Reevaluation of carbonate concentration and oxygen isotope records from Lake Qinghai, the northeastern Tibetan Plateau

Lake Qinghai is the largest lake on the Tibetan Plateau, and it is also one of the important sites for studying global environmental changes. Over the past 30 years, many studies have used oxygen isotope of authigenic carbonates from the lake as the proxy to infer past environmental and climate changes on the Plateau. However, debate on interpretations of isotopic data and their environmental implications still exist, largely due to the complex arid environment settings and multiple sources/species for carbonate minerals within the lake. In this study, we systematically analyze delta O-18 values in different-type carbonates collected [i.e. bulk carbonates, ostracode shells, Chara encrustations, and fine-grain (< 63 mu m) carbonate minerals] from modern lake sediments and surrounding soils, as well as the down-core delta O-18 values of bulk/fine-grain carbonates since the Last Glacial Maximum. Together with previously published delta O-18 records from ostracode shells, we try to re-evaluate the controlling factors of variations in lacustrine carbonate delta O-18 data and to infer environmental changes on the northeastern Tibetan Plateau since the Last Glacial Maximum. Our results show that the lake depth, or the size of the water body, is an important factor to influence the lake water and carbonate delta O-18 values. A shallow and small lake would be more easily influenced by precipitation delta O-18 which is characterized by negative values at Lake Qinghai region, while a deep and large lake would be better to reflect environmental changes such as the precipitation-evaporation balance. The "lake volume" effect might be an explanation for the negative carbonate delta O-18 values during the early Holocene, which was likely caused by an increased influence of negative delta O-18 values in precipitation and glacial melt water under a small and shallow water body. The delta O-18 values of ostracode shells and bulk carbonates show similar variations since both of them are dominated by lake water oxygen isotopic composition, but they still have distinct geochemical information. The isotopic differences between ostracode and bulk carbonates probably reflect the temperature differences between the surface and the bottom of lake water. In addition, the delta O-18 values of evaporative induced carbonates may correlate with carbonate contents, while those of Chara encrustations do not show any correlation with carbonate contents. Our results suggest that special caution would be necessary when using lacustrine delta O-18 values of authigenic carbonates to infer past hydrological and climate changes in an arid environment

Mid-late Holocene temperature and precipitation variations in the Guanting Basin, upper reaches of the Yellow River

The reconstruction of prehistoric temperature and precipitation variations in the upper reaches of the Yellow River is essential for understanding the cultural evolution of the region, but related information is sparse due to the limitations of the available proxies. Recent studies have shown that microbial glycerol dialkyl glycerol tetraethers (GDGTs) are promising tools for reconstructing mean annual temperature (MAT) and mean annual precipitation (MAP) in terrestrial deposits. In this study, we reconstructed mid-late Holocene climatic changes using GDGT distributions in a loess-paleosol sequence in the Lajia Ruins of the Neolithic Qijia Culture, Guanting Basin, in the southwestern end of the Chinese Loess Plateau. Our GDGT records show that MAP decreased from ca. 600 mm to 430 mm, while MAT decreased from 11.9 degrees C to 8.0 degrees C, during the past ca. 7000 yr, and a drastic decline in MAP (70 mm), accompanied by a 0.8 degrees C decline in MAT, occurred at 3800-3400 yr BP. Our results provide direct evidence supporting a hypothesis that the flourishing (4200-4000 yr BP) and decline (4000-3600 yr BP) of the Qijia culture (mainly based on millets cultivation) and subsequent rise of the Xindian/Kayue culture (3600-2600 yr BP), based on mixed agriculture of sheep husbandry and millets cultivation were triggered by climate change

Comprehensive analysis of the amino acid metabolism-related gene signature for prognosis, tumor immune microenvironment, and candidate drugs in hepatocellular carcinoma

IntroductionMetabolic rewiring satisfies increased nutritional demands and modulates many oncogenic processes in tumors. Amino acid metabolism is abnormal in many malignancies. Metabolic reprogramming of amino acids not only plays a crucial role in sustaining tumor cell proliferation but also influences the tumor immune microenvironment. Herein, the aim of our study was to elucidate the metabolic signature of amino acids in hepatocellular carcinoma (HCC).MethodsTranscriptome profiles of HCC were obtained from the TCGA and ICGC databases. Based on the expression of amino acid metabolism-related genes (AAMRGs), we clustered the HCC samples into two molecular subtypes using the non-negative matrix factorization algorithm. Then, we constructed the amino acid metabolism-related gene signature (AAMRGS) by Cox regression and LASSO regression. Afterward, the clinical significance of the AAMRGS was evaluated. Additionally, we comprehensively analyzed the differences in mutational profiles, immune cell infiltration, immune checkpoint expression, and drug sensitivity between different risk subgroups. Furthermore, we examined three key gene expressions in liver cancer cells by quantitative real-time PCR and conducted the CCK8 assay to evaluate the influence of two chemotherapy drugs on different liver cancer cells.ResultsA total of 81 differentially expressed AAMRGs were screened between the two molecular subtypes, and these AAMRGs were involved in regulating amino acid metabolism. The AAMRGS containing GLS, IYD, and NQO1 had a high value for prognosis prediction in HCC patients. Besides this, the two AAMRGS subgroups had different genetic mutation probabilities. More importantly, the immunosuppressive cells were more enriched in the AAMRGS-high group. The expression level of inhibitory immune checkpoints was also higher in patients with high AAMRGS scores. Additionally, the two AAMRGS subgroups showed different susceptibility to chemotherapeutic and targeted drugs. In vitro experiments showed that gemcitabine significantly reduced the proliferative capacity of SNU449 cells, and rapamycin remarkedly inhibited Huh7 proliferation. The five HCC cells displayed different mRNA expression levels of GLS, IYD, and NQO1.ConclusionsOur study explored the features of amino acid metabolism in HCC and identified the novel AAMRGS to predict the prognosis, immune microenvironment, and drug sensitivity of HCC patients. These findings might help to guide personalized treatment and improve the clinical outcomes of HCC

Ancient Great Wall Building Materials Reveal Paleoenvironmental Changes in Northwestern China

Plant material used in the construction of segments and beacon towers of the ancient Great Wall in northwestern China contain untapped potential for revealing paleoenvironmental conditions. Here, we characterize the molecular preservation and stable carbon and nitrogen isotope compositions of common reeds (Phragmites) collected from Great Wall fascines dated to the Han Dynasty in today’s Gansu and Xinjiang provinces using a combination of chromatographic techniques and isotope analyses. Our data demonstrates that ancient reeds were harvested from local habitats that were more diverse than exist today. The isotope data also capture differential rates of environmental deterioration along the eastern margin of the Tarim Basin, leading to the intense evaporative stress on modern plants. This study demonstrates the wealth of environmental and climate information obtainable from site-specific organic building material of ancient walls, which have received considerably less attention than the iconic brick and stone masonry walls of the later Ming Dynasty

Ancient Great Wall Building Materials Reveal Environmental Changes Associated with Oases in Northwestern China

Plant materials used in the construction of segments and beacon towers of the ancient Great Wall in northwestern China contain untapped potential for revealing local paleoclimatic and environmental conditions. For the first time, we characterize the molecular preservation and stable carbon and nitrogen isotope compositions of AMS-dated common reeds (Phragmites) collected from ancient Great Wall fascines in today’s Gansu and Xinjiang using a combination of chromatographic techniques and isotope analyses. Our molecular data, along with Scanning Electron Microscopy, demonstrate excellent preservation of these ancient reeds, which were harvested from nearby habitats during periods of significant expansion of Imperial China when climate conditions sustained sizeable oases in the region. Stable isotope data capture differential rates of environmental change along the eastern margin of the Tarim Basin since the Han Dynasty (170 BC), implying that significant surface-water hydrological changes occurred only after the Song Dynasty (1160 AD) due to regional climate change. This study reveals the wealth of environmental and climate information obtainable from these site-specific organic building materials and establishes the foundation for further applications of advanced molecular, biochemical, and isotopic technologies to study these common and widely-distributed organic archaeological materials

Decoupled Land and Ocean Temperature Trends in the Early-Middle Pleistocene

Record of long-term land temperature changes remains ephemeral, discontinuous, and isolated, thus leaving the common view that Pleistocene land temperature evolution should have followed ocean temperatures unconfirmed. Here, we present a continuous land surface temperature reconstruction in the Asian monsoon region over the past 3.0 Myr based on the distribution of soil bacterial lipids from the Chinese Loess Plateau. The land temperature record indicates an unexpected warming trend over the Pleistocene, which is opposite to the cooling trend in Pleistocene ocean temperatures, resulting in increased land-sea thermal contrast. We propose that the previously unrecognized increase of land-sea thermal contrast during much of the Pleistocene is a regional climate phenomenon that provides a likely mechanism in favor of the long-term enhancement of the Pleistocene East Asian summer monsoon

Terrestrial biomarker results from IODP Site 356-U1461 over the last 5 million years

This dataset presents biomarker-based records of terrestrial input to the northwest shelf of Australia over the last 5 million years, based on sedimentary core from IODP Site U1461. The biomarkers include ratio of n-C31 alkane over C28–30 sterols, brGDGT-based proxies, and δ13Corg. These records would eventually provide a framework of terrestrial input in many perspectives. We aim to disentangle the response of vegetation and dust transportation to climate variations in the northwestern Australian continent through the Pliocene-Pleistocene period

Soil temperature and brGDGTs along an elevation gradient on the northeastern Tibetan Plateau: A test of soil brGDGTs as a proxy for paleoelevation

The uplift history of the Tibetan Plateau is poorly constrained. A key problem is the discrepancy between reconstructions based on different paleoaltimeters. Branched glycerol dialkyl glycerol tetraethers (brGDGTs) produced by soil-dwelling bacteria offer a potential tool for paleoaltimetry reconstruction. However, because insitu soil temperature-the direct link between brGDGTs and altitude-is generally not well-constrained, the reliability and uncertainty of this approach remain uncertain. Here, we investigated brGDGT distributions and in-situ soil temperature along an altitudinal gradient at 2300-4000 m on Mt. Laji, northeastern Tibetan Plateau, to test the relationships among altitude, temperature, and brGDGTs. The results show that: 1. the measured mean annual soil temperature (MAST) is strongly correlated with altitude (R-2 = 0.73), but compared with those for mean annual air temperature (MAAT) derived from weather stations, the absolute values are substantially higher particularly at higher altitudes, while the lapse rate (-0.39 degrees C/100 m) is much lower; 2. brGDGT-reconstructed MAST using published soil temperature calibrations is generally consistent with in-situ soil temperature measurements, displaying similar lapse rates (-0.48 degrees C/100 m for MAST(ST) and - 0.41 degrees C/100 m for MAST(STS) at the sunny slope) to that for measured MAST; 3. the slope aspect may affect both measured and brGDGT-reconstructed MAST by up to >3 degrees C. Overall, our results demonstrate that soil brGDGTs can quantitatively capture elevation-dependent soil temperature variation on the Tibetan Plateau. However, the use of ex-situ air temperature instead of in-situ soil temperature, and the effect of slope aspect on temperature, may introduce uncertainties in evaluating the brGDGT paleoaltimeter in this region. In paleo-applications, suitable calibrations are required and soil temperature lapse rates should be constrained before applying brGDGTs to quantitatively reconstruct past uplift histories