are useful for developing novel As(V)-Cd(II)-compound contaminant management strategies for metallurgical waste residues and water treatment sludges.

Maximizing blue carbon stocks through saltmarsh restoration

Political discourse around coastal wetland restoration and blue carbon management strategies has increased in the past decade, yet carbon storage has neither been a reason for restoration, nor a criterion to measure the success of current saltmarsh restoration schemes in the UK. To maximise climate change mitigation through saltmarsh restoration, knowledge on the key drivers of carbon stock variability is required. We use restored saltmarshes of similar age, paired with adjacent natural marshes as references, to identify drivers of carbon stocks following managed realignment within an estuary in southeastern England. From surficial soil cores (top 30 cm), we measured carbon stock alongside environmental characteristics. Carbon stock between natural and restored sites were similar after ~ 30 years when restored sites were above mean high water neap (MHWN) tidal levels. Elevated marsh platforms likely provide suitable conditions for the development of mature plant communities associated with greater capture and production of organic carbon. The restored site at Tollesbury (Essex, UK) had a 2-fold lower carbon stock than other restored sites in the estuary. We attribute this to the site’s low position in the tidal frame, below MHWN tidal levels, coupled with low sediment supply and the dominance of pioneer plant communities. As blue carbon is anticipated to become an important facet of saltmarsh restoration, we recommend that sites above MHWN tidal levels are selected for managed realignment or that preference is given to coastlines with a high sediment supply that may rapidly elevate realignment sites above MHWN. Alternatively, elevation could be artificially raised prior to realignment. Restoration schemes aiming to maximise climate change mitigation should also encourage the establishment of key plant species (e.g., Atriplex portulacoides in our study) to enhance carbon stocks. However, the overall goal of restoration ought to be carefully considered as trade-offs in ecosystem services may ensue if restoration for climate change mitigation alone is pursued.

Installation Effects and Behavior of a Driven Prestressed High-Strength Concrete Nodular Pile in Deep Saturated Soft Clay

This paper investigated the installation effects of a driven prestressed high-strength concrete (PHC) nodular pile in deep soft clay through full-scale tests, and the behavior of a driven PHC nodular pile is analyzed based on the field test results. The test results demonstrated that the driven PHC nodular pile installation process induced significant disturbance in the surrounding soil. The excess pore water pressures (Δu) that were induced by the installation of a driven PHC nodular pile were larger than the Δu that were induced by the installation of a driven PHC pipe pile. The driven PHC nodular pile installation caused significant Δu in the soil down to 2 m below the pile base, and the Δu became much smaller in the soil at 4 m below the pile base. The Δu dissipated slowly in the soft clay layers, and the Δu in the surficial soil layers dissipated faster than that in the deep soil layers. The nodules along the PHC nodular pile shaft could increase the pile shaft capacity. The measured shaft resistances of 350(400)-mm PHC nodular piles were 1.17–1.18 times the calculated shaft resistances of 350-mm PHC pipe piles in soft clay layers.

The thermal response of permafrost to coastal floodplain flooding

Flooding of low-lying Arctic regions has the potential to warm and thaw permafrost by changing the surface reflectance of solar insolation, increasing subsurface soil moisture, and increasing soil thermal conductivity. However, the impact of flooding on permafrost in the continuous permafrost environment remains poorly understood. To address this knowledge gap, we used a combination of available flooding data on the Ikpikpuk delta and a numerical model to simulate the hydro-thermal processes under coastal floodplain flooding. We first constructed the three most common flood events based on water level data on the Ikpikpuk: snowmelt floods in the late spring and early summer, middle and late summer floods, and floods throughout the whole spring and summer. Then the impact of these flooding events on the permafrost was simulated for one-dimensional permafrost columns using the Advanced Terrestrial Simulator (ATSv1.0), a fully coupled permafrost-hydrology and thermal dynamic model. Our results show that coastal floods have an important impact on coastal permafrost dynamics with a cooling effect on the surficial soil and a warming effect on the deeper soil. Cumulative flooding events over several years can cause continuous warming of the deep subsurface but cool down the surficial layer. Flood timing is a primary control of the vertical extent of the permafrost thaw and the active layer deepening.

Case study on soil-reinforced embankment slope stability with natural fibre additives

In this work, an attempt was made to study the influence of jute fibre reinforcement with the help of three case studies. The first case study described laboratory model testing and numerical analysis performed on a modelled slope that simulated an existing embankment that failed on many occasions following overnight heavy rainfall. The second case study discussed how vegetation may minimise the likelihood of soil separation and the velocity of surface run-off by decreasing surficial soil erosion. Jute geotextiles have excellent hydrophilic characteristics that aid plant development; for this reason, they were used in the case study. The third case study developed a multi-fibre approach to traditional geotextiles to create an eco-sustainable product(s) with superior geotechnical qualities for improving the efficiency of earthen structures using soft revetments. The conclusion of these case studies expressed the novel objective of improvement of embankments with stability analysis. This research also involved soil sample testing and numerical modelling using the GeoStudio software suite. The slope model considers reinforcement with different numbers of rows of jute tassels on the embankment for enhanced stability and factor of safety. The presence of jute fibre geotextiles results in better performance in the stabilisation of soil and the minimum value of deformation and maximum value of the factor of safety.

Environmental and hydrologic controls on sediment and organic carbon export from a subalpine catchment: insights from a time series

Abstract. Studies engaging in tracking headwater carbon signatures downstream remain sparse, despite their importance for constraining transfer and transformation pathways of organic carbon (OC) and developing regional-scale perspectives on mechanisms influencing the balance between remineralization and carbon export. Based on a 40-month time series, we investigate the dependence of hydrology and seasonality on the discharge of sediment and OC in a small (350 km2) Swiss subalpine watershed (Sihl River basin). We analyze concentrations and isotopic compositions (δ13C, F14C) of particulate OC and use dual-isotope mixing and machine learning frameworks to characterize and estimate source contributions, transport pathways, and export fluxes. The majority of transferred OC is sourced from plant biomass and soil material. The relative amount of bedrock-derived (petrogenic) OC, abundant in headwater streams, progressively decreases downstream in response to a lack of source material and efficient overprinting with biospheric OC, illustrating rapid organic matter alteration over short distances. Large variations in OC isotopic compositions observed during baseflow conditions converge and form a homogenous mixture enriched in OC and characterized by higher POC-F14C values following precipitation-driven events. Particulate OC isotopic data and model results suggest that storms facilitate surface runoff and the inundation of riparian zones, resulting in the entrainment of loose plant-derived debris and surficial soil material. Although particle transport in the Sihl River basin is mainly driven by hydrology, subtle changes in bedrock erosivity, slope angle, and floodplain extent likely have profound effects on the POC composition, age, and export yields.

Precipitation amount and event intervals interact to change plant diversity during dry years in a desert shrubland

Variations in species diversity and soil properties in response to future climate change is a key focus area in ecological research. The influence of precipitation amount on plant community diversity and soil properties, in sandy desert ecosystems, is poorly studied. We chose the Artemisia ordosica community to examine how diversity, and the physical and chemical properties of soil vary in response to changes in precipitation. An in situ experimental platform was used to simulate total monthly precipitation at specific intervals in a desert-grassland region of northern China. The influence of precipitation on the community was investigated using three precipitation amount levels and two intervals. The relative density, coverage, and frequency of species in each experimental quadrat was analyzed for evaluating the community structure. Results showed that variability in precipitation amounts and intervals altered the species diversity in the A. ordosica communities. Increased precipitation amount enhanced whole community’s species diversity via improving the richness of perennial forbs. Lengthening the precipitation intervals enhanced whole community’s species diversity in the context of low precipitation amount but reduced species diversity in high precipitation amount condition. The precipitation patterns affected community species composition and diversity mainly by controlling soil moisture, secondly by changing the nitrogen and organic matter content of the surficial soils. This study revealed that effects of precipitation interval on the species diversity depended on annual precipitation amount and offer an innovative insight to evaluating the succession of desert ecosystems in the context of precipitation change in the future.

Water, environment, and socioeconomic justice in California: A multi-benefit cropland repurposing framework

Low-income, rural frontline communities of California's Central Valley experience environmental and socioeconomic injustice, water insecurity, extremely poor air quality, and lack of fundamental infrastructure (sewage, green areas, health services), which makes them less resilient. Many communities depend financially on agriculture, while water scarcity and associated policy may trigger farmland retirement further hindering socioeconomic opportunities. Here we propose a multi-benefit framework to repurpose cropland in buffers inside and around (400-m and 1600-m buffers) 154 rural disadvantaged communities of the Central Valley to promote socioeconomic opportunities, environmental benefits, and business diversification. We estimate the potential for (1) reductions in water and pesticide use, nitrogen leaching, and nitrogen gas emissions, (2) managed aquifer recharge, and (3) economic and employment impacts associated with clean industries and solar energy. Retiring cropland within 1600-m buffers can result in reductions in water use of 2.18 km3/year, nitrate leaching into local aquifers of 105,500 t/year, greenhouse gas emissions of 2,232,000 t CO2-equivalent/year, and 5388 t pesticides/year, with accompanying losses in agricultural revenue of US$4213 million/year and employment of 25,682 positions. Buffer repurposing investments of US$27 million/year per community for ten years show potential to generate US$101 million/year per community (total US$15,578 million/year) for 30 years and 407 new jobs/year (total 62,697 jobs/year) paying 67 % more than prior farmworker jobs. In the San Joaquin Valley (southern Central Valley), where groundwater overdraft averages 2.3 km3/year, potential water use reduction is 1.8 km3/year. We have identified 99 communities with surficial soils adequate for aquifer recharge and canals/rivers within 1600 m. This demonstrates the potential of managed aquifer recharge in buffered zones to substantially reduce overdraft. The buffers framework shows that well-planned land repurposing near disadvantaged communities can create multiple benefits for farmers and industry stakeholders, while improving quality of life in disadvantaged communities and producing positive externalities for society.

Stimulated leaching of metalloids along 3D-printed fractured rock vadose zone

Fractured rock aquifers are susceptible to contamination, with metal(loid)s rapidly migrating from poorly developed overburden to the fractured rock vadose zone and thus into groundwater. Compared to typical porous aquifers, retention effects within the rock matrix are small, and rapid advection along fractures leads to a higher risk of groundwater contamination. However, the highly complex anisotropic pathways of natural fractures hinder research in this field. To construct reproducible fractures, this study used 3D printing following Computed X-ray Microtomography (μCT) scans of a fractured rock collected in a natural limestone aquifer. Stimulated metalloid release was observed in the fractured rock during column leaching, and the leachate concentrations of arsenic (As) and antimony (Sb) increased by up to 17.5 and 36.4 times, respectively, compared with the porous vadose zone. Fluctuations in fracture metalloid release patterns in dissolved and adsorbed phases were attributed to retention and filtration effects induced by soil particles within fractures. Geophysical properties of the porous overburden, especially the aggregation characteristics, greatly affected the non-equilibrium leaching behavior of As, but had a limited effect on the near-equilibrium leaching of Sb, which was explored by modifying the surficial soil layer with either montmorillonite clay or charcoal. The results of this study provide a novel method and useful information for modeling and risk assessment of fractured rock aquifers.

Elements and Pb isotopic composition as evidence for contaminant-metal dispersal in surficial soil and sediment of drinking water source in Beijing, China.

Pb pollution in soils and sediments has adverse effects on human health and the environment. Identifying and quantifying the relative contribution of Pb pollution sources are key issues to control Pb pollution. In this study, U, Th and Pb concentration, Pb enrichment coefficient and Pb isotopic composition in the sediment and surface soil samples of the Miyun Reservoir and its upstream Chaohe, Baihe and Tanghe River were analysed to determine the source and relative contribution of Pb pollution. Results show a significant enrichment of Pb in the sediments of the Baihe River (2.7 ± 0.9). The enrichment of Pb in the soils in Baihe (8.0 ± 10.5) and Tanghe (313.3 ± 1139.4) is more obvious, and Pb is unevenly distributed in the soil in the Tanghe Basin. In general, soil is more seriously affected by human activities than sediment. The Pb isotope ratio indicates that mining activities and natural background are the main sources of Pb in soil and sediment. Based on the binary mixture model, the average contribution rate of mining activities to Pb pollution in the sediment is 21.5%, of which the contribution rates in the Miyun Reservoir, Chaohe, Baihe and Tanghe River are 14.86%, 17.20%, 41.03% and 26.32%, respectively. The average contribution rate of mining activities to soil Pb is 43.1%, among which the contribution rates in the Chaohe River Basin, Baihe River Basin and Tanghe River Basin are 58.79%, 60.98% and 36.24%, respectively. In summary, soils and sediments in the basin are affected by mining activities to varying degrees. Nevertheless, natural background is still the main source of Pb in the sediments in the basin and in soil in the Tanghe River. Mining activities are the main sources of Pb in soils in the Chaohe and Baihe River.

Long-term simulations of Nature-Based Solutions effects on runoff and soil losses in a flat agricultural area within the catchment of Lake Massaciuccoli (Central Italy)

Nature-Based Solutions (NBSs) are implemented worldwide to mitigate the impact of industrial agriculture on sediment and nutrient losses; however, their effectiveness depends on site-specific features such as surficial hydrology, soil permeability and erodability. This study analyzed the effects of vegetative buffer strips (VBSs) and winter cover crops (CCs) in a land reclamation area of the Catchment of Lake Massaciuccoli (Central Italy) by modelling water and soil dynamics at a very detailed scale, using a novel approach based on high-resolution input data. To this aim, SWAT+ was applied on digital terrain models (DTMs) from close-range photogrammetry, land-cover mapping, real crop rotations and a detailed calendar of farming practices. NBSs behaviour was investigated in two test areas, namely the Studiati and the Gioia areas, with uniform geomorphological settings but different soil types and annual crop rotations. NBS effects were compared with a baseline control scenario (without NBSs) and assessed under future climate conditions (RCP 4.5 and RCP 8.5). Specifically, VBSs and CCs showed different capabilities in mitigating runoff and sediment losses, and their combination provided maximum effectiveness. For the current climate scenarios, the implementation of VBSs produced a reduction of runoff depth of about 41% and 64% in the Studiati and Gioia areas, respectively, whereas showing a limited with the CCs implementation. Under the future climate conditions, similar patterns were observed, even if predicting significantly lower runoff depths. The sediment loss reduction was in the order of 79% and 64% in Studiati and Gioia areas, respectively. Concerning soil and water dynamics, the study remarked that slight topographic irregularities on flat morphologies can trigger concentrated flows responsible for high runoff and sediment losses. Furthermore, the differences in soil texture and organic matter content affected soil erodability rate on a local scale, driving the consistency of NBS mitigating effects. Future climate changes scenarios, exhibiting higher temperature and rarer but more concentrated rainfall events, emphasize the impact of different soil types. Results observed at a very local scale, with a spatialization of a few square meters - which clearly relates to the types of crop rotations, NBSs and soil distribution - noticed that SWAT+ is a suitable tool to aid farmers in cropping systems management and design.

Characterization of vegetated and ponded wetlands with implications towards coastal wetland marsh collapse

Coastal wetlands provide numerous ecosystem services; yet these ecosystems are increasingly vulnerable to climate change stressors, especially excessive flooding from sea-level rise and storm events. This study highlights the important contribution of vegetation belowground biomass to marsh stability and identifies loss of vegetation as a critical driver of marsh collapse. We investigated the shear strength of salt marshes and unvegetated interior ponds using a modified cone penetrometer along a chronosequence of wetland marsh collapse (0 to 21 + years following pond formation) to characterize changes in the structural integrity of the marsh soil. Following conversion from vegetated marsh to open water pond, the surficial soils experienced a dramatic loss in shear strength resulting from the loss of vegetation and compaction of soil pore space. The Cone Penetrometer Testing (CPT) data indicate that higher shear strength in the surficial layers of the vegetated marsh sites were never recovered, up to 21 + years following marsh collapse. Coupled with significant elevation loss from marsh collapse, additional sea-level rise, deep subsidence, and reduced sedimentation may contribute to conditions that can exceed critical flooding thresholds, making recovery from marsh collapse difficult or impossible. Therefore, characterizing mechanisms and thresholds of marsh collapse are critical for identifying those coastal marshes that are vulnerable to collapse before conversion from vegetated marsh to open water occurs.

Using citizen science to estimate surficial soil Blue Carbon stocks in Great British saltmarshes

A new saltmarsh soil dataset comprising of geochemical and physical property data from 752 soil samples collected through a sampling program supported by citizen scientists has been brought together with existing data to make the first national estimates of the surficial (top 10 cm) soil OC stock for Great British (GB) saltmarshes. To allow the inclusion of secondary data in the soil stock estimate a new bespoke organic matter to organic carbon conversion for GB saltmarsh soil was developed allowing organic matter data measured using loss-on-ignition to be convert to organic carbon content. The total GB surficial soil OC stock is 2.320 ± 0.470 Mt; English saltmarshes hold 1.601 ± 0.426 Mt OC, Scottish saltmarshes hold 0.368 ± 0.091 Mt OC, and Welsh saltmarshes hold 0.351 ± 0.082 Mt OC. The stocks were calculated within a Markov Chain Monte Carlo framework allowing robust uncertainty estimates to be derived for the first time. Spatial mapping tools are available to accompany these stock estimates at individual saltmarsh habitats throughout GB. This data will aid in the protection and management of saltmarshes and represents the first steps towards the inclusion of saltmarsh OC in the national inventory accounting of blue carbon ecosystems.

The effect of surficial soil on the seismic response characteristics and failure pattern of step-like slopes

Earthquake-induced shallow landslides are widely distributed in earthquake-affected areas. These hazards mainly originate from fragmented surface rock masses or surficial loose deposits overlaid on bedrock structure slopes. The seismic response of the surficial soil-bedrock slope is the key to revealing the dynamic failure mechanism of earthquake-induced landslides. This study investigates the seismic response of a surficial soil-bedrock step-like slope to evaluate the acceleration ground motion amplification along the slope. Parametric analysis focusing on the geometry of the surficial soil, thickness of the surficial soil, surficial soil-bedrock impedance contrast and geometry of the slope is conducted using the finite difference modeling code FLAC3D. The results show that both the surficial soil characteristics and geometry of the slope have great influences on the acceleration amplification factor in the horizontal direction (AAF). A maximum AAF zone is always formed near the interface between the surficial soil and bedrock, and the AAF always abruptly amplifies near the slope surface, especially at the crest of the slope. The potential dynamic failure surfaces under earthquakes are formed near the interface between the surficial soil and bedrock, which is in accordance with the AAF amplification zone of the slope, and the depth of the dynamic failure of the surficial bedrock slope is deeper than the static failure surface. It can be concluded that the topographic effect on the seismic response of the slope is strongly dependent on the surficial soil material characteristics and geometry. The findings of this study can contribute to a better understanding of the mechanism of shallow earthquake-induced landslides and have a number of important implications for disaster prevention and mitigation.