Extent Of Region Research Articles

Modeling the Impact of Land Use Optimization on Non-Point Source Pollution: Evidence from Chinese Reservoir Watershed

We assessed the effectiveness of land optimization for controlling non-point source (NPS) pollution by combining a multi-objective dynamic planning approach with the application of the Land Use and its Effects at Small regional extents model and the Soil and Water Assessment Tool. The combined modeling approach showed substantial ability to reduce NPS pollution in Shitoukoumen Reservoir, Changchun City, China, reducing the annual total loads of nitrogen and phosphorus in the study area by 8.7 and 10.12%, respectively. The total nitrogen load decreased significantly and stabilized at less than 8 kg/hm2 from a peak level of over 15 kg/hm2. Higher total phosphorus loads before land use optimization were concentrated in the central parts of the study area, with the highest values exceeding 2.3 kg/hm2, and tended to spread outward but resolved at 1.5 kg/hm2 after optimization. The results showed that from a macro-perspective, optimization of the spatial distribution and quantitative composition of land use can effectively control NPS pollution. The study also demonstrates the potential effectiveness of the coupled multi-model methodology for mitigating NPS in the future.

Efficient functional localization of language regions in the brain

Important recent advances in the cognitive neuroscience of language have been made using functional localizers to demarcate language-selective regions in individual brains. Although single-subject localizers offer insights that are unavailable in classic group analyses, they require additional scan time that imposes costs on investigators and participants. In particular, the unique practical challenges of scanning children and other special populations has led to less adoption of localizers for neuroimaging research with these theoretically and clinically important groups. Here, we examined how measurements of the spatial extent and functional response profiles of language regions are affected by the duration of an auditory language localizer. We compared how parametrically smaller amounts of data collected from one scanning session affected (i) consistency of group-level whole-brain parcellations, (ii) functional selectivity of subject-level activation in individually defined functional regions of interest (fROIs), (iii) sensitivity and specificity of subject-level whole-brain and fROI activation, and (iv) test-retest reliability of subject-level whole-brain and fROI activation. For many of these metrics, the localizer duration could be reduced by 50-75% while preserving the stability and reliability of both the spatial extent and functional response profiles of language areas. These results indicate that, for most measures relevant to cognitive neuroimaging studies, the brain's language network can be localized just as effectively with 3.5 min of scan time as it can with 12 min. Minimizing the time required to reliably localize the brain's language network allows more effective localizer use in situations where each minute of scan time is particularly precious.

Climate Change Habitat Model Forecasts for Eight Owl Species in the Southwestern US.

The high-resolution forecasting of vegetation type shifts may prove essential in anticipating and mitigating the impacts of future climate change on bird populations. Here, we used the US Forest Service Ecological Response Unit (ERU) classification to develop and assess vegetation-based breeding habitat profiles for eight owl species occurring in the foothills and mountains of the Southwestern US. Shifts in mapped habitat were forecast using an ecosystem vulnerability model based on the pre-1990 climate envelopes of ERUs and the Intergovernmental Panel on Climate Change's (IPCC) A1B moderate-emission scenario for the future climate. For five of the eight owl species, the regional breeding habitat extent was projected to decline by at least 60% by 2090. Three species, the boreal owl (Aegolius funereus; at the trailing edge of its distribution), flammulated owl (Psiloscops flammeolus), and northern pygmy-owl (Glaucidium gnoma), were projected to experience the steepest habitat loss rates of 85%, 85%, and 76%, respectively. Projected vegetation shifts overlaid with well-documented flammulated owl breeding populations showed the complete or near complete loss of habitat by 2090 in areas of montane forest currently supporting dense aggregations of owl territories. Generalist or lower-elevation owl species were predicted to be less impacted, while, for the whiskered screech-owl (Megascops trichopsis), the contraction of the current habitat was nearly offset by a projected northward expansion. In general, the results of this study suggest high exposure to climate change impacts for the upper-elevation forest owls of semi-arid Southwestern North America. Long-distance migration and low natal philopatry may prove important to some montane owl populations in adapting to the regional loss of habitat.

The impact of aerosol-cloud interaction on mesoscale numerical weather prediction when low-cloud and haze coexist in winter over major polluted regions of China

Compared with climate models, the role of aerosol-cloud interaction (ACI) in mesoscale numerical weather prediction (NWP) models still needs to be better understood, especially in haze regions with relatively high aerosol concentration. Here, we perform two sensitivity experiments with and without ACI (ACI and NO-ACI) in the atmospheric chemistry model GRAPES_Meso5.1/CUACE to investigate the impact of ACI on mesoscale NWP during the low-cloud period in winter 2016 over varying haze regions (severe polluted Jing-Jin-Ji (JJJ), polluted Yangtze River Delta (YRD), and weak polluted Pearl River Delta (PRD)) in China. The study results show that the real-time ACI improves underestimated cloud optical thickness (COT) and cloud water liquid path (CLWP) in haze regions, with the mean bias of simulated COT (CLWP) decreased by 27% (3%), 60% (14%), and 55% (3%) in JJJ, YRD, and PRD, respectively. The increased COT and CLWP lead to a decrease of 6.8, 21, and 13 W m−2 in daytime surface downward shortwave radiation (SDSR) in JJJ, YRD, and PRD, helping to reduce the mean bias of daytime SDSR by 6%, 13%, and 9%. In addition, ACI mitigates the warm bias of temperature at 2 m and dry bias of relative humidity (RH) at 2 m to a certain extent in haze regions, particularly in YRD with the mean absolute bias improved by 13% and 6%. The simulated vertical structure of temperature and RH in the ACI experiment is more consistent with observations than in the NO-ACI experiment. Further investigations find that the ACI effects on mesoscale NWP strongly depend on COT and CLWP magnitude over varying haze regions. Higher COT and CLWP, hence more significant meteorology changes due to ACI, occur in YRD, followed by PRD and JJJ. This study demonstrates the importance and complexity of ACI in modifying mesoscale NWP over varying haze regions of China, which promotes the further understanding of ACI in operational NWP models and bridges the gap with climate models.

Sound field reproduction based on physical-model-based pressure matching with frequency-dependent variable control regions

The pressure matching (PM) method, one of the numerical sound field reproduction methods, requires the measurement of many transfer functions. Thus, it was difficult to modify the extent of the control region and the number of control points. In our previous studies, we proposed physical-model-based PM method by using sparse equivalent sources. Since the sound field from each loudspeaker is modeled by the superposition of equivalent sources, we can obtain the transfer functions at any position from the loudspeaker. Thus, the density and extent of control points can be freely modified. On the other hand, the PM method has the limitation that the reproduction accuracy depends on the extent of the controlled region. In this study, we proposed physical-model-based PM method with frequency-dependent variable control regions. In the simulation experiment, we evaluate the relationship between the extent of the reproduction region and the reproduction accuracy at each frequency. We also discuss the total reproduction accuracy when the extent of the reproduction region is modified for each frequency.

Subjective evaluation of source distance in dynamic 2.5D local sound field synthesis

Many loudspeakers are required to reproduce the immersive and physically-accurate sound field up to high frequency. Especially, at high frequency, a limited number of loudspeakers degrade the reproduction accuracy because of spatial Nyquist frequency. When use the same number of loudspeakers, reducing the extent of the reproduction region can improve the reproduction accuracy. However, by narrowing the reproduction region, the extent of movement for the listener is reduced. In our previous studies, we proposed the dynamic reproduction system of local sound field by moving the reproduction region to the listener's current position. Using a limited number of loudspeakers, the proposed system achieved the sound reproduction with high accuracy allowing the freedom of listener movement. In this study, we conduct the subjective evaluation of the dynamic 2.5D local sound field synthesis for sound source distance. Especially, we investigate the distance perception by allowing listeners to move around freely.

Electronic effects on radiation damage in α-iron: A molecular dynamics study

Iron (Fe)-based alloys, which have been widely used as structural materials in nuclear reactors, can significantly change their microstructure properties and macroscopic properties under high flux neutron irradiation during operation, thus, the problems associated with the safe operation of nuclear reactors have been put forward naturally. In this work, a molecular dynamics simulation approach combined with electronic effects is developed for investigating the primary radiation damage process in α-Fe. Specifically, the influence of electronic effects on the collision cascade in Fe is systematically evaluated based on two commonly used interatomic potentials for Fe. The simulation results reveal that both electronic stopping (ES) and electron–phonon coupling (EPC) can contribute to the decrease of the number of defects in the thermal spike phase. The application of ES reduces the number of residual defects after the cascade evolution, whereas EPC has a reverse effect. The introduction of electronic effects promotes the formation of the dispersive subcascade: ES significantly changes the geometry of the damaged region in the thermal spike phase, whereas EPC mainly reduces the extent of the damaged region. Furthermore, the incorporation of electronic effects effectively mitigates discrepancies in simulation outcomes when using different interatomic potentials.

High velocity lower crust with anomalous rheological parameters under the Red Sea Passive Margin, SW Saudi Arabia – insight into the evolution of the Hijaz-Asir Escarpment Zone

SUMMARY The Red Sea Passive Margin (RSPM) in SW Saudi Arabia is characterized by two morphological provinces; the Red Sea Coastal Plains (RSCP) and the Hijaz-Asir Escarpment Zone (HAEZ) at the Arabian Shield Edge (ASE). Of these, the HAEZ is conspicuous by its seaward-facing heights of > 3 km. Based on the available receiver function analysis (REF) results from 25 seismic stations, we first present the Moho relief map underlying the RSPM to demonstrate that: (i) the transitional crust under the coastal region is 20–25 km thick which steadily increases landward to attain a thickness of ∼40 km below ASE, across an intervening region of depressed Moho with depths of 45–52 km. The latter exhibits significant regional extent and displays a close correlation with the topography of the HAEZ, suggesting a tectonic control on its formation. Eight rheological parameters for the upper as well as the lower crust are computed from the REF data, namely; Vp, Vp/Vs, density (ρ), Lame's first constant (λ), Lame's second constant (μ), Poisson's ratio (σ), bulk modulus (K) and acoustic impedance (AI). Their 2-D distribution for the lower crust unravels, for the first time, a high velocity lower crust (HVLC) underneath the HAEZ. The rheological character of the HVLC is further elucidated by investigating the relations between six rheological parameters: Vp–Vp/Vs, Vp/Vs–lower crustal thickness (hLC), Vs/ρ–hLC, λ–ρ, σ–ρ and λ–μ. The results indicate that lithology of the lower crust varies from diorite–felsic gneiss under RSCP to gabbro–diabase and mafic gneiss under HAEZ. We conjecture that the HVLC is an outcome of the exchange of materials from the subcrust at the hinterland of the RSPM directly underlying the HAEZ. Deep seismic control can only resolve the finer details of such crustal transformation.

Numerical investigation of wall-pressure fluctuations for Mach 2 turbulent shock-wave boundary layer interactions

Implicit large-eddy simulations of Mach 2.05 turbulent boundary layer interactions with oblique impinging shock-waves were carried out for shock generator angles of 8° and 9°. Both the streamwise extent of the separated region and the intensity of the velocity fluctuations are augmented when the strength of the impinging oblique shock-wave is increased from 8° to 9°. Temporal Fourier transforms of the spanwise-averaged wall-pressure coefficient indicate low-frequency unsteadiness at separation and mid-frequency content downstream of reattachment. The wall-pressure fluctuations were analyzed with the proper orthogonal decomposition. The modal analysis reveals pronounced 3D low-frequency wall-pressure fluctuations for the stronger interaction. Overall, the present findings provide advanced perspectives on low-frequency wall-pressure fluctuations in turbulent shock-wave boundary layer interactions that may lead to spanwise non-uniformity of the separation and shedding with possible implications for the design of structural panels on high-speed vehicles.

New Insights in the Bubble Wall of NGC 3324: Intertwined Substructures and a Bipolar Morphology Uncovered by JWST

We report the discovery of intertwined/entangled substructures toward the bubble wall of NGC 3324 below a physical scale of 4500 au, which is the sharp edge/ionization front/elongated structure traced at the interface between the H ii region and the molecular cloud. The sharp edge appears wavy in the Spitzer 3.6–8.0 μm images (resolution ∼2″). Star formation signatures have mostly been traced on one side of the ionization front, which lies on the molecular cloud’s boundary. The James Webb Space Telescope’s (JWST) near- and mid-infrared images (resolution ∼0.″07—0.″7) are employed to resolve the sharp edge, which has a curvature facing the exciting O-type stars. The elongated structures are associated with the 3.3 μm polycyclic aromatic hydrocarbon (PAH) emission, the 4.05 μm ionized emission, and the 4.693 μm H2 emission. However, the PAH-emitting structures are depicted between the other two. The H2 emission reveals numerous intertwined substructures that are not prominently traced in the 3.3 μm PAH emission. The separation between two substructures in the H2 emission is ∼1.″1 or 2420 au. The intertwined substructures are traced in the spatial areas associated with the neutral to H2 transition zone, suggesting the origin of these structures by “thin-shell” instability. Furthermore, an arc-like feature traced in the Spitzer 3.6–8.0 μm images is investigated as a bipolar H ii region (extent ∼0.35 pc) at T d ∼25–28 K using the JWST images. A massive-star candidate VPHAS-OB1 #03518 seems to be responsible for the bipolar H ii region.

New insight into pectic fractions of cell wall: Impact of extraction on pectin structure and in vitro gut fermentation

Pectic polysaccharides modulate gut fermentation ability, which is determined by structural characteristics. In this work, apple pectins were extracted by HCl (HAEP), NaOH (AEP), cellulase (EAEP), and in parallel cell wall pectic fractions were sequentially extracted by water (WEP), chelator (CEP) and NaOH (NEP). The aim is to comprehensively compare the impact of extraction on pectin structure and gut fermentation behavior. Results showed that high content of galacturonic acid (90.65 mol%) and large molecular weight (675 kg/mol) were detected in the HAEP. Molecular morphology of the HAEP presented high linearity, while AEP, EAEP and WEP exhibited compact filamentous structures with highly branched patterns. The AEP was characterized by high yield (33.1 g/100 g d.b.), moderate molecular weight (304 kg/mol) and large extent of rhamnogalacturonan-I region (24.88 %) with low degree of branching (1.77). After in vitro simulated gut fermentation for 24 h, total content of short-chain fatty acid (SCFA) generated with the AEP supplement increased to 36.8 mmol/L, followed by EAEP, HAEP and WEP (25.2, 24.2 and 20.3 mmol/L, respectively). Meanwhile, WEP simultaneously produced the highest ammonia content (22.4 mmol/L). This investigation suggests that the fermentation of AEP produces more beneficial SCFA and less ammonia, thus indicating a better gut fermentation property.

Climate Change Impacts on Species Composition and Floristic Regions in Thailand

Tropical forests are vulnerable to climate change including increased temperatures and changes to rainfall variation. Here, we use Thailand as a case study for assessing the impacts of the shared socio-economic pathway and climate scenarios on changes to the distribution and extent of floristic regions. To address this question, we assigned floristic regions based on a structured cluster analysis of modeled species ranges, and evaluated how those regions respond under scenarios of climate change. A total of 201 plant species with sufficient occurrence data obtained from the systematic forest inventory plots across the country and global datasets were chosen for distribution modeling. Environmental variables, including soils, topography and bioclimatic variables were compiled to model both current and 2050 distributions. Potential floristic regions were classified using a clustering algorithm on the pixel-wise species compositions—resulting in 12 floristic regions representative of both current climate species compositions and projected future species assemblages. Five floristic regions are projected to experience little change in their geographic distribution, while the remainder are projected to be substantially displaced spatially. Additionally, two of the identified floristic regions are not well represented in protected areas—with less than 50% of the current geographic distribution in each region in some form of protected status.

Comparison of two corticosteroid regimens on brain volumetrics in patients with Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is a neuromuscular disorder in which many patients also have neurobehavioral problems. Corticosteroids, the primary pharmacological treatment for DMD, have been shown to affect brain morphology in other conditions, but data in DMD are lacking. This study aimed to investigate the impact of two corticosteroid regimens on brain volumetrics in DMD using magnetic resonance imaging (MRI). In a cross-sectional, two-center study, T1-weighted MRI scans were obtained from three age-matched groups (9-18 years): DMD patients treated daily with deflazacort (DMDd, n = 20, scan site: Leuven), DMD patients treated intermittently with prednisone (DMDi, n = 20, scan site: Leiden), and healthy controls (n = 40, both scan sites). FSL was used to perform voxel-based morphometry analyses and to calculate intracranial, total brain, gray matter, white matter, and cerebrospinal fluid volumes. A MANCOVA was employed to compare global volumetrics between groups, with site as covariate. Both patient groups displayed regional differences in gray matter volumes compared to the control group. The DMDd group showed a wider extent of brain regions affected and a greater difference overall. This was substantiated by the global volume quantification: the DMDd group, but not the DMDi group, showed significant differences in gray matter, white matter, and cerebrospinal fluid volumes compared to the control group, after correction for intracranial volume. Volumetric differences in the brain are considered part of the DMD phenotype. This study suggests an additional impact of corticosteroid treatment showing a contrast between pronounced alterations seen in patients receiving daily corticosteroid treatment and more subtle differences in those treated intermittently.

A maximum entropy approach to defining geographic bounds on growth and yield model usage

Growth and yield models are essential tools in modern forestry, especially for intensively managed loblolly pine plantations in the southeastern United States. While model developers often have a good idea of where these models should be used with respect to geographic location, determining geographic bounds for model usage can be daunting. Such bounds provide suitable areas where model predictions are likely to behave as expected or identify areas where models may do a poor job of characterizing the growth of a resource. In this research, we adapted a niche model methodology, commonly used to identify suitable spots for species occurrence (maximum entropy), to identify areas for using growth and yield models built from plots established in the Lower Coastal Plain and Piedmont/Upper Coastal Plain in the southeastern United States. The results from this analysis identify areas with similar climatic envelopes and soil properties to the areas where data was collected to fit these growth and yield models. These areas show notable overlap with the areas prescribed for use by the evaluated growth and yield models and support practitioners use of these models throughout these regions. Furthermore, this methodology can be applied to different forest models built using large regional extents as long as climatic and soil values are available for each site.

Climate change dynamics and mercury temporal trends in Northeast Arctic cod (Gadus morhua) from the Barents Sea ecosystem

The Northeast Arctic cod (Gadus morhua) is the world's northernmost stock of Atlantic cod and is of considerable ecological and economic importance. Northeast Arctic cod are widely distributed in the Barents Sea, an environment that supports a high degree of ecosystem resiliency and food web complexity. Here using 121 years of ocean temperature data (1900–2020), 41 years of sea ice extent information (1979–2020) and 27 years of total mercury (Hg) fillet concentration data (1994–2021, n = 1999, ≥71% Methyl Hg, n = 20) from the Barents Sea ecosystem, we evaluate the effects of climate change dynamics on Hg temporal trends in Northeast Arctic cod. We observed low and consistently stable, Hg concentrations (yearly, least-square means range = 0.022–0.037 mg/kg wet wt.) in length-normalized fish, with a slight decline in the most recent sampling periods despite a significant increase in Barents Sea temperature, and a sharp decline in regional sea ice extent. Overall, our data suggest that recent Arctic amplification of ocean temperature, “Atlantification,” and other perturbations of the Barents Sea ecosystem, along with rapidly declining sea ice extent over the last ∼30 years did not translate into major increases or decreases in Hg bioaccumulation in Northeast Arctic cod. Our findings are consistent with similar long-term, temporal assessments of Atlantic cod inhabiting Oslofjord, Norway, and with recent investigations and empirical data for other marine apex predators. This demonstrates that Hg bioaccumulation is highly context specific, and some species may not be as sensitive to current climate change-contaminant interactions as currently thought. Fish Hg bioaccumulation-climate change relationships are highly complex and not uniform, and our data suggest that Hg temporal trends in marine apex predators can vary considerably within and among species, and geographically. Hg bioaccumulation regimes in biota are highly nuanced and likely driven by a suite of other factors such as local diets, sources of Hg, bioenergetics, toxicokinetic processing, and growth and metabolic rates of individuals and taxa, and inputs from anthropogenic activities at varying spatiotemporal scales. Collectively, these findings have important policy implications for global food security, the Minamata Convention on Mercury, and several relevant UN Sustainable Development Goals.

Habitat structure shapes temperate reef assemblages across regional environmental gradients

Intertidal artificial habitats are proliferating, but are generally simpler in structure and host lower biodiversity than natural rocky reefs. Eco-engineering aims to enhance the biodiversity of coastal infrastructure, often through physical structural modifications that mimic topographic properties of natural shores. Relationships between biotic assemblages and structural properties of natural and artificial reefs have been extensively studied at sampling scales of up to 1 m2. But evidence that quantified local structural variation has an appreciable influence on biotic assemblages, at a shore-wide scale across regional environmental gradients, is lacking. Here we addressed this knowledge gap with an observational study at 32 natural and artificial intertidal reef sites in Wales, UK. We used multivariate community analysis and permutation tests to examine associations between local physical structure, regional environmental variables and sessile biotic assemblages. A potential influence of local habitat structure on assemblage composition was evident across regional-scale environmental gradients. Compared to natural sites, artificial reefs had lower taxonomic richness, distinct and more variable assemblage composition, and different physical structure. After removing the effect of habitat (natural or artificial), canonical correspondence analysis showed that environmental variables (wave exposure, sea surface temperature and salinity variation), along with two metrics of physical structure (standard deviation in log-transformed detrended roughness and skewness of surface verticality, both at 0.5 m scale), explained 40 % of the variation in assemblage composition among sites. The two structural metrics independently explained 14.5 % of the variation. Associations identified between individual taxa and environmental variables indicated that sites with a higher proportion of horizontal surfaces hosted more canopy macroalgae, which in turn support other algae and invertebrates. Our findings provide evidence to inform scaling-up of structural eco-engineering interventions from experimental contexts to enhance the biodiversity of coastal infrastructure across regional extents.

Preoperative Immunocyte-Derived Ratios Predict Postoperative Recovery of Gastrointestinal Motility after Colorectal Cancer Surgery.

The aim of this study was to assess the role of immunocyte-derived ratios (IDRs), such as the systemic immune-inflammation index (SII), neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR), and lymphocyte-to-monocyte ratio (LMR), as markers for the postoperative recovery of gastrointestinal function following colorectal cancer surgery. A retrospective analysis was conducted on a consecutive cohort of 260 patients who underwent radical colorectal cancer surgery within the timeframe spanning from January 2016 to December 2022. Data concerning the postoperative recovery of gastrointestinal function included the I-FEED score, time to pass flatus, toleration for liquids in the first 48 h, and the need for nasogastric tube reinsertion in the immediate postoperative period. A special emphasis was allocated towards the examination of IDRs and their interrelation with the postoperative gastrointestinal functional parameters. The I-FEED score exhibited a positive correlation with the NLR, SII, and PLR. The univariate analysis indicated that all IDRs, multiorgan resection, hemoglobin and protein levels, regional nodal extent of the tumor (N), and obesity significantly affected nasogastric tube reinsertion. The multivariate analysis showed that the SII and N1 stages were risk factors for nasogastric tube reinsertion after colorectal cancer surgery. The SII and multiorgan resection were the only classifiers that remained significant in the multivariable analysis for the toleration for liquids. In summation, certain preoperative IDRs, such as the SII, PLR, and NLR, may hold potential as predictive determinants for postoperative gastrointestinal functional recovery following colorectal cancer surgery.

Evaluating Large‐Domain, Hecto‐Meter, Large‐Eddy Simulations of Trade‐Wind Clouds Using EUREC4A Data

AbstractThe meso‐scale variability in cloudiness of the marine trade‐wind layer is explored with large‐eddy simulations of regional extent and validated against observations of the EUREC4A field campaign. 41 days of realistically forced simulations present a representative, statistical view on shallow convection in the winter North Atlantic trades that includes a wide range of meso‐scale variability including the four recently identified patterns of spatial organization: Sugar, Gravel, Flowers and Fish. The results show that cloud cover is on average captured well but with discrepancies in its vertical and spatial distribution. Cloudiness at the lifting condensation level depends on the model resolution with the finer one producing on average a more realistic cloud profile. Independent of the resolution, the variability in cloudiness below the trade inversion is not captured, leading to a lack of stratiform cloudiness with implications on the detectability of meso‐scale patterns whose cloud patches are characterized by stratiform clouds. The simulations tend to precipitate more frequently than observed, with a narrower distribution of echo intensities. The observed co‐variability between cloudiness and environmental conditions is well captured.

Quantifying the Extent of Authigenic Carbonate Formation in Shallow Marine Sediments Through a Correlation Between Carbonate Precipitation Rate and Sulfate Flux

AbstractThe accumulation of authigenic carbonate in marine sediments has been regarded as a significant contributor to the carbon cycle over Earth's history. However, accurate quantification of the extent of authigenic carbonate formation in both modern and ancient oceans has been challenging due to limited approaches. Here, we analyzed calcium, magnesium, dissolved inorganic carbon, and alkalinity pore‐water profiles of 153 sites influenced by methane diffusion from the northern South China Sea. By combining these data with published data of diffusive sulfate flux, we found a significant positive correlation between carbonate precipitation rate and sulfate flux in the subseafloor. This correlation can be used to quantify the regional extent of authigenic carbonate formation, representing an advantage over a spatial interpolation approach. We therefore propose that the observed correlation can serve as a new approach for quantifying authigenic carbonate formation in shallow sediments along continental margins for both modern and ancient oceans.

Performance, effectiveness and computational efficiency of powerline extraction methods for quantifying ecosystem structure from light detection and ranging

ABSTRACT National and regional data products of the ecosystem structure derived from airborne laser scanning (ALS) surveys with Light Detection And Ranging (LiDAR) technology are essential for ecology, biodiversity, and ecosystem monitoring. However, noises like powerlines often remain, hindering the accurate measurement of 3D ecosystem structures from LiDAR. Currently, there is a lack of studies assessing powerline noise removal in the context of generating data products of ecosystem structures from ALS point clouds. Here, we assessed the (1) performance and accuracy, (2) effectiveness, and (3) time efficiency and execution time of three powerline extraction methods (i.e. two point-based methods based on deep learning and eigenvalue decomposition, respectively, and one hybrid method) for removing powerline noise when quantifying 3D ecosystem structures in landscapes with varying canopy heights and vegetation openness. Twenty-five LiDAR metrics representing three key dimensions of the ecosystem structure (i.e. vegetation height, cover, and vertical variability) across 10 study areas in the Netherlands were used for our assessment. The deep learning method had the best performance and showed the highest accuracy of powerline removal across various landscape types (average F 1 score = 96%), closely followed by the hybrid method (average F 1 score = 95%). In contrast, the accuracy of the eigenvalue decomposition method was lower (average F 1 score = 82%) and depended on landscape context and vegetation composition (e.g. the F 1 score decreased from 96% to 63% when the average canopy height increased across landscapes). Powerline noise removal had the highest effectiveness (i.e. generating LiDAR metrics closest to those derived from manually labeled ground truth data) for LiDAR metrics capturing height and cover of low- and high-vegetation layers. Time efficiency (processed points per second) was highest for the eigenvalue decomposition method, yet the hybrid method reduced the execution time by > 50% compared to the deep learning method (ranging from 20% to 89% in study areas with different landscape composition). Based on our findings, we recommend the hybrid method for upscaling powerline removal on multi-terabyte ALS datasets to a regional or national extent because of its high accuracy and computational efficiency. Remaining misclassifications in LiDAR metrics could be further minimized by improving the training dataset for deep learning models (e.g. including various shapes of transmission towers from different datasets). Our findings provide novel insights into the performance of different powerline extraction methods, how their effectiveness varies for improving vegetation metrics and mapping the 3D ecosystem structure from LiDAR, and their computational efficiency for upscaling powerline removal in multi-terabyte ALS datasets to a national extent.