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Advancing Leaf Carbon Isotopes as a Paleo Proxy

Schlanser, Kristen M
http://orcid.org/0000-0001-7711-010X
http://rave.ohiolink.edu/etdc/view?acc_num=ucin159584747503534

Abstract Details

2020, PhD, University of Cincinnati, Arts and Sciences: Geology.
Plant biomarkers are primarily derived from leaf waxes, the protective waxy coating that covers the cuticular layer of a leaf. These biomarkers and their carbon isotope compositions are important paleoclimate and paleovegetation tools for investigating how landscapes, climate, and the carbon cycle have changed in the Earth’s past and provide a mechanism to understand how climate change may affect vegetation dynamics and ecosystems in the future. This dissertation addresses several key gaps in knowledge about plant-derived d13C values including the effect of paleo pCO2, paleovegetation signals contributing to leaf carbon isotopes (d13Cleaf) in the sedimentary record, and the carbon isotopic composition of integrated vegetation communities, such as forests and grasslands. The first study (Chapter 2) investigates the relationship between ?leaf and pCO2, and the efficacy of this relationship to reconstruct pCO2 through geologic time. We utilize the geologic record as a natural laboratory operating on timescales over which plants evolve (millions of years). We measure d13C values from sediment-derived leaf wax n-C29 alkanes, primarily from angiosperms, to calculate leaf carbon isotope fractionation (?leaf) across North American paleoflora sites. These sites represent 40 million years from the Late Cretaceous into the Oligocene and capture a wide range of pCO2 values (200 to 900 pmmV; Foster et al., 2017). Using the fossil leaves at each site, we account for age, floral composition, mean annual precipitation (MAP), and mean annual temperature (MAT), thereby providing a means to test the sensitivity of ?leaf to pCO2 independent of confounding biotic and abiotic effects on geologic timescales. The second study (Chapter 3) examines a possible strategy to infer the major taxon sources of sediment n-alkanes using paleobotanical sites in North America from the Paleogene that capture a range of forest types, with high, mixed, and low conifer abundance. We utilize d13C values preserved in terpenoids, plant biomarkers produced by angiosperms and gymnosperms whose values are sensitive to vegetation source, as vegetation end members, to provide a framework for considering the source of n-alkanes from other sites and times dominated by conifers, a division of gymnosperms. The third study (Chapter 4) compiles a global dataset of C3 and C4 d13Cleaf values, delineated by tropical, temperate, and polar zones, vegetation community (i.e., forests, woodlands, savannas, shrublands, grasslands, and deserts), and other climatic parameters that are often accessible within the geologic record (i.e., mean annual precipitation, mean annual temperature). With this dataset, we establish a framework to isotopically define vegetation communities for future geologic studies and explore the advantages and disadvantages of using d13Cleaf values to track key vegetation transitions between temperate forests and grasslands and tropical forests and savannas across the landscape and through geologic time. Through a series of studies, we investigate the geologic and modern controls on this proxy system to improve understanding on how climate and vegetation influence d13Cleaf and make significant advances towards future application of d13Cleaf as a paleoclimate and paleovegetation proxy.
Aaron Diefendorf, Ph.D. (Committee Chair)
Brooke Crowley, Ph.D. (Committee Member)
Thomas Lowell, Ph.D. (Committee Member)
Kevin Mueller, Ph.D. (Committee Member)
Dylan Ward, Ph.D. (Committee Member)
162 p.
Geology
carbon isotopes; conifers; Paleogene; Cretaceous; n-alkanes; leaf wax

Recommended Citations

Citations

  • Schlanser, K. M. (2020). Advancing Leaf Carbon Isotopes as a Paleo Proxy [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin159584747503534

    APA Style (7th edition)

  • Schlanser, Kristen. Advancing Leaf Carbon Isotopes as a Paleo Proxy. 2020. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin159584747503534.

    MLA Style (8th edition)

  • Schlanser, Kristen. "Advancing Leaf Carbon Isotopes as a Paleo Proxy." Doctoral dissertation, University of Cincinnati, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin159584747503534

    Chicago Manual of Style (17th edition)

ucin159584747503534
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This open access ETD is published by University of Cincinnati and OhioLINK.
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