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Leaf Wax Stable Isotopes as Paleovegetation and Paleohydrologic Proxies: From a Modern Calibration Study to a Paleoclimate Application

Suh, Yeon Jee
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1512045032087257

Abstract Details

2017, PhD, University of Cincinnati, Arts and Sciences: Geology.
Long-chain leaf wax carbon (δ13;Cwax) and hydrogen (δDwax) isotopic compositions in geologic archives are important tools for assessing Earth’s climate perturbations through time as they record vegetation and hydrologic conditions during plant growth, respectively. Interpreting sedimentary leaf wax isotopes requires modern calibration studies to identify and constrain vegetation and climate controls on leaf waxes and their carbon and hydrogen isotopes. Calibrations have been carried out for numerous sites worldwide to characterize the biological and environmental controls on leaf wax isotopes. However, uncertainties still exist including i) seasonal and canopy controls on (δ13;Cwax) values, and ii) integration and transport of leaf waxes from catchment to sediment sink. This lack of information confounds interpretations of leaf wax isotopes in geologic archives. In this dissertation, I present three related research projects that address uncertainties in forest-level (δ13;Cwax) variations to basin-level leaf wax integration to paleoclimate applications. In the first study (Chapter 2), I identified and quantified temporal and canopy variation in n-alkane (δ13;C values (δ13;Calk) from buds to leaves among different tree species in a single temperate deciduous forest. I then constrained how canopy height and openness affect n-alkane production and(δ13;Calk) values. The results from seasonal and canopy variations were then compared to leaf litter (δ13;Calk) values to verify if canopy leaves dominate the leaf litter as commonly assumed. In the second study (Chapter 3), I constrained controls on integration and transport of leaf waxes from Mississippi River Basin (MRB) catchment to the Gulf of Mexico (GOM) using GIS-enabled mixing model. Spatial distribution of carbon and hydrogen leaf wax isotopes (i.e. isoscapes) were developed in the MRB for the Holocene without human interferences removed. Production and transport parameters such as runoff, net primary productivity (NPP), distance to river mouth, and wax production were weighted to quantify sourcing of leaf waxes, which then were compared to measured values in the Holocene sediments from northeastern GOM (ODP 625B). In the final study (Chapter 4), I utilized the new insights from the modern calibration and isoscape modeling to investigate water and vegetation changes in the MRB for the last ~150 kyr using the ODP 625B core in the GOM. This time-interval includes Marine Isotope Stage (MIS) 5e, from 130 to 115 kyr, when global average temperatures were 2°C higher than today. I compared vegetation and hydrologic conditions during the MIS 5e to the Holocene, and within MIS 5 (5a-5e). The results were used to infer changes in source and transport of precipitation sources over the MRB in relation to major climatic changes, and how these changes may have controlled terrestrial vegetation composition. Overall, this dissertation constrains and quantifies(δ13;Calk) variations within a forest and during transport to marine sediments to bridge the gap between modern and geologic leaf waxes. The results of this dissertation will advance interpretation and application of leaf wax isotope-based proxy and contribute to better understanding of Earth’s ecologic and hydrologic responses to global or regional changes in climate conditions.
Aaron Diefendorf, Ph.D. (Committee Chair)
Brooke Crowley, Ph.D. (Committee Member)
Heather Graham, Ph.D. (Committee Member)
Thomas Lowell, Ph.D. (Committee Member)
Yurena Yanes, Ph.D. (Committee Member)
149 p.
Paleoclimate Science
stable carbon isotope; stable hydrogen isotope; Paleohydrology; Paleovegetation; GIS; Mississippi River

Recommended Citations

Citations

  • Suh, Y. J. (2017). Leaf Wax Stable Isotopes as Paleovegetation and Paleohydrologic Proxies: From a Modern Calibration Study to a Paleoclimate Application [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1512045032087257

    APA Style (7th edition)

  • Suh, Yeon Jee. Leaf Wax Stable Isotopes as Paleovegetation and Paleohydrologic Proxies: From a Modern Calibration Study to a Paleoclimate Application. 2017. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1512045032087257.

    MLA Style (8th edition)

  • Suh, Yeon Jee. "Leaf Wax Stable Isotopes as Paleovegetation and Paleohydrologic Proxies: From a Modern Calibration Study to a Paleoclimate Application." Doctoral dissertation, University of Cincinnati, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1512045032087257

    Chicago Manual of Style (17th edition)

ucin1512045032087257
216
© 2017, some rights reserved.Creative Commons License Leaf Wax Stable Isotopes as Paleovegetation and Paleohydrologic Proxies: From a Modern Calibration Study to a Paleoclimate Application by Yeon Jee Suh is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. Based on a work at etd.ohiolink.edu.
This open access ETD is published by University of Cincinnati and OhioLINK.