| dc.description.abstract | This dissertation embodies the strengths of interdisciplinary science by bridging the fields of geology, ecology. Throughout the chapters of this work various perspectives are juxtaposed, demonstrating the value of research spanning disciplinary boundaries. Interdisciplinary methods combined with non-traditional paleoenvironmental archives have allowed this work to resolve long standing research barriers, such as (1) distinguishing human-set fires from wildfires in a paleorecord, (2) resolving the isotope systematics of bat guano archives, (3) improving our understanding of the ability of paleoclimate model simulations to reliably reconstruct fire activity, and (4) providing new methodological means for conservation-focused paleoecological research. The findings from this dissertation will advance future research using bat guano, stable isotopes, charcoal, and TraCE-21Ka climate model data as tools to understand paleoenvironmental conditions. Overall, the hope is that this dissertation will promote creativity and collaboration across scientific fields while also helping to inform natural resource management.
Chapter 1 provides a broad overview of this dissertation by introducing the main themes including the Holocene, stable isotope analysis, and paleoenvironmental archives. In chapter 2, I present bat guano deposits as a viable paleoenvironmental archive. I comprehensively examine isotopic compositions of a 12,000 year long bat guano core from Cave Springs Cave, Alabama as well as relevant isotopic data from other sources to improve our understanding of each ẟ13C, ẟ15N, and ẟ2H isotope system, the source-to-sink components of guano isotope pathways, and the fractionation occurring along each multi-step isotopic pathway from isotope sources (i.e., soil, atmosphere, rainfall) to guano formation. This chapter lays the groundwork for the application of isotopes of bat guano for paleoenvironmental research purposes. Chapter 3 analyzes ẟ13C and ẟ15N stable isotopes from American bison dung in the Great Plains region of the United States, to determine the amount of native versus invasive plants they are consuming. Chapter 4 similarly uses ẟ13C and ẟ15N stable isotopes but this time it is applied to native bee species across the United States. The goal of this chapter is to identify best methodological practices for future entomology research utilizing stable isotope analysis. Chapter 5 follows the theme of ẟ13C and ẟ15N stable isotope analysis applied to a modern, post-bomb bat guano core and compares these to state and county level land use data. This comparison provides an understanding of how agricultural land use changes cause bat diet shifts and provides insights relevant to bat conservation efforts. Chapter 6 investigates the mineralogy of bat guano. By examining mineral diagenesis and how bat guano chemically alters through time, I lay a foundation for future bat guano research that allows a better understanding of guano cores as archives. In chapter 7, I provide a cautionary tale for future researchers when attempting to use heavy metal concentrations as chronostratigraphic dates in bat guano archives. Chapter 8 presents innovative findings that demonstrate bat guano can differentiate between human-caused fires and wildfires in the paleoenvironmental record. Chapter 9 characterizes Holocene fire-climate relationships by comparing published charcoal records within the southeastern United States with TraCE-21Ka model simulations of surface air temperature, precipitation, and burned area fraction. By making these comparisons, I assess the reliability of modelled burned area fraction in capturing Holocene fire variability. Chapter 10 also compares Holocene length charcoal data with TraCE-21Ka data but over the expanded spatial scale of the continental United States. The findings from this study demonstrate that anthropogenic changes (i.e., population growth and fossil fuel emissions) intensify climate-related fire activity, underscoring the urgent need for resilient fire management strategies that integrate ecology and human-environment interactions. Last, chapter 11 provides a conclusion that cohesively unites the themes of this dissertation while highlighting their importance. | en_US |
