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Li H, Zhang H, Li H, Duan L, Zhang X, Gao Y, Hall IR, Hemming SR, LeVay LJ. Sedimentary DNA reveals the link between microbial community dynamics and climate during the late last glaciation in the offshore region of the Zambezi River, Southwest Indian Ocean. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 906:167787. [PMID: 37844644 DOI: 10.1016/j.scitotenv.2023.167787] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 10/04/2023] [Accepted: 10/10/2023] [Indexed: 10/18/2023]
Abstract
Reconstructing the relationship between microbial communities and past abrupt climate change is of great importance for understanding current biodiversity patterns and predicting changes under future climate scenarios. However, little is currently known about how microbial communities respond to changes in key environmental stages due to a lack of research in this area. Here, we examine the variability in the communities of bacteria, archaea, and fungi from sediments deposited offshore region of the Zambezi River between 21.7 and 9.6 thousand years ago (ka) (covering the last glacial maximum, or LGM, and the early Holocene) using DNA metabarcoding approach via high-throughput sequencing. The results showed that (1) microbial assemblages differed across three key time intervals, with the last deglaciation having the most homogeneous prokaryotic assemblages, while for fungal communities in the LGM, and the early Holocene and LGM differing the most; (2) the warm early Holocene showed the highest diversity, whereas the lowest diversity was found in the LGM; and (3) the selected indicator species better reflected the climatic characteristics of different environmental stages. These results highlight the power of ancient sedimentary DNA to refine our understanding of microbial dynamics in marine sedimentary systems near large rivers, thus providing a basis for better modeling ecological processes in further research.
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Affiliation(s)
- Haoyu Li
- Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, 650500 Kunming, China
| | - Hucai Zhang
- Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, 650500 Kunming, China.
| | - Huayong Li
- School of Resource Environment and Tourism, Anyang Normal University, Anyang 455000, China
| | - Lizeng Duan
- Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, 650500 Kunming, China
| | - Xiaonan Zhang
- Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, 650500 Kunming, China
| | - Youhong Gao
- Institute for Ecological Research and Pollution Control of Plateau Lakes, School of Ecology and Environmental Science, Yunnan University, 650500 Kunming, China
| | - Ian R Hall
- Department of Earth Sciences, Cardiff University, Main College, Park Place, PO Box 914, Cardiff, Wales CF10 3AT, United Kingdom
| | - Sidney R Hemming
- Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY, 10964, USA
| | - Leah J LeVay
- International Ocean Discovery Program, Texas A&M University, College Station, TX 77845, USA
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2
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Du X, Russell JM, Liu Z, Otto-Bliesner BL, Oppo DW, Mohtadi M, Zhu C, Galy VV, Schefuß E, Yan Y, Rosenthal Y, Dubois N, Arbuszewski J, Gao Y. North Atlantic cooling triggered a zonal mode over the Indian Ocean during Heinrich Stadial 1. SCIENCE ADVANCES 2023; 9:eadd4909. [PMID: 36598985 PMCID: PMC9812376 DOI: 10.1126/sciadv.add4909] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/23/2022] [Accepted: 11/23/2022] [Indexed: 06/17/2023]
Abstract
Abrupt changes in the Atlantic meridional overturning circulation (AMOC) are thought to affect tropical hydroclimate through adjustment of the latitudinal position of the intertropical convergence zone (ITCZ). Heinrich Stadial 1 (HS1) involves the largest AMOC reduction in recent geological time; however, over the tropical Indian Ocean (IO), proxy records suggest zonal anomalies featuring intense, widespread drought in tropical East Africa versus generally wet but heterogeneous conditions in the Maritime Continent. Here, we synthesize proxy data and an isotope-enabled transient deglacial simulation and show that the southward ITCZ shift over the eastern IO during HS1 strengthens IO Walker circulation, triggering an east-west precipitation dipole across the basin. This dipole reverses the zonal precipitation anomalies caused by the exposed Sunda and Sahul shelves due to glacial lower sea level. Our study illustrates how zonal modes of atmosphere-ocean circulation can amplify or reverse global climate anomalies, highlighting their importance for future climate change.
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Affiliation(s)
- Xiaojing Du
- Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, USA
- Institute at Brown for Environment and Society, Brown University, Providence, RI, USA
| | - James M. Russell
- Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI, USA
- Institute at Brown for Environment and Society, Brown University, Providence, RI, USA
| | - Zhengyu Liu
- Atmospheric Science Program, Department of Geography, The Ohio State University, Columbus, OH, USA
| | - Bette L. Otto-Bliesner
- Climate and Global Dynamics Laboratory, National Center for Atmospheric Research, Boulder, CO, USA
| | - Delia W. Oppo
- Geology and Geophysics Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Mahyar Mohtadi
- MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Chenyu Zhu
- Frontier Science Center for Deep Ocean Multispheres and Earth System (FDOMES) and Physical Oceanography Laboratory, Ocean University of China, Qingdao, China
| | - Valier V. Galy
- Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Enno Schefuß
- MARUM-Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Yan Yan
- State Key Laboratory of Isotope Geochemistry, CAS Center for Excellence in Deep Earth Science, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China
| | - Yair Rosenthal
- Department of Marine and Coastal Sciences and Department of Earth and Planetary Sciences, Rutgers, State University of New Jersey, New Brunswick, NJ, USA
| | - Nathalie Dubois
- Department of Surface Waters Research and Management, Eawag, Dübendorf, Switzerland
- Department of Earth Sciences, ETH Zürich, Zürich, Switzerland
| | - Jennifer Arbuszewski
- Geology and Geophysics Department, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
| | - Yu Gao
- Department of Atmospheric and Oceanic Sciences, School of Physics, Peking University, Beijing, China
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3
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Judd EJ, Tierney JE, Huber BT, Wing SL, Lunt DJ, Ford HL, Inglis GN, McClymont EL, O'Brien CL, Rattanasriampaipong R, Si W, Staitis ML, Thirumalai K, Anagnostou E, Cramwinckel MJ, Dawson RR, Evans D, Gray WR, Grossman EL, Henehan MJ, Hupp BN, MacLeod KG, O'Connor LK, Sánchez Montes ML, Song H, Zhang YG. The PhanSST global database of Phanerozoic sea surface temperature proxy data. Sci Data 2022; 9:753. [PMID: 36473868 PMCID: PMC9726822 DOI: 10.1038/s41597-022-01826-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Accepted: 11/08/2022] [Indexed: 12/12/2022] Open
Abstract
Paleotemperature proxy data form the cornerstone of paleoclimate research and are integral to understanding the evolution of the Earth system across the Phanerozoic Eon. Here, we present PhanSST, a database containing over 150,000 data points from five proxy systems that can be used to estimate past sea surface temperature. The geochemical data have a near-global spatial distribution and temporally span most of the Phanerozoic. Each proxy value is associated with consistent and queryable metadata fields, including information about the location, age, and taxonomy of the organism from which the data derive. To promote transparency and reproducibility, we include all available published data, regardless of interpreted preservation state or vital effects. However, we also provide expert-assigned diagenetic assessments, ecological and environmental flags, and other proxy-specific fields, which facilitate informed and responsible reuse of the database. The data are quality control checked and the foraminiferal taxonomy has been updated. PhanSST will serve as a valuable resource to the paleoclimate community and has myriad applications, including evolutionary, geochemical, diagenetic, and proxy calibration studies.
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Affiliation(s)
- Emily J Judd
- Smithsonian National Museum of Natural History, Department of Paleobiology, Washington, DC, 20560, USA.
| | - Jessica E Tierney
- University of Arizona, Department of Geosciences, Tuscon, AZ, 85721, USA
| | - Brian T Huber
- Smithsonian National Museum of Natural History, Department of Paleobiology, Washington, DC, 20560, USA
| | - Scott L Wing
- Smithsonian National Museum of Natural History, Department of Paleobiology, Washington, DC, 20560, USA
| | - Daniel J Lunt
- University of Bristol, School of Geographical Sciences, Bristol, BS8 1SS, UK
| | - Heather L Ford
- Queen Mary University of London, School of Geography, London, E1 4NS, UK
| | - Gordon N Inglis
- University of Southampton, School of Ocean and Earth Science, National Oceanography Centre Southampton, Southampton, SO14 3ZH, UK
| | | | | | | | - Weimin Si
- Brown University, Department of Earth, Environmental and Planetary Sciences, Providence, RI, 02912, USA
| | - Matthew L Staitis
- University of Edinburgh, School of Geosciences, Edinburgh, EH8 9XP, UK
| | | | - Eleni Anagnostou
- GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148, Kiel, Germany
| | - Marlow Julius Cramwinckel
- University of Southampton, School of Ocean and Earth Science, National Oceanography Centre Southampton, Southampton, SO14 3ZH, UK
- Utrecht University, Department of Earth Sciences, Utrecht, 3584 CB, The Netherlands
| | - Robin R Dawson
- University of Massachusetts Amherst, Department of Geosciences, Amherst, MA, 01003, USA
| | - David Evans
- Goethe University Frankfurt, Institute of Geosciences, 60438, Frankfurt am Main, Germany
| | - William R Gray
- Université Paris-Saclay, Laboratoire des Sciences du Climat et de l'Environnement, Gif-sur-Yvette, France
| | - Ethan L Grossman
- Texas A&M University, Department of Geology and Geophysics, College Station, TX, 77843, USA
| | - Michael J Henehan
- GFZ German Research Centre for Geosciences, Section 3.3 Earth Surface Geochemistry, 14473, Potsdam, Germany
| | - Brittany N Hupp
- Oregon State University, College of Earth, Ocean and Atmospheric Sciences, Corvallis, OR, 97331, USA
| | - Kenneth G MacLeod
- University of Missouri, Department of Geological Sciences, Columbia, MO, 65211, USA
| | - Lauren K O'Connor
- University of Manchester, Department of Earth and Environmental Sciences, Manchester, M13 9PL, UK
| | | | - Haijun Song
- China University of Geosciences, State Key Laboratory of Biogeology and Environmental Geology, School of Earth Sciences, Wuhan, 430074, China
| | - Yi Ge Zhang
- Texas A&M University, Department of Oceanography, College Station, TX, 77843, USA
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4
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Higher sea surface temperature in the Indian Ocean during the Last Interglacial weakened the South Asian monsoon. Proc Natl Acad Sci U S A 2022; 119:e2107720119. [PMID: 35238640 PMCID: PMC8915836 DOI: 10.1073/pnas.2107720119] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Understanding the drivers of South Asian monsoon intensity is pivotal for improving climate forecasting under global warming scenarios. Solar insolation is assumed to be the dominant driver of monsoon variability in warm climate regimes, but this has not been verified by proxy data. We report a South Asian monsoon rainfall record spanning the last ∼130 kyr in the Ganges–Brahmaputra–Meghna river catchment. Our multiproxy data reveal that the South Asian monsoon was weaker during the Last Interglacial (130 to 115 ka)—despite higher insolation—than during the Holocene (11.6 ka to present), thus questioning the widely accepted model assumption. Our work implies that Indian Ocean warming may increase the occurrence of severe monsoon failures in South Asia. Addressing and anticipating future South Asian monsoon changes under continuing global warming is of critical importance for the food security and socioeconomic well-being of one-quarter of the world’s population. However, climate model projections show discrepancies in future monsoon variability in South Asian monsoon domains, largely due to our still limited understanding of the monsoon response to warm climate change scenarios. Particularly, climate models are largely based on the assumption that higher solar insolation causes higher rainfall during similar warm climatic regimes, but this has not been verified by proxy data for different interglacial periods. Here, we compare Indian summer monsoon (ISM) variability during the Last Interglacial and Holocene using a sedimentary leaf wax δD and δ13C record from the northern Bay of Bengal, representing the Ganges–Brahmaputra–Meghna (G-B-M) river catchment. In combination with a seawater salinity record, our results show that ISM intensity broadly follows summer insolation on orbital scales, but ISM intensity during the Last Interglacial was lower than during the Holocene despite higher summer insolation and greenhouse gas concentrations. We argue that sustained warmer sea surface temperature in the equatorial and tropical Indian Ocean during the Last Interglacial increased convective rainfall above the ocean but dampened ISM intensity on land. Our study demonstrates that besides solar insolation, internal climatic feedbacks also play an important role for South Asian monsoon variability during warm climate states. This work can help to improve future climate model projections and highlights the importance of understanding controls of monsoonal rainfall under interglacial boundary conditions.
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5
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Li F, Leu A, Poff K, Carlson LT, Ingalls AE, DeLong EF. Planktonic Archaeal Ether Lipid Origins in Surface Waters of the North Pacific Subtropical Gyre. Front Microbiol 2021; 12:610675. [PMID: 34589060 PMCID: PMC8473941 DOI: 10.3389/fmicb.2021.610675] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Accepted: 08/23/2021] [Indexed: 01/04/2023] Open
Abstract
Thaumarchaeota and Thermoplasmatota are the most abundant planktonic archaea in the sea. Thaumarchaeota contain tetraether lipids as their major membrane lipids, but the lipid composition of uncultured planktonic Thermoplasmatota representatives remains unknown. To address this knowledge gap, we quantified archaeal cells and ether lipids in open ocean depth profiles (0–200 m) of the North Pacific Subtropical Gyre. Planktonic archaeal community structure and ether lipid composition in the water column partitioned into two separate clusters: one above the deep chlorophyll maximum, the other within and below it. In surface waters, Thermoplasmatota densities ranged from 2.11 × 106 to 6.02 × 106 cells/L, while Thaumarchaeota were undetectable. As previously reported for Thaumarchaeota, potential homologs of archaeal tetraether ring synthases were present in planktonic Thermoplasmatota metagenomes. Despite the absence of Thaumarchaeota in surface waters, measurable amounts of intact polar ether lipids were found there. Based on cell abundance estimates, these surface water archaeal ether lipids contributed only 1.21 × 10–9 ng lipid/Thermoplasmatota cell, about three orders of magnitude less than that reported for Thaumarchaeota cells. While these data indicate that even if some tetraether and diether lipids may be derived from Thermoplasmatota, they would only comprise a small fraction of Thermoplasmatota total biomass. Therefore, while both MGI Thaumarchaeota and MGII/III Thermoplasmatota are potential biological sources of archaeal GDGTs, the Thaumarchaeota appear to be the major contributors of archaeal tetraether lipids in planktonic marine habitats. These results extend and confirm previous reports of planktonic archaeal lipid sources, and further emphasize the need for Thermoplasmatota cultivation, to better characterize the membrane lipid constituents of marine planktonic Thermoplasmatota, and more precisely define the sources and patterns of archaeal tetraether lipid distributions in marine plankton.
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Affiliation(s)
- Fuyan Li
- Daniel K. Inouye Center for Microbial Oceanography: Research and Education, University of Hawai'i at Mânoa, Honolulu, HI, United States
| | - Andy Leu
- Daniel K. Inouye Center for Microbial Oceanography: Research and Education, University of Hawai'i at Mânoa, Honolulu, HI, United States
| | - Kirsten Poff
- Daniel K. Inouye Center for Microbial Oceanography: Research and Education, University of Hawai'i at Mânoa, Honolulu, HI, United States
| | - Laura T Carlson
- School of Oceanography, University of Washington, Seattle, WA, United States
| | - Anitra E Ingalls
- School of Oceanography, University of Washington, Seattle, WA, United States
| | - Edward F DeLong
- Daniel K. Inouye Center for Microbial Oceanography: Research and Education, University of Hawai'i at Mânoa, Honolulu, HI, United States
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6
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Liu J. Seasonality of the altitude effect on leaf wax n-alkane distributions, hydrogen and carbon isotopes along an arid transect in the Qinling Mountains. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 778:146272. [PMID: 33725603 DOI: 10.1016/j.scitotenv.2021.146272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Revised: 02/25/2021] [Accepted: 02/28/2021] [Indexed: 06/12/2023]
Abstract
Reconstructing paleoelevation allows the temporal evolution of biogeochemical processes and hydroclimate regimes to be understood and quantified. A dual-isotope biomarker of clumped hydrogen and carbon isotopes of leaf wax n-alkanes was recently proposed in humid tropical forests, and it was proven to be superior to a single-isotope proxy that was previously reported. However, it remains unknown whether the dual-isotope biomarker is suitable in arid conditions. The present study investigated leaf wax n-alkane distribution, hydrogen (δ2Hwax) and carbon (δ13Cwax) isotopes in terrestrial plants along an arid mountainous transect. We found that the effects of seasonality on n-alkane distribution, δ2Hwax and δ13Cwax were minimal for all species (p > 0.05), and that species-specific δ2Hwax values remained almost unchanged for most species, in contrast to δ13Cwax values. Significant correlations between altitude and δ2Hwax values (R2 = 0.54, 0.58, and 0.75 for spring, summer, and autumn, respectively), instead of δ13Cwax values (R2 = 0.08, 0.43, and 0.12 with p = 0.24, 0.01, and 0.19 for spring, summer, and autumn, respectively), were observed, suggesting that δ2Hwax values, but not δ13Cwax values, can be reliably used as a proxy for reconstructing paleoelevation in arid conditions. Therefore, it will be necessary to identify other proxies to supplement δ2Hwax values under a dual-isotope approach in future research.
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Affiliation(s)
- Jinzhao Liu
- State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi'an 710061, China; CAS Center for Excellence in Quaternary Science and Global Change, Xi'an 710061, China.
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7
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Kylander ME, Holm M, Fitchett J, Grab S, Martinez Cortizas A, Norström E, Bindler R. Late glacial (17,060-13,400 cal yr BP) sedimentary and paleoenvironmental evolution of the Sekhokong Range (Drakensberg), southern Africa. PLoS One 2021; 16:e0246821. [PMID: 33730018 PMCID: PMC7968709 DOI: 10.1371/journal.pone.0246821] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2020] [Accepted: 01/26/2021] [Indexed: 11/24/2022] Open
Abstract
Southern Africa sits at the junction of tropical and temperate systems, leading to the formation of seasonal precipitation zones. Understanding late Quaternary paleoclimatic change in this vulnerable region is hampered by a lack of available, reliably-dated records. Here we present a sequence from a well-stratified sedimentary infill occupying a lower slope basin which covers 17,060 to 13,400 cal yr BP with the aim to reconstruct paleoclimatic variability in the high Drakensberg during the Late Glacial. We use a combination of pollen, total organic carbon and nitrogen, δ13C, Fourier transform infrared spectroscopy attenuated total reflectance (FTIR-ATR) spectral and elemental data on contiguous samples with high temporal resolution (10 to 80 years per sample). Our data support a relatively humid environment with considerable cold season precipitation during what might have been the final stage of niche-glaciation on the adjoining southern aspects around 17,000 cal yr BP. Then, after an initial warmer and drier period starting ~15,600 cal yr BP, we identify a return to colder and drier conditions with more winter precipitation starting ~14,380 cal yr BP, which represents the first local evidence for the Antarctic Cold Reversal (ACR) in this region. On decadal to centennial timescales, the Late Glacial period was one marked by considerable climatic fluctuation and bi-directional environmental change, which has not been identified in previous studies for this region. Our study shows complex changes in both moisture and thermal conditions providing a more nuanced picture of the Late Glacial for the high Drakensburg.
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Affiliation(s)
- Malin E. Kylander
- Department of Geological Sciences and the Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
| | - Mikaela Holm
- Department of Geological Sciences and the Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
| | - Jennifer Fitchett
- School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Johannesburg, South Africa
| | - Stefan Grab
- School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, Johannesburg, South Africa
| | - Antonio Martinez Cortizas
- Facultade de Bioloxía, EcoPast (GI-1553), Universidad de Santiago de Compostela, Santiago de Compostela, Spain
| | - Elin Norström
- Department of Physical Geography and the Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
| | - Richard Bindler
- Department of Ecology and Environmental Sciences, Umeå University, Umeå, Sweden
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Basu S, Sanyal P, Pillai AAS, Ambili A. Response of grassland ecosystem to monsoonal precipitation variability during the Mid-Late Holocene: Inferences based on molecular isotopic records from Banni grassland, western India. PLoS One 2019; 14:e0212743. [PMID: 30995235 PMCID: PMC6469751 DOI: 10.1371/journal.pone.0212743] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 02/08/2019] [Indexed: 11/19/2022] Open
Abstract
Banni, located in the arid western India, is one of the largest tropical grasslands of the Asian continent. The net primary production in this grassland ecosystem is currently mediated by precipitation during the Indian summer monsoon (ISM). However, timing of the grassland expansion and its link to the intensity of monsoonal precipitation remains enigmatic due to the paucity of datasets. The major objective of this study is to understand the changes in monsoonal precipitation and vegetation for the last 4600 cal yr BP using hydrogen and carbon isotopic composition of n-alkanes (δDn-alkane and δ13Cn-alkane) measured from two core sediments (Chachi and Luna) in Banni region. The δ13CC29 and δ13CC31 values for Chachi core sediments vary from −30.9 ‰ to −27.2 ‰ and −34.4 ‰ to −25 ‰ respectively. The δ13Cn-alkane values from the core sediments are converted into %C4 plants based on a binary mixing model using the end-member δ13Cn-alkane values derived from the dominant modern vegetation in the Banni region. The prominent feature of the paleovegetation curve is the marked increase in the δ13Cn-alkane values after 2500 cal yr BP, which suggests proliferation of C4 grasses in this region. Similar changes after 2500 cal yr BP have also been observed in the δDn-alkane values. The δDC29 values are used to calculate δD value of paleoprecipitation that varied from 10 ‰ to −60.2 ‰. A significant increase in the δD values of paleoprecipitation (ca. 25 ‰) indicates a weakened ISM precipitation after ca. 2500 cal yr BP. The regional aridification and frequent fire events may have helped the expansion of C4 plant dominated grassland ecosystem in Banni region. Correlation between paleoclimatic records suggests that the southward migration of intertropical convergence zone and more frequent warm phases of El-Nino Southern Oscillation have triggered the weakening of monsoonal precipitation in the tropical region.
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Affiliation(s)
- Sayak Basu
- Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India
- * E-mail:
| | - Prasanta Sanyal
- Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India
| | - Anusree A. S. Pillai
- National Centre for Biological Sciences (NCBS), GKVK Campus, Bangalore, Karnataka, India
- Manipal Institute of Higher Education, Madhav Nahar, Manipal, Karnataka, India
| | - Anoop Ambili
- Indian Institute of Science Education and Research Kolkata, Mohanpur, West Bengal, India
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9
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Magill CR, Eglinton G, Eglinton TI. Isotopic variance among plant lipid homologues correlates with biodiversity patterns of their source communities. PLoS One 2019; 14:e0212211. [PMID: 30811453 PMCID: PMC6392421 DOI: 10.1371/journal.pone.0212211] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Accepted: 01/29/2019] [Indexed: 11/18/2022] Open
Abstract
Plant diversity is important to human welfare worldwide, and this importance is exemplified in subtropical and tropical [(sub)tropical] African savannahs where regional biodiversity enhances the sustaining provision of basic ecosystem services available to millions of residents. Yet, there is a critical lack of knowledge about how savannahs respond to climate change. Here, we report the relationships between savannah vegetation structure, species richness, and bioclimatic variables as recorded by plant biochemical fossils, called biomarkers. Our analyses reveal that the stable carbon isotope composition (δ13C) of discrete sedimentary plant biomarkers reflects vegetation structure, but the isotopic range among plant biomarkers–which we call LEaf Wax Isotopic Spread (LEWIS)–reflects species richness. Analyses of individual biomarker δ13C values and LEWIS for downcore sediments recovered from southeast Africa reveal that the region’s species richness mirrored trends in atmospheric carbon dioxide concentration (pCO2) throughout the last 25,000 years. This suggests that increasing pCO2 levels during post-industrialization may prompt future declines in regional biodiversity (1–10 species per unit CO2 p.p.m.v.) through imminent habitat loss or extinction.
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Affiliation(s)
- Clayton R. Magill
- Lyell Centre, Heriot-Watt University, Edinburgh, United Kingdom
- Geological Institute, ETH Zürich, Zurich, Switzerland
- * E-mail:
| | - Geoffrey Eglinton
- Department of Earth Sciences, University of Bristol, Bristol, United Kingdom
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10
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A Window into Africa’s Past Hydroclimates: The SISAL_v1 Database Contribution. QUATERNARY 2019. [DOI: 10.3390/quat2010004] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Africa spans the hemispheres from temperate region to temperate region and has a long history of hominin evolution. Although the number of Quaternary palaeoclimatic records from the continent is increasing, much of the history of spatial and temporal climatic variability is still debated. Speleothems, as archives of terrestrial hydroclimate variability, can help reveal this history. Here we review the progress made to date, with a focus on the first version of the Speleothem Isotopes Synthesis and AnaLysis (SISAL) database. The geology of Africa has limited development of large karst regions to four areas: along the northern coast bordering the Mediterranean, eastern Africa and the Horn of Africa, southwestern Africa and southern Africa. Exploitation of the speleothem palaeoclimate archives in these regions is uneven, with long histories of research, e.g., in South Africa, but large areas with no investigations such as West Africa. Consequently, the evidence of past climate change reviewed here is irregularly sampled in both time and space. Nevertheless, we show evidence of migration of the monsoon belt, with enhanced rainfall during interglacials observed in northeast Africa, southern Arabia and the northern part of southern Africa. Evidence from eastern Africa indicates significant decadal and centennial scale rainfall variability. In northwestern and southern Africa, precession and eccentricity influence speleothem growth, largely through changing synoptic storm activity.
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11
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Fox DL, Pau S, Taylor L, Strömberg CAE, Osborne CP, Bradshaw C, Conn S, Beerling DJ, Still CJ. Climatic Controls on C4 Grassland Distributions During the Neogene: A Model-Data Comparison. Front Ecol Evol 2018. [DOI: 10.3389/fevo.2018.00147] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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12
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Caley T, Extier T, Collins JA, Schefuß E, Dupont L, Malaizé B, Rossignol L, Souron A, McClymont EL, Jimenez-Espejo FJ, García-Comas C, Eynaud F, Martinez P, Roche DM, Jorry SJ, Charlier K, Wary M, Gourves PY, Billy I, Giraudeau J. A two-million-year-long hydroclimatic context for hominin evolution in southeastern Africa. Nature 2018; 560:76-79. [PMID: 29988081 DOI: 10.1038/s41586-018-0309-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 04/25/2018] [Indexed: 12/21/2022]
Abstract
The past two million years of eastern African climate variability is currently poorly constrained, despite interest in understanding its assumed role in early human evolution1-4. Rare palaeoclimate records from northeastern Africa suggest progressively drier conditions2,5 or a stable hydroclimate6. By contrast, records from Lake Malawi in tropical southeastern Africa reveal a trend of a progressively wetter climate over the past 1.3 million years7,8. The climatic forcings that controlled these past hydrological changes are also a matter of debate. Some studies suggest a dominant local insolation forcing on hydrological changes9-11, whereas others infer a potential influence of sea surface temperature changes in the Indian Ocean8,12,13. Here we show that the hydroclimate in southeastern Africa (20-25° S) is controlled by interplay between low-latitude insolation forcing (precession and eccentricity) and changes in ice volume at high latitudes. Our results are based on a multiple-proxy reconstruction of hydrological changes in the Limpopo River catchment, combined with a reconstruction of sea surface temperature in the southwestern Indian Ocean for the past 2.14 million years. We find a long-term aridification in the Limpopo catchment between around 1 and 0.6 million years ago, opposite to the hydroclimatic evolution suggested by records from Lake Malawi. Our results, together with evidence of wetting at Lake Malawi, imply that the rainbelt contracted toward the Equator in response to increased ice volume at high latitudes. By reducing the extent of woodland or wetlands in terrestrial ecosystems, the observed changes in the hydroclimate of southeastern Africa-both in terms of its long-term state and marked precessional variability-could have had a role in the evolution of early hominins, particularly in the extinction of Paranthropus robustus.
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Affiliation(s)
- Thibaut Caley
- EPOC, UMR 5805, CNRS, University of Bordeaux, Pessac, France.
| | - Thomas Extier
- EPOC, UMR 5805, CNRS, University of Bordeaux, Pessac, France.,Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, Gif-sur-Yvette, France
| | - James A Collins
- GFZ - German Research Center for Geosciences, Section 5.1 Geomorphology, Organic Surface Geochemistry Laboratory, Potsdam, Germany.,Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany
| | - Enno Schefuß
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Lydie Dupont
- MARUM - Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany
| | - Bruno Malaizé
- EPOC, UMR 5805, CNRS, University of Bordeaux, Pessac, France
| | - Linda Rossignol
- EPOC, UMR 5805, CNRS, University of Bordeaux, Pessac, France
| | - Antoine Souron
- PACEA, UMR 5199, CNRS, University of Bordeaux, Pessac, France
| | | | | | - Carmen García-Comas
- Research and Development Center for Global Change, (JAMSTEC), Yokohama, Japan.,Ecology Group, University of Vic - Central University of Catalonia, Barcelona, Spain
| | | | | | - Didier M Roche
- Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Université Paris-Saclay, Gif-sur-Yvette, France.,Vrije Universiteit Amsterdam, Faculty of Science, Cluster Earth and Climate, Amsterdam, The Netherlands
| | - Stephan J Jorry
- Unité Géosciences Marines, Institut Français de Recherche pour l'Exploitation de la Mer (IFREMER), Plouzané, France
| | - Karine Charlier
- EPOC, UMR 5805, CNRS, University of Bordeaux, Pessac, France
| | - Mélanie Wary
- EPOC, UMR 5805, CNRS, University of Bordeaux, Pessac, France
| | | | - Isabelle Billy
- EPOC, UMR 5805, CNRS, University of Bordeaux, Pessac, France
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13
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Reconstructing vapor pressure deficit from leaf wax lipid molecular distributions. Sci Rep 2018; 8:3967. [PMID: 29500405 PMCID: PMC5834636 DOI: 10.1038/s41598-018-21959-w] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2017] [Accepted: 02/13/2018] [Indexed: 11/08/2022] Open
Abstract
Estimates of atmospheric moisture are critical for understanding the links and feedbacks between atmospheric CO2 and global climate. At present, there are few quantitative moisture proxies that are applicable to deep time. We present a new proxy for atmospheric moisture derived from modern climate and leaf biomarker data from North and Central America. Plants have a direct genetic pathway to regulate the production of lipids in response to osmotic stress, which is manifested in a change in the distribution of simple aliphatic lipids such as n-alkanes. The Average Chain Length (ACL) of these lipids is therefore statistically related to mean annual vapor pressure deficit (VPDav), enabling quantitative reconstruction of VPD from sedimentary n-alkanes. We apply this transfer function to the Armantes section of the Calatayud-Daroca Basin in Central Spain, that spans the Middle Miocene Climatic Optimum (MMCO) and the Middle Miocene Climate Transition (MMCT). Reconstructed VPDav rises from 0.13 to 0.92 kPa between 16.5 and 12.4 Ma, indicating a substantial drying through the MMCT. These data are consistent with fossil assemblages and mammalian stable isotope data, highlighting the utility of this new organic molecular tool for quantifying hydrologic variability over geologic timescales.
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14
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Linder HP. East African Cenozoic vegetation history. Evol Anthropol 2017; 26:300-312. [DOI: 10.1002/evan.21570] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/13/2017] [Indexed: 11/10/2022]
Affiliation(s)
- Hans Peter Linder
- Institute of Systematic and Evolutionary Botany; University of Zurich; Zollikerstrasse Switzerland
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15
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Simon MH, Ziegler M, Bosmans J, Barker S, Reason CJC, Hall IR. Eastern South African hydroclimate over the past 270,000 years. Sci Rep 2015; 5:18153. [PMID: 26686943 PMCID: PMC4685309 DOI: 10.1038/srep18153] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Accepted: 11/09/2015] [Indexed: 11/13/2022] Open
Abstract
Processes that control the hydrological balance in eastern South Africa on orbital to millennial timescales remain poorly understood because proxy records documenting its variability at high resolution are scarce. In this work, we present a detailed 270,000 year-long record of terrestrial climate variability in the KwaZulu-Natal province based on elemental ratios of Fe/K from the southwest Indian Ocean, derived from X-ray fluorescence core scanning. Eastern South African climate variability on these time scales reflects both the long-term effect of regional insolation changes driven by orbital precession and the effects associated with high-latitude abrupt climate forcing over the past two glacial-interglacial cycles, including millennial-scale events not previously identified. Rapid changes towards more humid conditions in eastern South Africa as the Northern Hemisphere entered phases of extreme cooling were potentially driven by a combination of warming in the Agulhas Current and shifts of the subtropical anticyclones. These climate oscillations appear coherent with other Southern Hemisphere records but are anti-phased with respect to the East Asian Monsoon. Numerical modelling results reveal that higher precipitation in the KwaZulu-Natal province during precession maxima is driven by a combination of increased local evaporation and elevated moisture transport into eastern South Africa from the coast of Mozambique.
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Affiliation(s)
- Margit H Simon
- School of Earth and Ocean Sciences, Cardiff University, Cardiff, CF10 3AT, United Kingdom
| | - Martin Ziegler
- School of Earth and Ocean Sciences, Cardiff University, Cardiff, CF10 3AT, United Kingdom.,Faculty of Geosciences, Utrecht University, 3584 CD Utrecht, Netherlands
| | - Joyce Bosmans
- Faculty of Geosciences, Utrecht University, 3584 CD Utrecht, Netherlands
| | - Stephen Barker
- School of Earth and Ocean Sciences, Cardiff University, Cardiff, CF10 3AT, United Kingdom
| | - Chris J C Reason
- Department of Oceanography, University of Cape Town, South Africa
| | - Ian R Hall
- School of Earth and Ocean Sciences, Cardiff University, Cardiff, CF10 3AT, United Kingdom
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16
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Continuous 1.3-million-year record of East African hydroclimate, and implications for patterns of evolution and biodiversity. Proc Natl Acad Sci U S A 2015; 112:15568-73. [PMID: 26644580 DOI: 10.1073/pnas.1512864112] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The transport of moisture in the tropics is a critical process for the global energy budget and on geologic timescales, has markedly influenced continental landscapes, migratory pathways, and biological evolution. Here we present a continuous, first-of-its-kind 1.3-My record of continental hydroclimate and lake-level variability derived from drill core data from Lake Malawi, East Africa (9-15° S). Over the Quaternary, we observe dramatic shifts in effective moisture, resulting in large-scale changes in one of the world's largest lakes and most diverse freshwater ecosystems. Results show evidence for 24 lake level drops of more than 200 m during the Late Quaternary, including 15 lowstands when water levels were more than 400 m lower than modern. A dramatic shift is observed at the Mid-Pleistocene Transition (MPT), consistent with far-field climate forcing, which separates vastly different hydroclimate regimes before and after ∼800,000 years ago. Before 800 ka, lake levels were lower, indicating a climate drier than today, and water levels changed frequently. Following the MPT high-amplitude lake level variations dominate the record. From 800 to 100 ka, a deep, often overfilled lake occupied the basin, indicating a wetter climate, but these highstands were interrupted by prolonged intervals of extreme drought. Periods of high lake level are observed during times of high eccentricity. The extreme hydroclimate variability exerted a profound influence on the Lake Malawi endemic cichlid fish species flock; the geographically extensive habitat reconfiguration provided novel ecological opportunities, enabling new populations to differentiate rapidly to distinct species.
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17
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Life form-specific gradients in compound-specific hydrogen isotope ratios of modern leaf waxes along a North American Monsoonal transect. Oecologia 2015; 179:981-97. [DOI: 10.1007/s00442-015-3432-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2013] [Accepted: 08/15/2015] [Indexed: 10/23/2022]
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18
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Woodborne S, Hall G, Robertson I, Patrut A, Rouault M, Loader NJ, Hofmeyr M. A 1000-Year Carbon Isotope Rainfall Proxy Record from South African Baobab Trees (Adansonia digitata L.). PLoS One 2015; 10:e0124202. [PMID: 25970402 PMCID: PMC4430471 DOI: 10.1371/journal.pone.0124202] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 03/10/2015] [Indexed: 11/24/2022] Open
Abstract
A proxy rainfall record for northeastern South Africa based on carbon isotope analysis of four baobab (Adansonia digitata L.) trees shows centennial and decadal scale variability over the last 1,000 years. The record is in good agreement with a 200-year tree ring record from Zimbabwe, and it indicates the existence of a rainfall dipole between the summer and winter rainfall areas of South Africa. The wettest period was c. AD 1075 in the Medieval Warm Period, and the driest periods were c. AD 1635, c. AD 1695 and c. AD1805 during the Little Ice Age. Decadal-scale variability suggests that the rainfall forcing mechanisms are a complex interaction between proximal and distal factors. Periods of higher rainfall are significantly associated with lower sea-surface temperatures in the Agulhas Current core region and a negative Dipole Moment Index in the Indian Ocean. The correlation between rainfall and the El Niño/Southern Oscillation Index is non-static. Wetter conditions are associated with predominantly El Niño conditions over most of the record, but since about AD 1970 this relationship inverted and wet conditions are currently associated with la Nina conditions. The effect of both proximal and distal oceanic influences are insufficient to explain the rainfall regime shift between the Medieval Warm Period and the Little Ice Age, and the evidence suggests that this was the result of a northward shift of the subtropical westerlies rather than a southward shift of the Intertropical Convergence Zone.
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Affiliation(s)
- Stephan Woodborne
- iThemba LABS, Private Bag 11, Wits 2050, South Africa
- Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
- * E-mail:
| | - Grant Hall
- Mammal Research Institute, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
| | - Iain Robertson
- Department of Geography, Swansea University, Swansea SA2 8PP, United Kingdom
| | - Adrian Patrut
- Faculty of Chemistry, Babes-Bolyai University, Arany Janos 11, 400028 Cluj-Napoca, Romania
| | - Mathieu Rouault
- Nansen-Tutu Center for Marine Environment, University of Cape Town, Cape Town, South Africa
- Dept of Oceanography, Mare Institute, University of Cape Town, Cape Town, South Africa
| | - Neil J. Loader
- Department of Geography, Swansea University, Swansea SA2 8PP, United Kingdom
| | - Michele Hofmeyr
- SANParks Scientific Services, Pvt Bag X402, Skukuza, 1350, South Africa
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19
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Sachse D, Dawson TE, Kahmen A. Seasonal variation of leaf wax n-alkane production and δ(2)H values from the evergreen oak tree, Quercus agrifolia. ISOTOPES IN ENVIRONMENTAL AND HEALTH STUDIES 2015; 51:124-142. [PMID: 25704898 DOI: 10.1080/10256016.2015.1011636] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In order to understand the timing of leaf wax synthesis in higher plants, we analysed the variability in leaf wax n-alkane concentration, composition (expressed as average chain length (ACL)), and δ(2)Hwax values as well as plant source water δ(2)H values (xylem and leaf water) in the evergreen tree Quercus agrifolia over a period of 9 months, beginning with leaf flush. We identified three distinct periods of leaf development with the first month following leaf flush being characterized by de novo synthesis and possibly removal of n-alkanes. During the following 3 months, n-alkane concentrations increased sevenfold and δ(2)Hwax and ACL values increased, suggesting this period was the major leaf wax n-alkane formation period. During the remaining 4 months of the experiment, stable values suggest cessation of leaf wax n-alkane formation. We find that n-alkane synthesis in Q. agrifolia takes place over 4 months, substantially longer than that observed for deciduous trees.
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Affiliation(s)
- Dirk Sachse
- a Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences , Section 5.1: Geomorphology, Potsdam , Germany
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20
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Otto-Bliesner BL, Russell JM, Clark PU, Liu Z, Overpeck JT, Konecky B, deMenocal P, Nicholson SE, He F, Lu Z. Coherent changes of southeastern equatorial and northern African rainfall during the last deglaciation. Science 2014; 346:1223-7. [PMID: 25477460 DOI: 10.1126/science.1259531] [Citation(s) in RCA: 146] [Impact Index Per Article: 14.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
During the last deglaciation, wetter conditions developed abruptly ~14,700 years ago in southeastern equatorial and northern Africa and continued into the Holocene. Explaining the abrupt onset and hemispheric coherence of this early African Humid Period is challenging due to opposing seasonal insolation patterns. In this work, we use a transient simulation with a climate model that provides a mechanistic understanding of deglacial tropical African precipitation changes. Our results show that meltwater-induced reduction in the Atlantic meridional overturning circulation (AMOC) during the early deglaciation suppressed precipitation in both regions. Once the AMOC reestablished, wetter conditions developed north of the equator in response to high summer insolation and increasing greenhouse gas (GHG) concentrations, whereas wetter conditions south of the equator were a response primarily to the GHG increase.
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Affiliation(s)
- Bette L Otto-Bliesner
- Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, CO 80307-3000, USA.
| | - James M Russell
- Department of Earth, Environmental, and Planetary Sciences, Brown University, Providence, RI 02912, USA
| | - Peter U Clark
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA
| | - Zhengyu Liu
- Center for Climatic Research and Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA. Laboratory for Climate, Ocean and Atmosphere Studies, School of Physics, Peking University, Beijing 100871, P. R. China
| | - Jonathan T Overpeck
- Department of Geosciences and Institute of the Environment, University of Arizona, Tucson, AZ 85721, USA
| | - Bronwen Konecky
- College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, USA. Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO 80309, USA
| | - Peter deMenocal
- Department of Earth and Environmental Sciences, Columbia University, New York, NY 10027, USA
| | - Sharon E Nicholson
- Department of Earth, Ocean, and Atmospheric Science, Florida State University, Tallahassee, FL 32306, USA
| | - Feng He
- Center for Climatic Research and Department of Atmospheric and Oceanic Sciences, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Zhengyao Lu
- Laboratory for Climate, Ocean and Atmosphere Studies, School of Physics, Peking University, Beijing 100871, P. R. China
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21
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Gao L, Edwards EJ, Zeng Y, Huang Y. Major evolutionary trends in hydrogen isotope fractionation of vascular plant leaf waxes. PLoS One 2014; 9:e112610. [PMID: 25402476 PMCID: PMC4234459 DOI: 10.1371/journal.pone.0112610] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 10/15/2014] [Indexed: 11/23/2022] Open
Abstract
Hydrogen isotopic ratios of terrestrial plant leaf waxes (δD) have been widely used for paleoclimate reconstructions. However, underlying controls for the observed large variations in leaf wax δD values in different terrestrial vascular plants are still poorly understood, hampering quantitative paleoclimate interpretation. Here we report plant leaf wax and source water δD values from 102 plant species grown in a common environment (New York Botanic Garden), chosen to represent all the major lineages of terrestrial vascular plants and multiple origins of common plant growth forms. We found that leaf wax hydrogen isotope fractionation relative to plant source water is best explained by membership in particular lineages, rather than by growth forms as previously suggested. Monocots, and in particular one clade of grasses, display consistently greater hydrogen isotopic fractionation than all other vascular plants, whereas lycopods, representing the earlier-diverging vascular plant lineage, display the smallest fractionation. Data from greenhouse experiments and field samples suggest that the changing leaf wax hydrogen isotopic fractionation in different terrestrial vascular plants may be related to different strategies in allocating photosynthetic substrates for metabolic and biosynthetic functions, and potential leaf water isotopic differences.
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Affiliation(s)
- Li Gao
- Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island, United States of America
| | - Erika J. Edwards
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island, United States of America
| | - Yongbo Zeng
- Department of Electrical, Computer, and Biomedical Engineering, University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Yongsong Huang
- Department of Earth, Environmental and Planetary Sciences, Brown University, Providence, Rhode Island, United States of America
- * E-mail:
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22
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North Atlantic forcing of tropical Indian Ocean climate. Nature 2014; 509:76-80. [PMID: 24784218 DOI: 10.1038/nature13196] [Citation(s) in RCA: 160] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2013] [Accepted: 02/28/2014] [Indexed: 11/09/2022]
Abstract
The response of the tropical climate in the Indian Ocean realm to abrupt climate change events in the North Atlantic Ocean is contentious. Repositioning of the intertropical convergence zone is thought to have been responsible for changes in tropical hydroclimate during North Atlantic cold spells, but the dearth of high-resolution records outside the monsoon realm in the Indian Ocean precludes a full understanding of this remote relationship and its underlying mechanisms. Here we show that slowdowns of the Atlantic meridional overturning circulation during Heinrich stadials and the Younger Dryas stadial affected the tropical Indian Ocean hydroclimate through changes to the Hadley circulation including a southward shift in the rising branch (the intertropical convergence zone) and an overall weakening over the southern Indian Ocean. Our results are based on new, high-resolution sea surface temperature and seawater oxygen isotope records of well-dated sedimentary archives from the tropical eastern Indian Ocean for the past 45,000 years, combined with climate model simulations of Atlantic circulation slowdown under Marine Isotope Stages 2 and 3 boundary conditions. Similar conditions in the east and west of the basin rule out a zonal dipole structure as the dominant forcing of the tropical Indian Ocean hydroclimate of millennial-scale events. Results from our simulations and proxy data suggest dry conditions in the northern Indian Ocean realm and wet and warm conditions in the southern realm during North Atlantic cold spells.
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23
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Development of Middle Stone Age innovation linked to rapid climate change. Nat Commun 2013; 4:1905. [PMID: 23695699 PMCID: PMC4354264 DOI: 10.1038/ncomms2897] [Citation(s) in RCA: 137] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2012] [Accepted: 04/16/2013] [Indexed: 12/04/2022] Open
Abstract
The development of modernity in early human populations has been linked to pulsed phases of technological and behavioural innovation within the Middle Stone Age of South Africa. However, the trigger for these intermittent pulses of technological innovation is an enigma. Here we show that, contrary to some previous studies, the occurrence of innovation was tightly linked to abrupt climate change. Major innovational pulses occurred at times when South African climate changed rapidly towards more humid conditions, while northern sub-Saharan Africa experienced widespread droughts, as the Northern Hemisphere entered phases of extreme cooling. These millennial-scale teleconnections resulted from the bipolar seesaw behaviour of the Atlantic Ocean related to changes in the ocean circulation. These conditions led to humid pulses in South Africa and potentially to the creation of favourable environmental conditions. This strongly implies that innovational pulses of early modern human behaviour were climatically influenced and linked to the adoption of refugia. The South African archaeological record contains evidence of the early flourishing of the human mind. Ziegler et al. provide new paleoclimate reconstructions, which suggest that rapid fluctuations in global climate have played a key role in the evolution of these early human cultures.
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Mercader J, Bennett T, Esselmont C, Simpson S, Walde D. Phytoliths from Middle Stone Age habitats in the Mozambican Rift (105–29 ka). J Hum Evol 2013; 64:328-36. [PMID: 23507525 DOI: 10.1016/j.jhevol.2012.10.013] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Revised: 10/16/2012] [Accepted: 10/22/2012] [Indexed: 10/27/2022]
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