Field Samples Research Articles

Unlikely allies: Camel crickets play a role in the seed dispersal of an Asian autotrophic shrub

Societal Impact StatementDust seeds, which are minute and contain minimal energy reserves, are often associated with heterotrophy (plants that obtain carbon without photosynthesis). Consequently, previous studies have mainly focused on the relationships between dust seeds and heterotrophy. However, dust seeds are also found in green plants. This manuscript focuses on the seed ecology of the apparently autotrophic shrub Rhynchotechum discolor that produces dust seeds. Using time‐lapse photography, feeding experiments, and germination tests, we show that camel crickets effectively disperse the seeds of this autotrophic shrub. This is the first study to document insect‐mediated internal seed dispersal of an autotrophic plant in regions inhabited by terrestrial mammals, offering new insights into the evolutionary ecology of dust seeds.Summary Although angiosperms exhibit a wide range of seed sizes, the mechanisms driving these differences are poorly understood. The evolution of dust seeds, which contain minimal energy reserves, is traditionally linked to heterotrophy, in which external carbon sources are provided to the embryo or seedling. Dispersal by small animals may be another important but underexplored evolutionary driver of minute seed size. However, insect endozoochory has been documented only in the seeds of heterotrophic species and autotrophic species in New Zealand (i.e., in communities without native terrestrial mammals). Here, we investigate this seed dispersal mechanism in the Japanese shrub Rhynchotechum discolor (Gesneriaceae), which produces white berries with numerous tiny ellipsoid seeds, using time‐lapse photography, feeding experiments, and germination tests, particularly focusing on potential interactions with insect internal seed dispersers. Our time‐lapse photography indicated that camel crickets predominantly feed on fallen fruits of R. discolor. Field sampling revealed that camel crickets excreted numerous intact R. discolor seeds. Feeding experiments confirmed that some camel crickets excreted a high proportion of intact seeds, many of which successfully germinated into autotrophic seedlings. The present study provides the first evidence of insects acting as endozoochorous seed dispersers in fully autotrophic plants within regions inhabited by terrestrial mammals. Our findings suggest that orthopteran‐mediated seed dispersal is more widespread than previously thought, and that dust seeds can evolve from selective pressures beyond heterotrophy, specifically through insect‐mediated seed dispersal.

Model-assisted estimation of domain totals, areas, and densities in two-stage sample survey designs

Model-assisted, two-stage forest survey sampling designs provide a means to combine airborne remote sensing data, collected in a sampling mode, with field plot data to increase the precision of national forest inventory estimates, while maintaining important properties of design-based inventories, such as unbiased estimation and quantification of uncertainty. In this study, we present a comprehensive set of model-assisted estimators for domain-level attributes in a two-stage sampling design, including new estimators for densities, and compare the performance of these estimators with standard poststratified estimators. Simulation was used to assess the statistical properties (bias, variability) of these estimators, with both simple random and systematic sampling configurations, and indicated that 1) all estimators were generally unbiased. and 2) the use of lidar in a sampling mode increased the precision of the estimators at all assessed field sampling intensities, with particularly marked increases in precision at lower field sampling intensities. Variance estimators are generally unbiased for model-assisted estimators without poststratification, while model-assisted estimators with poststratification were increasingly biased as field sampling intensity decreased. In general, these results indicate that airborne remote sensing data, collected as an intermediate level of sampling, can be used to increase the efficiency of national forest inventories in remote regions.

The toxic legacy of artisanal and informal mining: XRF and gis analysis of soil contamination by Hg, Pb and As in the Secocha annex, Camaná, Peru

Hg, used as the main input in the gold amalgamation process in artisanal mining, along with lead Pb and As present in the toxic waste resulting from mining activity, cause serious effects on the environment and human health, as it occurs in the Secocha annex (Camaná, Peru). The objectives of the present study were to determine the concentrations of Hg, Pb, and As in the soil of the Secocha annex, evaluate the level of contamination of the site, determine the spatial distribution of contamination and the concentrations of the evaluated elements, and determine the origin of these contaminants. To achieve these objectives, satellite imagery, field sampling, X-ray fluorescence techniques, soil quality environmental regulations, geo-accumulation indices (Igeo), and geographic information system techniques were used. The results revealed maximum concentrations of 350 and 176.6 mg/kg for Hg and Pb, respectively. Of the 72 soil samples collected, the concentrations of Hg located within the urban/industrial area, where gold recovery activities are carried out, exceeded environmental regulations to a greater extent. In turn, the calculated Igeo revealed extreme soil contamination (5 < Igeo) due to the presence of Hg in most of the study area (95%), followed by moderate to heavy contamination (2 < Igeo < 3) due to the presence of Pb and As (0.5 and 5%, respectively). To reduce contamination and the concentrations of the evaluated elements, it is recommended to carry out studies to reuse inputs, change gold processing methodologies, and/or relocate the generated waste.

Advanced Modeling of Electro‐Optic Sampling: Nonlinear Vectoral‐Field Solutions to Maxwell's Equations

AbstractA comprehensive modeling approach for elucidating the intricacies of electro‐optic (EO) sampling is presented, which fully encapsulates the EO sampling process by accounting for all linear and second‐order nonlinear optical effects. The developed approach implements a multi‐step procedure, involving a vectorial‐field modeling of the second‐order nonlinear interactions occurring within the EO crystal, followed by a theoretical evaluation of the subsequent optical EO sampling components. To assess the efficacy of the approach, it is used for the sampling of terahertz electric fields (<1–>60 THz) within the bulk crystals of ZnTe and LiNbO3, as well as a ZnTe‐based waveguide. Nonetheless, this versatile method enables the investigation of EO sampling within any crystal incorporated within any geometry. This model provides a powerful tool for the in‐depth exploration of EO sampling, paving the way for advancements in various applications.

The effect of land use and land cover on soil carbon storage in the Yellow River Delta, China: Implications for wetland restoration and adaptive management

Gaining a comprehensive understanding of the effect of land use/land cover (LULC) and soil depth on soil carbon storage, through the manipulation of external carbon input and turnover processes, is crucial for accurate predictions of regional soil carbon storage. Numerous research investigations have been conducted to examine the impact of LULC on the storage and cycling of carbon in the surface soils of coastal wetlands. Nevertheless, there remains a dearth of understanding concerning the implications of this phenomenon on subterranean soils, a crucial factor in discerning the capacity for carbon sequestration in coastal wetlands and implementing measures for their preservation. The study focused on the Yellow River Delta (YRD) in China, which serves as a representative model system. It aimed to assess the impact of LULC as well as soil depth on carbon storage. This was achieved by a combination of remote sensing interpretation and field samplings. The findings of the study indicate that there was an increase in soil organic carbon storage with both the area covered and the depth of the soil across the four different land use types, namely forest, grass, tidal flat, and cultivated land. Cultivated land was identified as the predominant LULC type, encompassing 41.73% of the entire YRD. Furthermore, it accounted for a substantial carbon storage of 76.08%. In comparison to soil layers at depths of 0–20 cm and 20–40 cm, 40–60 cm was discovered to have the maximum carbon storage, accounting for 42.29% of total carbon storage. Furthermore, one of the main factors influencing carbon storage is salinity, which shows a negative association with carbon storage. Moreover, the aforementioned findings underscore the significance of the conjoined physical and chemical properties induced by LULC in influencing the dynamics of soil carbon. This suggests that the inclusion of deep soil carbon in the estimation and restoration of soil carbon storage is necessary. This inclusion will support the realization of the United Nations' “Toward Zero Carbon” effort and facilitate the implementation of China's national carbon neutrality objectives.

A study on source identification of contaminated soil with total petroleum hydrocarbons (aromatic and aliphatic) in the Ahvaz oil field.

The oil industry in Khuzestan province (Southwest Iran) is one of the main reasons contributing to the pollution of the environment in this area. TPH, including both aromatic and aliphatic compounds, are important parameters in creating pollution. The present study aimed to investigate the source of soil contamination by TPH in the Ahvaz oil field in 2022. The soil samples were collected from four oil centers (an oil exploitation unit, an oil desalination unit, an oil rig, and a pump oil center). An area outside the oil field was determined as a control area. Ten samples with three replicates were taken from each area according to the standard methods. Aromatic and aliphatic compounds were measured by HPLC and GC methods. The positive matrix factorization (PMF) model and isomeric ratios were used to determine the source apportionment of aromatic compounds in soil samples. The effects range low and effects range median indices were also used to assess the level of ecological risk of petroleum compounds in the soil samples. The results showed that Benzo.b.fluoranthene had the highest concentration with an average of 5667.7 ug/kg in soil samples in the Ahvaz oil field. The highest average was found in samples from the pump oil center area at 7329.48 ug/kg, while the lowest was found in control samples at 1919.4 ug/kg-1. The highest level of aliphatic components was also found in the pump oil center, with a total of 3649 (mg. Kg-1). The results of source apportionment of petroleum compounds in soil samples showed that oil activities accounted for 51.5% of the measured PAHs in soil. 38.3% of other measured compounds had anthropogenic origins, and only 10.1% of these compounds were of biotic origin. The results of the isomeric ratios also indicated the local petroleum and pyrogenic origin of PAH compounds, which is consistent with the PMF results. The analysis of ecological risk indices resulting from the release of PAHs in the environment showed that, except for fluoranthene, other PAHs in the oil exploitation unit area were above the effects range median level (ERM) and at high risk. The results of the study showed that soil pollution by total petroleum hydrocarbons (TPH), both aromatic and aliphatic, is at a high level, and is mainly caused by human activities, particularly oil activities.

Development and Application of Reverse Transcription Nanoplate-Based Digital PCR Assay for Sensitive and Accurate Detection of Rice Black-Streaked Dwarf Virus in Cereal Crops.

The emergence of rice black-streaked dwarf virus (RBSDV) poses a significant threat to global cereal crop cultivation, necessitating the urgent development of reliable detection and quantification techniques. This study introduces a reliable approach for the precise and sensitive quantification of the RBSDV in cereal crop samples, employing a reverse transcription digital polymerase chain reaction (RT-dPCR) assay. We assessed the specificity and sensitivity of the RT-dPCR assay proposed for precise RBSDV detection and quantification. Our findings demonstrate that RT-dPCR was specific for detection of RBSDV, with no cross-reactivity observed with other viruses infecting cereal crops. The RT-dPCR sensitivity was over 10 times that of RT-quantitative PCR (RT-qPCR). The detection limit of RT-dPCR was 0.096 copies/μl. In addition, evaluation of RT-dPCR assay with field samples was conducted on 60 different cereal crop samples revealed that RT-dPCR (45/60) exhibited superior accuracy compared with RT-qPCR (23/60). In this study, we present a specific and accurate RT-dPCR assay for the detection and quantification of RBSDV.

The effect of soil parameters and earthworm abundance on the fine-scale nocturnal habitat use of the Eurasian woodcock (Scolopax rusticola).

The Eurasian woodcock prefers habitats where its main prey, earthworms, can be found in higher densities. Although they are forest-dwelling birds, they regularly visit pastures and natural grasslands at night, where earthworm abundance is generally higher. However, there is little information on fine-scale habitat use in relation to variation in habitat characteristics and prey availability, particularly beyond the breeding season. In our study, we investigated if the nocturnal occurrence of woodcocks during migratory stopover periods differed between two neighbouring fields, or management units, with similar vegetation structure, and if within-field variation in the spatial patterns of woodcock sightings were associated with fine-scale earthworm densities and soil parameters. Specifically, we used GPS tracking data of two tagged woodcocks and direct observation data to study patterns of occurrence of birds in a mixed forest-pasture landscape in Hungary during pre- and post-breeding periods. We compared these patterns with fine-scale soil characteristics and earthworm abundance, acquired by field sampling. We found that the field with higher earthworm abundance was visited by woodcocks more frequently, and this correlation was similarly observed at the intra-field level. Our results demonstrate that woodcocks select foraging sites with higher earthworm densities at multiple spatial scales, both between fields (coarse scale), and within fields (fine-scale). Considering that woodcocks tended to return to the same field to forage at night, the strong associations between occupancy and resources provide a basis for developing habitat management strategies at the field level for conservation. As earthworm densities and soil parameters are good indicators of woodcock foraging habitat, measuring those variables, at least at a coarse scale, could aid in predicting important habitats for the species across the landscape.

Charging Properties and Particle Dynamics of Chang’e-5 Lunar Sample in an External Electric Field

Facing the challenges of in-situ utilization of lunar regolith resources, applying an external electric field to manipulate lunar particles has become a promising method for space particle control, which mainly depends on the particle charging properties in the applied electric field. Using the surficial lunar regolith samples brought back from the Moon by the Chang’e-5 mission (CE5 LS), this work successively studied their charging properties, particle dynamics, and their collision damages to aerospace materials under the action of an external electric field in high-vacuum conditions. The results indicated that the charging process and electrostatic projection of lunar regolith particles under high-vacuum conditions were different from those under atmosphere conditions. The particle diameter range of CE5 LS used in the experiment is 27.7–139.0 μm. For electric field strength of 3–12 kV·cm−1, the charge obtained by CE5 LS is 4.8 × 10−15–4.7 × 10−13 C and the charge-to-mass ratio is 1.2 × 10−5–6.8 × 10−4 C·kg−1. The CE5 LS is easier to be negatively charged in an external electric field. Furthermore, significant damages were observed on the target impact surfaces, indicating severe influences of lunar regolith particles on aerospace materials. Our work contributes to a more comprehensive understanding of physical mechanisms controlling the lunar regolith shielding and utilization, and will inspire broad efforts to develop the lunar in-situ engineering solutions.

Experimental constraints on barium isotope fractionation during adsorption–desorption reactions: Implications for weathering and erosion tracer applications

Constraining the processes that fractionate barium isotopes is essential for utilising barium isotope ratios as environmental tracers. Barium concentration measurements from soils, rivers, and estuaries demonstrate that adsorption–desorption reactions significantly influence the distribution of fluid–mobile barium at the Earth’s surface, potentially driving isotopic fractionation. To quantify the direction and magnitude of isotopic fractionation resulting from these reactions, a riverine and an estuarine series of batch experiments were conducted using environmentally important adsorbent minerals and surface waters. Himalayan river sediment and water samples were used to validate the experimental results.Adsorption–desorption reactions were found to be rapid, relative to the average transit time of sediment and water in catchments, and largely reversible. The direction and magnitude of isotopic fractionation in the riverine experiment series were consistent with the riverine field samples (preferential adsorption of the lighter isotopes). The reaction rate, reversibility, and magnitude of isotopic fractionation were found to depend primarily on the mineral. Experiments performed with iron oxyhydroxides (goethite and ferrihydrite) resulted in a greater degree of fractionation compared to clay minerals (kaolinite and montmorillonite). Estuarine experiments, designed to simulate sediment passage through a salinity gradient, demonstrated a high degree of reversibility, with 77% to 94% of adsorbed barium desorbed upon the addition of seawater to freshwater-equilibrated clay minerals.The results of the estuarine experiments suggest that barium isotope ratios measured in marine paleo-archives (e.g., corals) will reflect both the adsorbed and dissolved freshwater barium inputs to the ocean. The combined findings of this study indicate that the chemical and isotopic behaviour of barium differs from more conventional group 1 and 2 metal isotope systems due to a significant proportion of barium released from bedrock dissolution partitioning to mineral surfaces, rapid reaction rates between fluid–mobile phases, and a high degree of reaction reversibility. Consequently, riverine barium isotope ratios are likely to provide unique insights into the complex array of terrestrial weathering and erosion processes that sustain life on Earth.

Development of Precision Controllable Magnetic Field-Assisted Platform for Micro Electrical Machining.

In order to introduce the magnetic field into micro electrical machining technology to explore the influence of magnetic field on micro electrical machining, the development of a precision controllable magnetic field-assisted platform is particularly important. This platform needs to precisely control the spatial magnetic field. This study first completes the hardware design and construction of the magnetic field generation device, using electromagnetic coils with soft iron cores as the sources of the magnetic field. Mathematical models of the magnetic field are established and calibrated. Since the magnetic dipole model cannot effectively describe the magnetic field generated by the electromagnetic coil, this study adopts a more precise description method: the spherical harmonic function expansion model and the magnetic multipole superposition model. The calibration of the magnetic field model is based on actual excitation magnetic field data, so a magnetic field sampling device is designed to obtain the excitation magnetic field of the workspace. The model is calibrated based on a combination of the theoretical model and magnetic field data, and the performance of the constructed setup is analyzed. Finally, a magnetic field-assisted platform has been developed which can generate magnetic fields in any direction within the workspace with intensities ranging from 0 to 0.2 T. Its magnetic field model arrives at an error percentage of 2.986%, a variance of 0.9977, and a root mean square error (RMSE) of 0.71 mT, achieving precise control of the magnetic field in the workspace.

A novel dual CRISPR-Cas assay for detection of infectious hypodermal and hematopoietic necrosis virus (IHHNV) in penaeid shrimp without false positives from its endogenous viral elements (EVEs)

Infectious hypodermal and hematopoietic necrosis virus (IHHNV) is a single-stranded DNA virus posing significant economic challenges in shrimp aquaculture. Depending on the shrimp species, IHHNV infections can lead to mass mortalities, deformities, or growth retardation, all of which impact production output. Timely identification of IHHNV, particularly using nucleic acid detection methods, is paramount for effective prevention. However, PCR and methods relying on nucleic acid probes face challenges due to the presence of chromosome-integrated, endogenous viral elements (EVEs) of IHHNV sharing identical sequences to their infectious counterparts. While long-range PCR assays, such as LongAmp PCR (LA-PCR), have shown promise in minimizing false positive results, their applicability in the field is limited by their long turnaround times and reliance on costly equipment. To address these limitations, we have developed a rapid and potentially field-deployable platform termed Cas9-RPA-Cas12a (“CRPAC”) capable of differentiating the infectious form of IHHNV from EVEs, capitalizing on the fact that the genome of IHHNV is single-stranded, while EVEs are double-stranded DNA. This method employs Cas9 endonuclease to deplete EVEs, thereby enriching for single-stranded genomic DNA. This enriched DNA is then subjected to recombinase polymerase amplification (RPA) coupled with the Cas12a diagnostic assay. Here, we show that CRPAC gives positive results exclusively for infectious IHHNV, appearing as strong fluorescence or a distinct pattern on lateral flow strips that facilitates naked-eye evaluation. In field sample testing, CRPAC demonstrated excellent agreement with LA-PCR, identifying 8 out of 16 samples containing infectious IHHNV, while the WOAH-recommended PCR assays gave false positive results to all samples containing EVEs. Collectively, our findings underscore the utility of CRPAC as a robust and field-adaptable tool for distinguishing between infectious IHHNV and EVEs, irrespective of their nucleotide sequence similarities.

Mapping air quality variations in industrial and agricultural zones: Understanding spatial and temporal patterns of selected air pollutants

With the escalating threat of air pollution on the biota, the need for research on pollutants has become imperative in industrial, urbanized and heavily populated cities. This study aimed to determine the level of major outdoor atmospheric pollutants (PM10, PM2.5, TVOCs, and HCHO) in specific locations including industrial and agricultural zones. Field measurements for this research, spanning 52 locations, were collected in the spring season using a portable instrument, and spatial variation maps were developed using ArcGIS software. The study measured PM10 concentrations ranging from 31 μg/m3 to 267 μg/m3 and PM2.5 concentrations ranging from 27 μg/m3 to 253 μg/m3. PM2.5 levels at most sites exceeded USEPA, WHO, and PEQS standards, while PM10 levels generally met these standards. The highest values of coarse and fine particulate matter were observed in areas dominated by emissions from the textile industry. Furthermore, particulate matter concentrations showed spatial variations, increasing towards the North and East directions. The Total Volatile Organic Compounds (TVOCs) concentrations, ranging from 0 mg/m3 to 4.019 mg/m3, exceeded Hong Kong SAR standards at five locations, thereby elevating health risks for residents in these areas. Similarly, formaldehyde levels, ranging from 0 mg/m3 to 0.754 mg/m3, surpassed the Hong Kong SAR standard at seven locations, indicating a substantial threat of exposure for the local population. In general, air quality at most field sampling sites was registered as UNQUALIFIED but was also observed to be FRESH at a few locations. This research is significant for understanding the levels of major pollutants so that the concerned authorities can take appropriate measures to tackle air pollution by introducing pollution control technologies in industries, switching to renewable energy options, and managing road dust.

Assessment of macrozoobenthic community dynamics in the Ijuk River: Implications for freshwater ecosystem health and conservation management

Background: Nestled within the Isau-Isau Wildlife Reserve, the Ijuk River stretches approximately 3 kilometers, serving as a vital conservation area. Its upstream region plays multiple ecological roles, including watershed management, hydrological regulation, microclimate control, soil fertility maintenance, microbial habitat provision, air quality regulation, and carbon sequestration. However, escalating human activities, particularly changes in land use, pose significant threats to its ecological balance. The particular concern is the conversion of forested areas into agricultural lands, primarily for coffee cultivation and mixed gardens, encroaching dangerously close to the riverbanks. This encroachment necessitates a critical reevaluation of the river's water quality, given its crucial role in supporting biodiversity and ecological equilibrium. Benthic insects dwelling in the riverbed serve as invaluable bioindicators, offering insights into the overall health of aquatic ecosystems. Methods: Conducted between January and July 2022 in the Isau-Isau Wildlife Refuge, Lawang Agung Village, Mulak Ulu District, Lahat Regency, the study aimed to assess the macrozoobenthic community structure across three river segments: upstream, midstream, and downstream. Employing field sampling, observational surveys, taxonomic identification, and data analysis, the research aimed to unravel the river's ecological dynamics. Findings: Through meticulous examination of benthic insect communities, the study revealed relatively favorable water quality in the Ijuk River. However, discernible declines in various ecological parameters, as evidenced by evaluation results, highlight the urgency of conservation efforts and proactive management strategies to mitigate further degradation and preserve the river's ecological integrity. Conclusion: Such endeavors are crucial for safeguarding the biodiversity and sustainability of this vital freshwater ecosystem. Novelty/Originality of this Study: The study uniquely assesses the macrozoobenthic community dynamics in the Ijuk River, revealing significant changes over two decades that highlight the river's ecological health and underscore the urgent need for conservation efforts. It offers a comprehensive, updated evaluation of the macrozoobenthic community structure, providing critical insights into the impacts of land use changes and human activities on freshwater ecosystems.

AI-based rock strength assessment from tunnel face images using hybrid neural networks

In geological engineering and related fields, accurately and quickly identifying lithology and assessing rock strength are crucial for ensuring structural safety and optimizing design. Traditional rock strength assessment methods mainly rely on field sampling and laboratory tests, such as uniaxial compressive strength (UCS) tests and velocity tests. Although these methods provide relatively accurate rock strength data, they are complex, time-consuming, and unable to reflect real-time changes in field conditions. Therefore, this study proposes a new method based on artificial intelligence and neural networks to improve the efficiency and accuracy of rock strength assessments. This research utilizes a Transformer + UNet hybrid model for lithology identification and an optimized ResNet-18 model for determining rock weathering degrees, thereby correcting the strength of the tunnel face surrounding rock. Experimental results show that the Transformer + UNet hybrid model achieves an accuracy of 95.57% in lithology identification tasks, while the optimized ResNet model achieves an accuracy of 96.13% in rock weathering degree determination. Additionally, the average relative error in tunnel face strength detection results is only 9.33%, validating the feasibility and effectiveness of this method in practical engineering applications. The multi-model neural network system developed in this study significantly enhances prediction accuracy and efficiency, providing robust scientific decision support for tunnel construction, thereby improving construction safety and economy.

Zinc Orthophosphate Can Reduce Nitrate-Induced Corrosion of Lead Solder.

Nitrate-induced spallation of lead-bearing solder particles into drinking water is not sufficiently controlled by phosphate-based inhibitors, although adding zinc can improve their performance. Studies using copper coupons coated with new lead-tin solder in water with up to 12 mg/L nitrate demonstrated that zinc orthophosphate reduced lead release by more than 90% and outperformed orthophosphate alone. Lead release and spallation from harvested pipes with decades-old lead-tin solder in a high nitrate water were improved but not eliminated with zinc orthophosphate over a period of months. When applied at a water utility with high source water nitrate, monthly in-home field sampling showed that 90th percentile lead levels dropped below the action level after dosing zinc orthophosphate at full scale for 6 months. Scanning electron microscopy (SEM) analysis of pipe scales revealed that zinc and orthophosphate codeposit at the copper-solder interface and may act as a mixed inhibitor, with zinc inhibiting the cathodic reaction on the copper pipe, phosphate limiting the anodic reaction, and an added benefit of zinc orthophosphate preferentially precipitating at the galvanic interface between the anode and the cathode. Updates to corrosion control guidance for waters with higher nitrate due to seasonal runoff or source water changes are needed.

Magnetic capacity in manganese sulfides with rare earth substitution Mn<sub>1–x</sub>Re<sub>x</sub>S

Polycrystalline samples Mn1–xGdxS and Mn1–xYbxS with a concentration x = 0.2, near the concentration of ion flow through the fcc lattice, are studied in order to determine fluctuations in the valence of the ytterbium ion on dielectric properties. Dielectric constant and dielectric losses were determined from measurements of capacitance and loss tangent in the frequency range 102–106 Hz at temperatures of 80–500 K without a magnetic field and in a magnetic field. The magnetic capacity and dielectric losses in the magnetic field of the sample were determined from the relative change in the real and imaginary parts of the dielectric constant of the sample in a magnetic field H = 12 kOe applied parallel to the capacitor plates. A temperature range with a sharp increase in dielectric constant and with a maximum dielectric loss has been discovered, which shifts with increasing frequency and magnetic field. An increase in dielectric constant and dielectric losses in a magnetic field above 170 K was found in Mn1-xYbxS. The increase in dielectric losses is explained by an increase in relaxation time, as a result of local deformations near ytterbium ions during valence fluctuations. The mechanism for reducing reactance in a magnetic field in Mn1–xYbxS at low frequencies due to capacitance, and at high frequencies due to inductance, has been determined. In the Mn0.8Gd0.2S compound, the imaginary part of the dielectric constant has two maxima. The low-temperature maximum shifts in a magnetic field towards high temperatures and is described in the model of localized electrons with freezing of dipole moments. Dielectric losses decrease in a magnetic field. The magnetic capacity decreases by an order of magnitude in Mn0.8Gd0.2S compared to Mn0.8Yb0.2S. The dielectric constant in both compounds is described in the Debye model with the activation dependence of the relaxation time on temperature, where the activation energies differ for ytterbium and gadolinium ions.

Monitoring the Spatial Distribution of Cover Crops and Tillage Practices Using Machine Learning and Environmental Drivers across Eastern South Dakota

The adoption of conservation agriculture methods, such as conservation tillage and cover cropping, is a viable alternative to conventional farming practices for improving soil health and reducing soil carbon losses. Despite their significance in mitigating climate change, there are very few studies that have assessed the overall spatial distribution of cover crops and tillage practices based on the farm’s pedoclimatic and topographic characteristics. Hence, the primary objective of this study was to use multiple satellite-derived indices and environmental drivers to infer the level of tillage intensity and identify the presence of cover crops in eastern South Dakota (SD). We used a machine learning classifier trained with in situ field samples and environmental drivers acquired from different remote sensing datasets for 2022 and 2023 to map the conservation agriculture practices. Our classification accuracies (>80%) indicate that the employed satellite spectral indices and environmental variables could successfully detect the presence of cover crops and the tillage intensity in the study region. Our analysis revealed that 4% of the corn (Zea mays) and soybean (Glycine max) fields in eastern SD had a cover crop during either the fall of 2022 or the spring of 2023. We also found that environmental factors, specifically seasonal precipitation, growing degree days, and surface texture, significantly impacted the use of conservation practices. The methods developed through this research may provide a viable means for tracking and documenting farmers’ agricultural management techniques. Our study contributes to developing a measurement, reporting, and verification (MRV) solution that could help used to monitor various climate-smart agricultural practices.

Grassland degradation affected vegetation carbon density but not soil carbon density

BackgroundWith the profound changes in the global climate, the issue of grassland degradation is becoming increasingly prominent. Grassland degradation poses a severe threat to the carbon cycle and carbon storage within grassland ecosystems. Additionally, it will adversely affect the sustainability of food production. The grassland ecosystem in the northwest region of Liaoning Province, China, is particularly vulnerable due to factors such as erosion from the northern Horqin Sandy Land, persistent arid climate, and issues related to overgrazing and mismanagement of grassland. The degradation issue is especially pronounced in this ecological environment. However, previous research on the carbon density of degraded grasslands in Northeast China has predominantly focused on Inner Mongolia, neglecting the impact on the grasslands in the northwest of Liaoning Province. Therefore, this experiment aims to assess the influence of grassland degradation intensity on the vegetation and soil carbon density in the northwest of Liaoning Province. The objective is to investigate the changes in grassland vegetation and soil carbon density resulting from different degrees of grassland degradation.MethodologyThis study focuses on the carbon density of grasslands at different degrees of degradation in the northwest of Liaoning Province, exploring the variations in vegetation and soil carbon density under different levels of degradation. This experiment employed field sampling techniques to establish 100 × 100 m plots in grasslands exhibiting varying degrees of degradation. Six replications of 100 × 100 m plots per degradation intensity were sampled. Vegetation and soil samples were collected for analysis of carbon density.ResultsThe results indicate that in the context of grassland degradation, there is a significant reduction in vegetation carbon density. Furthermore, it was found that root carbon density is the primary contributor to vegetation carbon density. In comparison to mildly degraded grasslands, moderately and severely degraded grasslands experience a reduction in vegetation carbon density by 25.6% and 52.6%, respectively. However, with regard to the impact of grassland degradation on soil carbon density, it was observed that while grassland degradation leads to a slight decrease in soil carbon density, there is no significant change in soil carbon density in the short term under the influence of grassland degradation.ConclusionsTherefore, grassland degradation has exerted a negative impact on aboveground vegetation carbon density, reducing the carbon storage of above-ground vegetation in grasslands. However, there was no significant effect on grassland soil carbon density.

Estimation of Coastal Wetland Vegetation Aboveground Biomass by Integrating UAV and Satellite Remote Sensing Data

Aboveground biomass (AGB) serves as a crucial indicator of the carbon sequestration capacity of coastal wetland ecosystems. Conducting extensive field surveys in coastal wetlands is both time-consuming and labor-intensive. Unmanned aerial vehicles (UAVs) and satellite remote sensing have been widely utilized to estimate regional AGB. However, the mixed pixel effects in satellite remote sensing hinder the precise estimation of AGB, while high-spatial resolution UAVs face challenges in estimating large-scale AGB. To fill this gap, this study proposed an integrated approach for estimating AGB using field sampling, a UAV, and Sentinel-2 satellite data. Firstly, based on multispectral data from the UAV, vegetation indices were computed and matched with field sampling data to develop the Field–UAV AGB estimation model, yielding AGB results at the UAV scale (1 m). Subsequently, these results were upscaled to the Sentinel-2 satellite scale (10 m). Vegetation indices from Sentinel-2 data were calculated and matched to establish the UAV–Satellite AGB model, enabling the estimation of AGB over large regional areas. Our findings revealed the AGB estimation model achieved an R2 value of 0.58 at the UAV scale and 0.74 at the satellite scale, significantly outperforming direct modeling from field data to satellite (R2 = −0.04). The AGB densities of the wetlands in Xieqian Bay, Meishan Bay, and Hangzhou Bay, Zhejiang Province, were 1440.27 g/m2, 1508.65 g/m2, and 1545.11 g/m2, respectively. The total AGB quantities were estimated to be 30,526.08 t, 34,219.97 t, and 296,382.91 t, respectively. This study underscores the potential of integrating UAV and satellite remote sensing for accurately assessing AGB in large coastal wetland regions, providing valuable support for the conservation and management of coastal wetland ecosystems.