Slope Area Research Articles

The relative impacts of vegetation, topography and weather on landscape patterns of burn severity in subtropical forests of southern China

Understanding the landscape patterns of burn severity is vital for managing fire-prone ecosystems. Relatively limited research has been done about fire and burn severity patterns in subtropical forests. Here, we derived the pre-fire forest type data from a global land-cover product at 30 m resolution based on time-series Landsat imageries. Using Landsat 8 OLI remote sensing imagery and field-based composite burn index (CBI), this study spatially mapped the burn severity of 27 forest fires in the subtropical forest ecosystems in southern China from 2017 to 2021. The landscape pattern of patches with different burn severity was quantified using landscape indices. In addition, factors influencing the patterns of burn severity across the landscape were determined using the Geodetector model. Burn severity of patches varied significantly over space. High burn severity was common in forest patches with low fragmentation, low patch density, and regular shape. In contrast, moderate and low burn severity was prevalent in patches with smaller patch size, high patch density, and complex shapes. Extensively burned forest patches were located at higher elevations, while more fragmented patches were located in gently sloping areas. Topographic factors were the most significant factors influencing variances in burn severity across the forest patches, followed by weather conditions. Compared to low elevation areas, vegetation types at the high elevation areas (dominated by Masson pine) are more singular, with higher fuel loads, thus resulting in a more regularly-shaped distribution of highly severe burning patches. A detailed understanding of burn severity patterns and driving factors in a landscape can help develop sustainable forest management and restoration strategies. Practically, fire managers should conduct mechanical fuel treatments or thinning of forests at high-elevation areas to reduce the potential of severe fire behavior and the continuity of fire spread.

Petrogenesis and Tectonic Setting of Early Cretaceous A-Type Granite from the Southern Great Xing’an Range, Northeastern China: Geochronological, Geochemical, and Hf Isotopic Evidence

The southern Great Xing’an Range is located in the eastern Central Asian Orogenic Belt, where voluminous igneous rocks developed during the Late Mesozoic period. The east slope of the southern Great Xing’an Range has been the topic of numerous debates on the level of influence of the Mongol-Okhotsk and the Paleo-Pacific regimes in the Late Mesozoic period. Therefore, this area is a suitable region in which to study the temporal changes in magma sources and tectono-magmatic evolution. In this paper, whole-rock geochemical data, zircon U-Pb geochronology, and zircon Hf isotope studies were carried out on the granitoids in the east slope area of the southern Great Xing’an Range. LA-ICP-MS zircon U-Pb dating revealed the ages of four granitoid samples: 135.0 ± 0.6 Ma, 130.7 ± 1.4 Ma, 130.4 ± 1.0 Ma, and 127.6 ± 0.8 Ma, respectively. The Hf isotope values 176Hf/177Hf = 0.282751–0.283015, εHf (t) = +2.0~+11.5, and T2DM = 583~1442 Ma suggest that the magma was generated by partial melting of Meso- and Neoproterozoic accreted and thickened low crust. The whole-rock geochemical data implied that these granitoids are A-type granite and their formation is closely linked to the subduction of the Paleo-Pacific Ocean plate. These geochemical, isotopic, and geochronological data suggest that the Early Cretaceous magmatism in the east slope area of the southern Great Xing’an Range formed in an extensional back-arc tectonic setting associated with the slab roll-back of the Paleo-Pacific plate subduction.

Measuring the Multi-Scale Landscape Pattern of China’s Largest Archipelago from a Dual-3D Perspective Based on Remote Sensing

Measuring the landscape pattern from a three-dimensional perspective is of great significance for comprehensively revealing the complex spatial characteristics of island ecosystems. However, the archipelago composed of rocky islands has received little attention as its three-dimensional landscape characteristics are difficult to quantify. This study took the largest archipelago in China, the Zhoushan Archipelago, as the study area and constructed an island landscape pattern evaluation model from a dual-three-dimensional (dual-3D) perspective. The model divided the island into upper and lower layers, namely the surface landscape based on topography and the landscape elements above the surface (i.e., vegetation and buildings), and then evaluated their landscape patterns from a three-dimensional perspective, respectively. The landscape pattern model based on a dual-3D perspective and multiple scales achieved excellent results in the archipelago. First, the island landscape pattern was evaluated from three-dimensional perspectives, including human interference, landscape fragmentation, vegetation space, and building space. Second, landscape indices such as the human interference three-dimensional index (HITI), the landscape fragmentation three-dimensional index (LFTI), the vegetation three-dimensional index (VTI), and the building three-dimensional index (BTI) established at multiple spatial scales revealed spatial heterogeneity within and between islands. Environmental factors such as elevation, slope, and island area exhibited significant correlations with them. There were significant differences in landscape pattern indices between the two-dimensional (2D) and the three-dimensional (3D) perspectives, and high values were mainly distributed in areas with significant topographic changes and larger islands. In addition, as the evaluation unit increased, the landscape indices increased, and HITI became more responsive to the transitions from 2D to 3D, while LFTI was the opposite. Therefore, the multiscale landscape pattern measurement of China’s largest archipelago based on high-resolution remote sensing was carried out from three-dimensional perspectives to accurately reveal the spatial heterogeneity.

Cascading failure mechanism of major drainage system in mountainous city: Taking the basin of the main urban area of Chongqing as an example, China

Failure of major drainage systems is almost always accompanied by waterlogging. Understanding the operation and failure mechanism of major drainage systems is an important prerequisite for understanding and managing waterlogging. The natural and artificial environments in mountainous cities are more complex, and the major drainage system, as an open system for excessive surface runoff discharge and storage, is more prone to local overload and cascading failure. Existing theories and methods are difficult to explain and analyze the cascading failure characteristics and principles of major drainage systems in mountainous cities. Based on the complex network technology and the principle of runoff balance, the cascade failure model of major drainage system was constructed, and the characteristics and laws of cascade failure under six kinds of terrain, six kinds of short duration rainstorm and two kinds of surface environments were quantitatively analyzed. Research has found that the cascading failure of major drainage systems and waterlogging in mountainous cities should be the same phenomenon from different perspectives, and the simulated matching degree between the two can reach 79.5%. Meanwhile, 456 potential waterlogging locations were discovered in the study area, which is much larger than the actual 73 locations. When urban construction and rainfall conditions change, these unstable potential waterlogging locations are easily apparent. Among them, terrain is the main factor restricting the cascading failure of major drainage systems. Low lying valley areas often quickly accumulate a large amount of overflow, while flat areas are prone to overflow spreading to the surrounding areas; Slope areas are not prone to overflow, but are prone to local flooding. The change of short duration rainstorm and the difference of surface environmental openness will further interfere with the cascade failure of the major drainage system. The longer the return period of the short duration rainstorm or the increase of the peak value of the rainfall pattern, the greater the discharge and storage pressure of the major drainage system per unit time, resulting in intensified waterlogging. The open and unobstructed surface environment will lead to the small-scale spread of waterlogging, but this will significantly reduce the overall degree of waterlogging in the late rainstorm. The study revealed the spatiotemporal principles and basic laws of cascading failure of major drainage systems in mountainous cities. The conclusion is helpful for mountainous cities to formulate urban construction management strategies and climate change adaptation strategies, and to cope with current and future potential waterlogging disasters.

Dynamics of Phytomass Spatial Organization in a Reserved Steppe Landscape: Case Study of Burtynskaya Steppe, Orenburg Reserve

The “hot spot analysis” was applied to materials from 51 Landsat satellite images using the example of the “Burtinskaya Steppe” area of the Orenburgsky Nature Reserve, to study the dynamics of areas of positive phytomass anomalies relative to a neighborhood with a radius of 300 m. The purpose of the study was to establish the dependence of the variability of areas of increased phytomass on the landscape structure and hydrothermal conditions. We concluded that the switching of phytocenoses in transition zones from steppe to meadow type of functioning is ensured by varying the ratio of xerophytes and mesophytes depending on fluctuations in hydrothermal conditions. The frequency and area of positive phytomass anomalies in the bottoms of gullies correlates with their area on partially forested slopes, which indicates the positive role of forest vegetation in the stabilization of moisture influx into the bottoms. In deforested catchment areas of the south-facing slopes, the area of positive phytomass anomalies is determined by the supply of snow moisture, and in the catchment areas of north-facing slopes, by warm-period precipitation. The binding factors for the most stable positive anomalies of phytomass are the moisture convergence and the landform concavity rather than the catchment area.

The Effect of Changes in Rainfall Patterns due to Climatic Change on the Cutting Slope Stability of Landslides Case in East Java, Indonesia

This study was conducted to determine the causes of landslides that often occur on the cutting slope on the side of the Gempol-Pandaan toll road in East Java. Furthermore, this study aims to ascertain the relationship between alterations in rainfall intensity due to climatic change on slope stability. Observation of conditions in the field, topographic contour measurements, field soil testing, real-time data processing of rain intensity, and numerical simulation for parametric study were carried out to determine the effect of changes in daily rainfall on slope stability. Also, numerical analysis using limit equilibrium as well as finite element methods with SEEP/W and SLOPE/W was carried out. The results of field observations showed there was no rainwater collection channel in the slope area, causing the water to infiltrate into the cutting slope body. The fluctuating and increasing rainfall intensity during 90 days of observation can reduce the safety factor of slope by up to 25%. This decrease in safety factors is believed to increase when the duration and intensity of the rain increase as a result of climatic change. Therefore, the integration between the impact of climate change on alterations in rain intensity in an area needs to be considered as an effort to mitigate landslides.

GAS GEOCHEMICAL ANOMALIES IN THE BOTTOM SEDIMENTS OF THE TATAR TROUGH (SEA OF JAPAN)

The paper presents the results of gas geochemical and lithogeochemical studies of bottom sediments in the Tatar Strait trough (Sea of Japan) based on cruise data from the R/V “Akademik M.A. Lavrentyev” (LV-81 and LV-85). Anomalies of hydrocarbon gases (HCG) and chemical elements in surface bottom sediments were determined. It has been established that sediments with anomalous methane contents are significantly enriched in Mn, Sc, V, Co, Ni, Cu, As, Se, Mo, Cd, Sb, Te, Tl, U, the concentration coefficients (Kk) of which are 1.3–5.9 times higher than their similar values at other stations. The data obtained allow us to assume the presence of gas sources of hydrocarbon migration, the continental slope and deep water area of the Tatar trough is promising for setting up detailed work on the assessment of oil and gas potential and gas hydrate content.

Native arbuscular mycorrhiza colonization in seedling root of dogfruit (Archidendron pauciflorum) planted as seed-ball in field

Arbuscular mycorrhiza (AM) is a mutualistic symbiosis between soil fungi and plants, including dogfruit (Archidendron pauciflorum). Archidendron pauciflorum is a local plant from Southeast Asia, including Indonesia that is used for food and animal forest feed. Planting A. pauciflorum seedlings on revegetation land with a sharp slope is difficult and dangerous to workers. Therefore, seed-ball planting technique is required for revegetation of post-mining sharp slope areas. This research aimed to study the ability of the native AM fungi to colonize A. pauciflorum seedlings grown as a seed-ball in the field for revegetation purposes. The seed-ball was made using three types of fungal inoculum sources, namely control without AM fungi, natural forest, and stockpile inoculum. All colonization structures, such as entry points, coils, arbuscules, and vesicles, were observed. All seedlings were colonized by AM fungi, with root colonization ranging from 2% to 16%. Stockpile inoculum had a higher AM colonization than the natural forest inoculum. Both sources of native AM fungi tended to improve the growth of the seedling. There were two types of AM spores found in all treatments, Glomus sp. 1 and Glomus sp. 2. Glomus sp. 2 is the dominant species of AM fungi in all treatments.

The Global Spectrum of Seafloor Morphology on Mid‐Ocean Ridge Flanks Related to Magma Supply

AbstractMagma supply likely exerts primary control on seafloor morphology of oceanic crust, but most studies have related morphology to spreading rate. Here we examine global patterns of morphology on mid‐ocean ridge (MOR) flanks in relation to magma supply derived from residual mantle Bouguer gravity anomaly (proxy for relative crustal thickness) and spreading rate. We use multibeam bathymetry to characterize morphology using both qualitative (descriptive) and quantitative approaches, and we compare results to both magma supply and spreading rate. Morphology becomes more isotropic and abyssal hills are more irregular and discontinuous as magma supply decreases, while roughness, area of steeper slopes, and anomalous fabric orientation increase. We interpret these changes to reflect changing magma distribution along‐axis, from large‐volume and spatially extensive to progressively reduced, increasingly localized, and more irregularly emplaced. Observed relations between crustal thickness and morphology imply that average thickness of purely magmatic crust in the Atlantic and parts of the Indian ridge system is significantly less than average seismically determined crust. Thus seismically defined crustal thickness in those regions likely includes significant non‐magmatic components such as serpentinized mantle. Excepting regions of extensive mantle exposure, most morphologic parameters that we examined are sensitive to estimated magma supply but not necessarily to spreading rate alone. We summarize our results in schematic models that relate morphologic variations to changes in magma supply and mantle serpentinization throughout the global MOR system. Finally, we note that combined qualitative and quantitative results of our study may be useful for developing automated morphologic classification schemes.

Electrochemical corrosion study of chitosan-hydroxyapatite coated dental implant

Chitosan (Ch) is a naturally occurring biocompatible and bio-degradable material with high corrosion protective capacities for metals in various corrosive media. Hydroxyapatite (HA) is a significant biodegradable and bioactive material. In the present work, chitosan-hydroxyapatite (Ch-HA) composite coatings with various concentrations of chitosan were made on 316L stainless steel (316L SS) using sol–gel dip coating technique. The coatings were characterized by X-ray diffraction (XRD), FTIR, SEM, and electrochemical measurements. The surface morphology results (SEM) of coated implants exposed the fairly dense microstructures having uniformity without cracks and pores indicating that coating was successfully deposited. From electrochemical analyses, it was observed that the value of corrosion current density and the corrosion rate decreased from 6.03 to 0.15 and 5.56-0.13 respectively indicating that 1.5gCh-HA is the best coating concentration. The electrochemical results demonstrated an improvement in the corrosion resistance of 316L SS than the bare one. The decrease in slope and loop area of cyclic voltammograms reveals about improvement in corrosion resistance. This increment in corrosion resistance of the Ch-HA coated SS implant in the artificial saliva is as 1.5gCh-HA > 2gCh-HA >1gCh-HA >0.5gCh-HA. Furthermore, Ch-HA coatings revealed appropriate adhesion with 316L SS substrate for its use in dental implants.

One-dimensional numerical model of landslide over high-steep slopes: Theory and verification to the analytical solution

At the steep slope areas, landslide events may suddenly occur due to prolonged heavy rain and seriously affect humans’ lives and their properties. Numerical models simulating landslides help us to predict the real landslide phenomenon effectively because they are not only time-saving compared to physical models but also acceptable accuracy. In this paper, the one-dimensional nonlinear shallow water equations using the global coordinate system are established as the proposed model governing equations. The hybrid finite difference-finite volume method, the implicit method and the automatical time step controlling technique are employed to stably simulate the landslide events over the high-steep slopes. To validate the proposed numerical model to the analytical solution, authors continuously derive the non-dimensional governing equations in one dimension as well as using the global coordinate system. The numerical results are in good agreement with the analytical solution. The proposed numerical model can be used to simulate the landslides and the landslide-induced tsunami events, especially for simulating the high-steep slope conditions.

Research of the borehole moisture capacity of deeply loosened soils in the south of the Rostov region

The article presents the results of studies of the water absorption rate and the change in the possible limiting moisture capacity of the soil, deeply loosened flat and sloping areas of ordinary (Pre-Caucasian) chernozem, taking into account climatic changes in southern Russia. The current state of the climate and indicators of the physical and mechanical properties of the soil of cultivated flat and sloping lands require the development of new technologies and technical means to create the necessary conditions for increasing the water permeability of cultivated soils. For research, cultivated lands of the Federal State Budgetary Institution of Higher Education UNPK Donskoy "Uchkhoz Grain" DGAU, Rostov Region, Zernogradsky District were used. The coefficient of natural moisture varies from 0.30-0.35 in a predominantly dry year to 0.7-0.9 in a wet year. Precipitation during the growing season - 310-470 mm. The heat consumption for their evaporation is in the range from 80 to 118 kJ/cm2. Soil moisture deficit is 400-550 mm, while evaporation is 1050-1200 mm. The deficit of water consumption is 300-390 mm. Mostly since the last ten days of June, there has been a significant lack of soil moisture. Data processing was carried out using standard and special techniques. On the field cultivated by plowing to 0.20-0.25 m at a depth of 0.30 m, water was absorbed by the soil on average 38 % worse than in the area cultivated by deep loosening up to 0.60 m with the innovative chisel GNCh-0.6M in mode "Processing flat areas". On plowing, the moisture capacity of a meter layer of soil is approximately 1.5 times lower compared to deep loosening. The use of the innovative chisel-subsoiler GNCH-0.6M in the "Treatment of flat areas" mode allows: firstly, to increase the maximum moisture capacity of a meter horizon of cultivated land by 1.5 times in comparison with plowing; secondly, to reduce the impact of surface water runoff; thirdly, in a meter layer of soil to increase the reserves of productive moisture by more than 50 %.

Responses of soil and water-related ecosystem services to landscape dynamics in the eastern Afromontane biodiversity Hotspot

The investigation of soil and water-related ecosystem services (ES) and recognizing the spatiotemporal effects of land-use and land cover changes (LULC) are essential for the formulation of conservation strategies. The research employed the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) and the Revised Universal Soil Loss Equation (RUSLE) models for the assessment of ES. The study was carried out in the Kaffa Forest Biosphere Reserve in Ethiopia, which is part of the eastern Afromontane biodiversity hotspots. The aim of this investigation was to examine and map the temporal and spatial fluctuations in sediment retention, soil erosion, and water yield resulting from LULC modifications between 1986 and 2019, and to provide forecasts for the next three decades. According to the RUSLE analysis, the landscapes exhibited estimated soil losses ranging from zero to 1.5 tons ha-1 yr-1 in 1986, 2009, and 2019, respectively. The mean annual sediment exports for the years 1986, 1999, and 2019 were estimated to be 12.6, 9.9-, and 28.7-tons ha−1, respectively. The water yield of the site experienced a notable increase from 9.8 × 109 m3 in 1986 to 19.6 × 10 9 m3 in 1999, and subsequently rose to 39.3 × 109 m3 in 2019, which is considered to be a disadvantageous to the site. The study found a significant positive correlation between water yield and the expansion of settlement area (r = 0.99, P = 0.015) as well as agricultural land (r = 0.99, P = 0.05). It was also found that significant positive correlation found between vegetation dense area such as forest (r < 0.999, P < 0.001) and shrub & bamboo (r = 0.998, P = 0.036) with sediment retention service. The investigation discovered that there existed tradeoffs between the ES of sediment retention and water yield as the slope increased. The results may be attributed to the presence of dense vegetation cover on the elevated slope regions, rendering them unsuitable for agricultural activities, and the concurrent expansion of arable lands in the lower slope areas, which are flat terrains more conducive to cultivation. The transition from land with more vegetation density to land with lower or no vegetation coverage resulted in an increase in soil loss and water yield, while simultaneously decreasing the sediment retention service. Therefore, the findings can be used as a document to guide decision-makers to design soil-water conservation technologies to enhance the ecological integrity of the biosphere reserve.

Contrast-Enhanced Ultrasound and Conventional Ultrasound Characteristics of Breast Cancer With Different Molecular Subtypes

BackgroundIdentifying molecular subtypes of breast cancer (BC) is of great significance in selecting optimal treatment strategy. Different molecular subtypes of BC have various vascular distribution characteristics. Contrast-enhanced ultrasound (CEUS) can dynamically display the microcirculation of tumor. This study intends to explore the conventional ultrasound and CEUS characteristics of different molecular subtypes of BC. MethodsDuring this prospective study, 86 patients with BC who were divided into Luminal A (LA), Luminal B (LB), HER2 over-expression (H2), and triple-negative (TN). The CEUS qualitative and quantitative characteristics of BC with different molecular subtypes was explored, as well as the conventional ultrasound features. In addition, the diagnostic efficiency of CEUS quantitative parameters in differentiating molecular subtypes of BC was analyzed. ResultsOur study found that the Adler grade differed significantly among 4 molecular subtypes (P < .05). The enhancement speed, enhancement degree and size after enhancement of 4 molecular subtypes were statistically different (P < .05). The wash in slope (WIS), peak intensity (PI), and wash-in area under the curve (WiAUC) differed significantly among 4 subtypes (P < .05). The diagnostic efficiency of PI was better for detecting LA and H2 subtype with the areas under the receiver operating characteristic curve was 0.778 and 0.734, respectively. ConclusionDifferent molecular subtypes of BC have different CEUS and conventional ultrasound characteristics. CEUS can provide valuable imaging basis for precise clinical diagnosis and individualized therapy of BC with different molecular subtypes.

The uncertain future of mountaintop-removal-mined landscapes 2: Modeling the influence of topography and vegetation

Erosion following human disturbance threatens ecosystem health and inhibits effective land use. Mountaintop removal/valley fill (MTR/VF) mined landscapes of the Appalachian Coalfields region, USA, provide a unique opportunity to quantify the geomorphic trajectory of disturbed lands. Here we assess how MTR/VF-induced changes to topography and vegetation influence spatiotemporal erosion patterns in five mined watersheds. We use landscape evolution models starting from pre- and post-MTR/VF topographic data to isolate the influence of mining-induced topographic change. We then constrain ranges of erodibility from incision depths of gully features on mine margins, and use those estimates to model the influence of vegetation recovery trends on erosion.Topographic alterations alone reduce total sediment export from mined catchments. Model runs that incorporate the disturbance and recovery of vegetation in mined watersheds show that complete vegetation recovery keeps millennial sediment export from mined catchments within the range of unmined catchments. If vegetation recovery is anything less than complete, vegetation disturbance drives greater total sediment export from mined catchments than unmined catchments. Full vegetation recovery causes sediment fluxes to decline over millennia beyond the recovery period, while watersheds without full recovery experience fluxes that increase over the same time period. Spatiotemporal erosion trends depend on 1) the extent of vegetation recovery and 2) the extent to which MTR/VF creates slope–area disequilibrium. Valley fills and mine scarps experience erosion rates several times higher than those found in the unmined landscapes. Rapid erosion of mined areas drives deposition in colluvial hollows, headwater stream valleys, and below scarps. Our experiments suggest that reclamation focused on maximizing vegetation recovery and reducing hotspots of slope–area disequilibrium would reduce MTR's influence on Appalachian watersheds both during and long after the vegetation recovery period. Insights from MTR/VF-influenced landscapes can inform mined land management as the renewable energy transition drives increased surface mining.

Study on the Crop Suitability and Planting Structure Optimization in Typical Grain Production Areas under the Influence of Human Activities and Climate Change: A Case Study of the Naoli River Basin in Northeast China

Optimizing crop planting structures under the influence of climate change and human activities is crucial for sustainable food production and global food security. Taking the Naoli River Basin in Northeast China as a case area, a machine learning model based on maximum entropy was used to explore the suitability distribution of crops under the influence of both environmental factors and human activities. The optimized planting structure strategies were tested in combination with future climate change. The results show that considering human activities can more accurately simulate crop suitability than considering only natural environmental factors. The suitable planting areas for maize, rice, and soybeans are 18,553.54 km2, 10,335.98 km2, and 5844.80 km2, respectively. Highly adapted areas for major crops are concentrated in the plain areas of the middle reaches of the river basin, rather than in populated areas, and there are overlaps among the suitable planting areas for each crop. The optimal crop distribution for the planting structure is to plant rice in the hydrophilic areas of the plain hinterland, soybeans in the plain hinterland farther from the water source, and corn in the peripheral plains and gently sloping mountainous areas. Human activities exerted a strong influence on the potential scatter of soybeans, while climate change had the most significant implications for maize. Future climate change may reduce the area of suitable crop zones, posing challenges to regional food production. It is necessary to reflect on how to rationally balance soil and water resources, as well as how to cope with climate change in the future.

Classification of seabed landforms on continental and island shelves

The increasing availability and quality of high-resolution bathymetry data has led to a growing need for automated classification approaches to extract seabed features and better understand our ever-changing and complex seascapes. Here we present a new set of GIS tools designed to classify seabed landforms on continental and island shelf settings. The classification approach utilises bathymetry data and its derivatives of slope, ruggedness and bathymetric position index to delineate key components of the seabed surface. The user is guided through a series of steps to break down the seabed surface into components termed ‘surface elements’ (e.g. smooth, rugose, slope areas), which are subsequently grouped into prominent seabed features termed ‘seabed landforms’ (e.g. reefs, channels, scarps). Manual review and editing are incorporated into the workflow, striking a balance between automation and expert manual interpretation. We present the toolset using examples from the statewide marine lidar dataset from New South Wales, Australia, and explore tool settings using bathymetric data representing different data sources (multibeam and marine lidar), environmental seascapes, data resolutions (2, 5, 10 and 20 m cell size) and data preparation treatments (with and without data smoothing). The GIS toolset presented offers an effective and flexible method to extract key features from high-resolution shelf bathymetry data. Such mapping provides fundamental baseline data for vast applications within marine planning, research and management.

Distribution of dissolved methane in seawater from the East China Sea to the Ryukyu forearc

Methane is a greenhouse gas, and the East China Sea acts as a source of emissions to the atmosphere. On the other hand, the distribution of methane concentration in the Ryukyu Arc shelf and forearc region has not been clarified. Therefore, we investigated the continental slope and continental shelf areas from the Okinawa Trough to the landward side and the island shelf and forearc areas to the seaward side of the East China Sea. The methane concentration in the Kuroshio Current region was very low, and the methane concentration in the seawater just above the seafloor in the area directly above the hydrothermal systems was exceptionally high. In addition, methane concentration in seawater just above the seafloor where cold seeps and mud volcanoes are known is higher than the background, and higher methane concentrations were found in continental slope area and the island shelf area. The results suggest the existence of previously unreported methane sources such as cold seeps and mud volcanoes in the continental slope region and the island shelf region.

Steady-state forms of channel profiles shaped by debris flow and fluvial processes

Abstract. Debris flows regularly traverse bedrock channels that dissect steep landscapes, but our understanding of bedrock erosion by debris flows and their impact on steepland morphology is still rudimentary. Quantitative models of steep bedrock channel networks are based on geomorphic transport laws designed to represent erosion by water-dominated flows. To quantify the impact of debris flow erosion on steep channel network form, it is first necessary to develop methods to estimate spatial variations in bulk debris flow properties (e.g., flow depth, velocity) throughout the channel network that can be integrated into landscape evolution models. Here, we propose and evaluate two methods to estimate spatial variations in bulk debris flow properties along the length of a channel profile. We incorporate both methods into a model designed to simulate the evolution of longitudinal channel profiles that evolve in response to debris flow and fluvial processes. To explore this model framework, we propose a general family of debris flow erosion laws where erosion rate is a function of debris flow depth and channel slope. Model results indicate that erosion by debris flows can explain the occurrence of a scaling break in the slope–area curve at low-drainage areas and that upper-network channel morphology may be useful for inferring catchment-averaged erosion rates in quasi-steady landscapes. Validating specific forms of a debris flow incision law, however, would require more detailed model–data comparisons in specific landscapes where input parameters and channel morphometry can be better constrained. Results improve our ability to interpret topographic signals within steep channel networks and identify observational targets critical for constraining a debris flow incision law.

Geochemical properties, mechanism of formation, and source of solid bitumen in the Ediacaran Dengying Formation from the central to northern Sichuan Basin, China

Several large gas reservoirs, including the Weiyuan and Anyue gas fields, have been discovered in the Ediacaran Dengying Formation in the Sichuan Basin, indicating vast opportunities for deep-petroleum exploration. Understanding the origin and evolution process of these gas reservoirs is crucial for further petroleum exploration and development. Although the burial history of the Sichuan Basin and its surrounding areas is basically dominated by Paleozoic burial and preservation, and Meso-Cenozoic uplift and erosion. However, the source of the Dengying Formation natural gas in the Sichuan Basin is still a subject of controversy between the Ediacaran and Cambrian source rocks due to high thermal maturity, secondary alteration, and multistage tectonic activities. This study aims to examine the investigation on the properties and genetics of Dengying solid bitumens that existed in the central to northern Sichuan Basin, in order to provide insights into the source and evolution history of the Dengying paleo-oil reservoirs. For this purpose, petrologic, elemental, and organic geochemical analyses were used to investigate the properties, origin, and formation mechanism of solid bitumens. The results indicate that these solid bitumens have suffered intense thermal alteration (EqVRo 2.1%–5.3%), and are classified as pyrobitumens. Solid bitumens in the Gaoshiti bulge and the north slope area were subjected to tectonic thermal events (e.g., Emeishan igneous province) and relatively strong thermochemical sulfate reduction (TSR) alteration. These solid bitumens were assumed to be pyrolysis products of light (condensate) oil. In contrast, solid bitumens in the Weiyuan bulge and the Micangshan uplift area were not influenced by tectonic thermal events but experienced weak TSR alteration, and originated from either normal or heavy crude oil. Moreover, a systematic bitumen-source correlation was carried out using δ13Corg values, bound steranes, and trace element distributions. Results reveal that the solid bitumens in the central Sichuan paleo-uplift were mainly derived from the lower Cambrian Maidiping Formation, those in the north slope area originated from the lower Cambrian Qiongzhusi Formation, while those in the Micangshan area were sourced from the Ediacaran Doushantuo Formation. Structural and burial history analysis implies that the differences in the source of the Dengying paleo-oil reservoir (i.e., solid bitumen) between these study areas are attributed to the distribution of source rocks and their contact relationship with reservoirs. This research successfully obtained insights into the source and genetic mechanism of paleo-oil reservoirs by analyzing the properties of high-maturity solid bitumens, which can guide further exploration and development of deep petroleum resources.