Tibet Research Articles

An improved global Tm stratification model for GNSS-PWV retrieval

The atmospheric weighted mean temperature (Tm) is a key parameter for converting tropospheric wet delay (ZWD) into precipitable water vapor (PWV) and plays a vital role in Global Navigation Satellite System (GNSS) meteorology. Existing Tm models suffer from limitations such as the lack of consideration of full periodicity, poor accuracy at high altitudes, and the adoption of single-resolution grid data for modeling. Hence, an improved global Tm stratification model is developed based on ERA5 hourly reanalysis data from 2015 to 2019, called IGTmS, which takes seasonal and intraday variations into consideration and adopts a stratification mode to improve the vertical accuracy of Tm estimation. The accuracy and applicability of the IGTmS model are evaluated using Tm data at 417 radiosonde stations in 2020. The results show that the mean bias and RMS of Tm for the IGTmS model are −0.34 K and 3.53 K, and the accuracy is improved by approximately 7.8 %, 4.6 % and 2.5 % compared with that of GPT3, GTm-III and GTrop models on a global scale, respectively. IGTmS model can achieve the mean σPWV and σPWV/PWV values of 0.38 mm and 1.3 %, respectively, which shows optimal performance among the four models, especially in the Antarctic and Tibetan Plateau regions. Furthermore, three resolutions of the IGTmS models have been developed and all show high accuracy compared to GPT3 models. Users can choose the suitable model according to the desired accuracy and resolution. The developed stratification model IGTmS can effectively weaken the influence of large height difference on Tm estimation and can obtain high-accuracy and stable Tm over the globe and provide data support for real-time GNSS PWV retrieval.

Spatiotemporal coupling analysis of surface water and groundwater in Tibet based on multi-source sensors

Abstract. Lakes and groundwater are two crucial components of the global terrestrial water cycle, collectively forming a vital network for Earth's water resources. However, in the Tibetan region, the spatiotemporal relationship between lakes and groundwater and their impact on the local hydrological cycle remain inadequately understood. Satellite remote sensing serves as an effective observational tool, enabling comprehensive investigation and analysis of surface lakes and groundwater in Tibet with high spatial resolution. Therefore, this study integrates Landsat and Cryosat-2 satellite data to examine the spatiotemporal patterns of surface lake extents and water levels in Tibet. Additionally, combining Gravity Recovery and Climate Experiment (GRACE) satellite observations with the Global Land Data Assimilation System (GLDAS) model data, we quantitatively analyze the spatiotemporal variations in groundwater storage and its correlation with lake water. The results indicate that: 1) Rivers and lakes in Tibet are mainly located in the central and northwest regions, displaying noticeable intra-annual variations; 2) Substantial lagged relationships exist between groundwater storage and lake water levels and areas, revealing that lakes contribute significantly to groundwater replenishment, especially in the Ngari prefecture and Lhokha prefecture. This study comprehensively utilizes multi-source remote sensing data to dynamically monitor surface and groundwater in Tibet, providing robust support for a better understanding of the interaction between groundwater and surface water.

Dynamic Changes in Ecosystem Service Value and Ecological Compensation in Original Continuous Poverty-Stricken Areas of China

The original contiguous poverty-stricken areas of China (OCPSAC) are a regional complex with natural and human attributes. Their ecosystem services are highly complex in their contribution to human well-being. The region’s ecosystem is unstable and socio-economic development is unbalanced, making it a key area for research and the implementation of the United Nations Sustainable Development Goals. Therefore, it has become the focus of social attention. This study obtained satellite remote sensing images of the Landsat8 based on the Google Earth Engine. The dynamic characteristics of the spatial and temporal distribution of the OCPSAC’s land use changes in 2015 and 2022 were analyzed. The characteristics of the changes in ecosystem service value (ESV) were quantitatively evaluated through the revised ESV equivalent scale, and the ecological compensation (EC) standards and EC priority level suitable for the region were explored. The research results showed that: (1) the OCPSAC land use types were mainly grassland, forests, and deserts, accounting for more than 80% of the research area; (2) the OCPSAC’s ESV reached CNY 115.578 billion, and the Tibet Region (TR) and Tibetan Region of Four Provinces (TRFP) had the highest ESVs, accounting for 32.28% and 19.64%, respectively. Among individual ESVs, hydrological regulation (HR) and climate regulation (CR) had the highest values, accounting for 55.23% of the research area; (3) the ESV of the research area presented the characteristics of being high in the middle and low at both ends. From the terrain perspective, the areas with a higher ESV per unit area were distributed in the second altitude gradient, followed by China’s third altitude gradient, and the first altitude gradient was the lowest; (4) in the period of 2015–2022, the ESV increased by CNY 21.39 billion, of which TR’s ESV increased by CNY 17.44 billion. From the perspective of a single ESV, the value of waste treatment (WT), HR, nutrient cycle (NC), and provide aesthetic landscape (PAL) increased by CNY 24.38 billion; and (5) in 2022, the EC standard of the OCPSAC was CNY 917.14 billion. High-EC-value areas were mainly distributed in TR and TRFP, accounting for 72.79% of the total compensation amount, of which only TR’s EC amount exceeded a GDP of 2022, accounting for 4.77% of the total compensation. The purpose of this study was to provide a reference for ecosystem sustainability and EC.

GIS-Based assessment of geological hazard susceptibility in Southeastern Tibetan region: An information entropy approach

The terrain and geological conditions in southeastern Tibetan region are complex, especially under the influence of hydraulic and hydroelectric development, and susceptibility to geological hazards has increased. This study focused on three counties in Changdu City. We aimed to assess the susceptibility to geological hazards in this region using Geographic Information System (GIS) technology and information entropy models. Historical geological hazard data from the local area, remote sensing data, and GIS were utilized to develop an information entropy model for landslide geological hazard analysis. Key triggering factors for landslide geological hazards in the southeastern Tibetan region were identified, and a comprehensive dataset was compiled. Information entropy model was applied to consider various influencing factors and calculate their impact on geological hazards, Landslide risk in the area was analyzed and generate a susceptibility map for geological hazards. Our results indicate significant correlations between factors, such as steep terrain, human engineering activities, and land types with landslide occurrences. The established evaluation model can reasonably predict potential geological hazard risk in Nujiang River region and partially reflect the distribution characteristics of geological hazards in the southeastern Tibetan region. This offers a scientific foundation for relevant authorities to formulate disaster prevention and response strategies.

Mechanical Performance Degradation of Decaying Straight Mortise and Tenon Joints: Tusi Manor, Yunnan–Tibet Region

The straight mortise and tenon joints (SMTJs) of Tusi Manor, situated in the Yunnan–Tibet region of China, tend to undergo decay. This study aims to investigate the mechanism performance degradation of SMTJs due to decay. Five full-scale SMTJs were constructed and incubated with wood-rot fungi for 0, 6, 12, 18, and 24 weeks. Cyclic loading tests were conducted to assess the damage mechanisms and extent of mechanical property degradation at these different stages of decay, supported by ABAQUS finite element simulation software. The results revealed a progressive increase in damage with prolonged decay time. Comparison between decayed and undecayed specimens showed a maximum load-bearing performance degradation rate of 5.17%, 11.83%, 17.34%, and 23.54% after 6, 12, 18, and 24 weeks of fungal incubation, respectively. The cumulative energy efficiency degradation rates were 8.38%, 9.51%, 23.13%, and 33.31%, respectively. SMTJs mechanical performance degradation is correlated with wood mechanical property degradation as a function of the S-family. Finite element simulations further indicated a reduction in tenon strength from the outer parts towards the inner parts of the structure.

Epidemiology and Clinical Characteristics of Cerebral Alveolar Echinococcosis in the Tibetan Region of Sichuan, China.

This study aimed to examine the epidemiology and clinical characteristics of cerebral alveolar echinococcosis in the Tibetan region of Sichuan, China. A retrospective analysis of hospitalized cases of cerebral alveolar echinococcosis from six medical units in the Garze Tibetan Autonomous Prefecture, Sichuan Province, from January 2016 to June 2021 was conducted. The study focused on the characteristics, clinical presentation, and imaging features of the disease. Of 119 cerebral alveolar echinococcosis patients, 76 were male and 43 were female. Occupationally, 62 were farmers, 46 were herdsmen, nine were monks, and two were students. The mean age was 43.9 (± 13.9) years. The primary clinical manifestations were dizziness, headaches, and epilepsy. The incidence of cerebral alveolar echinococcosis was most concentrated within 4 years after the diagnosis of hepatic alveolar echinococcosis (77/119, 64.7%). There were 86 cases (72.3%) with multiple intracranial echinococcosis lesions, with an average size of 2.0 cm × 2.5 cm. The imaging features showed that the lesion was mainly concentrated in the anterior circulation blood supply area, and the lesion had multiple aggregated small vesicular structures as its unique imaging feature. Among 98 follow-up cases, 62 could live independently (63.3%); 18 deaths were recorded (18.4%), with an approximate 5-year survival rate of 81.6%. Regular examination of patients with first diagnosis of hepatic alveolar echinococcosis without a combination of echinococcosis in other parts of the body can help monitor and prevent the occurrence of cerebral alveolar echinococcosis, improve the understanding of cerebral alveolar echinococcosis in Tibetan areas of Sichuan.

Whole genome sequencing and analysis of probiotic characteristics for Lactiplantibacillus plantarum EL2 isolated from yak yogurt

The traditional yak yogurt from Gannan Tibetan Autonomous Prefecture harbors a rich microbial community, from which a strain of Lactiplantibacillus plantarum (Lp. plantarum EL2) was isolated. Through whole genome sequencing and probiotic activity assays, the genomic characteristics of this strain and its genes related to probiotic properties were analyzed. The results demonstrate that EL2 exhibits excellent antibacterial effects against Staphylococcus aureus and Salmonella, as well as favorable antioxidative properties, acid and bile salt tolerance, and strong adhesive ability. The genome of EL2 is 3.48 Mb in size, with a total length of 3,318,230 bp and a GC content of 44.48%. It contains 3155 open reading frames, spanning 2,773,647 bp, with a GC content of 45.58%. Bagel analysis reveals a bacteriocin gene cluster size of 20.3 kb in EL2, consisting of 22 genes encoding bacteriocins, as well as the identification of genes and pathways associated with gastrointestinal acid resistance and antioxidative properties. This is beneficial for the health of Tibetan individuals, and the research findings hold significant importance not only for the preservation and inheritance of probiotic strains in the Tibetan region, but also for the production and application of Lactiplantibacillus plantarum strains.

Characteristics and Influence Rules of Roadside Ponding along the Qinghai–Tibet Highway

Due to climate change and seasonal precipitation, water conditions in the Qinghai–Tibet region are a significant factor affecting the stability of subgrades. The accumulation of large amounts of surface water leads to subgrade diseases along the Qinghai–Tibet Highway. Based on remote sensing photos obtained from Google Earth Engine and processing the photos using ENVI 5.6.3 and CAD 2019 software, this paper analyzed the distribution characteristics of surface water and studied the impact of roadside ponding on subgrade diseases. The results showed that the total area of surface water was more than 3.7 million m2, and the surface water was most widely distributed in large river areas such as the Tuotuo River and Buqu River. The subgrade diseases of the Qinghai–Tibet Highway could be categorized into three types: settlement, longitudinal crack, and frost boiling, which accounted for 71.09%, 17.13%, and 11.78% of the total number of subgrade diseases, respectively. Additionally, the ground mean annual temperature was an important factor affecting the distribution of surface water, with the surface water area showing an increasing trend with the increase in ground mean annual temperature, and roadside ponding was most likely to form in the high-temperature extremely unstable permafrost area.

Effects of Tibetan medicine Longdan zhike tablet on chronic obstructive pulmonary disease through MAPK pathway

Ethnopharmacological relevanceLongdan zhike tablet (LDZK) is a Tibetan medicine formula commonly used in the highland region of Tibet, China, to ameliorate respiratory diseases, such as acute bronchitis and asthma. In Chinese traditional medicine, some herbal formulas with anti-inflammatory properties targeting the respiratory system are clinically adopted as supplementary therapies for chronic obstructive pulmonary disease (COPD). However, the specific anti-COPD effects of LDZK remain to be evaluated. Aim of the studyThe aim of this study is to identify the principal bioactive compounds in LDZK, and elucidate the effects and mechanisms of the LDZK on COPD. MethodsHigh-resolution mass spectrometry was utilized for a comprehensive characterization of the chemical composition of LDZK. The therapeutic effects of LDZK were assessed on the LPS-papain-induced COPD mouse model, and LPS-induced activation model of A549 cells. The safety of LDZK was evaluated by orally administering a single dose of 30 g/kg to rats and monitoring physiological and biochemical indicators after a 14-day period. Network pharmacology and Western blot analysis were employed for mechanism prediction of LDZK. ResultsA comprehensive analysis identified a total of 45 compounds as the major constituents of LDZK. Oral administration of LDZK resulted in notable ameliorative effects in respiratory function, accompanied by reduced inflammatory cell counts and cytokine levels in the lungs of COPD mice. Acute toxicity tests demonstrated a favorable safety profile at a dose equivalent to 292 times the clinically prescribed dose. In vitro studies revealed that LDZK exhibited protective effects on A549 cells by mitigating LPS-induced cellular damage, reducing the release of NO, and downregulating the expression of iNOS, COX2, IL-1β, IL-6, and TNF-α. Network pharmacology and Western blot analysis indicated that LDZK primarily modulated the MAPK signaling pathway and inhibited the phosphorylation of p38/ERK/JNK. ConclusionsLDZK exerts significant therapeutic effects on COPD through the regulation of the MAPK pathway, suggesting its potential as a promising adjunctive therapy for the treatment of chronic inflammation in COPD.

Quantitative characteristics and influencing factors of Tibetan Buddhist religious space with monasteries as the carrier: a case study of U-Tsang, China

Tibetan Buddhism has an inseparable connection with the spatial characteristics, development process, and human-natural environment of the Tibetan Plateau. This paper takes monasteries as carriers of Tibetan Buddhist culture in U-Tsang region which is one of the traditional geographical units of Tibet. Using geospatial analysis methods, this study explores the spatial quantification characteristics of Tibetan Buddhist monasteries and qualitatively and quantitatively analyzes the factors that influence the spatial distribution of monasteries. The results indicate that: (1) Political activities of human society influence the pattern of political power. Under the unique context of Tibetan theocracy system, the scope of political authority has a significant influence and affects the religious spatial pattern in the U-Tsang region throughout history. The distribution of monasteries in the U-Tsang region shows significant spatial differences at three sub-regional scales. (2) The religious spatial pattern in the U-Tsang is the result of the diverse interaction of human-natural factors. The results indirectly endorse that religious space is an inevitable product of the interaction between humans and the environment. (3) The religious spatial distribution patterns in the three major Tibetan regions have distinct characteristics, closely related to the superior conditions of their respective historical and geographical environments.

A Spatiotemporal Enhanced SMAP Freeze/Thaw Product (1980–2020) over China and Its Preliminary Analyses

The soil freeze/thaw (FT) state has emerged as a critical role in the ecosystem, hydrological, and biogeochemical processes, but obtaining representative soil FT state datasets with a long time sequence, fine spatial resolution, and high accuracy remains challenging. Therefore, we propose a decision-level spatiotemporal data fusion algorithm based on Convolutional Long Short-Term Memory networks (ConvLSTM) to expand the SMAP-enhanced L3 landscape freeze/thaw product (SMAP_E_FT) temporally. In the algorithm, the Freeze/Thaw Earth System Data Record product (ESDR_FT) is sucked in the ConvLSTM and fused with SMAP_E_FT at the decision level. Eight predictor datasets, i.e., soil temperature, snow depth, soil moisture, precipitation, terrain complexity index, area of open water data, latitude and longitude, are used to train the ConvLSTM. Direct validation using six dense observation networks located in the Genhe, Maqu, Naqu, Pali, Saihanba, and Shandian river shows that the fusion product (ConvLSTM_FT) effectively absorbs the high accuracy characteristics of ESDR_FT and expands SMAP_E_FT with an overall average improvement of 2.44% relative to SMAP_E_FT, especially in frozen seasons (averagely improved by 7.03%). The result from indirect validation based on categorical triple collocation also shows that ConvLSTM_FT performs stable regardless of land cover types, climate types, and terrain complexity. The findings, drawn from preliminary analyses on ConvLSTM_FT from 1980 to 2020 over China, suggest that with global warming, most parts of China suffer from different degrees of shortening of the frozen period. Moreover, in the Qinghai–Tibet region, the higher the permafrost thermal stability, the faster the degradation rate.

Artificial afforestation increased the distribution area and landscape complexity of planted forests in Tibet over the past 30 years

Afforestation plays an important role in improving the ecological environment and promoting local economic development in countries around the world. Although the artificial afforestation project in Tibet has been conducted for more than 30 years since in 1990 s, few studies have examined the dynamic changes in landscape patterns of planted forests in this region since the implementation of the project. This study used Google Earth Engine (GEE) and Landsat data from 1990, 2000, 2010 and 2020 to construct a Normalized Difference Vegetation Index (NDVI) time series curves and an optimal classification model based on the Jeffries-Matusita (J-M) distance. Then, the changes in landscape indices of planted forests in the Tibet Autonomous Region over the past 30 years were examined. The results showed that the area of planted forests increased from 9889.20 ha to 165,879.36 ha by artificial planting, with an average annualized growth rate of about 9.86%. In terms of the landscape pattern, the connectivity and aggregation degree of planted forests increased; the Cohesion (COH) and Aggregation Index (AI) increased by 44.60% and 26.03%, respectively. However, the fragmentation indices also increased to a certain extent due to the increased area and discontinuous planting; the Number of Patches (NP), Patch Density (PD) and Landscape Shape Index (LSI) increased by 32,262, 0.03 and 138.88, respectively. Among the seven regions of Tibet, these changes were most obvious in Lhasa, Qamdo and Shannan regions. Our results indicate that the planted forest area has significantly increased over the past 30 years although the landscape complexity has also increased because of discontinuous planting. These findings highlight the remarkable achievements of the Tibetan afforestation project over the past 30 years.

Association between soybean product consumption and executive function in Chinese Tibetan children and adolescents.

This sought to explore the association between soybean product consumption and executive function (EF) in Chinese Tibetan adolescents in high-altitude areas. A total of 1,184 Tibetan children and adolescents were tested on demographic variables, soybean product consumption, and executive function in Lhasa and Nagchu regions of Tibet, China, using stratified whole population sampling. One-way ANOVA, linear regression analysis, and logistic regression analysis were used to analyze the associations existing between soybean product consumption and executive function. The proportions of Hardly ever, Occasionally, and Often in Soy Consumption among Tibetan children and adolescents in high altitude areas of Tibet, China were 21.7, 50.3, and 28.0%, respectively. The difference in 2 back reaction time among Tibetan children and adolescents with different soybean product consumption was statistically significant (F = 6.374, p = 0.002). The difference in conversion function reaction time was also statistically significant (F = 8.129, p < 0.001). Taking the soybean product consumption ≥6 t/w group as the reference group, after adjusting the relevant factors, those with soybean product consumption ≤1 t/w showed a statistically significant increase in Inhibit Function Dysfunction (OR = 1.844, 95% CI: 1.152, 2.951) and Conversion Function Dysfunction (OR = 2.008, 95% CI: 1.106, 3.646) had an increased risk of Conversion Function Dysfunction (OR = 2.008, 95% CI: 1.106, 3.646), which was significantly different (p < 0.05). There is an association between soybean product consumption and inhibitory control and translational flexibility of brain executive functions in Chinese Tibetan children and children and adolescents at high altitude.

Pluralistic ecological governance: A comparative analysis of conservation practices among Tibetan communities of China

Extant scholarly discourse on ecological governance within China predominantly underscores the salient role of the central state. This is unsurprising given the statist policy trajectory transitioned from an emphasis on swift economic growth to focusing on emerging ecological challenges in the last decade. However, this article deviates from this prevailing emphasis, pivoting instead to the tangible practices and realities of ecological governance at the grassroots level. Through an ethnographic investigation, this article delves into the nuances of ecological governance within the Tibetan regions of Qinghai Province, China, emphasising the interplay between local communities, environmental non‐governmental organisations and the local state. The article introduces the concept of ‘pluralistic ecological governance’, advocating for the integration of diverse governance structures, institutional frameworks and stakeholder involvements. This approach encompasses a thorough consideration of diverse knowledge systems, motivations of community participation and local‐state relations, vital for addressing the complex nature of ecological issues. The study contends that ‘pluralistic ecological governance’ not only encompasses different stakeholders but also critically examines various forms of knowledge and motivations, along with the diverse interests these stakeholders contribute to both the discourse and practice of ecological conservation on the ground.

Temporal and Spatial Dynamics in Carbon Utilization Efficiency and Driving Mechanisms in Southeast Tibet from 2012 to 2022

Carbon utilization efficiency (CUE) in terrestrial ecosystems stands as a pivotal metric for assessing ecosystem functionality. Investigating the spatiotemporal dynamics of regional CUE within the context of global climate change not only provides a theoretical foundation for understanding terrestrial carbon cycling but also furnishes essential data support for formulating sustainable management strategies at a regional scale. This study focuses on the southeastern region of Tibet. Utilizing monthly and yearly MOD17A2HGF as primary sources, we employ Thiel–Sen estimation and Mann–Kendall trend analysis to scrutinize the spatiotemporal dynamics of CUE. Systematic analysis of the stability of CUE spatiotemporal changes in the Southeast Tibet region is conducted using the coefficient of variation analysis. The Hurst model is then applied to prognosticate future CUE changes in Southeast Tibet. Additionally, a comprehensive analysis of CUE is undertaken by integrating meteorological data and land-use data. The findings reveal the following: (1) At the monthly scale, regional CUE exhibits discernible variations synchronized with the growth season, with different vegetation types displaying diverse fluctuation patterns. The high-altitude forest area manifests the least annual CUE fluctuations, while evergreen needleleaf forests and evergreen broadleaf forests demonstrate larger variations. At the yearly scale, CUE reveals a non-significant upward trend overall, but there is an augmented fluctuation observed from 2019 to 2022. (2) CUE in Southeast Tibet demonstrates sensitivity to temperature and precipitation variations, with temperature exhibiting a more pronounced and strongly correlated impact, especially in Gongjo County and Qamdo Town. Temperature and precipitation exert opposing influences on CUE changes in the Southeast Tibet region. In the southern (below 28° N) and northern (above 31° N) regions of Southeast Tibet, the response of CUE to temperature and precipitation variations differs. Moreover, over 62.3% of the areas show no sustained trend of change. (3) Vegetation type emerges as a principal factor determining the scope and features of vegetation CUE changes. Grassland and sparse grassland areas exhibit markedly higher CUE values than evergreen broadleaf forests, deciduous broadleaf forests, evergreen needleleaf forests, and deciduous needleleaf forests. Notably, the CUE fluctuation in shrublands and areas with embedded farmland vegetation surpasses that of other vegetation types.

Eocene monsoon climate expansion in East Asia: Evidence from orbital‐cycle driven terrestrial successions in the Jianghan Basin, Central China

ABSTRACTEast Asia experienced complex climatic changes during the Eocene. Due to the lack of a high‐precision time framework covering the Eocene, the characteristics of sedimentary and climate evolution in this period remain unclear. The Jianghan Basin (Central China) developed an Eocene continental succession, which is composed of lower red beds and upper salt‐lake deposits exhibiting clear sedimentary rhythms, making these strata an ideal target for astronomical cycle analysis. Based on the established floating astronomical timescale, the lower red beds in the basin formed during the early–middle Eocene and were dominated by eccentricity cycles. The upper salt‐lake deposits formed during the middle–late Eocene and recorded obliquity cycles. The change in facies indicates that the climate transitioned from continuously arid to less arid with periodic relative wetness, which was forced by orbital cycles. Significant obliquity signals recorded by salt rhythmites responded to Eocene global temperature changes and Tibetan region uplift, which can be important markers of a monsoon‐like climate. Comparing the sedimentary and climatic characteristics of other Eocene lake basins in East Asia, the extension of the Eocene East Asian monsoon may have initiated during ca 43.6 to 40.0 Ma. This study provides a new perspective for understanding the early evolution of the East Asian monsoon.

Geodynamic models of Indian continental flat slab subduction with implications for the topography of the Himalaya-Tibet region

The slab structure and high elevation of the Himalaya-Tibet region and their underlying mechanisms have been widely discussed. Many studies interpret a flat slab segment of Indian continental lithosphere located below the overriding plate, but interpretations of the northward extent of the flat slab differ substantially, with minimum estimates placing the boundary at the northern margin of the Himalaya (Indus-Yarlung Tsangpo suture), and maximum estimates placing it at the northern boundary of Tibet. In this study, we investigate for the first time if a flat slab segment of subducted buoyant Indian continental lithosphere below the Himalaya-Tibet region is geodynamically feasible and we quantify its northward extent, as well as its contribution to the high topography of the region. We conduct three large-scale fully-dynamic (buoyancy-driven) analogue experiments to simulate the subduction of the Indian continent. Our preferred, and geodynamically most feasible, model shows a continental flat slab extending northward up to ~ 320 km from the Himalayan thrust front, in agreement with recent estimates. Furthermore, it suggests that the positively buoyant flat slab segment of the Indian continent contributes some ~ 1.5–2 km to the high topography of the Himalaya-Southern Tibet region by providing an upward force to elevate the overriding Eurasian plate.

Site selection and hydropower potential assessment in Upper Sutlej River Basin: a case study of Indian and Tibetan regions using RS-GIS, SWAT and T-F models

Site selection and hydropower potential assessment in Upper Sutlej River Basin: a case study of Indian and Tibetan regions using RS-GIS, SWAT and T-F models

Numerous Tibetan lower-crustal and upper-mantle earthquakes, detected by Sn/Lg ratios, suggest crustal delamination or drip tectonics

Whether intermediate-depth earthquakes beneath Tibet and the Himalaya are in the lower crust or upper mantle should provide insight into rheology, hence composition and temperature, of continental lower crust and upper mantle. Based on the waveguide theory that earthquakes respectively above or below the Moho will excite higher Lg or Sn energy, we develop an Sn/Lg amplitude-ratio analysis using a single permanent station to investigate earthquake depths with respect to the Moho. First, we use synthetics to show the ubiquitous sharp increase of the Sn/Lg ratio for hypocenters beneath the crust. A deep-crustal high-vs layer appropriate for eclogitized Indian lower crust causes a more gradual increase of Sn/Lg ratios for hypocenters within or below the eclogite layer. We measured Sn/Lg ratios of 595 Tibetan earthquakes from 1998 to 2022 with nominal (catalog) hypocentral depths >30 km and magnitudes >3.2 in five regions (west Tibet, southwest Tibet, south Tibet, southeast Tibet, and Qiangtang). As predicted by our normal-mode synthetics, earthquakes in west and south Tibet show Sn/Lg ratios that increase sharply as catalog depths approach the independently determined receiver-function Moho. Numerous earthquakes with high Sn/Lg ratios and nominal depths around the reported Moho are identified between the Karakoram fault and Altyn-Tagh fault (ATF) in west Tibet, which we attribute to an eclogitized Indian lower crust extending north to the ATF. Impingement of this underthrust Indian slab against the Tarim craton and consequent eclogite delamination or dripping may cause the observed below-Moho seismicity which occupies a region 100 km across and 200 km along orogenic strike and extends 30–50 km below published Moho depths. Similarly dense seismicity spans the Moho and occupies a similar volume below the Moho beneath the High Himalaya in south Tibet. The south Tibet Sn/Lg patterns may indicate an eclogitized Indian layer beginning to delaminate or drip south of the Yarlung-Zangpo suture. Our southeast Tibet and southwest Tibet Sn/Lg observations are less clear cut, perhaps due to less appropriate epicentral distances from the available observing stations. The Qiangtang region of Tibet likely has sparse mid-to-lower-crustal earthquakes, but no definitive below-Moho earthquakes. Our work expands the catalog of continental intraplate earthquakes below the Moho by >100 events with mb>3.2, as well as identifying tens of mb>3.2 lower-crustal events, so that Tibet fits neither an ideal crême-brulée nor an ideal jelly-sandwich crustal-strength paradigm. Two clusters of earthquakes that each span the Moho may be best explained by the delamination or dripping of a strong eclogitized lower crust into the upper mantle.

Mapping the Ophiocordyceps sinensis value chain: actors, profits and social institutions in south-west China

AbstractCommercial use of wildlife is booming. However, knowledge of trade, price structure and benefit distribution mechanisms remain limited for many endemic, threatened and economically valuable species, impeding efforts to develop conservation intervention schemes in line with sustainable objectives. We illustrate the nature of commercialization of the caterpillar fungus Ophiocordyceps sinensis, collected in a high-altitude Tibetan region. Using the value-chain approach, we document how caterpillar fungus is collected in a remote mountainous region and traded across a wide range of middlemen until it finally reaches high-end markets in urban centres. Mapping the caterpillar fungus value chain helps identify the actors involved and the social institutions (i.e. the rules, norms and arrangements that shape people's behaviours) facilitating access to markets and influencing profit distribution and price structure. We present the complex dynamics of this commercialization process, providing a holistic value-chain analysis that encompasses actors, profits and institutions.