Northeast Qinghai-Tibet Plateau Research Articles

Combining phylogeography and landscape genetics reveals genetic variation and distribution patterns of Stipa breviflora populations

• Stipa. breviflora originated on the northeastern QTP and the eastern Helan mountains. • S. breviflora originated in the late Miocene. • The genetic differentiation of S. breviflora was mainly caused by IBD. Historical and contemporary microevolutionary processes influence the extent and structure of genetic variation. Combining phylogeography and landscape genetics is an important approach for delineating the formation mechanisms about the patterns of genetic structures. Grassland ecosystems comprise approximately one-third of Earth's vegetative cover. The spatial distribution of genetic variations derived from dominant plant species in steppes is helpful to understand the origin and evolution of this kind of vegetation. In this paper, we took Stipa breviflora , a dominant species of desert steppe, as an example, and conducted the research on both chloroplast DNA sequences and microsatellite loci of populations. The results of analyzing haplotype and microsatellite diversity revealed that S. breviflora most probably originated from the region in eastern Helan Mountains and northeast of Qinghai-Tibet Plateau (QTP) during the late Miocene. The genetic variation distribution of the species was in accordance with the core-periphery hypothesis (CPH), i.e., populations located at the periphery of a species’ range should have lower levels of genetic variation than those at the center of the range. Paleoclimatic fluctuations contributed to haplotype evolution, while geographical distance played an important role in driving contemporary genetic differentiation. Our findings highlight the complexity of intraspecific evolution and clarify the biogeographical history of desert steppes based on molecular signals.

Formation and variations of dew and hoarfrost in the Hulu Catchment on Northeast Qinghai-Tibet Plateau, China

Study regionThe Hulu Catchment on Northeast Qinghai-Tibet Plateau, China Study focusDew and hoarfrost (DH) are prominent components of the Non-Precipitation Water Inputs in arid and semi-arid regions, but research into them is mostly neglected in alpine regions. To understand the formation and variations of DH, as well as whether DH has a significant impact on the water balance and ecosystem, a field measurement experiment of dew was conducted in the Hulu Catchment. Meanwhile, the amount, duration, and frequency of DH at different elevations in the Hulu Catchment from 2016 to 2020 were estimated using the Penman equation. New hydrological insights for the regionDH was common weather phenomenon in the Hulu Catchment, with small interannual and large monthly variations in amount, duration, and frequency. DH showed significant seasonal pattern and elevation dependence, which depending on the seasonal pattern and elevation dependence of meteorological factors. The mean annual amount of DH ranged from 3 mm to 33 mm, contributing 0.3–7.3% of precipitation, indicating that DH was not a critical component of water balance. Nevertheless, DH was ecologically important in replenishing surface soil water deficits and mitigating diurnal fluctuations in surface temperature, protecting vegetation and microorganisms from water and temperature stress in alpine regions. This study has important implications for understanding the energy transfer, water cycle and ecosystem operation in alpine regions.

Seasonal Variation in Soil and Herbage CO2 Efflux for a Sheep-Grazed Alpine Meadow on the North-East Qinghai-Tibetan Plateau and Estimated Net Annual CO2 Exchange.

The Qinghai-Tibetan Plateau is a vast geographic area currently subject to climate warming. Improved knowledge of the CO2 respiration dynamics of the Plateau alpine meadows and of the impact of grazing on CO2 fluxes is highly desirable. Such information will assist land use planning. We measured soil and vegetation CO2 efflux of alpine meadows using a closed chamber technique over diurnal cycles in winter, spring and summer. The annual, combined soil and plant respiration on ungrazed plots was 28.0 t CO2 ha−1 a−1, of which 3.7 t ha−1 a−1occurred in winter, when plant respiration was undetectable. This suggests winter respiration was driven mainly by microbial oxidation of soil organic matter. The winter respiration observed in this study was sufficient to offset the growing season CO2 sink reported for similar alpine meadows in other studies. Grazing increased herbage respiration in summer, presumably through stimulation of gross photosynthesis. From limited herbage production data, we estimate the sustainable yield of these meadows for grazing purposes to be about 500 kg herbage dry matter ha−1 a−1. Addition of photosynthesis data and understanding of factors affecting soil carbon sequestration to more precisely determine the CO2 balance of these grasslands is recommended.

Spatial variation of soil organic carbon in the Qinghai Lake watershed, northeast Qinghai-Tibet Plateau

Soil organic carbon (SOC) on the Qinghai-Tibet plateau is of global significance, due to the high carbon density and potential positive feedbacks to climate warming. Qinghai Lake watershed is an important soil pool in Qinghai-Tibet plateau, but the magnitude and characteristics of SOC stock in the high-altitude basin were not clear. To understand better how much SOC was stored and its spatial patterns in the watershed, this study analyzed the vertical variation of SOC content, quantified its influence by varied environmental factors, and further predict its storage in the entire basin. Results showed that, the SOC content decreased with the increasing depth, and was the highest in the alpine meadow in all depths, following by the alpine steppe and temperate steppe, respectively. It was generally higher in the permafrost region than that in the non-permafrost region at all depths. Soil profile depth, soil water content and NDVI could together explain about 72.6% of total variation in SOC density. The regression-kriging method was the best upscaling approach for the prediction of SOC in the study area. Approximately 317 Tg organic carbon was stored in the entire soil profile of Qinghai Lake watershed, in which 136, 140, and 41 Tg were at 0–30 cm, 30–100 cm, and below 100 cm, respectively. The higher SOC density mainly appeared on the northeast and southern region of Qinghai Lake, while the high-altitude area in the northwest of the watershed had the lower values. Moreover, it increased firstly and then decreased with the increase of altitude, with the maximum values at 3350–3400 m, which was dominated by the elevational variation of soil profile depth and NDVI. Overall, the comprehensive assessment of SOC demonstrated high storage and strong heterogenicity of soil carbon in the Qinghai Lake watershed, and it is critical for the sustainability of regional terrestrial ecosystem with future climate change.

Leaf Stoichiometry of Potentilla fruticosa Across Elevations in China's Qilian Mountains.

As an individual plant species can develop its own leaf stoichiometry to adapt to environmental changes, this stoichiometry can provide critical information about a plant species’ growth and its potential management in the ecosystem housing it. However, leaf stoichiometry is largely undocumented in regions with large environmental changes arising from differences in elevation. The leaf stoichiometry of Potentilla fruticosa L., a major alpine shrub playing an important role in supporting ecosystem functions and services in China’s Qilian Mountains (Northeast Qinghai–Tibetan Plateau), was investigated at different elevations (2,400, 2,600, 2,800, 3,000, 3,200, 3,500, and 3,800 m). At each elevation, leaf elemental (C, N, and P) concentrations were measured in P. fruticosa leaves sampled from three plots (10 × 10 m), and edaphic properties were assessed in nine quadrats (1 × 1 m, three quadrats per plot). Temperature and precipitation were calculated using an empirical formula. Maximum and minimum leaf carbon (C) concentrations ([C]leaf) of 524 ± 5.88 and 403 ± 3.01 g kg–1 were measured at 2,600 and 3,500 m, respectively. Leaf nitrogen (N) concentration ([N]leaf) showed a generally increasing trend with elevation and peaked at 3,500 m (27.33 ± 0.26 g kg–1). Leaf phosphorus (P) concentration ([P]leaf) varied slightly from 2,400 to 3,200 m and then dropped to a minimum (0.60 ± 0.10 g kg–1) at 3800 m. The [C]leaf:[N]leaf, [C]leaf:[P]leaf, and [N]leaf:[P]leaf varied little from 2,400 to 3,000 m but fluctuated somewhat at higher elevations. The main factors affecting P. fruticosa leaf stoichiometry were soil organic C, pH, and soil total P, and the main limiting element for the growth of P. fruticosa in the study area was P. In conclusion, changes in elevation affected leaf stoichiometry of P. fruticosa mainly due to altered soil properties, and addressing phosphorus limitation, especially at higher elevations mainly due to losses caused by high precipitation and sparse vegetation, is a key measure to promote P. fruticosa growth in this region.

Diurnal Evapotranspiration and Its Controlling Factors of Alpine Ecosystems during the Growing Season in Northeast Qinghai-Tibet Plateau

It is generally believed that evapotranspiration at night is too miniscule to be considered. Thus, few studies focus on the nocturnal evapotranspiration (ETN) in alpine region. In this study, based on the half-hour eddy and meteorological data of the growing season (from May to September) in 2019, we quantified the ETN of alpine desert (AD), alpine meadow (AM), alpine meadow steppe (AMS), and alpine steppe (AS) in the Qinghai Lake Basin and clarified the different response of evapotranspiration to climate variables in daytime and nighttime with the variation of elevation. The results show that: (1) ETN accounts for 9.88~15.08% of total daily evapotranspiration and is relatively higher in AMS (15.08%) and AD (12.13%); (2) in the daytime, net radiation (Rn), temperature difference (TD), vapor pressure difference (VPD), and soil moisture have remarkable influence on evapotranspiration, and Rn and VPD are more important at high altitudes, while TD is the main factor at low altitudes; (3) in the nighttime, VPD and wind speed (WS) control ETN at high altitudes, and TD and WS drive ETN at low altitudes. Our results are of great significance in understanding ETN in the alpine regions and provide reference for further improving in the evapotranspiration estimation model.

Geochemical and Statistical Analyses of Trace Elements in Lake Sediments from Qaidam Basin, Qinghai-Tibet Plateau: Distribution Characteristics and Source Apportionment.

The safety of lake ecosystems on the Qinghai-Tibet Plateau (QTP) has attracted increasing attention, owing to its unique location and ecological vulnerability. Previous studies have shown that the aquatic systems on the QTP have been polluted to varying degrees by trace elements. However, little is known of the distribution and sources of trace elements in lakes in the northeast QTP. Here, 57 sediment samples were collected from six lakes (Dasugan Lake, Xiaoqaidam Lake, Kreuk Lake, Toson Lake, Gahai Lake and Xiligou Lake) in the Qaidam Basin, northeast QTP, and the trace elements (V, Cr, Ni, Cu, Zn, As, Ba, Tl, Cd, Pb, and U) were analyzed. The results indicated that Ba, Zn, V, and Cr had a higher content and a wider distribution relative to the other tested elements. Correlation coefficient matrix results showed that the trace elements in the study area were strongly correlated, revealing their source of similarity. Self-organizing maps (SOM, an artificial neural network algorithm) results indicated that the degree of pollution in Xiaoqaidam Lake was the highest, and that of Dasugan Lake was the lowest. Furthermore, all sampling points were clustered into four categories through K-means clustering. The positive matrix factorization (PMF) results indicated that atmospheric deposition and anthropogenic inputs were the main trace elements sources in these lakes, followed by traffic emission and geological sources. Collectively, trace elements of six lakes in Qinghai-Tibet Plateau presented high-content and pollution characteristics. This research provides a scientific basis for better water environment management and ecological protection on the QTP.

Holocene Aeolian Activity Recorded by Mountain Paleosols, Gonghe Basin, Northeast Qinghai-Tibet Plateau

The Gonghe Basin (GHB) on the northeastern Qinghai-Tibet Plateau (NE-QTP) is sensitive to climatic change due to the interplay of the Asian summer monsoon and the westerlies. Extensive aeolian sediments in the basin represent important archives of regional environmental evolution. However, the paleosol development timing is still not clear because of limited number of optically stimulated luminescence (OSL) sampling and dating, which restricts our understanding of past aeolian activities during the Holocene in GHB. In this study, a loess-paleosol section, Najiao (NJ), from the southeastern margin of GHB was investigated. Eighteen OSL samples were obtained from the 400-cm section in order to construct a high-resolution chronological framework. Paleoenvironmental proxies including grain size distribution (GS), magnetic susceptibility (MS), total organic carbon (TOC), and geochemical elements were measured to reconstruct the Holocene aeolian activity. Results show a successive accumulation from Early to Middle Holocene at NJ section, but a c. 3 ka sedimentary hiatus is found between c. 5 and 1.5 ka. Paleosol ages are constrained by high-resolution OSL ages which are from c. 7–5 ka. Consistent with previous studies, strong aeolian activities occurred in GHB during the Early Holocene (c. 13–9 ka), indicating dry climate conditions. Initiation of pedogenesis was at c. 9 ka, and the intensified soil development and lowest aeolian activity were between c. 7 and 5 ka. The increased sand content after c. 1.5 ka indicates enhanced human activities in the interior of GHB in the Late Holocene.

Dispersal into the Qinghai-Tibet plateau: evidence from the genetic structure and demography of the alpine plant Triosteum pinnatifidum.

Triosteum pinnatifidum Maxim., an alpine plant, is traditionally used for several medicinal purposes. Here, both chloroplast DNA sequences and nuclear low copy sequence markers were used to investigate the genetic diversity and population structure of T. pinnatifidum. Materials were collected from thirteen localities in the northeast Qinghai–Tibet Plateau (QTP) and adjacent highlands and advanced analytical toolkits were used to access their origin and range shifts. The results revealed a higher level of population differentiation based on chloroplast DNA (cpDNA) concatenated sequences compared with the nuclear DNA sequences (FST = 0.654 for cpDNA, FST = 0.398 for AT103), indicating that pollen flow was still extensive in T. pinnatifidum. A decline in haplotype variation was observed from the plateau edge and adjoining highlands toward the platform of the QTP. The hypothesis “dispersal into the QTP,” proposing that T. pinnatifidum experienced migration from the plateau edge and adjacent highlands to the platform, was supported. These results were in line with the hypothesis that multiple refugia exist on the plateau edge and adjacent highlands rather than on the plateau platform. Our unimodal mismatch distribution, star-like network supported a recent expansion in T. pinnatifidum.

Using Leaf Ecological Stoichiometry to Direct the Management of Ligularia virgaurea on the Northeast Qinghai-Tibetan Plateau

Leaf ecological stoichiometry not only reflects the plasticity and adaptability, but also the growth of plants within environments where temperature, precipitation, and soil properties vary across an elevation gradient. Ligularia virgaurea (Maxim.) Mattf. ex Rehder & Kobuski — an invasive poisonous plant — is common in the northeast portion of China’s Qinghai-Tibetan Plateau and its presence greatly affects the native ecosystem. Based on L. virgaurea leaf carbon ([C]leaf), nitrogen ([N]leaf) and phosphorus ([P]leaf) concentrations, and their ratios, the species’ coping strategies across an elevation gradient (2,600 m, 3,000 m, and 3,300 m) were identified, and served to inform the development of improved management strategies. Mean [C]leaf, [N]leaf and [P]leaf in L. virgaurea across all elevations were 413.14 g·kg−1, 22.76 g·kg−1, and 1.34 g·kg−1, respectively, while [C]leaf: [N]leaf, [C]leaf: [P]leaf, and [N]leaf: [P]leaf were 18.27, 328.76, and 17.93. With an increase in precipitation and decrease in temperature from 2,600 m to 3,000 m–3,300 m, [C]leaf, [C]leaf: [N]leaf and [C]leaf: [P]leaf of L. virgaurea decreased at first and then increased. The [N]leaf and [P]leaf gradually increased, whereas [N]leaf: [P]leaf showed little change. Although temperature, precipitation and soil water content were the main factors affecting the ecological stoichiometry of L. virgaurea leaves, their roles in influencing leaf elements were different. The [C]leaf was mainly influenced by soil water content, [N]leaf by temperature and soil water content, and [P]leaf by all of them. With potential future climate change in the study area, L. virgaurea may grow faster than at present, although soil P may still be a growth-limiting element. As L. virgaurea can reduce plant diversity and the quality of forage, while increasing biomass, management of L. virgaurea should receive greater attention.

基于地表土壤动物与植物完整性指数评估若尔盖沼泽湿地受扰现状

利用地表土壤动物与植物群落生物完整性指数评价若尔盖沼泽湿地受扰现状，为若尔盖沼泽湿地恢复提供依据。2018年7月与2019年7月对若尔盖10处典型湿地（参照区4个，受扰区6个）地表土壤动物与湿地植被群落进行调查。通过对74个候选指标的分布范围、判别能力及相关分析，确定中生性植物、一年生植物、龙胆科植物、一年生植物/多年生植物比4个植物核心指标，地表土壤动物总个体数量、中小型动物类群数量、蜘蛛目物种数量、菌食性土壤动物与腐食性土壤动物5个核心指标，构建若尔盖沼泽湿地地表土壤动物与植物完整性指数。以所有采样点95%分位数为最佳期望值，四分位法确定研究区域未受干扰、轻度干扰程度、中度干扰与重度干扰4个等级，作为判断若尔盖沼泽湿地受扰状况。结果显示，若尔盖沼泽湿地相对原始沼泽、花湖沼泽化草甸2、长期低强度排水疏干区、短期高强度排水疏干区分别处于未受干扰、轻度干扰、中度干扰与重度干扰状态。所调查的若尔盖典型湿地中，20%的湿地未受到干扰，30%的湿地受到轻度干扰，30%的湿地受到中度干扰，20%的湿地受到重度干扰。Pearson相关系数分析显示，地表土壤动物完整性指数与植物完整性指数存在显著正相关关系（r=0.722，P<0.05），表明地表土壤动物完整性指数与植物完整性指数评价结果具有一致性。;The Zoige wetland, located at the northeast of Qinghai-Tibet Plateau, is the largest plateau wetland in China. There have been substantial changes in Zoige wetland due to natural (climate, soil, and vegetation) and anthropogenic (drainage and overgrazing) impacts. The index of biotic integrity is a comprehensive method for assessing the ecological status of wetlands. The ground-dwelling soil animal and wetland plant are the most widely used biological indicators owing to their distinct advantages for wetland ecosystem monitoring, while there is no indicator framework to determine the disturbed status and benefit of returning grazing to wetland of the Zoige area. The aim of this study is to evaluate disturbance status of Zoige wetland using the ground-dwelling soil animal and wetland plant-based index of biotic integrity to providing data for the restoration of Zoige wetland. In July 2018 and July 2019, the ground dwelling soil animal and plant were investigated from 10 typical wetlands of Zoige were chosen, including 4 wetlands which were undisturbed or less disturbed, and 6 wetlands which were disturbed. The ground-dwelling soil animal and plant-based index of biotic integrity in Zoige wetland were determined through a range of index value distribution, discrimination ability, and correlation analysis of 74 candidate indicators, which included 5 metrics of the number of soil animal individuals, the number of meso/micro soil animal individual, the number of ground spiders, Fungivorous form animal and Saprozoic animal, while plant integrity index including 4 metrics of mesophyte, annuals plant, Gentians, ration of annuals/Perennials. Use the quartile method to determine four grades of undisturbed, mild, moderate, severe disturbance in the study area with 95% quantile of all sampling points as the best-expected value and judge the disturbance status of the Zoige swamp wetland. The results showed that the relatively primary wetland was undisturbance, swamp meadow 2 was mild disturbance, long-term low intensity drainage stress area was moderate disturbance, and short-term high intensity drainage stress area was severe disturbance. Among the investigated typical wetland of Zoige, 20% of wetlands were undisturbance, 30% were mild disturbance, 30% were moderate disturbance, and 20% were the severe disturbance. According to the Pearson correlation coefficient analysis, there was a significantly positive correlation between surface soil animal integrity index and plant communities integrity index (r=0.722, P<0.05), indicating that the evaluation results of surface soil animal integrity index and plant integrity index were consistent.

How Does Spring Phenology Respond to Climate Change in Ecologically Fragile Grassland? A Case Study from the Northeast Qinghai-Tibet Plateau

Vegetation phenology is an important indicator of global climate change, and the response of grassland phenology to climate change is particularly sensitive in ecologically fragile areas. To enhance the ecological security of the Tibetan Plateau, it is crucial to determine the relationship between fluctuations in the start of the growing season (SOS) and the response to environmental factors. We investigated the trends of the intra-annual (ten-day) and interannual spatiotemporal dynamics of the SOS on the Northeast Qinghai-Tibet Plateau (NQTP) from 2000–2020 with MOD09GA data. We identified the response relationships with environmental factors (climate, terrain) using the maximum value composite method and the Savitzky–Golay filtering and dynamic threshold method. The SOS was concentrated from the 110th to 150th days; the average annual SOS was on the 128th day, with a spatial pattern of “early in the east and late in the west”. The overall trend of the SOS was advanced (45.48%); the regions with the advanced trend were mainly distributed in the eastern part of the NQTP. The regions with a delayed SOS were mainly concentrated in the higher-altitude regions in the southwest (38.31%). The temperature, precipitation and SOS exhibited a reverse fluctuation trend around the midpoint of 2010. Precipitation affected the SOS earlier than temperature. When temperature became a limitation of the SOS, precipitation had a more significant regulatory effect on the SOS. The SOS and aspect, slope and altitude were distributed in axisymmetric, pyramidal and inverted pyramidal shapes, respectively. The SOS on shaded slopes was earlier and more intensive than that on sunny slopes. With increasing slope, the area of the SOS decreased, and it occurred later. The SOS area was largest at 4500–5000 m and decreased at lower and higher altitude intervals. The SOS occurred later as altitude increased.

Accumulation of potentially toxic trace elements (PTEs) by native plant species growing in a typical gold mining area located in the northeast of Qinghai-Tibet Plateau.

Though gold mines provide significant economic benefits to local governments, mining causes soil pollution by potentially toxic trace elements (PTEs) in mining areas, especially in the Qinghai-Tibet Plateau. Screening of native plant species from mining areas is now an effective, inexpensive, and eco-friendly method for the remediation of PTEs in situ. In the present study, we conducted experiments to assess the accumulation of As, Cd, Pb, and Zn in 12 native plant species growing on a typical gold mining area in the Qinghai-Tibet Plateau. Our results showed that rhizosphere soils have high soil organic matter content, high levels of As, and moderate levels of Cd. Geranium pylzowianum accumulated relatively higher As in its shoots and exhibited translocation factor (TF) higher than 1 for As (4.65), Cd (1.87), and Pb (1.36). Potentilla saundersiana had bioconcentration factor of shoot (BCF-S) higher than 1 for Cd (4.52) and Pb (1.70), whereas its TF was higher than 1 for As, Cd, Pb, and Zn. These plant species exhibit strong tolerance to these PTEs. Furthermore, Elymus nutans accumulated low levels of As, Cd, Pb, and Zn in their shoots and exhibited TF values lower than 1 for the four PTEs. Therefore, G. pylzowianum is a promising candidate for the in situ phytoextraction of As, and P. saundersiana can be used as an effective plant for Cd and Pb phytoextraction. E. nutans is better suited for the phytostabilisation of multiple PTEs. This work is of significant importance for screening native plant species that can provide a reference for phytoremediation of PTE-contaminated soils in this area or other place with similar climate, and has a good potential for developing PTE phytoremediation strategies at mining sites.

Changing controls of soil water retention in an alpine catchment: Integrating sedimentological and pedological processes

Soil’s hydrological and ecological functions depend largely on soil water retention, which is affected by both structural and compositional soil properties. Studies have shown that alpine soils derived from sediments with different origins in the northeast Qinghai-Tibetan Plateau differ significantly in terms of particle size distribution, bulk density and soil organic carbon content. However, the variation pattern and its drivers of soil water retention in this region remain unclear. In this study, soil water retention characteristics (saturated soil water capacity, field capacity, wilting point and plant available water capacity) from different geomorphic settings (i.e., hillslopes, alluvial fans and floodplains) of an alpine catchment in the western part of the Qilian Mountains were analyzed in relation to sediment types and soil properties. Results show that soil water retention varies significantly with sediment types. Soils with an aeolian origin have a higher capacity to retain water compared with soils developed on fluvial sediments. Variations in soil water retention are mainly controlled by particle size distribution for fluvial sediments and by soil organic carbon content for aeolian sediments. The accumulation of soil organic carbon enhances plant available water capacity for sandy fluvial sediments but not for silty fluvial and aeolian sediments. The critical eco-hydrological functions of the mattic surface soil horizon in relation to water retention, runoff regulation and erosion control were highlighted for the alpine ecosystems. By deciphering sedimentological and pedological controls of soil water retention, this study improves the understanding of the evolution and functioning of alpine soils, which has further implications for other sedimentary ecosystems.

Mineralogical and mineral composition analysis of lacustrine sediments from Lake Toson, NE Qinghai-Tibet Plateau, China

Mineralogy is very important in the study of lake, especially in the study of regional and past global change using lake sediments. In the final analysis, mineralogy could be involved in the study of the in-depth mechanism of lake sediments. In this paper, analysis the minerals by XRD in the sediments of Toson lake in the northeast of Qinghai-Tibet Plateau, the results showed that the main minerals in Toson lake were aragonite, calcite, quartz, halite, albite, muscovite, clinochlore and dolomite. And the main categories were detrital minerals and carbonate minerals with obvious reverse correlation. It suggested that Toson lake was mainly situated carbonate sedimentary stage, and the input of carbonate was lacustrine authigenic carbonate.

Spatial-temporal trends of hydrological transitions in thermokarst lakes on Northeast Qinghai-Tibet Plateau based on stable isotopes

Regarded as the water towers of numerous large rivers in Asia, the Source Area of Yellow River (SAYR) on Northeast Qinghai-Tibet Plateau (QTP) contains substantial thermokarst lakes, which have exerted significant roles on the regional hydrology and water resources under permafrost degradation. To address the potential impact of climate- and permafrost-induced changes in surface hydrological processes in the SAYR, the hydrological transitions and water balance of thermokarst lakes were characterized on large scales during three years using stable isotope method. Spatial and seasonal deviations in hydrological processes of thermokarst lakes were remarkable. Calculations of evaporation-to-inflow (E/I) ratios based on an isotope-mass balance model revealed substantial evaporation for all thermokarst lakes during June due to the control of climate conditions and limited input water. Substantial feeds from summer/fall rain and permafrost meltwater resulted in lower evaporation and positive water balance of lakes during July, August, September, and October. Based on the relationship between lake-specific input water isotope compositions (δI) and annual average isotope value of precipitation (δP), the recharge patterns of thermokarst lakes in the SAYR were classified: supra-permafrost water/rainfall-dominated lakes were mainly concentrated during June and October regardless of spatial divergences, and summer precipitation/ permafrost thaw-dominated lakes are popular during July and August. Qualitatively, seasonal diversities in the water balance of thermokarst lakes are combinatively controlled by air temperature, precipitation regimes, permafrost degradation in the SAYR. Lastly, the future hydrological trajectories of thermokarst lakes are expected under climatic warming and permafrost degradation. This study serves as an important contribution for understanding future hydrological changes and allocation of water resources on the QTP, as well as an indication of permafrost degradation under climate warming.

Characteristics of groundwater in Northeast Qinghai-Tibet Plateau and its response to climate change and human activities: A case study of Delingha, Qaidam Basin

Delingha is located in the northeast margin of Qaidam Basin. Bayin River alluvial proluvial fan is the main aquifer of Delingha, in which groundwater generally flows from north to south. The hydrochemistry results showed that two different hydrochemical evolution paths formed along southeast and southwest directions, respectively. Cl-Na type groundwater was formed in front of Gahai Lake, and SO4·HCO3-Na·Ca type groundwater was formed in front of Keluke Lake. The results of deuterium (D) and 18O revealed that the groundwater mainly originated from the continuous accumulation of precipitation during geological history under cold and humid climate conditions. In addition, results of 14C indicated that the groundwater age was more than 1140 years, implying relatively poor renewal capability of regional groundwater. Moreover, our numerical modeling results showed that the regional groundwater level will continue to rise under the warm and humid climate conditions.© 2021 China Geology Editorial Office.

Evaluation of the eco-geo-environment in the Qaidam Basin, China

Eco-geo-environment quality refers to the degree of the merits of eco-geo-environment, which reflects the suitability of eco-geo-environment for sustainable development of human activities and socioeconomics in a specific time and space. The ultimate purpose of eco-geo-environment investigation and evaluation is to guide human production and life practice. Qaidam Basin, situated in the northeast Qinghai-Tibet Plateau of China, possesses a unique ecological environment, complicated geological features, and relatively underdeveloped economy. Evaluation of eco-geo-environment quality could ascertain the ecological background value and support policy makers in making decisions that promote economic development while ensuring the least damage to the environmental resources. However, there is no unified and authoritative evaluation index system to evaluate the quality of the eco-geo-environment. Based on the “Technical Criterion for Ecosystem Status Evaluation (HJ 192-2015)”, we add the eco-geo-environment restriction index and revise the existing Ecological Index formula. Further, we define the eco-geo-environment index to evaluate the quality of the eco-geo-environment. The computed eco-geo-environment index of the Qaidam Basin was found to be 26.088, belonging to the “Poor”. The result suggests that the eco-geo-environment quality of Qaidam Basin is quite fragile. Our results highlight the need for the judicious use of resources and promoting eco-geo-environment protection with a focus on sustainable development. More importantly, our evaluation system contributes to a policy-relevant and solution-oriented template for other similar regional assessments.

Modeling of CO2-driven cold-water geyser in the northeast Qinghai-Tibet plateau

CO2-driven geysers are important natural analogs of CO2 leakage in geologic carbon sequestration. This study investigated a CO2-driven cold-water geyser evolved within an abandoned wellbore in the northeast Qinghai-Tibet plateau, maintaining a steady eruption period of 330 s and a maximum instantaneous aqueous phase discharge rate of ~ 67.53 kg/s. Based on the geological conditions and wellbore configuration, a 3D wellbore-reservoir coupled numerical model was developed. The simulation results are in good agreement with the experimental data, and the CO2 emission of the geyser was estimated as 315.36 t/yr. The mechanism of the periodic eruptions was analyzed by the spatiotemporal variation in various primary variables including pressure, temperature, gas saturation, fluid flow rates, and phase velocities within the wellbore, and is coherent with the reports by Lu et al. (2005) and Watson et al. (2014), i.e., the eruption is controlled by the evolution of flow patterns, and the periodicity is regulated by the coupling of the self-enhancing and self-limiting process. The parameter sensitivity analysis indicated that the wellbore diameter, reservoir permeability, thickness, pressure gradient, and CO2 mass fraction in groundwater have a profound effect on the behavior of the periodic eruptions, and these causalities could serve as a reference to identify the direct inducement for the evolution of analogous periodic eruptions.

Technological strategy and mobility of Middle Holocene hunter-gatherers in the high-altitude Qinghai-Tibetan Plateau: a case study from Tshem gzhung kha thog

Microblade technology occupies an important position for understanding the process of peopling of the Qinghai-Tibetan Plateau; however, the region’s specific technological behaviour has been unclear due to a lack of research. Here, we introduce the newly excavated site of Tshem gzhung kha thog (TGKT, in Chinese is Canxionggashuo), located at 4016 m above sea level on the northeast Qinghai-Tibetan Plateau, with a focus on its lithic assemblage. Following the approach of chaine operatoire, we reconstruct the reduction sequence, and, from the perspective of the organization of technology, we explore the technology’s implications for hunter-gatherer mobility in this area. Combining the lithic assemblage and the chronological sequence, we hypothesize that TGKT was a workshop occupied by logistically organized hunter-gatherers who used high-quality siliceous rocks found near the site to produce microblades, primarily, to adapt to a limited stay in this high-elevation area. The gradual climatic warming during the Holocene provided better conditions for peopling the high-elevation area; however, considering the distance between the higher and lower elevation areas, we hypothesize that TGKT was not used logistically by lower-elevation foragers but by foragers whose residential base was located elsewhere in the region near the TGKT.