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Advancing Leaf Wax Paleohydrology: From Plant Source to Sediment Sink

Freimuth, Erika Jacob
http://orcid.org/0000-0001-8331-0394
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535381306803793

Abstract Details

2018, PhD, University of Cincinnati, Arts and Sciences: Geology.
Plant wax hydrogen isotopes (dDwax) are important archives of water isotopes in the geologic past. Plant waxes are common in lacustrine sediments, providing widely distributed terrestrial records of hydrologic change in locations where other water isotope proxies (e.g., ice sheets, cave deposits) do not exist. However, application of dDwax to reconstruct past precipitation hydrogen isotopes (dDp) is subject to uncertainties resulting from modification of original water isotope signals in plants and sediments. This dissertation addresses several of these uncertainties through a series of studies that identify controls on this proxy system at increasing spatial scales, from individual plants to a single bog catchment to a regional survey of multiple lake catchments. Chapter 2 examines the seasonal timing of leaf wax production for two commonly used paleohydrology proxies, n-alkanes and n-alkanoic acids. The goals of this project are to constrain the drivers of seasonal dDwax variability among tree species and to determine whether leaf waxes in temperate forests record seasonally-biased precipitation. This study monitors the dD of environmental and plant waters and resulting leaf waxes as they evolve over a growing season from bud break to leaf fall at Brown’s Lake Bog (BLB), Ohio, USA. This is the first study to track seasonal changes in both n-alkanes and n-alkanoic acids, and offers novel insight into systematic differences in water isotope fractionation and the timing, duration and amount of wax production between compound classes. Chapter 3 compares the abundance, molecular distribution and isotopic composition (dD and d13C) of n-alkanes and n-alkanoic acids in bog sediments with all major plant species growing in the catchment of BLB. This project aims to identify factors that influence the integration of leaf waxes from source (plants) to sink (sediments) in a single catchment. Results of this study offer insight into sediment bias toward particular plant sources and a framework for estimating apparent fractionation (eapp) between water and wax dD in temperate forested settings. Chapter 4 expands from a single catchment to asses dDwax variability at the sediment level for multiple lakes across the Adirondack Mountains, NY, USA. We evaluate plant waxes in surface sediments from 12 Adirondack lakes that have similar dDp but a range of different catchment properties. The goals of this study are to 1) quantify the variability in sediment dDwax in the absence of major differences in dDp among sites within the same region; 2) identify possible catchment-level drivers of this variability (e.g., vegetation cover, fluvial complexity, depositional setting); and 3) compare the molecular and dD composition of two plant wax compounds (n-alkanes and n-alkanoic acids) to assess potential differences in their sources. Results from this project underscore the influence that site-specific factors can have on dDwax records. This dissertation identifies factors and processes that influence the biological production, spatial integration and regional variation in dDwax signals from forested temperate settings. The results reveal promising directions for future proxy research, and ultimately will contribute to reducing uncertainties inherent in proxy-based observations of hydrologic responses to climate perturbations in the geologic past.
Aaron Diefendorf, Ph.D. (Committee Chair)
Brooke Crowley, Ph.D. (Committee Member)
Thomas Lowell, Ph.D. (Committee Member)
Broxton W. Bird, Ph.D. (Committee Member)
Dylan Ward, Ph.D. (Committee Member)
155 p.
Geochemistry
Paleohydrology; Biomarkers; Stable isotopes; Lake sediment

Recommended Citations

Citations

  • Freimuth, E. J. (2018). Advancing Leaf Wax Paleohydrology: From Plant Source to Sediment Sink [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535381306803793

    APA Style (7th edition)

  • Freimuth, Erika. Advancing Leaf Wax Paleohydrology: From Plant Source to Sediment Sink. 2018. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535381306803793.

    MLA Style (8th edition)

  • Freimuth, Erika. "Advancing Leaf Wax Paleohydrology: From Plant Source to Sediment Sink." Doctoral dissertation, University of Cincinnati, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535381306803793

    Chicago Manual of Style (17th edition)

ucin1535381306803793
148
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