Qinghai Lake Basin Research Articles

Modeling the environmental suitability for Bacillus anthracis in the Qinghai Lake Basin, China.

Bacillus anthracis is a gram-positive, rod-shaped and endospore-forming bacterium that causes anthrax, a deadly disease to livestock and, occasionally, to humans. The spores are extremely hardy and may remain viable for many years in soil. Previous studies have identified East Qinghai and neighbouring Gansu in northwest China as a potential source of anthrax infection. This study was carried out to identify conditions and areas in the Qinghai Lake basin that are environmentally suitable for B. anthracis distribution. Anthrax occurrence data from 2005–2016 and environmental variables were spatially modeled by a maximum entropy algorithm to evaluate the contribution of the variables to the distribution of B. anthracis. Principal Component Analysis and Variance Inflation Analysis were adopted to limit the number of environmental variables and minimize multicollinearity. Model performance was evaluated using AUC (area under the curve) ROC (receiver operating characteristics) curves. The three variables that contributed most to the suitability model for B. anthracis are a relatively high annual mean temperature of -2 to 0°C, (53%), soil type classified as; cambisols and kastanozems (35%), and a high human population density of 40 individuals per km2 (12%). The resulting distribution map identifies the permanently inhabited rim of the Qinghai Lake as highly suitable for B. anthracis. Our environmental suitability map and the identified variables provide the nature reserve managers and animal health authorities readily available information to devise both surveillance strategy and control strategy (administration of vaccine to livestock) in B. anthracis suitable regions to abate future epidemics.

Human impacts on vegetation exceeded the hydroclimate control 2 ka ago in the Qinghai Lake basin revealed by n-alkanes of loess

Vegetation is one of the most important components of the land ecosystem. Human activity and climate change are the two main factors that control the changes in regional vegetation distribution. The past vegetation changes have been extensively studied all over the world, while few had focused on the relative contributions of human activities and climate change on vegetation change. Due to its key geographic position, the Qinghai Lake basin (QLB), located on northeastern Qinghai-Tibetan Plateau, is an ideal locality to carry out such study as its vegetation dynamics are more sensitive to any natural and anthropogenic disturbances. In this study, we analyzed the chain length distribution and concentration of n-alkanes of a 3.6 m thick loess profile (QH-18) in the QLB to infer the information about past vegetation change and its controlling factors. The proxy for aquatic macrophytes (Paq) and carbon preference index (CPI) values have been applied to distinguish the relative contributions from aquatic or terrestrial higher plants to the n-alkanes. Combining with luminescence-based chronology and magnetic susceptibility data of the QH-18 section, the resulted showed that the n-alkane distribution was characterized with two remarkable variations at ∼11.5 ka and ∼2 ka, respectively. The first major variation in n-alkanes was considered to be correlate to the gradual climate warming and humidification during the last deglaciation period, suggesting the response of loess n-alkanes to natural environmental changes over the orbital scales. The second markedly change at ∼2 ka was mainly controlled by the enhanced human activities. We concluded that the hydroclimate has played the dominant role before 2 ka, but human impacts have overwhelmed the natural variabilities thereafter and become the major controlling factor of n-alkane variations and vegetation change in QLB.

Spatial distribution of modern pollen and fungal spores and their ecological indication in Qinghai Lake on northeastern Tibetan Plateau, China

The Qinghai-Tibet Plateau (QTP) – also called the “third pole” – is an ideal area to study the long-term relationship between people and the environment due to its sensitivity to both climate change and anthropogenic activities. Qinghai Lake in the north-eastern QTP is considered a key site to explore this issue. Fossil pollen and fungal spores extracted from lake sediments are effective proxies of palaeoecological evolution and ancient anthropogenic activities, but rely on the modern studies of pollen and fungal spores for an accurate interpretation of the fossil record. In this study, 36 surface-sediment samples from Qinghai Lake were collected from different water depths for pollen and fungal spore analyses to explore the modern characteristics of assemblages and dispersion of pollen and fungal spores. Our results show that the modern pollen assemblages of Qinghai Lake are mainly dominated by Artemisia, Cyperaceae, Poaceae, and Chenopodiaceae, with similar pollen assemblages across the lake, while pollen concentrations show a significant enrichment towards the sedimentary centres of the lake. The modern pollen assemblages reflect the characteristics of the vegetation communities and land use in the basin well. The percentages of Artemisia and Chenopodiaceae pollen are significantly higher in the lake surface-sediment samples than those from topsoil samples of the basin, while percentages of Cyperaceae pollen are lower than those in the topsoil samples. Rivers are an important vector for transporting pollen of intrazonal vegetation, including Cyperaceae, Poaceae, and Hippophae, into Qinghai Lake. Additionally, Cerealia Poaceae pollen (>37 µm) is an effective indicator of farming activities in the Qinghai Lake basin. Fungal spores have higher heterogeneity in their percentages and concentrations from different sampling sites, with Glomus spp. and Delitschia spp. being more abundant near the lakeshore, while other fungal spores, including Sordaria spp., Sporormiella spp. Pleospora spp., Coniochaeta spp., Savoryella spp., and Urocystis sp., having higher percentages and concentrations towards the centre of the lake, with the particle size of the fungal spores being an important factor affecting their transportation and deposition in the lake. This study provides essential data on modern processes and a theoretical basis for accurately interpreting fossil pollen and fungal spore records from lake sediments on the QTP.

Plio-Pleistocene cooling of the northeastern Tibetan Plateau due to global climate change and surface uplift

It has been proposed that the northeastern Tibetan Plateau (NETP) was the most recent plateau sub-region to gain elevation, leading to profound environmental changes in northern East Asia around the mid-Pliocene (ca. 3.6 Ma). Alternatively, environmental changes in the region have been linked to ongoing global cooling and glacial intensification after 3.3 Ma. Here, we test these hypotheses using Plio-Pleistocene estimates of paleotemperatures and paleoelevations in the NETP derived from oxygen and carbon stable isotopic composition (n = 792) and clumped isotope measurements (n = 32) of carbonates from a Lake Qinghai Basin sediment core, eastern NETP. From 5 to 2 Ma, basinal mean annual air temperatures (MAATs) decreased by 4.9 ± 2.8 °C at rates of 1.6 °C ± 0.5 °C/myr, concurrently with regional and global cooling. However, the largest MAAT decline occurs between ca. 4.8−3.7 Ma (4.1 ± 3.2 °C) and ca. 3.4−2.0 Ma (−0.3 ± 2.8 °C) and may correspond with an elevation change of 1.0 ± 1.0 km at 3.6 Ma, coincident with tectonic activity in the Lake Qinghai Basin and several other basins in the NETP and its foreland. Taken together, these results suggest a combination of global cooling and a small magnitude of surface uplift (<1 km) at ca. 3.6 Ma may have contributed to the regional evolution of climate in the Lake Qinghai Basin.

Improved CASA model based on satellite remote sensing data: simulating net primary productivity of Qinghai Lake basin alpine grassland

Abstract. The Carnegie–Ames–Stanford Approach (CASA) model is widely used to estimate vegetation net primary productivity (NPP) at regional scales. However, the CASA is still driven by multisource data, e.g. satellite remote sensing (RS) data, and ground observations that are time-consuming to obtain. RS data can conveniently provide real-time regional information and may replace ground observation data to drive the CASA model. We attempted to improve the CASA model in this study using the Moderate Resolution Imaging Spectroradiometer (MODIS) RS products, the GlobeLand30 RS product, and the digital elevation model data derived from radar RS. We applied it to simulate the NPP of alpine grasslands in the Qinghai Lake basin, which is located in the northeastern Qinghai–Tibetan Plateau, China. The accuracy of the RS-data-driven CASA, with a mean absolute percent error (MAPE) of 22.14 % and root mean square error (RMSE) of 26.36 g C m−2 per month, was higher than that of the multisource-data-driven CASA, with a MAPE of 44.80 % and RMSE of 57.43 g C m−2 per month. The NPP simulated by the RS-data-driven CASA in July 2020 shows an average value of 108.01 ± 26.31 g C m−2 per month, which is similar to published results and comparable with the measured NPP. The results of this work indicate that simulating alpine grassland NPP with satellite RS data rather than ground observations is feasible. We may provide a workable reference for rapid simulation of grassland NPP to satisfy the requirements of accounting carbon stocks and other applications.

Spatial distribution, ecological risk, and human health assessment of heavy metals in lake surface sections - a case study of Qinghai Lake, China.

Qinghai Lake is the largest inland saltwater lake in China, with a drainage area of 29,661 km2. This study sought to conduct an ecological and human health risk assessment of metals and heavy metals, including copper, as well as investigate their concentration, distribution, and source distribution. In terms of seasonal variation, the increases in Fe, Cr, As, Pb, and Hg were relatively large, and the spatial distribution of metals presented a three-level stepped distribution trend, gradually increasing from east to west. By further exploring the source and migration path of pollutants, our study found that the source of metals in the sediments of Qinghai Lake is mainly controlled by five rivers entering the lake. Enrichment factor (EF) calculations indicated that the metal accumulation or enrichment capacity of the three central points in Qinghai Lake Basin was strong. Interestingly, the enrichment capacity of Cu and Zn was the strongest among all metals but occurred at low and medium concentration levels, respectively. The Igeo and [Formula: see text] ecological risk assessment results indicated that the individual metals posed little to no ecological risks to the Qinghai Lake Basin. However, the multi-element environmental risk comprehensive index (RI) indicated that Hg (RI = 147.97) represented a slight ecological hazard, Mn (RI = 181.13) posed moderate ecological hazards, and Zn (RI = 386.66) posed strong ecological hazards. The human health risk assessment results showed that the heavy metals in the surface sediments of Qinghai Lake currently do not pose a threat to human health. This information may facilitate the implementation of more stringent monitoring programs in the aquatic ecosystem by the relevant regulatory authorities.

Diversity and distribution of fish in the Qilian Mountain Basin.

The Qilian Mountain Basin, on the north-eastern edge of the Qinghai-Tibet Plateau (QTP), supports a high diversity of native and endemic fish. However, the detailed species inventory and distribution patterns concerning fish in the whole Basin remain unknown, which hinders the conservation of biodiversity and assessment of ecological health. We compiled a comprehensive species richness and distribution database of freshwater fish in the Qilian Mountain Basin, based on field investigations and exhaustive data collection from 50 rivers or lakes. Then, we elucidated a distribution pattern using clustering and ordination analyses based on a βdissim matrix with species presence/absence data. A total of 79 freshwater fish species within eight orders, 17 families and 42 genera were recorded. The Qilian Mountain Basin could be grouped into six systems, which match the six Basins (i.e. Heihe River Basin, HHR; Qaidam Basin, QDM; Qinghai Lake Basin, QHL; Shule River Basin, SLR; Shiyang River Basin, SYR; Yellow River Basin, YR), based on the fish distribution pattern. Additionally, the spatial pattern of species distribution showed the distance decay of taxonomic similarity. Our results demonstrate that riverine connectivity resulting from historical processes plays a vital role in shaping the freshwater ichthyofauna of High Central Asia. These findings will be valuable for future systematic conservation of fish in the Qilian Mountain Basin.

Characteristics of Soil Temperature, Humidity, and Salinity on Bird Island within Qinghai Lake Basin, China

The temperature, moisture, and salt content of soil in alpine regions are sensitive to changes in climatic factors and are important indicators of ecosystem functions. In this study, we collected soil moisture, temperature and electrical conductivity data at different depths at a sampling site on Bird Island in Qinghai Lake during winter using a continuous soil temperature, moisture and salt content monitoring system and analyzed their variations and influential factors. The variation in soil moisture showed an obvious ‘V-shaped’ pattern from 00:00 to 23:00 and an upward trend with soil layer depth. From 00:00 to 23:00, the overall soil temperature data fitted a ‘unimodal’ curve and showed a clear and continuous upward trend with soil layer depth at a rate of 0.684 (p < 0.001). Soil electrical conductivity data also exhibited a distinct ‘V-shaped’ pattern from 00:00 to 23:00 and a continuous increase with increasing soil depth. The correlation between soil temperature, moisture, and conductivity and the spatial distribution of five climate factors indicated that climate factors accounted for 53.6% of the changes in soil temperature, moisture, and salinity. Climate factors showed a significant positive correlation with soil temperature, moisture, and conductivity (p < 0.001), and air temperature was the most important factor influencing soil temperature and soil moisture changes, whereas wind direction was the most important factor influencing soil conductivity. (Wind direction and wind speed affect soil evapotranspiration, and then affect soil moisture and solute transport process). The results of this preliminary study reveal the characteristics associated with soil temperature, moisture, and salinity changes in winter within the wetlands of Bird Island on Qinghai Lake in the context of climate change, and they can be used as valuable reference data in further studies investigating associated changes in ecosystem functions.

Distinguishing the Impacts of Human Activities and Climate Change on the Livelihood Environment of Pastoralists in the Qinghai Lake Basin

Grassland vegetation is the largest terrestrial ecosystem in the Qinghai Lake Basin (QLB), and it is also the most important means of production for herders’ livelihoods. Quantifying the impact of climate change and human activities on grassland vegetation changes is an essential task for ensuring the sustainable livelihood of pastoralists. To this end, we investigated vegetation cover changes in the QLB from 2000 to 2020 using the normalized difference vegetation index (NDVI), meteorological raster data, and digital elevation and used residual analysis of multiple linear regression to evaluate the residuals of human activities. The residual analysis of partial derivatives was used to quantify the contribution of climate change and human activities to changes in vegetation cover. The results showed that: (1) The vegetation coverage of the QLB increased significantly (0.002/a, p < 0.01), with 91.38% of the area showing a greening trend, and 8.62% of the area suffering a degrading trend. The NDVI decreased substantially along the altitude gradient (−0.02/a, p < 0.01), with the highest vegetation coverage at 3600–3700 m (0.37/a). The vegetation degraded from 3200–3300 m, vegetation greening accelerated from 3300–3500 m, and vegetation greening slowed above 3500 m. (2) The contribution of climate change, temperature (T), and precipitation (P) to vegetation cover change were 1.62/a, 0.005/a, and 1.615/a, respectively. Below 3500 m, the vegetation greening was more limited by P. Above 3500 m, the vegetation greening was mainly limited by T. (3) Residual analysis showed that the contribution of human activities to vegetation cover was −1.618/a. Regarding the altitude gradient, at 3300–3500 m, human activities had the highest negative contribution to vegetation coverage (−2.389/a), and at 3200–3300 m, they had the highest positive contribution (0.389/a). In the past 21 years, the impact of human activities on vegetation coverage changed from negative to positive. Before 2009, the annual average NDVIres value was negative; after 2010, the average yearly NDVIres value turned positive. In general, the vegetation greening of the QLB depends on climate warming and humidification. The positive impact of human activities over the past decade was also essential for vegetation greening. These findings deepen our understanding of the QLB vegetation changes under climate change and human activities.

Vegetation variations and its driving factors in the transition zone between Tibetan Plateau and arid region

The Qilian Mountains (QLMs) has functioned as an ecological barrier area; water connotation area; priority area for biodiversity conservation; practice area; bearing area; and demonstration area for the construction of ecological civilization in China; and its ecological function and demonstration role cannot be ignored. To investigate the response of vegetation to climate change and human activities, the GIMMS NDVI3g, MODIS NDVI, meteorological data, and nighttime light data were analyzed using Theil-Sen trend analysis, Mann-Kendall significance test, Hurst index, and correlation analysis to explore the spatial and temporal characteristics and trends of vegetation in the QLMs from 1982 to 2020. The results show that from 1982 to 2020, the NDVI in the QLMs showed an increasing trend in the interannual, growing season (0.0011/a), and through the four seasons—spring (0.0003/a), summer (0.0015/a), autumn (0.0007/a), and winter; and demonstrated a high spatial pattern in the southeast and low spatial pattern in the northwest. The NDVI showed a gradual increase in the improved area (46.43% → 79.32%), a gradual decrease in the unchanged area (50.81% → 18.23%), and a stable degraded area (2.76% → 2.45%), but the distribution of the degraded area shifted from the northern part of Daxue Mountain to the Qinghai Lake and Datong River basin, and the intersection of Qinghai South Mountain and Laji Mountain. Additionally, the vegetation cover was not persistent, and the area of unclear future was more than half and distributed in the central and western parts of the QLMs, with obvious anti-sustainability characteristics. Temperature was the dominant climatic factor for vegetation growth in the QLMs, and from the spatial distribution, the area controlled by temperature (63.81%) was significantly higher than that controlled by precipitation (29.95%). On a temporal scale, NDVI during spring, autumn, and winter was positively correlated with the temperature and negatively correlated with precipitation; and vegetation growth was influenced by temperature for a longer period of time during the year. NDVI has an obvious lagging effect on climate change, with a maximum response to temperature and precipitation lagging by approximately 2–3 months and 0–1 month, respectively. Human activities have both promoting and inhibiting effects on vegetation. In human activity areas, NDVI shows an increasing trend, and the ecological environment is improving annually.

The Effect of Vegetative Coverage and Altitude on the Vegetation Water Consumption in the Alpine Inland River Basin of the Northeastern Qinghai–Tibet Plateau

Estimating accurately the vegetation water consumption (VWC) in the Qinghai Lake Basin (QLB) is conducive to the effective utilization and management of water resources in the QLB, which is of great significance to the construction of a national park in the QLB. We used Geographic Information System (GIS) technology and remote sensing (RS) technology based on potential evapotranspiration data to calculate the VWC in the QLB from 2000 to 2020, and analyzed the influencing factors of the VWC in the QLB from 2000 to 2020. The results showed that (1) the average value of the VWC in the QLB varied from 242.96 mm to 287.99 mm, the average value of the VWC was 267.07 mm, and the average value of the total VWC was 79.05 × 108 m3 from 2000 to 2020. (2) In terms of spatial variation of the VWC, the VWC in the QLB did not increase significantly from 2000 to 2014, however, the VWC in the QLB showed a significant increase from 2015 to 2020. (3) As the altitude gradient increases, the VWC in the QLB from 2000 to 2020 showed a significant downward trend with the increase in altitude. When the altitude increases by 100 m, the value of the VWC decreases by 13.47 mm from 2000 to 2014 and 22.8 mm from 2015 to 2020, respectively. (4) Exploring the influencing factors of the VWC in the QLB from 2000 to 2020, the results showed that the VWC was mainly affected by the average annual precipitation and normalized difference vegetation index (NDVI) from 2000 to 2014. It was mainly affected by the combined effects of annual temperature, precipitation, and vegetation coverage from 2015 to 2020. The VWC was mainly affected by the average annual temperature, precipitation, and vegetation coverage along the altitude gradient from 2000 to 2014. It was mainly affected by the average annual temperature and vegetation coverage in the QLB from 2015 to 2020. Obviously, vegetation coverage was the most important factor affecting the VWC regardless of spatial or altitude gradient variations.

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.

A 1,400-year eolian dust activity record from Lake Erhai in the northeastern Tibetan Plateau

Dust raised from Arid Central Asia (ACA) affects the global climate, global biogeochemical cycles, and human health. Studies on the ACA dust activities thus are crucial for understanding dust forcing mechanisms and the mitigation of hazardous storms. Located at the downwind margin of the ACA, the Lake Qinghai basin is an ideal trap for dust activities documentation. However, isolating eolian dust signals from Lake Qinghai sediments is difficult as the dust signals are well-mixed with riverine input signals. As a satellite of Lake Qinghai, Lake Erhai is much smaller and has only one inflow river. Lake Erhai, therefore, is much less sensitive to riverine input and its sediments theoretically contain more explicit dust signals. In this study, a 111.5-cm core was taken from Lake Erhai in 2016. The sediments’ grain size distribution (GSD) of this core was analyzed, and end-member (EM) analyses were applied to the GSDs to detect dust signals. Sediment carbonate content and carbonate oxygen isotopes (δ18Ocarb) were also measured to provide independent climate background information. Our results showed that the first EM is attributed to lake level dynamics due to its resemblances with carbonate content and δ18Ocarb records; the third EM, which peaked in the coarser grain size, is attributed to the riverine input; the remaining second EM likely captures the changes of regional dust activity and suggests that the Lake Qinghai basin has experienced multiple intense eolian dust activity intervals, i.e., 1000–1110, 1180–1290, and 1450–1560 AD over the past 1400 years. A further comparison of EMs with well-established climatic records in the northeastern Tibetan Plateau suggests that the rise and fall of regional dust activities are likely mainly controlled by wetness conditions and are secondarily affected by human activities.

Divergent change patterns observed in hydrological fluxes entering China's two largest lakes

Large lakes are key components of hydrological processes and have critical ecological and economic functions. Streamflow and riverine sediment loads exported from tributary rivers to lakes provide inputs of water and nutrients and greatly impact the health of lacustrine ecosystems. Understanding the spatiotemporal patterns of water and sediment transport dynamics within the basins of large lakes is therefore required for informed management of their resources. In particular, the hydrological processes of large lake basins in western China were not fully explored yet. This study investigated changes in runoff and sediment fluxes entering the two largest lakes in China (Qinghai Lake and Poyang Lake) over the past half century. Our results showed that the regional trends of the two lake basins have changed in divergent way. The patterns of change of streamflow and sediment transport—including the trends, periodicity, and transition points as well as the relationship between streamflow and sediment flux—were quite different. The results obtained by a Sediment Identity method revealed that increases of the precipitation and runoff coefficient controlled the observed increase of streamflow and sediment flux within the Qinghai Lake basin, whereas the decrease of the sediment flux entering Poyang Lake was caused mainly by a reduction in sediment concentration. Climate change was the dominant driver influencing the recent increases in surface water resources and sediment load in the Qinghai Lake basin as well as the long-term fluctuations of streamflow within the Poyang Lake basin. In contrast, the observed abrupt reduction in total sediment flux entering Poyang Lake was due mainly to declining sediment discharge from the Gan River; this decrease is attributed primarily to human activities, especially reservoir construction and soil conservation practices. Overall, this study discovers the divergent change patterns when investigating hydrological processes, and highlights the importance of developing policies for managing soil and water resources within large lake basins to the northwest and southeast of the Hu Line. Management policies should consider the tremendous differences in geography, climate, and population across China.

Frozen soil change and its impact on hydrological processes in the Qinghai Lake Basin, the Qinghai-Tibetan Plateau, China

Study regionThe Qinghai Lake Basin, Qinghai-Tibetan Plateau. The Qinghai Lake is the largest inland saltwater lake in China. Study focusSignificant increase in runoff into the Qinghai Lake has been reported; however, the relationship between frozen soil changes and runoff remains poorly understood. This study investigated the temporal and spatial variations in frozen soil and associate effects on streamflow and soil moisture in the study region by a distributed eco-hydrological model. New hydrological insightsThe results illustrate that the coverage of permafrost decreased by about 13% from 1971 to 2015, and permafrost degradation mainly occurred in the elevation interval of 3600–4200 m. The maximum frozen depth averaged in the seasonally frozen ground significantly decreased by 0.06 m/10a, while the active layer thickness averaged in the permafrost enhanced by 0.02 m/10a. Permafrost degradation caused enhanced soil liquid water storage and an increase in freezing season runoff. The increase in runoff in the thawing season was dominated by changes in precipitation. The results suggest that frozen soil degradation altered the seasonal flow regime, leading to lags in the monthly runoff peak, and it increased the base flow and reduced the thawing season runoff. This offset of the competing impacts of frozen soil changes in different seasons led to a negative effect on annual runoff. This study provides new understandings of cryospheric hydrological responses to climate change.

Characteristics of Desertification Change in Lake Basin Area in Gangcha County

Qinghai Lake Basin area in Gangcha county is selected as the study area in terms of desertification change features in this paper. Based on the remote sensing (RS) and global positioning system (GPS) technologies, the desertification information range from 1989 to 2014 in the study area is extracted. Using the method of the decision tree, the desertification in the research area is been divided into four grades including mild desertification, moderate desertification, severe desertification and serious desertification. The change characteristics of desertification in the study area were analyzed in detail, which showed that the desertification in the study area experienced a process of first development and then a reversal. The rapid development of desertification appears in the 1990s, where about 1101.22 kilometers of desertification area was increased in this stage. Since the twenty-first Century, the desertification is gradually significant recovered and local area exist intensified desertification. There are tendencies of interactive transform in different types of desertification. The tendencies of different degrees of desertification land are rising, and there’re some differences in rising rates, where the expansion rate of moderate desertification is the biggest, increasing by 7.27 kilometers per year.

Differential Responses of Plant Primary Productivity to Nutrient Addition in Natural and Restored Alpine Grasslands in the Qinghai Lake Basin.

Climate, land-use changes, and nitrogen (N) deposition strongly impact plant primary productivity, particularly in alpine grassland ecosystems. In this study, the differential responses of plant community primary productivity to N and phosphorus (P) nutrient application were investigated in the natural (NG) and “Grain for Green” restored (RG) alpine grasslands by a continuous 3-year experiment in the Qinghai Lake Basin. N addition only significantly promoted plant aboveground biomass (AGB) by 42% and had no significant effect on belowground biomass (BGB) and total biomass (TB) in NG. In comparison with NG, N addition elevated AGB and BGB concurrently in RG by 138% and 24%, respectively, which further significantly increased TB by 41% in RG. Meanwhile, N addition significantly decreased BGB and the AGB ratio (R/S) both in NG and RG. Compared with N addition, P addition did not perform an evident effect on plant biomass parameters. Additionally, AGB was merely negatively influenced by growing season temperatures (GST) under the N addition treatment in NG. AGB was negatively associated with GST but positively related to growing season precipitation (GSP) in RG. By contrast, changes in the R/S ratio in RG were positively correlated with GST and negatively related to GSP. In sum, the results revealed that plant community biomass exhibited convergent (AGB and R/S) and divergent (BGB and TB) responses to N addition between NG and RG. In addition, the outcomes suggested that climate warming would enhance plant biomass allocation to belowground under ongoing N deposition, and indicated the significance of precipitation for plant growth and AGB accumulation in this restored alpine grassland ecosystem.

Vegetation change and human-environment interactions in the Qinghai Lake Basin, northeastern Tibetan Plateau, since the last deglaciation

The nature of the interaction between prehistoric humans and their environment, especially the vegetation, has long been of interest. The Qinghai Lake Basin in North China is well-suited to exploring the interactions between prehistoric humans and vegetation in the Tibetan Plateau, because of the comparatively dense distribution of archaeological sites and the ecologically fragile environment. Previous pollen studies of Qinghai Lake have enabled a detailed reconstruction of the regional vegetation, but they have provided relatively little information on vegetation change within the Qinghai Lake watershed. To address the issue we conducted a pollen-based vegetation reconstruction for an archaeological site (YWY), located on the southern shore of Qinghai Lake. We used high temporal-resolution pollen records from the YWY site and from Qinghai Lake, spanning the interval since the last deglaciation (15.3 kyr BP to the present) to quantitatively reconstruct changes in the local and regional vegetation using Landscape Reconstruction Algorithm models. The results show that, since the lateglacial, spruce forest grew at high altitudes in the surrounding mountains, while the lakeshore environment was occupied mainly by shrub-steppe. From the lateglacial to the middle Holocene, coniferous woodland began to expand downslope and reached the YWY site at ∼ 7.1 kyr BP. The living environment of the local small groups of Paleolithic-Epipaleolithic humans (during 15.3–13.1 kyr BP and 9–6.4 kyr BP) changed from shrub-steppe to coniferous forest–steppe. The pollen record shows no evidence of pronounced changes in the vegetation community corresponding to human activity. However, based on a comparison of the local and regional vegetation reconstructions, low values of biodiversity and a significant increase in two indicators of vegetation degradation, Chenopodiaceae and Rosaceae, suggest that prehistoric hunters-gatherers likely disturbed the local vegetation during ∼ 9.0–6.4 kyr BP. Our findings are a preliminary attempt to study human-environment interactions at Paleolithic-Epipaleolithic sites in the region, and they contribute to ongoing environmental archaeology research in the Tibetan Plateau.

Regional hydroclimates regulate the Holocene aeolian accumulation processes of the Qinghai Lake basin on the northeastern Tibetan plateau

Aeolian sediments are widely distributed in the Qinghai Lake basin on the northeastern Tibetan Plateau (TP), and have been extensively investigated for the palaeoclimate reconstruction. However, due to the relatively scanty of dating materials and applicable techniques, and also the commonly existed hiatus in aeolian sequences, the details of the Holocene aeolian activities in the Qinghai Lake basin remain unclear. In this study, we applied the optically stimulated luminescence (OSL) dating technique to a 3.6 m thick loess-palaeosol sequence (QH-18) located on the southern bank of the Qinghai Lake to establish a high-resolution chronology of the aeolian accumulation history. The quartz OSL chronology demonstrated that the loess accumulation commenced since the last deglaciation and continued during the Holocene (∼14.6–0.5 ka), characterized with a remarkably low sedimentation rate period from 6 ka to 2 ka. Similar phenomenon has been recorded in previously investigated aeolian sequences not only in the Qinghai Lake basin but also across the northeastern TP, which was likely owing to the optimal environment conditions that have suppressed the dust emission from the source areas in the extensive arid and semiarid areas. The end-member (EM) analysis of grain-size distribution in QH-18 yielded an optimal model with three EMs, i.e., EM1 (6 μm, background dust), EM2 (56 μm, fraction of medium or long-distance transportation) and EM3 (447 μm, fraction from proximal or local source). The EM3 fraction can only be transported with saltation process in short distances that derived from proximal or local sources. In addition to the regional climatic conditions, according to the variation and contribution of the EMs, we consider that the Holocene aeolian activity in the Lake Qinghai basin was also modulated by the lake-level fluctuations of Lake Qinghai, in the way of changing the supply of sandy materials.

Lake-level history of Qinghai Lake on the NE Tibetan Plateau and its implications for Asian monsoon pattern - A review

The paper presents a comprehensive review on lake-level history of Qinghai Lake since marine isotope stage (MIS) 5, after re-examining the sedimentary and geomorphological nature of highstand deposits and re-evaluating the published dating results (318 luminescence ages and 17 14C ages) of shorelines, near shoreline, lacustrine, alluvial, and aeolian deposits. It is concluded that 1) Three lake shoreline sets were classified in the Qinghai Lake Basin with the corresponding elevations of 3220–3260, 3206–3215 and 3194–3205 m. 2) 14C dating on lake sediments is restricted by the upper dating limit of ∼35 thousand years (ka) BP in practice, availability of dating materials and reservoir effect, and that quartz optically stimulated luminescence (OSL) ages older than 80–60 ka may be underestimated while feldspar post-infrared infrared stimulated luminescence (pIRIR) ages could be reliable for dating these older samples. 3) Four highstands were detected by ages. The highest lake-levels at elevations of 3220–3260 m with 26–66 m above the present lake-level occurred in MIS 5, and highstands also occurred in MIS 3 (∼42–38 ka), the last deglaciation (∼16–12 ka), and the Holocene (∼6–5 ka) with similar heights at elevations of ∼3200–3209 m. During the Holocene, lake-levels were relatively low in the early Holocene (∼11–8 ka), increasing substantially after ∼8 ka and reaching the highest lake-levels (elevation of 3203.1 m) at ∼6–5 ka, then decreasing with an interruption by a highstand (elevation of 3202.4 m) at ∼1.8 ka. 4) Shoreline-based lake-level variations are consistent with major climatic proxies (e.g., δ13Corg and %thaum) of drilling cores from the lake, regional aeolian activity/pedogenesis and climate change. 5) Compared with the representative lake-levels and moisture records in the Westerlies and East Asia summer monsoon (EASM) dominances, it is suggested that lake-level variations in the southern Qilian Mountains exhibited simultaneity with changes in the intensity of EASM, while those in the northern part were synchronous with the moisture records in arid central Asia, suggesting that EASM did not extend further to the northern Qilian Mountains where the Westerlies prevailed.