ABSTRACT FOWLER, FALLON ELISE. How Dung Beetles affect Dung-Generated Greenhouse Gases in Cattle Pastures: Experimental Studies and Literature Review. (Under the direction of Dr. David W. Watson). Humans are accelerating climate change through the overuse, replacement, and destruction of native ecosystems – the very entities that regulate the world’s greenhouse gases (GHGs). With such a burgeoning population it becomes more imperative to find ways that promote healthy habitats through biodiversity and sustainability. While this research is no substitute for more impactful strategies, such as resource conservation (i.e. flexitarian diets, fossil fuel reduction), ecosystem restoration (e.g. afforestation, desertification renovation), and green practices (e.g. solar energy, food waste reduction, elimination of single-use plastics); my goal is to address some of climate science’s concerns with animal agriculture. This research demonstrates how effective and robust dung beetle populations can influence the dung and soil microbes that regulate GHG pathways in cattle-based pastures. Chapter 1 discusses the various dung beetle collection methodologies and their purposes to better understand their guild-level advantages, limitations, and survival rates when using mass-scale flotation and self-sorting techniques for dung beetles. Chapter 2 discusses the various GHG chamber designs and extraction methods, and proposes a unique chamber design and methodology (the “mobile” GHG chamber) accompanied by step-by-step building instructions, required items and costs, advantage-disadvantage lists, and how-to guides on standard curve creation, vial blanking (purging), and standard operating procedure. Both Chapters 1 and 2 represent the underlying methodology and internal validation experiments that form the basis of Chapters 3, 4, and 5. These last chapters detail a series of experiments that ask: do dung beetles reduce GHGs enough to impact local warming and under what conditions? Chapter 3 explores the current literature and combines the results from our first semi- field experiment to suggest that the current literature shows negligible dung beetle effects. It also disproves the hypothesis that manually mixing dung reduces anaerobic-based GHGs and thereby dispels the notion that methodological practices are a potential confounding practice. Chapter 4 explores population density effects: how many dung beetles per unit dung does it take to drastically reduce GHGs? Again, I found dung beetles had a negligible atmospheric effect despite obvious visual dung damage and treatments containing nearly 2.5x the abundance of dung beetles per liter dung reported across currently published literature. In each reported experiment, time was the strongest and most reliable predictor of GHG trajectory. Chapter 5 ends this experiment series with one last question: do pastures with naturally robust and active dung beetle populations, with 24-hour dung access, drastically reduce GHGs? We’re the first to show that robust dung beetle activity can indeed accelerate dung decay by drastically reducing methane and increasing nitrous oxide emissions within a single day (with dung beetles) compared with a week-long decomposition process (without dung beetles). We are also the first to document rigorous dung beetle communities reducing the sum-total GHG effect – albeit, by a small amount. Regardless, dung beetles also simultaneously improve pasture fertilization, aerate soil, support earthworm communities, refill groundwater tables, and reduce pests and pestilence by accelerating and/or burying dung when in robust populations. Dung beetles, thereby, provide many ecosystems services besides GHG reduction that make their presence necessary for environmental well-being. © Copyright 2020 by Fallon Elise Fowler All Rights Reserved How Dung Beetles affect Dung-Generated Greenhouse Gases in Cattle Pastures: Experimental Studies and Literature Review by Fallon Elise Fowler A dissertation submitted to the Graduate Faculty of North Carolina State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Entomology Raleigh, North Carolina 2020 APPROVED BY: _______________________________ _______________________________ Dr. David W. Watson Dr. Shuijin Hu Committee Chair _______________________________ _______________________________ Dr. Robb Dunn Dr. Marcé Lorenzen _______________________________ Dr. Vivek Fellner DEDICATION I dedicate this dissertation to my wonderful dad, Raymond Fowler, and my role models, Dr. Bradley Mullens and Steve Denning. Thank you for all your support and guidance. ii BIOGRAPHY Fallon Elise Fowler was born on May 17, 1992, to Meredith Coffman and Raymond Fowler in the desert valley of Lancaster, CA. She grew up in a family of six including her twin, Elliott; her brothers and stepbrothers, Dyllon, Tanner, and Josh; and her stepsister, Alicia. They lived in and around Lancaster, Palmdale, and Rosamond attending various schools. She graduated from Lancaster High School in 2010 and attended University of California, Riverside, where she majored in Entomology and minored in Chemistry. She graduated Cum Laude in 2014 with a BS in Entomology, was awarded the Chancellor’s Research Fellowship, and authored and co-authored three publications under the wonderful guidance of Dr. Bradley Mullens. In the summer of 2014, she moved to Raleigh, NC to attend graduate school as a MS, though eventually became a Ph.D. when granted the National Scholarship Foundation Graduate Research Fellowship, at the North Carolina State University. There she studied under Dr. D. Wes Watson and worked alongside Steven Denning to eventually produce this dissertation. iii ACKNOWLEDGMENTS First, I would like to thank my advisor, Dr. Wes Watson, for supporting me throughout my graduate project, as well as all my committee members for redirecting me and providing advice while serving on my committee. A special thanks also goes to Alan Franzluebbers, Coby Schal, and Bradley Mullens for providing me with one-on-one assistance and reviewing my manuscripts and projects in detail. I would not have accomplished this massive undertaking without the ever-present and thoughtful assistance from Steve Denning whose extensive knowledge of physics, engineering, and plain common sense helped make my project what it is. I would also like to thank Cong Tu for showing me the ropes of beginner gas techniques and chamber building strategies. Thank you to all of the cattle personnel who allowed me to poke, prod, and revel in the local cattle dung – this includes both the Center for Environmental Farming Systems (CEFS) center in Goldsboro, NC and the NCSU Lake Wheeler Field Lab Center in Raleigh, NC. I also want to thank Amelia Weaver, Annabel Parker, Morgan Malone, and Tashiana Wilcox for being wonderful undergraduate research assistants and scientists in general. Lastly, I am grateful to the Department of Entomology for funding half of my research appointment, and to the National Science Foundation and CEFS Graduate Student Scholarship for funding the other half. I especially want to thank Hannah Burrack, Steve Frank, and Meredith Beaulieu for giving me wonderful feedback on my major grants and/or manuscripts. Without funding and feedback, well, things would’ve been much harder. Thank you all. iv TABLE OF CONTENTS LIST OF TABLES ....................................................................................................................... vii LIST OF FIGURES ...................................................................................................................... ix Chapter 1: Sampling Efficacy and Survival Rates of Labarrus pseudolividus (Coleoptera: Scarabaeidae) and Onthophagus taurus (Coleoptera: Scarabaeidae) using Flotation and Sieve-Separation Methodology ................................................................................................... 1 Abstract .............................................................................................................................. 1 Introduction ........................................................................................................................ 2 Materials and Methods ....................................................................................................... 5 Results ................................................................................................................................ 7 Discussion .......................................................................................................................... 8 Acknowledgements .......................................................................................................... 11 References Cited .............................................................................................................. 12 Tables ............................................................................................................................... 15 Figures.............................................................................................................................. 16 Appendix A (Supplementary Materials) ........................................................................ 166 Chapter 2: Gases on the Go: Mobile Chamber Designs and Gas Techniques for Field Research ............................................................................................................................ 20 Abstract ...........................................................................................................................