Natural Distribution Patterns Research Articles

Enhancing RNA-seq bias mitigation with the Gaussian self-benchmarking framework: towards unbiased sequencing data

BackgroundRNA sequencing is a vital technique for analyzing RNA behavior in cells, but it often suffers from various biases that distort the data. Traditional methods to address these biases are typically empirical and handle them individually, limiting their effectiveness. Our study introduces the Gaussian Self-Benchmarking (GSB) framework, a novel approach that leverages the natural distribution patterns of guanine (G) and cytosine (C) content in RNA to mitigate multiple biases simultaneously. This method is grounded in a theoretical model, organizing k-mers based on their GC content and applying a Gaussian model for alignment to ensure empirical sequencing data closely match their theoretical distribution.ResultsThe GSB framework demonstrated superior performance in mitigating sequencing biases compared to existing methods. Testing with synthetic RNA constructs and real human samples showed that the GSB approach not only addresses individual biases more effectively but also manages co-existing biases jointly. The framework’s reliance on accurately pre-determined parameters like mean and standard deviation of GC content distribution allows for a more precise representation of RNA samples. This results in improved accuracy and reliability of RNA sequencing data, enhancing our understanding of RNA behavior in health and disease.ConclusionsThe GSB framework presents a significant advancement in RNA sequencing analysis by providing a well-validated, multi-bias mitigation strategy. It functions independently from previously identified dataset flaws and sets a new standard for unbiased RNA sequencing results. This development enhances the reliability of RNA studies, broadening the potential for scientific breakthroughs in medicine and biology, particularly in genetic disease research and the development of targeted treatments.

Distribution of Heavy Metals along the Mediterranean Shoreline from Baltim to El-Burullus (Egypt): Consequences for Possible Contamination

This work is mainly concerned with the effect of anthropogenic activities, the presence of black sand spots, factory construction, and shipping, in addition to other activities like agriculture, on soil heavy metal pollution along the Mediterranean shores of Lake El-Burullus, Egypt, to assess the contamination levels and to identify possible sources and the distribution of these metals. This study focuses on the various heavy metal contamination levels in El-Burullus Lake coastal sediments. Sediment samples were collected and analyzed by the XRF technique for heavy metals, including Cr, Cu, Ni, Zn, Zr, Pb, Ba, Sr, Ga, Rb, V, and Nb. Statistical analyses, including correlation coefficient, factor analysis, and cluster analysis, were employed to understand the interactions and sources of these metals. The highest concentrations recorded were for Zr (84–1436 mg/kg) and Pb (1–1166 mg/kg), with average concentrations of 455.53 mg/kg and 79.27 mg/kg, respectively. Cr, Zr, Nb, and Pb showed average values higher than the average shale concentration, indicating potential pollution. Correlation analysis revealed strong associations between several metals, suggesting common sources of both natural and anthropogenic origin and similar distribution patterns. Factor analysis indicated four main factors accounting for 94.069% of the total variance, with the first factor heavily dominated by Cr, Ni, Zn, and Ba. The contamination factor (Cf) and degree (DC) analyses revealed varying contamination levels, with most metals exhibiting the greatest values in the western half of the area. The pollution load index (PLI) indicated high-quality sediment samples without significant pollution. Our findings highlight the importance of continued monitoring and management techniques to reduce possible environmental and health concerns associated with these pollutants.

Fracturing parameter optimization technology for highly deviated wells in complex lithologic reservoirs

Highly-deviated wells are the key technology to reduce the risk of drilling accidents and improve the utilization of reservoirs. However, for reservoirs with complex lithology, highly-deviated wells are faced with the problems of geomechanical transformation and fracturing parameter optimization. The research on fracturing parameter optimization technology of high-deviated wells in complex lithologic reservoirs is helpful to the research and application of geomechanics in deep unconventional reservoirs. This paper is based on geological mechanics laboratory experiments and logging interpretation, combined with regional geological background, to clarify the geological and mechanical characteristics of the Fengcheng Formation shale oil region in the Mabei Slope. On this basis, based on the current geostress field and natural fracture distribution pattern of the Mabei Slope, an integrated model of shale oil geological engineering in local well areas was established. Based on the finite element method, optimization design was carried out for the cluster spacing, construction fluid volume, displacement, and sand volume of highly deviated well fracturing, and three-dimensional simulation of fracturing fractures was completed. The research results indicate that: (1) The current dominant direction of the maximum principal stress in the Fengcheng Formation on the Mabei Slope is from northeast to southwest, with the maximum horizontal principal stress generally ranging from 90 to 120 MPa and the minimum horizontal principal stress generally ranging from 70 to 110 MPa. (2) The difference in stress between the two horizontal directions is relatively large, generally greater than 8 MPa. Two sets of natural fractures have developed in the research area, one with a northwest southeast trend and the other with a northeast southwest trend. The natural fracture density of the Fengcheng Formation shale reservoir in the Mabei Slope is 0.32–1.12/m, with an average of 0.58/m, indicating a moderate to high degree of fracture development. (3) The geological model and three-dimensional geo-mechanical model are established according to the actual drilling geological data, and different schemes are designed to carry out single parameter optimization. The optimization results show that the optimal cluster spacing of the subdividing cutting volume pressure of the highly deviated wells in the Fengcheng Formation of the Mabei Slope is 12 m, the optimal construction fluid volume is 1400–1600 m3/section, the optimal construction displacement is 8 m3/min, and the optimal sanding strength is 2.5 m3/m. At the same time, by comparing the fracturing implementation effect with the fracturing scheme design, it is proven that the artificial parameter optimization method for highly deviated wells based on the finite element method based on the regional stress background and the natural fracture development law proposed in this paper is feasible and can provide a scientific basis for the fracturing development of highly deviated wells in complex lithologic reservoirs. This research has been well applied in Mahu area of Xinjiang oilfield.

Origin, Migration, and Characterization of Gas in the Xinglongtai Area, Liaohe Subbasin (Northeast China): Insight from Geochemical Evidence and Basin Modeling

Buried hill zones in the rift basins have a significant impact on the enrichment of natural gas resources, and this is of great significance for exploration and development. This study aims to unravel the origins, migration, and dynamic accumulation process of natural gas in the Xinglongtai structural belt, Liaohe Subbasin. A comprehensive geological and geochemical analysis was performed on source rocks and natural gas samples from various geological structures within the Xinglongtai structural belt. Moreover, basin modeling techniques were employed to trace the genesis and migration of natural gas, offering an in-depth understanding of the dynamic process of accumulation. We identified the Fourth Mbr (Es4) and Third Mbr (Es3) of the Shahejie Fm as the main source rocks in the Qingshui and Chenjia Sags. The Es4, primarily Shallow Lacustrine Mudstones, contributed mainly type II organic matter, while the Es3, consisting of Nearshore Subaqueous Fan and Deep Lacustrine Mudstones, contributed mainly type III and type II organic matter, respectively. Two distinct hydrocarbon accumulation systems were observed, one inside and one outside the buried hills. The system outside the buried hill is governed by a complex fault system within the lacustrine basin, resulting in dual-source directions, dual-source rock types, two migration phases, and late-stage accumulation. In contrast, the system within the buried hill primarily involves reservoirs nested in the basement, exhibiting dual-source directions, dual-source rock types, a single migration phase, and early-stage charging. The understanding of this interplay, alongside dynamic simulation of generation, migration, and accumulation, can provide valuable insights for predicting natural gas distribution and accumulation patterns in terrestrial faulted lacustrine basins. This knowledge can guide more effective exploration and development strategies for natural gas.

Detection of Meloidogyne graminicola (RRKN) in Kumaon region of the Indian Himalayas

Rice root-knot nematode (RRKN), Meloidogyne graminicola is a serious pest of rice (Oryza sativa L.) reported globally. In India, RRKN has been reported from various parts of the rice growing region and causing 17–30% yield loss. In the present study, RRKN population infesting rice growing region of Kumaon hills of Uttarakhand, Indian Himalayan region was isolated during 2019–20, characterized using integrative taxonomy by combining molecular analysis using ITS, morphology of male, juveniles, adult female and morphometry measurements of different stages. The data presented in the comparative analysis of morphometry parameters for Meloidogyne graminicola isolate from the Kumaon region of the Indian Himalayas, as compared to the original description by Golden and Birchfield (1965) from Louisiana, USA, reveals some differences in the morphological characteristics of adult females, adult males, and 2nd stage juveniles (J2) of M. graminicola. The ITS sequence from the present study appeared as a single clade between the Fujian isolate (KM111531.1) and the Brazilian M. graminicola isolate (KY962651). To our knowledge, this is the first authentic characterization and report of RRKN from the Hilly region of Uttarakhand state. The detection of M. graminicola in the mid Indian Himalayan region provides valuable information for further studies on the natural population dynamics and distribution patterns of this nematode species. The findings highlight the need for regular monitoring and surveillance of nematode populations in the region to better understand their distribution and potential impact on rice production.

A review of megafauna diversity and abundance in an exploration area for polymetallic nodules in the eastern part of the Clarion Clipperton Fracture Zone (North East Pacific), and implications for potential future deep-sea mining in this area

The Clarion Clipperton Fracture Zone (CCZ) is an abyssal region in the north-east Pacific that is currently being explored for metal-rich polymetallic nodules, but also harbors a highly diverse megabenthic community. This community is influenced by multiple environmental gradients including bathymetric structures as well as differences in habitat and food availability. This study focuses on the benthic megafauna investigated in an exploration area positioned in the very east of the CCZ, which exhibits the lowest water depths (mean: 4200 m) and the highest flux of particulate organic carbon (POC) of the CCZ. Case studies using seafloor images for the detection of megafauna have revealed differences between seamounts and abyssal hills compared to nodule fields, as well as differences in the community composition between areas with and without nodule coverage and rock outcrop. Extrapolations suggest a richness of more than 300 morphotypes in the study area, including multiple invertebrate groups such as corals, sponges, echinoderms, and crustaceans as well as fish. Focusing on sampled specimens, diversities of Ophiuroidea, Porifera, and Bryozoa are high and more species are likely to be discovered in the study area. This also applies for the taxon Ophiuroidea, which is among the taxa investigated in the greatest detail so far. In the context of deep-sea mining, megafauna has been in the focus of a variety of environmental studies including baseline analyses, disturbance experiments, and/or testing of mining components or systems. These studies identify and address key factors responsible for the observed natural and impacted distribution patterns and thereby help to constrain expected anthropogenic impacts to the deep-sea environment in the context of deep-sea mining. Specifically in the area of focus of this study, 10 years of megafauna analyses have shown that the biodiversity in the selected preservation reference zone (PRZ) is not as similar to that of the impact reference zone (IRZ) as originally hypothesized based mainly on geological parameters. We suggest that recent area-wide habitat classifications and faunal mapping exercises (e.g., Uhlenkott et al. 2020, 2022) are used to designate a new PRZ that is more similar to the IRZ to meet its purpose, but that the current PRZ is maintained for scientific and conservation purposes.

A Numerical Model for Pressure Analysis of a Well in Unconventional Fractured Reservoirs

Fractured reservoirs are highly heterogeneous in both matrix and fracture properties, which results in significant variations in well production. Assessing and quantifying the influence of fractures on fluid flow is essential for developing unconventional reservoirs. The complicated effects of fractures in unconventional fractured reservoirs on fluid flow highly depend on fracture geometry, fracture distribution, and fracture properties, which can be reflected in pressure transient testing. The biggest challenge lies in delineating the pre-existing natural fracture distribution pattern, density, azimuth, and connectivity. Using the advanced finite element method, this paper builds a finely characterized near-wellbore model to numerically simulate the pressure transient testing process in naturally fractured reservoirs and further evaluates fracture-related effects to obtain a more accurate solution. First, the numerical program is benchmarked by the analytical solutions and numerical results of Eclipse. Next, different fracture models with single fractures or fracture networks are set up to investigate the effects of fracture parameters numerically (e.g., fracture location, fracture dip angle, fracture spacing, the ratio of fracture permeability to matrix permeability, fracture network orientation, horizontal fracture distribution, etc.) on pressure transient behaviors in naturally fractured reservoirs. Velocity and pressure profiles are presented to visualize and analyze their effects, and new features in the flow regimes of the derivative plots of the bottom-hole pressure are identified and discussed. Finally, based on geological and geophysical data, including image logs, core descriptions, wireline logs, and seismic and well test data, a practical fractured model of the Dalwogan 2 well in the Surat basin is built, analyzed, and compared with homogenous and measured data. The results show significance in characterizing the complex fracture networks in near-wellbore models of unconventional fractured reservoirs.

The response of plant diversity to human dominance in the meta-watershed ecosystem of Southwest China

• Intensified urban development threatened forest and riparian plant diversity. • Socioeconomic and water conservancy development deteriorated plant diversity. • Riparian plants were more susceptible to artificial development than forest plants. • Human dominance destroys ecosystem services provision in meta-watershed ecosystems. Plant diversity is essential to maintain terrestrial ecosystem stability and balance, but it is highly susceptible to environmental changes that are generally dominated by human activities. In the natural habitat, plant growth and distribution patterns are known to be regulated by abiotic environments such as water, temperature, and nutrient. However, how growing human dominance impacts plant diversity at the watershed scale remains unclear. From the view of the meta-watershed ecosystem, this study constructed indicators to examine the plant diversity responses in karst watersheds of different urban development intensities. The results revealed that the growing urban development intensity deteriorated plant diversity and riparian plant diversity in the meta-watershed ecosystem. Both socioeconomic and water conservancy development had noticeable adverse effects on plant diversity. The riparian plants were more susceptible to artificial development than forest plants. The predicted results of various development scenarios suggest that, by the middle of the 21st century, plant diversity and food production in the watershed will meet a crisis unless forest protection policies are applied, and large-scale urban expansion is curbed. In the meta-watershed ecosystem, growing human dominance increasingly destroys plant diversity and the ecosystem supply. Policies and measures are urgently needed to reverse the potential deteriorating trend of the ecosystem, maintain the stability of the ecosystem, and promote the sustainable development of human society.

Assessment of Natural Radionuclide Distribution Pattern and Radiological Risk from Rocks in Precambrian Oban Massif, Southeastern Nigeria

A gamma spectrometric analysis of rock samples collected from the Precambrian Oban Massif, southeastern Nigeria, was performed to determine some primordial radioelements’ activity concentrations: U-238, Th-232, and K-40, and their associated radiological hazards. The mean activity of the primordial radionuclides was determined to be 1073.06 ± 0.65, 160.74 ± 1.32, and 250.76 ± 0.91 Bq·kg−1 for 40K, 238U, and 232Th, respectively, showing that they are inhomogeneously distributed, with activity changing with the rock type and location. The activity concentrations are highest in biotite garnet schist, quartz diorite, and biotite gneiss rock domains. The mean values of the radiological hazards are 0.08 Bq·kg−1 (alpha index), 2.15 Bq·kg−1(gamma index), 2.06 Bq·kg−1(internal) and 1.63 Bq·kg−1 (external4.30 Bq·kg−1(representative level index6), 602.23 Bq·kg−1, (radium equivalent), 780 nGy·h−1 (total absorbed dose rate), 270.91 nGy·h−1 (indoor), 509.78 nGy·h−1 (outdoor), 624.99, 1329.07 and 1954.06 mSv·yr−1 (outdoor, indoor and total annual effective dose equivalent, respectively), 6448.40 (cumulative excess lifetime cancer risk) and 248.94–3761.47 Bq·kg−1 (annual gonadal dose equivalent). These results are higher than their various permissible limits (except at Ako Community) and suggest that rocks in the area may be unsuitable for constructing dwelling places. It is strongly advised that basic safety standards and precautionary measures recommended by the European Commission should be strictly adhered to while dealing with these rocks.

Foraminiferal Distribution in Two Estuarine Intertidal Mudflats of the French Atlantic Coast: Testing the Marine Influence Index

This study focuses on the foraminiferal distribution on intertidal mudflats of two contrasted estuaries (Auray and Vie) along the French Atlantic coast. In both estuaries, the foraminiferal communities are dominated by Haynesina germanica and the Ammonia tepida group. Stations located near the outlets show a high diversity and abundance of species of the genus Elphidium. Stations in the inner estuary show a higher proportion of agglutinated species (Ammotium salsum, Ammobaculites agglutinans). Multivariate statistical analysis suggests that the distance to the sea and the percentage of fine sediment (<63 µm) are the two main parameters explaining the foraminiferal distribution. Chemical analyses of the sediment show that the two studied estuaries are not affected by major anthropogenic pollution, so that the faunas should mainly reflect the natural controlling parameters. Three indices of environmental quality commonly used in coastal areas show counter-intuitive differences between stations, suggesting that these indices may be less reliable for use in intertidal estuarine mudflats. The newly developed Marine Influence Index (MII) integrates three major ecological factors: the position of the sampling point on the salinity gradient, the emergence time at low tide and the relative importance of fresh water discharge. In our dataset, MII shows significant correlations with the controlling environmental parameters (distance to the sea, percentage grains < 63 µm), as well as with the foraminiferal patterns (PCA axis 1, species richness, percentage of Elphidium spp. and Quinqueloculina spp.). These results suggest that the MII explains a substantial part of the faunal variability on estuarine intertidal mudflats, and can be used to detect deviations from the natural distribution patterns in response to anthropogenic pollution.

Southeast Asia as One of World’s Primary Sources of Biotic Recolonization Following Anthropocene Extinctions

The plight of Southeast Asia’s animals, plants and ecosystems in the face of unsustainable exploitation and habitat destruction has been illustrated in several recent studies, despite often falling outside the global discourse on global conservation priorities. Here, we collate biogeographic and phylogenetic information to argue that this beleaguered region is one of world’s primary macrorefugia, and possibly its best chance of regaining its natural biodiversity distribution patterns after the current Anthropocene upheaval. The region uniquely combines top diversity values in (a) ancient lineage diversity and (b) cosmopolitan lineage diversity, suggesting that it has acted in the past as a biodiversity museum and source of global colonization. This is at least partly due to the interplay between latitudinal diversity gradients and continental connectivity patterns. However, the peak values in South China/North Indochina for cosmopolitan tetrapods and their sister lineages suggest that a key feature is also the availability of diverse climatic conditions. In particular, the north-south orientation of the mountain ranges here has allowed for rapid recolonization within the region following past climatic changes, resulting in high survival values and overall exceptional relict lineage diversity. From this starting point, global colonization occurred on multiple occasions. It is hoped that, with urgent action, the region can once again fulfill this function.

Vertical differentiation of land cover in the central Himalayas

Characterized by obvious altitudinal variation, habitat complexity, and diversity in land cover, the Mt. Qomolangma region within the central Himalayas is one of the most sensitive areas to climate change in the world. At the same time, because the Mt. Qomolangma region possesses the most complete natural vertical spectrum in the world, it is also an ideal place to study the vertical structure of alpine land cover. In this study, land cover data for 2010 along with digital elevation model data were used to define three methods for dividing the northern and southern slopes in the Mt. Qomolangma region, i.e., the ridgeline method, the sample transect method, and the sector method. The altitudinal distributions of different land cover types were then investigated for both the northern and southern slopes of the Mt. Qomolangma region by using the above three division methods along with ArcGIS and MATLAB tools. The results indicate that the land cover in the study region was characterized by obviously vertical zonation with the south-six and north-four pattern of vertical spectrum that reflected both the natural vertical structure of vegetation and the effects of human activities. From low to high elevation, the main land cover types were forests, grasslands, sparse vegetation, bare land, and glacier/snow cover. The compositions and distributions of land cover types differed significantly between the northern and southern slopes; the southern slope exhibited more complex land cover distributions with wider elevation ranges than the northern slope. The area proportion of each land cover type also varied with elevation. Accordingly, the vertical distribution patterns of different land cover types on the southern and northern slopes could be divided into four categories, with glaciers/snow cover, sparse vegetation, and grasslands conforming to unimodal distributions. The distribution of bare land followed a unimodal pattern on the southern slope but a bimodal pattern on the northern slope. Finally, the use of different slope division methods produced similar vertical belt structures on the southern slope but different ones on the northern slope. Among the three division methods, the sector method was better to reflect the natural distribution pattern of land cover.

Current and future suitable habitat areas for Nasuella olivacea (Gray, 1865) in Colombia and Ecuador and analysis of its distribution across different land uses.

Nasuella olivacea is an endemic mammal from the Andes of Ecuador and Colombia. Due to its rarity, aspects about its natural history, ecology and distribution patterns are not well known, therefore, research is needed to generate knowledge about this carnivore and a first step is studying suitable habitat areas. We performed Ecological Niche Models and applied future climate change scenarios (2.6 and 8.5 RCP) to determine the potential distribution of this mammal in Colombia and Ecuador, with current and future climate change conditions; furthermore, we analysed its distribution along several land covers. We found that N. olivacea is likely to be found in areas where no records have been reported previously; likewise, climate change conditions would increase suitable distribution areas. Concerning land cover, 73.4% of N. olivacea potential distribution was located outside Protected Areas (PA), 46.1% in Forests and 40.3% in Agricultural Lands. These findings highlight the need to further research understudied species, furthering our understanding about distribution trends and responses to changing climatic conditions, as well as informig future PA designing. These are essential tools for supporting wildlife conservation plans, being applicable for rare species whose biology and ecology remain unknown.

珍稀濒危树种陆均松天然种群结构与空间分布格局

PDF HTML阅读 XML下载 导出引用 引用提醒 珍稀濒危树种陆均松天然种群结构与空间分布格局 DOI: 10.5846/stxb201905090948 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 中央级公益性科研院所基本科研业务费专项资金（CAFBB2017ZB004） Natural population structure and spatial distribution pattern of rare and endangered species Dacrydium pectinatum Author: Affiliation: Fund Project: Study on the Monitoring and Exhaustion Mechanism of Dacrydium Pierrei Resources 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为研究陆均松（Dacrydium pectinatum）种群生存现状及分布格局，对BWL、DLS、JFL 三种不同分布区域的陆均松天然种群进行了调查，分析了其天然群落乔木层物种多样性及优势种组成、龄级结构及分布格局三个方面的空间异质性，结果表明：（1）三种陆均松天然群落乔木层物种丰富度及多样性指数均较高，基本表现为BWL>JFL>DLS，且远高于中高纬度温带及亚热带森林群落；群落内多为小密度种群，少有占绝对优势地位的树种，符合热带山地雨林物种组成的一般规律。（2）龄级结构有所差异，BWL和JFL种群呈衰退趋势，共同特点是幼年树数量较少，成年和老年树比例较高；DLS种群幼年树数量在所有个体中比例最高，属于增长型种群。（3）BWL和DLS种群整体呈聚集分布，幼年至老年阶段由聚集分布转变为均匀分布，JFL种群整体及不同发育阶段均呈均匀分布状态；聚集强度表现为DLS > BWL > JFL，幼年树 > 成年树 > 老年树。陆均松是热带山地雨林的关键种和建群种，对研究海南热带雨林的起源及其区系特征具有重要意义，针对其生存现状，可根据实际情况，利用人工辅助措施如开辟林窗、合理疏伐等方式进行保护及更新复壮。 Abstract:In order to study the survival status and distribution pattern of Dacrydium pectinatum population, we investigated three different distribution areas, namely BWL, DLS, and JFL in Hainan Island. The spatial heterogeneity in three aspects of the species diversity and dominant species composition of the natural community arbor layer, age structure, and distribution pattern was analyzed. The results showed that (1) the arbor layer species abundance and diversity index of the three D. pectinatum natural community were higher as a whole, which followed the order of BWL > JFL > DLS, and much higher than those of the mid-high latitude temperate zone and subtropical forest community. The populations in the community were mostly small-density populations, and there were few absolutely dominant species, which is consistent with the general rule of species composition of tropical mountain rainforests. (2) The age structure of these three populations had its own characteristics. BWL and JFL showed a recession trend. The common feature was that the number of Juvenile tree was small, and the proportion of adult trees and elderly trees was high. The number of Juvenile tree in DLS was the most for all individuals and belonged to the growth population. (3) The overall state of the D. pectinatum population of BWL and JFL was aggregate clustered distribution. The juvenile tree stage was also a clustered distribution, but in the elderly tree stage, it changed from clustered distribution to uniform distribution. The JFL D. pectinatum population showed a uniform distribution throughout all individuals and different developmental stages. Their aggregation intensity was expressed as DLS > BWL > JFL and juvenile > adult > elderly. D. pectinatum is a key species of tropical mountain rainforests, which is of great significance for studying the origin and flora characteristics of Hainan tropical rainforest. For its current survival status, we can use manual auxiliary measures such as opening forest windows and rational thinning to protect and rejuvenate D. pectinatum population based on the actual situation. 参考文献 相似文献 引证文献

Modelling gas supply systems with a high role of autonomous consumers (the case of Mongolia)

The paper presents a tool to optimize gas infrastructure systems and analyses some aspects of modelling related to autonomous gas consumers. A model of national gas infrastructure creation in Mongolia is proposed. The model is linked with the model of the regional Northeast Asian gas market and the financial models of gas infrastructure facilities. The model determines the optimal design of the national gas infrastructure system, i.e. the number of the facilities, their capacities, locations and the transport modes for connecting the consumption centres. The role of autonomous consumers is considered by introducing the demand for liquefied natural gas separately from the demand for pipeline gas. The scope of the model application is demonstrated by an illustrative example. The results show the rational natural gas import and distribution patterns. The need for expanding the energy cooperation between Mongolia and the other Northeast Asian countries to create gas industry in Mongolia is highlighted.

Scientific literature on invasive alien species in a megadiverse country: advances and challenges in Mexico

Interest in invasive species has increased around the world over the last several decades. In Mexico, studies on invasive species date as early as 1939 and the number of publications has increased considerably in recent decades. However, to our knowledge, the analysis of information gaps and research priorities is lacking. Therefore, it is necessary to identify gaps in the knowledge of invasive species in order to define future research priorities and focus conservation efforts. We assessed the current state of knowledge of biological invasions in Mexico based on the existing literature. Our aim was to identify in which areas information is absent or insufficient and which areas should be prioritised. We identified a total of 869 references. The number of references increased over time and the topics were strongly biased towards two areas: 1) natural history and geographical distribution patterns and 2) effects on native biota and ecosystems. The remaining topics were only moderately or poorly studied. Most studies focused on vascular plants (n = 280) and fishes (n = 174). Notably, a large portion of the references (n = 215) focused on only eight invasive alien species, including their ecological and socioeconomic impacts. Only 95 references examined the effects of alien species on biodiversity; these studies were mainly carried out on islands (n = 41) or in terrestrial or freshwater ecosystems in protected natural areas (n = 165). The findings of the present review can guide future studies in filling in the existing research gaps on biological invasions. Additionally, future studies should aim to define national priorities of the impacts of biological invasions and to promote the prevention and control of alien species by considering the distinct vectors and pathways of introduction and movement.

Acoustic occurrence and behavior of ribbon seals (Histriophoca fasciata) in the Bering, Chukchi, and Beaufort seas

Due to the difficulty of studying ice seals in their natural environment, distribution and movement patterns of ribbon seals (Histriophoca fasciata) over large spatio-temporal scales are poorly understood. In this study, we analyzed their distribution patterns in the Bering, Chukchi, and Beaufort seas, using passive acoustic data collected between August 2012 and July 2013 at 53 recording sites. Ribbon seal downsweeps were found using spectrogram correlation autodetection, at 30 of these recording sites. These detections were further manually analyzed to investigate the vocal repertoire and quantify the diel pattern in acoustic presence. We found that the Beaufort Sea shelf and the northern Bering Strait/southern Chukchi Sea are ecologically important for ribbon seals during the open-water season. Our results suggest that the northeastern Chukchi Sea serves as part of a migration corridor to and from the Chukchi Plateau and/or Beaufort Sea. In the Bering Sea, most detections occurred from February to June. Vocal activity was higher at nighttime than during the daytime prior to the peak calling period, while during the peak calling period, diel rhythm became less pronounced. The number of calls, proportional use of downsweeps, and bandwidth of downsweeps (estimated broadband source level 170–178 dB re 1 μPa-m) increased during the breeding period, from March to June, peaking in May. An additional call type, the “shuffle”, was identified in this study. These results improve our understanding of the migration, occurrence, and acoustic behavior of ribbon seals in the Bering, Chukchi, and Beaufort seas.

Contrasting effects of dams with and without reservoirs on the population density of an amphidromous goby in southwestern Japan

Dam construction affects the distribution and abundance of freshwater fishes, particularly for diadromous species. Amphidromous fishes spawn in rivers, and hatched larvae descend to the sea (or standing water body such as lakes) immediately after hatching, grow there typically for a few months, and then ascend rivers as small juveniles. Landlocked populations of amphidromous fishes above dams and their migration between dam reservoirs and inlet streams (landlocked migration) have often been reported. In these cases, population density in the inlet streams may be increased by dam reservoirs, owing to reduced migration distance, which results in higher return rates. On the other hand, dams without reservoirs do not promote landlocked migration and merely act as a barrier to their upstream migration, resulting in decreased population density. In this study, we examined such contrasting effects of dams with and without reservoirs on the population density of an amphidromous goby, Rhinogobius fluviatilis, in two river systems (the Shigenobu and Yoshino Rivers) of Shikoku Island, Japan. In the Shigenobu River, where more than 300 sediment-control dams and weirs (barriers without reservoirs) have been installed, our analysis showed that the goby density decreased sharply with increasing the number of barriers higher than or equal to 2 m. On the other hand, in the Yoshino River, where we investigated both landlocked populations above water storage dams (with reservoirs) and non-landlocked populations in tributaries without water storage dams, the analysis showed that the goby density increased with decreasing the distance from standing water body (i.e. the sea or dam reservoirs). Furthermore, monthly surveys at sites above and below a water storage dam showed that the recruitment of ascending juveniles above the dam was more abundant and seasonally earlier than that below the dam, probably owing to reduced migration distance and increased return rates. Our results have implications for understanding how dams alter natural distribution patterns of amphidromous fishes.

Applying microbial biogeography in soil forensics

The ubiquity, heterogeneity and transferability of soil makes it useful as evidence in criminal investigations, especially using new methods that survey the microbial DNA it contains. However, to be used effectively and reliably, more needs to be learned about the natural distribution patterns of microbial communities in soil. In this study we examine these patterns in detail, at local to regional scales (2 m–260 km), across an environmental gradient in three different soil types. Geographic location was found to be more important than soil type in determining the microbial community composition: communities from the same site but different soil types, although significantly different from each other, were still much more similar to each other than were communities from the same soil type but from different sites. At a local scale (25–1000 m), distance-decay relationships were observed in all soil types: the farther apart two soil communities were located, even in the same soil type, the more they differed. At regional-scale distances (1–260 km), differences between communities did not increase with increased geographic distance between them, and the dominant factor determining the community profile was the physico-chemical environment, most notably annual precipitation (R2 = 0.69), soil sodium (R2 = 0.49) and soil ammonium (R2 = 0.47) levels. We introduce a likelihood-ratio framework for quantitative evaluation of soil microbial DNA profile evidence in casework. In conclusion, these profiles, along with detailed knowledge of natural soil microbial biogeography, provide valuable forensic information on soil sample comparison and allow the determination of approximate source location on large (hundreds of km) spatial scales. Moreover, at small spatial scales it may enable pinpointing the source location of a sample to within at least 25 m, regardless of soil type and environmental conditions.

Random network model of electrical conduction in two-phase rock

We developed a cell-type lattice model to clarify the interconnected conductivity mechanism of two-phase rock. We quantified electrical conduction networks in rock and evaluated electrical conductivity models of the two-phase interaction. Considering the existence ratio of conductive and resistive cells in the model, we generated natural matrix cells simulating a natural mineral distribution pattern, using Mersenne Twister random numbers. The most important and prominent feature of the model simulation is a drastic increase in the pseudo-conductivity index for conductor ratio R > 0.22. This index in the model increased from 10−4 to 100 between R = 0.22 and 0.9, a change of four orders of magnitude. We compared our model responses with results from previous model studies. Although the pseudo-conductivity computed by the model differs slightly from that of the previous model, model responses can account for the conductivity change. Our modeling is thus effective for quantitatively estimating the degree of interconnection of rock and minerals.