ITPCAS OpenIR中国科学院青藏高原研究所http://ir.itpcas.ac.cn:802024-03-19T11:32:37Z2024-03-19T11:32:37ZA Middle Eocene lowland humid subtropical "Shangri-La" ecosystem in central TibetSu, T (Su, Tao)Spicer, RA (Spicer, Robert A.)Wu, FX (Wu, Fei-Xiang)Farnsworth, A (Farnsworth, Alexander)Huang, J (Huang, Jian)Del Rio, C (Del Rio, Cedric)Deng, T (Deng, Tao)Ding, L (Ding, Lin)Deng, WYD (Deng, Wei-Yu-Dong)Huang, YJ (Huang, Yong-Jiang)Hughes, A (Hughes, Alice)Jia, LB (Jia, Lin-Bo)Jin, JH (Jin, Jian-Hua)Li, SF (Li, Shu-Feng)Liang, SQ (Liang, Shui-Qing)Liu, J (Liu, Jia)Liu, XY (Liu, Xiao-Yan)Sherlock, S (Sherlock, Sarah)Spicer, T (Spicer, Teresa)Srivastava, G (Srivastava, Gaurav)Tang, H (Tang, He)Valdes, P (Valdes, Paul)Wang, TX (Wang, Teng-Xiang)Widdowson, M (Widdowson, Mike)Wu, MX (Wu, Meng-Xiao)Xing, YW (Xing, Yao-Wu)Xu, CL (Xu, Cong-Li)Yang, J (Yang, Jian)Zhang, C (Zhang, Cong)Zhang, ST (Zhang, Shi-Tao)Zhang, XW (Zhang, Xin-Wen)Zhao, F (Zhao, Fan)Zhou, ZK (Zhou, Zhe-Kun)http://ir.itpcas.ac.cn:80/handle/131C11/94662021-06-11T02:43:13Z2021-06-11T02:37:30ZTitle: A Middle Eocene lowland humid subtropical "Shangri-La" ecosystem in central Tibet
Authors: Su, T (Su, Tao); Spicer, RA (Spicer, Robert A.); Wu, FX (Wu, Fei-Xiang); Farnsworth, A (Farnsworth, Alexander); Huang, J (Huang, Jian); Del Rio, C (Del Rio, Cedric); Deng, T (Deng, Tao); Ding, L (Ding, Lin); Deng, WYD (Deng, Wei-Yu-Dong); Huang, YJ (Huang, Yong-Jiang); Hughes, A (Hughes, Alice); Jia, LB (Jia, Lin-Bo); Jin, JH (Jin, Jian-Hua); Li, SF (Li, Shu-Feng); Liang, SQ (Liang, Shui-Qing); Liu, J (Liu, Jia); Liu, XY (Liu, Xiao-Yan); Sherlock, S (Sherlock, Sarah); Spicer, T (Spicer, Teresa); Srivastava, G (Srivastava, Gaurav); Tang, H (Tang, He); Valdes, P (Valdes, Paul); Wang, TX (Wang, Teng-Xiang); Widdowson, M (Widdowson, Mike); Wu, MX (Wu, Meng-Xiao); Xing, YW (Xing, Yao-Wu); Xu, CL (Xu, Cong-Li); Yang, J (Yang, Jian); Zhang, C (Zhang, Cong); Zhang, ST (Zhang, Shi-Tao); Zhang, XW (Zhang, Xin-Wen); Zhao, F (Zhao, Fan); Zhou, ZK (Zhou, Zhe-Kun)
Description: <p>Tibet's ancient topography and its role in climatic and biotic evolution remain speculative due to a paucity of quantitative surface-height measurements through time and space, and sparse fossil records. However, newly discovered fossils from a present elevation of similar to 4,850 m in central Tibet improve substantially our knowledge of the ancient Tibetan environment. The 70 plant fossil taxa so far recovered include the first occurrences of several modern Asian lineages and represent a Middle Eocene (similar to 47 Mya) humid subtropical ecosystem. The fossils not only record the diverse composition of the ancient Tibetan biota, but also allow us to constrain the Middle Eocene land surface height in central Tibet to similar to 1,500 +/- 900 m, and quantify the prevailing thermal and hydrological regime. This "Shangri-La"-like ecosystem experienced monsoon seasonality with a mean annual temperature of similar to 19 degrees C, and frosts were rare. It contained few Gondwanan taxa, yet was compositionally similar to contemporaneous floras in both North America and Europe. Our discovery quantifies a key part of Tibetan Paleogene topography and climate, and highlights the importance of Tibet in regard to the origin of modern Asian plant species and the evolution of global biodiversity.</p>2021-06-11T02:37:30ZPhotoperiod plays a dominant and irreplaceable role in triggering secondary growth resumption REPLYHuang, JG (Huang, Jian-Guo)Campelo, F (Campelo, Filipe)Ma, QQ (Ma, Qianqian)Zhang, YL (Zhang, Yaling)Bergeron, Y (Bergeron, Yves)Deslauriers, A (Deslauriers, Annie)Fonti, P (Fonti, Patrick)Liang, E (Liang, Eryuan)Makinen, H (Makinen, Harri)Oberhuber, W (Oberhuber, Walter)Rathgeber, CBK (Rathgeber, Cyrille B. K.)Tognetti, R (Tognetti, Roberto)Treml, V (Treml, Vaclav)Yang, B (Yang, Bao)Zhai, LH (Zhai, Lihong)Zhang, JL (Zhang, Jiao-Lin)Antonucci, S (Antonucci, Serena)Camarero, JJ (Camarero, J. Julio)Cufar, K (Cufar, Katarina)Cuny, HE (Cuny, Henri E.)De Luis, M (De Luis, Martin)Giovannelli, A (Giovannelli, Alessio)Gricar, J (Gricar, Jozica)Gruber, A (Gruber, Andreas)Gryc, V (Gryc, Vladimir)Guney, A (Guney, Aylin)Guo, XL (Guo, Xiali)Huang, W (Huang, Wei)Jyske, T (Jyske, Tuula)Kaspar, J (Kaspar, Jakub)King, G (King, Gregory)Krause, C (Krause, Cornelia)Lemay, A (Lemay, Audrey)Liu, F (Liu, Feng)Lombardi, F (Lombardi, Fabio)del Castillo, EM (del Castillo, Edurne Martinez)Morin, H (Morin, Hubert)Nabais, C (Nabais, Cristina)Nojd, P (Nojd, Pekka)Peters, RL (Peters, Richard L.)Prislan, P (Prislan, Peter)Saracino, A (Saracino, Antonio)Swidrak, I (Swidrak, Irene)Vavrcik, H (Vavrcik, Hanus)Vieira, J (Vieira, Joana)Yu, BY (Yu, Biyun)Zhang, SK (Zhang, Shaokang)Zeng, Q (Zeng, Qiao)Ziaco, E (Ziaco, Emanuele)Rossi, S (Rossi, Sergio)http://ir.itpcas.ac.cn:80/handle/131C11/94652021-06-11T02:40:29Z2021-06-11T02:37:24ZTitle: Photoperiod plays a dominant and irreplaceable role in triggering secondary growth resumption REPLY
Authors: Huang, JG (Huang, Jian-Guo); Campelo, F (Campelo, Filipe); Ma, QQ (Ma, Qianqian); Zhang, YL (Zhang, Yaling); Bergeron, Y (Bergeron, Yves); Deslauriers, A (Deslauriers, Annie); Fonti, P (Fonti, Patrick); Liang, E (Liang, Eryuan); Makinen, H (Makinen, Harri); Oberhuber, W (Oberhuber, Walter); Rathgeber, CBK (Rathgeber, Cyrille B. K.); Tognetti, R (Tognetti, Roberto); Treml, V (Treml, Vaclav); Yang, B (Yang, Bao); Zhai, LH (Zhai, Lihong); Zhang, JL (Zhang, Jiao-Lin); Antonucci, S (Antonucci, Serena); Camarero, JJ (Camarero, J. Julio); Cufar, K (Cufar, Katarina); Cuny, HE (Cuny, Henri E.); De Luis, M (De Luis, Martin); Giovannelli, A (Giovannelli, Alessio); Gricar, J (Gricar, Jozica); Gruber, A (Gruber, Andreas); Gryc, V (Gryc, Vladimir); Guney, A (Guney, Aylin); Guo, XL (Guo, Xiali); Huang, W (Huang, Wei); Jyske, T (Jyske, Tuula); Kaspar, J (Kaspar, Jakub); King, G (King, Gregory); Krause, C (Krause, Cornelia); Lemay, A (Lemay, Audrey); Liu, F (Liu, Feng); Lombardi, F (Lombardi, Fabio); del Castillo, EM (del Castillo, Edurne Martinez); Morin, H (Morin, Hubert); Nabais, C (Nabais, Cristina); Nojd, P (Nojd, Pekka); Peters, RL (Peters, Richard L.); Prislan, P (Prislan, Peter); Saracino, A (Saracino, Antonio); Swidrak, I (Swidrak, Irene); Vavrcik, H (Vavrcik, Hanus); Vieira, J (Vieira, Joana); Yu, BY (Yu, Biyun); Zhang, SK (Zhang, Shaokang); Zeng, Q (Zeng, Qiao); Ziaco, E (Ziaco, Emanuele); Rossi, S (Rossi, Sergio)2021-06-11T02:37:24ZBiomass burning source identification through molecular markers in cryoconites over the Tibetan PlateauLi, QL (Li, Quanlian)Wang, NL (Wang, Ninglian)Barbante, C (Barbante, Carlo)Kang, SC (Kang, Shichang)Callegaro, A (Callegaro, Alice)Battistel, D (Battistel, Dario)Argiriadis, E (Argiriadis, Elena)Wan, X (Wan, Xin)Yao, P (Yao, Ping)Pu, T (Pu, Tao)Wu, XB (Wu, Xiaobo)Han, Y (Han, Yu)Huai, YP (Huai, Yanping)http://ir.itpcas.ac.cn:80/handle/131C11/94642020-12-03T07:31:44Z2020-11-24T02:28:08ZTitle: Biomass burning source identification through molecular markers in cryoconites over the Tibetan Plateau
Authors: Li, QL (Li, Quanlian); Wang, NL (Wang, Ninglian); Barbante, C (Barbante, Carlo); Kang, SC (Kang, Shichang); Callegaro, A (Callegaro, Alice); Battistel, D (Battistel, Dario); Argiriadis, E (Argiriadis, Elena); Wan, X (Wan, Xin); Yao, P (Yao, Ping); Pu, T (Pu, Tao); Wu, XB (Wu, Xiaobo); Han, Y (Han, Yu); Huai, YP (Huai, Yanping)
Description: <p>Cryoconite is a dark, dusty aggregate of mineral particles, organic matter, and microorganisms transported by wind and deposited on glacier surfaces. It can accelerate glacier melting and alter glacier mass balances by reducing the surface albedo of glaciers. Biomass burning in the Tibetan Plateau, especially in the glacier cryoconites, is poorly understood. Retene, levoglucosan, mannosan and galactosan can be generated by the local fires or transported from the biomass burning regions over long distances. In the present study, we analyzed these four molecular markers in cryoconites of seven glaciers from the northern to southern Tibetan Plateau. The highest levels of levoglucosan and retene were found in cryoconites of the Yulong Snow Mountain and Tienshan glaciers with 171.4 +/- 159.4 ng g(-1) and 47.0 +/- 10.5 ng g(-1) dry weight (d.w.), respectively. The Murtag glacier in the central Tibetan Plateau contained the lowest levels of levoglucosan and retene with mean values of 59.8 ng g(-1) and 0.4 +/- 0.1 ng g(-1) d.w., respectively. In addition, the vegetation changes and the ratios of levoglucosan to mannosan and retene indicate that combustion of conifers significantly contributes to biomass burning of the cryoconites in the Yulong Snow Mountain and Tienshan glacier. Conversely, biomass burning tracers in cryoconites of Dongkemadi, Yuzhufeng, Murtag, Qiyi and Laohugou glaciers are derived from the combustion of different types of biomass including softwood, hardwood and grass. (C) 2018 Elsevier Ltd. All rights reserved.</p>2020-11-24T02:28:08ZHeavy near-surface PM2.5 pollution in Lhasa, China during a relatively static winter periodLi, CL (Li, Chaoliu)Han, XW (Han, Xiaowen)Kang, SC (Kang, Shichang)Yan, FP (Yan, Fangping)Chen, PF (Chen, Pengfei)Hu, ZF (Hu, Zhaofu)Yang, JH (Yang, Junhua)Ciren, DJ (Ciren, Duojie)Gao, SP (Gao, Shaopeng)Sillanpaa, M (Sillanpaa, Mika)Han, YM (Han, Yongming)Cui, YY (Cui, Yuyan)Liu, S (Liu, Shang)Smith, KR (Smith, Kirk R.)http://ir.itpcas.ac.cn:80/handle/131C11/94632020-12-03T07:30:46Z2020-11-24T02:28:07ZTitle: Heavy near-surface PM2.5 pollution in Lhasa, China during a relatively static winter period
Authors: Li, CL (Li, Chaoliu); Han, XW (Han, Xiaowen); Kang, SC (Kang, Shichang); Yan, FP (Yan, Fangping); Chen, PF (Chen, Pengfei); Hu, ZF (Hu, Zhaofu); Yang, JH (Yang, Junhua); Ciren, DJ (Ciren, Duojie); Gao, SP (Gao, Shaopeng); Sillanpaa, M (Sillanpaa, Mika); Han, YM (Han, Yongming); Cui, YY (Cui, Yuyan); Liu, S (Liu, Shang); Smith, KR (Smith, Kirk R.)
Description: <p>Fairly high near-surface PM2.5 concentrations were found during relatively static winter conditions within Lhasa - a Tibetan Plateau city normally considered to have a clean atmosphere. The average daily PM2.5 concentration reached 118 +/- 60 mu g m(-3) during the study period, was approximately 3.4 times the United States Environmental Protection Agency 24-h standard. PM2.5 concentration of Lhasa increased from 20:00 until 23:00, which was probably caused by space heating, waste incineration activities and decreased boundary layer at night. Furthermore, we found traditional religious butter lamp lighting of local Tibetan residents during festivals could cause PM2.5 concentration to reach an alarmingly high level, 240 +/- 3014 m(-3). Therefore, to protect the atmosphere of Lhasa, the government may wish to conduct more complete monitoring and find ways to encourage clean heating and cooking fuels, enforce the supervision on illegal emission activities such as waste incineration, and guide residents to transfer to more environmentally friendly activities during festivals. (C) 2018 Elsevier Ltd. All rights reserved.</p>2020-11-24T02:28:07ZAnalysis of rainfall trends of two complex mountain river basins on the southern slopes of the Central HimalayasShrestha, S (Shrestha, Suraj)Yao, TD (Yao, Tandong)Adhikari, TR (Adhikari, Tirtha Raj)http://ir.itpcas.ac.cn:80/handle/131C11/94622020-12-03T07:29:50Z2020-11-24T02:28:05ZTitle: Analysis of rainfall trends of two complex mountain river basins on the southern slopes of the Central Himalayas
Authors: Shrestha, S (Shrestha, Suraj); Yao, TD (Yao, Tandong); Adhikari, TR (Adhikari, Tirtha Raj)
Description: <p>Understanding rainfall characteristics plays a vital role in sustainable watershed development and management, but at the same time it is challenging in mountainous regions, due to its topography complexities. This study investigates the seasonal along its associated months and annual rainfall characteristics and their variations over two distinct river basins; Kaligandaki in central west and Koshi in eastern Nepal, located on the southern slopes of the central Himalayas, which is crucial to the research of the climate change in these regions. The rainfall data series over the period of 34-year (1981-2015) of 43 stations between the elevation range of 143 m asl to 3870 m asl was used for this study. The analysis was carried out to assess the significance of rainfall trend along with its magnitude followed by its abrupt shift by using the Mann-Kendall test, Sen's test and Sequential Mann-Kendall test respectively. Furthermore, multitaper method was used to confirm the influence of large-scale circulation indices over the study area. An increasing pattern of rainfall from south to north was observed throughout all season in Koshi basin which was not seen in the Kaligandaki basin, indicating the effects of orography along with monsoon. Both basins share a similar pattern of rainfall between annual and monsoonal rainfall, supporting that both basins are dominated by the monsoon. The transition months between the seasons showed almost similar spatial distribution but different from other months of respective seasons. The results showed that the seasonal and annual rainfall declined in most of the stations of both the basins, except during pre-monsoon where it showed increased rainfall. But only a few stations showing such changes were statistically significant. In fact, these noticeable significant decreases were observed especially in the southern and northern region of Koshi basin while in Kaligandaki basin, it was found either in central or in the southern region. Furthermore, the trend shift analysis identified change points during 1980s or early 1990s, but most significant shifts were observed in recent years with some exceptions. Spectral analysis showed significant peaks at periodicity ranging 2-5 years, suggesting a potential association with Quasi-Biennial Oscillations (QBO) and El Nifio-Southern Oscillation (ENSO).</p>2020-11-24T02:28:05ZGlobal trends in carbon sinks and their relationships with CO2 and temperatureFernandez-Martinez, M (Fernandez-Martinez, M.)Sardans, J (Sardans, J.)Chevallier, F (Chevallier, F.)Ciais, P (Ciais, P.)Obersteiner, M (Obersteiner, M.)Vicca, S (Vicca, S.)Canadell, JG (Canadell, J. G.)Bastos, A (Bastos, A.)Friedlingstein, P (Friedlingstein, P.)Sitch, S (Sitch, S.)Piao, SL (Piao, S. L.)Janssens, IA (Janssens, I. A.)Penuelas, J (Penuelas, J.)http://ir.itpcas.ac.cn:80/handle/131C11/94612020-12-03T07:28:50Z2020-11-24T02:28:03ZTitle: Global trends in carbon sinks and their relationships with CO2 and temperature
Authors: Fernandez-Martinez, M (Fernandez-Martinez, M.); Sardans, J (Sardans, J.); Chevallier, F (Chevallier, F.); Ciais, P (Ciais, P.); Obersteiner, M (Obersteiner, M.); Vicca, S (Vicca, S.); Canadell, JG (Canadell, J. G.); Bastos, A (Bastos, A.); Friedlingstein, P (Friedlingstein, P.); Sitch, S (Sitch, S.); Piao, SL (Piao, S. L.); Janssens, IA (Janssens, I. A.); Penuelas, J (Penuelas, J.)
Description: <p>Elevated CO2 concentrations increase photosynthesis and, potentially, net ecosystem production (NEP), meaning a greater CO2 uptake. Climate, nutrients and ecosystem structure, however, influence the effect of increasing CO2. Here we analysed global NEP from MACC-II and Jena CarboScope atmospheric inversions and ten dynamic global vegetation models ( TRENDY), using statistical models to attribute the trends in NEP to its potential drivers: CO2, climatic variables and land-use change. We found that an increased CO2 was consistently associated with an increased NEP (1995-2014). Conversely, increased temperatures were negatively associated with NEP. Using the two atmospheric inversions and TRENDY, the estimated global sensitivities for CO2 were 6.0 +/- 0.1, 8.1 +/- 0.3 and 3.1 +/- 0.1 PgC per 100 ppm (similar to 1 degrees C increase), and -0.5 +/- 0.2, -0.9 +/- 0.4 and -1.1 +/- 0.1 PgC degrees C-1 for temperature. These results indicate a positive CO2 effect on terrestrial C sinks that is constrained by climate warming.</p>2020-11-24T02:28:03ZHigh-Angle Normal Faulting at the Tangra Yumco Graben (Southern Tibet) since similar to 15 MaWolff, R (Wolff, Reinhard)Hetzel, R (Hetzel, Ralf)Dunkl, I (Dunkl, Istvan)Xu, Q (Xu, Qiang)Brocker, M (Broecker, Michael)Anczkiewicz, AA (Anczkiewicz, Aneta A.)http://ir.itpcas.ac.cn:80/handle/131C11/94602020-12-03T07:27:09Z2020-11-24T02:28:02ZTitle: High-Angle Normal Faulting at the Tangra Yumco Graben (Southern Tibet) since similar to 15 Ma
Authors: Wolff, R (Wolff, Reinhard); Hetzel, R (Hetzel, Ralf); Dunkl, I (Dunkl, Istvan); Xu, Q (Xu, Qiang); Brocker, M (Broecker, Michael); Anczkiewicz, AA (Anczkiewicz, Aneta A.)
Description: <p>Several active graben systems in Tibet and the Himalaya are the expression of ongoing east-west extension, but the significance and history of normal faulting in this large region are still debated. Here, we present geo- and thermochronological data for a granite intrusion in the footwall of an active high-angle normal fault at the Tangra Yumco graben to constrain the onset and history of normal faulting. Crystallization of the granitic rocks occurred at 87 +/- 1 Ma, as revealed by U/Pb zircon dating. After an initial phase of rapid cooling from magmatic temperatures, a later phase of slow cooling is recorded by Rb/Sr biotite ages between similar to 72 and similar to 60 Ma. The elevation dependence of the Rb/Sr ages suggests that cooling was controlled by erosion, which proceeded at a rate of similar to 0.05 km/My during the latest Cretaceous and early Paleocene. The subsequent history of normal faulting is recorded by zircon (U-Th)/He ages of 12.5 +/- 1.1 and 9.7 +/- 0.7 Ma, apatite fission-track ages between 10.8 +/- 1.7 and 7.8 +/- 1.2 Ma, and apatite (U-Th)/He ages from 4.9 +/- 0.4 to 3.0 +/- 0.2 Ma. Thermokinematic modeling of these age data indicates that normal faulting started at 14.5 +/- 1.8 Ma at a rate of similar to 0.3 km/My and accelerated to similar to 0.7 km/My in the Pliocene. Our age constraint for the initiation of faulting supports a widespread onset of rifting in Tibet at similar to 15-10 Ma, as reported for other graben systems. Finally, we suggest that the distribution of high-angle and low-angle normal faults is controlled by their position relative to the India-Asia convergence vector and by lateral variations in the thermal state of the lithosphere.</p>2020-11-24T02:28:02ZClimatic significance of the stable carbon isotopic composition of surface soils in northern Iran and its application to an Early Pleistocene loess sectionWang, Q (Wang, Qiang)Wang, X (Wang, Xin)Wei, HT (Wei, Haitao)Khormali, F (Khormali, Farhad)Xie, HC (Xie, Haichao)Zhang, JH (Zhang, Jinhui)Chen, FH (Chen, Fahu)http://ir.itpcas.ac.cn:80/handle/131C11/94592020-12-03T07:25:18Z2020-11-24T02:27:59ZTitle: Climatic significance of the stable carbon isotopic composition of surface soils in northern Iran and its application to an Early Pleistocene loess section
Authors: Wang, Q (Wang, Qiang); Wang, X (Wang, Xin); Wei, HT (Wei, Haitao); Khormali, F (Khormali, Farhad); Xie, HC (Xie, Haichao); Zhang, JH (Zhang, Jinhui); Chen, FH (Chen, Fahu)
Description: <p>The stable carbon isotopic composition of bulk organic matter (delta C-13(org)) in paleosols has been widely used as a proxy indicator for reconstructing past vegetation and climate. Previous studies generally show a negative correlation between the delta C-13(org) values of modern C-3 plants and surface soils under C-3 plant-dominated ecosystems and mean annual precipitation (MAP). However, the relationship between delta(13)Corg and MAP varies among different climatic regimes, resulting in uncertainties in paleoprecipitation reconstructions. In this study, we analyzed the delta C-13(org) values of surface soil samples collected along a north-south climatic gradient in northern Iran, in the western part of arid central Asia (ACA). Our aims were to explore the relationship between surface soil delta C-13(org) values and climatic factors; to use it to develop a transfer function for ACA; and then to apply the transfer function to a well-dated loess-paleosol sequence (AB1) to reconstruct early Pleistocene (2.4-1.8 Ma) MAP in northern Iran. The results show that: (1) the delta C-13(org) values of 44 surface soil samples range from -27.56%, to -23.61%,, with an average of -25.77%,, indicating that the modern natural ecosystem in northern Iran is dominated by C-3 vegetation; (2) The delta C-13(org) values of the surface soil samples are strongly negatively correlated with MAP (y = -0.0079x - 22.8418, R-2 = 0.4419, p < 0.001), with a coefficient of -0.79%/100 mm. We infer that the effects of mean annual temperature (MAT) and elevation on the relationship are minimal; (3) Reconstructed early Pleistocene MAP in northern Iran was similar to 649 mm, much wetter than the present day (similar to 331 mm); (4) The loess delta C-13(org) values from ACA exhibit similar trends to records from monsoonal Asia, suggesting a similar history of Quaternary climate change between ACA and monsoonal Asia, which is likely related to the growth and decay of Northern Hemisphere ice sheets. (C) 2018 Elsevier Ltd. All rights reserved.</p>2020-11-24T02:27:59ZVegetation effects on temperature calibrations of branched glycerol dialkyl glycerol tetraether (brGDGTs) in soilsLiang, J (Liang, Jie)Russell, JM (Russell, James M.)Xie, HC (Xie, Haichao)Lupien, RL (Lupien, Rachel L.)Si, GC (Si, Guicai)Wang, J (Wang, Jian)Hou, JZ (Hou, Juzhi)Zhang, GX (Zhang, Gengxin)http://ir.itpcas.ac.cn:80/handle/131C11/94582020-12-03T07:24:14Z2020-11-24T02:27:58ZTitle: Vegetation effects on temperature calibrations of branched glycerol dialkyl glycerol tetraether (brGDGTs) in soils
Authors: Liang, J (Liang, Jie); Russell, JM (Russell, James M.); Xie, HC (Xie, Haichao); Lupien, RL (Lupien, Rachel L.); Si, GC (Si, Guicai); Wang, J (Wang, Jian); Hou, JZ (Hou, Juzhi); Zhang, GX (Zhang, Gengxin)
Description: <p>Distributions of branched glycerol dialkyl glycerol tetraether (brGDGT) lipids are sensitive to environmental parameters, which enables their use in paleoenvironmental studies. In particular, the degree of methylation of brGDGTs (MBT and MBT') and the cyclization ratio of brGDGTs (CBT) are often used to estimate changes in temperature in paleoclimate studies. Application of these proxies requires reliable and precise calibrations to temperature. However, available calibrations of brGDGT proxies to temperature have large calibration errors in arid areas which suggests that other environmental variables influence brGDGT distributions in these areas. Here we analyze brGDGT distributions in soils from the Tibetan Plateau, an arid/semi-arid region with gradients in vegetation cover (forest, grassland, and desert) to examine: (1) the applicability of MBT'/CBT calibrations to reconstruct mean annual air temperature (MAAT); and (2) the effects of vegetation cover on temperature calibrations. We show that temperatures reconstructed using the global soil MBT'/CBT calibrations are warmer than instrumentally observed temperature, and that the calibrations are significantly influenced by the presence or absence of vegetation. Excluding sample sites without vegetation (bare soil) from temperature calibrations substantially improves the correlation between observed and reconstructed temperatures. Within the vegetated soils, we reanalyzed published global soil calibration datasets, including results of analyses that either did or did not separate 5- and 6-methyl brGDGT isomers, and find that the correlation between MBT'(5Me) and MBT' and temperature varies for different vegetation types (grass and forest) and that the error of temperature calibrations is reduced if calibrations are separated by the type of vegetative cover (grass or forest). We test these new calibrations in sequences from the Lantian and Mangshan loess of the Chinese Loess Plateau and find that reconstructed temperatures from both modern and Last Glacial Maximum sediments are more consistent with other reconstructions and climate model simulations when vegetation-specific calibrations are applied to the brGDGT data. The results indicate that changes in vegetation should be taken into consideration when applying brGDGT proxies to reconstruct past changes in climate. (C) 2018 Published by Elsevier Ltd.</p>2020-11-24T02:27:58ZResponse of larger benthic foraminifera to the Paleocene-Eocene thermal maximum and the position of the Paleocene/Eocene boundary in the Tethyan shallow benthic zones: Evidence from south TibetZhang, QH (Zhang, Qinghai)Willems, H (Willems, Helmut)Ding, L (Ding, Lin)Xu, XX (Xu, Xiaoxia)http://ir.itpcas.ac.cn:80/handle/131C11/94572020-12-03T07:23:06Z2020-11-24T02:27:54ZTitle: Response of larger benthic foraminifera to the Paleocene-Eocene thermal maximum and the position of the Paleocene/Eocene boundary in the Tethyan shallow benthic zones: Evidence from south Tibet
Authors: Zhang, QH (Zhang, Qinghai); Willems, H (Willems, Helmut); Ding, L (Ding, Lin); Xu, XX (Xu, Xiaoxia)
Description: <p>The Paleocene-Eocene thermal maximum (PETM) is one of the most pronounced global warming events in the Cenozoic. This event was associated with a large negative carbon isotope excursion (CIE) and with major changes in the atmosphere, hydrosphere, and biosphere. However, how the larger benthic foraminifera (LBFs) in the shallow Tethyan Ocean responded to the PETM remains controversial. In this study, we investigate two shallow-marine, LBF-rich carbonate sections from south Tibet, aiming to locate the position of the Paleocene/Eocene (P/E) boundary in the Tethyan shallow benthic zones (SBZs) and to examine the response of the LBFs to the PETM. Carbon isotope compositions of bulk carbonate were measured to constrain the stratigraphic position of the CIE onset marking the P/E boundary in the sections, and the LBFs were studied in rock thin sections in order to assess their biostratigraphy and to construct the SBZs. The combination of the carbon isotope data and constructed SBZs shows that the P/E boundary is located within SBZS, not at the SBZ4/SBZ5 transition as proposed in the Western Tethyan domain. At the P/E boundary, no evident compositional change in LBF assemblages can be observed. However, a major compositional change in LBF assemblages occurs in the CIE recovery, characterized by the sudden disappearance of Miscellanea, Ranikothalia, Setia, Orbitosiphon, and the initial dominance of porcellaneous-walled Alveolina and Orbitolites together with small miliolids and rotaliids. We tentatively speculate that this compositional change in LBF assemblages may be related to a eutrophication event, likely resulting from intensified continental weathering during the CIE recovery of the PETM.</p>2020-11-24T02:27:54Z