1
|
Milligan JN, Flynn AG, Wagner JD, Kouwenberg LL, Barclay RS, Byars BW, Dunn RE, White JD, Zechmann B, Peppe DJ. Quantifying the effect of shade on cuticle morphology and carbon isotopes of sycamores: present and past. AMERICAN JOURNAL OF BOTANY 2021; 108:2435-2451. [PMID: 34636420 PMCID: PMC9306692 DOI: 10.1002/ajb2.1772] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 09/16/2021] [Accepted: 09/16/2021] [Indexed: 06/13/2023]
Abstract
PREMISE Reconstructing the light environment and architecture of the plant canopy from the fossil record requires the use of proxies, such as those derived from cell wall undulation, cell size, and carbon isotopes. All approaches assume that plant taxa will respond predictably to changes in light environments. However, most species-level studies looking at cell wall undulation only consider "sun" or "shade" leaves; therefore, we need a fully quantitative taxon-specific method. METHODS We quantified the response of cell wall undulation, cell size, and carbon isotopes of Platanus occidentalis using two experimental setups: (1) two growth chambers at low and high light and (2) a series of outdoor growth experiments using green and black shade cloth at different densities. We then developed and applied a proxy for daily light integral (DLI) to fossil Platanites leaves from two early Paleocene floras from the San Juan Basin in New Mexico. RESULTS All traits responded to light environment. Cell wall undulation was the most useful trait for reconstructing DLI in the geological record. Median reconstructed DLI from early Paleocene leaves was ~44 mol m-2 d-1 , with values from 28 to 54 mol m-2 d-1 . CONCLUSIONS Cell wall undulation of P. occidentalis is a robust, quantifiable measurement of light environment that can be used to reconstruct the paleo-light environment from fossil leaves. The distribution of high DLI values from fossil leaves may provide information on canopy architecture; indicating that either (1) most of the canopy mass is within the upper portion of the crown or (2) leaves exposed to more sunlight are preferentially preserved.
Collapse
Affiliation(s)
- Joseph N. Milligan
- Terrestrial Paleoclimatology Research Group, Department of GeosciencesBaylor UniversityWacoTXUSA
| | - Andrew G. Flynn
- Terrestrial Paleoclimatology Research Group, Department of GeosciencesBaylor UniversityWacoTXUSA
| | - Jennifer D. Wagner
- Department of Integrative BiologyUniversity of California Berkeley, and UC Museum of PaleontologyBerkeleyCAUSA
| | | | - Richard S. Barclay
- Department of PaleobiologyNational Museum of Natural History, Smithsonian Institution, 10th & Constitution Avenue NWWashingtonD.C.USA
| | | | - Regan E. Dunn
- Natural History Museums of Los Angeles County, La Brea Tar PitsLos AngelesCAUSA
| | | | - Bernd Zechmann
- Center for Microscopy and ImagingBaylor UniversityWacoTXUSA
| | - Daniel J. Peppe
- Terrestrial Paleoclimatology Research Group, Department of GeosciencesBaylor UniversityWacoTXUSA
| |
Collapse
|
2
|
Abstract
During the Eocene, high-latitude regions were much warmer than today and substantial polar ice sheets were lacking. Indeed, the initiation of significant polar ice sheets near the end of the Eocene has been closely linked to global cooling. Here, we examine the relationship between global temperatures and continental-scale polar ice sheets following the establishment of ice sheets on Antarctica ∼34 million years ago, using records of surface temperatures from around the world. We find that high-latitude temperatures were almost as warm after the initiation of Antarctic glaciation as before, challenging our basic understanding of how climate works, and of the development of climate and ice volume through time. Falling atmospheric CO2 levels led to cooling through the Eocene and the expansion of Antarctic ice sheets close to their modern size near the beginning of the Oligocene, a period of poorly documented climate. Here, we present a record of climate evolution across the entire Oligocene (33.9 to 23.0 Ma) based on TEX86 sea surface temperature (SST) estimates from southwestern Atlantic Deep Sea Drilling Project Site 516 (paleolatitude ∼36°S) and western equatorial Atlantic Ocean Drilling Project Site 929 (paleolatitude ∼0°), combined with a compilation of existing SST records and climate modeling. In this relatively low CO2 Oligocene world (∼300 to 700 ppm), warm climates similar to those of the late Eocene continued with only brief interruptions, while the Antarctic ice sheet waxed and waned. SSTs are spatially heterogenous, but generally support late Oligocene warming coincident with declining atmospheric CO2. This Oligocene warmth, especially at high latitudes, belies a simple relationship between climate and atmospheric CO2 and/or ocean gateways, and is only partially explained by current climate models. Although the dominant climate drivers of this enigmatic Oligocene world remain unclear, our results help fill a gap in understanding past Cenozoic climates and the way long-term climate sensitivity responded to varying background climate states.
Collapse
|
3
|
Westerhold T, Marwan N, Drury AJ, Liebrand D, Agnini C, Anagnostou E, Barnet JSK, Bohaty SM, De Vleeschouwer D, Florindo F, Frederichs T, Hodell DA, Holbourn AE, Kroon D, Lauretano V, Littler K, Lourens LJ, Lyle M, Pälike H, Röhl U, Tian J, Wilkens RH, Wilson PA, Zachos JC. An astronomically dated record of Earth’s climate and its predictability over the last 66 million years. Science 2020; 369:1383-1387. [DOI: 10.1126/science.aba6853] [Citation(s) in RCA: 352] [Impact Index Per Article: 88.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2019] [Accepted: 07/28/2020] [Indexed: 11/02/2022]
Abstract
Much of our understanding of Earth’s past climate comes from the measurement of oxygen and carbon isotope variations in deep-sea benthic foraminifera. Yet, long intervals in existing records lack the temporal resolution and age control needed to thoroughly categorize climate states of the Cenozoic era and to study their dynamics. Here, we present a new, highly resolved, astronomically dated, continuous composite of benthic foraminifer isotope records developed in our laboratories. Four climate states—Hothouse, Warmhouse, Coolhouse, Icehouse—are identified on the basis of their distinctive response to astronomical forcing depending on greenhouse gas concentrations and polar ice sheet volume. Statistical analysis of the nonlinear behavior encoded in our record reveals the key role that polar ice volume plays in the predictability of Cenozoic climate dynamics.
Collapse
Affiliation(s)
- Thomas Westerhold
- MARUM–Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
| | - Norbert Marwan
- Potsdam Institute for Climate Impact Research (PIK), Member of the Leibniz Association, 14412 Potsdam, Germany
- University of Potsdam, Institute of Geosciences, 14469 Potsdam, Germany
| | - Anna Joy Drury
- MARUM–Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
- Department of Earth Sciences, University College London, Gower Street, London WC1E 6BT, UK
| | - Diederik Liebrand
- MARUM–Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
| | - Claudia Agnini
- Dipartimento di Geoscienze, Università degli Studi di Padova, Via Gradenigo 6, I-35131 Padova, Italy
| | - Eleni Anagnostou
- GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, Wischhofstrasse 1-3, 24148 Kiel, Germany
| | - James S. K. Barnet
- Camborne School of Mines and Environment and Sustainability Institute, University of Exeter, Penryn Campus, Penryn, UK
- School of Earth and Environmental Sciences, University of St Andrews, St Andrews, Scotland, UK
| | - Steven M. Bohaty
- Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, UK
| | - David De Vleeschouwer
- MARUM–Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
| | - Fabio Florindo
- Istituto Nazionale di Geofisica e Vulcanologia, INGV, Rome, Italy
- Institute for Climate Change Solutions, Pesaro e Urbino, Italy
| | - Thomas Frederichs
- MARUM–Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
- Faculty of Geosciences, University of Bremen, Bremen, Germany
| | - David A. Hodell
- Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, University of Cambridge, Cambridge, UK
| | - Ann E. Holbourn
- Institute of Geosciences, Christian-Albrechts-University, Kiel 24118, Germany
| | - Dick Kroon
- School of GeoSciences, University of Edinburgh, Edinburgh, UK
| | | | - Kate Littler
- Camborne School of Mines and Environment and Sustainability Institute, University of Exeter, Penryn Campus, Penryn, UK
| | - Lucas J. Lourens
- Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Princetonlaan 8a, 3584 CB Utrecht, Netherlands
| | - Mitchell Lyle
- College of Earth, Ocean, and Atmospheric Science, Oregon State University, Corvallis, OR 97331, USA
| | - Heiko Pälike
- MARUM–Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
| | - Ursula Röhl
- MARUM–Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany
| | - Jun Tian
- State Key Laboratory of Marine Geology, Tongji University, Siping Road 1239, Shanghai 200092, PR China
| | - Roy H. Wilkens
- School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, HI 96822, USA
| | - Paul A. Wilson
- Ocean and Earth Science, University of Southampton, National Oceanography Centre, Southampton, UK
| | - James C. Zachos
- Department of Earth and Planetary Sciences, University of California, Santa Cruz, California, USA
| |
Collapse
|
4
|
Reichgelt T, D'Andrea WJ. Plant carbon assimilation rates in atmospheric CO 2 reconstructions. THE NEW PHYTOLOGIST 2019; 223:1844-1855. [PMID: 31081929 DOI: 10.1111/nph.15914] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 05/08/2019] [Indexed: 06/09/2023]
Abstract
Fossil plant gas-exchange-based CO2 reconstructions use carbon (C) assimilation rates of extant plant species as substitutes for assimilation rates of fossil plants. However, assumptions in model species adoption can lead to systematic error propagation. We used a dataset of c. 2500 extant species to investigate the role of phylogenetic relatedness and ecology in determining C assimilation, an essential variable in gas-exchange-based CO2 models. We evaluated the effect on random and systematic error propagation in atmospheric CO2 caused by adopting different model species. Phylogenetic relatedness, growth form, and solar exposure are important predictors of C assimilation rate. CO2 reconstructions that apply C assimilation rates from modern species based solely on phylogenetic relatedness to fossil species can result in CO2 estimates that are systematically biased by a factor of > 2. C assimilation rates used in CO2 reconstructions should be determined by averaging assimilation rates of modern plant species that are (1) in the same family and (2) have a similar habit and habitat as the fossil plant. In addition, systematic bias potential and random error propagation are greatly reduced when CO2 is reconstructed from multiple fossil plant species with different modern relatives at the same site.
Collapse
Affiliation(s)
- Tammo Reichgelt
- Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY, 10964, USA
| | - William J D'Andrea
- Lamont-Doherty Earth Observatory, Columbia University, 61 Route 9W, Palisades, NY, 10964, USA
| |
Collapse
|