Effects of Human Actions on Four Ecological Systems, with a Focus on Trophic Relationships
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Effects of human actions on four ecological systems, with a focus on trophic relationships A DISSERTATION SUBMITTED TO THE FACULTY OF THE UNIVERSITY OF MINNESOTA BY Margaret Candace Kosmala IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY Dr. Craig Packer, Dr. G. David Tilman December 2013 © Margaret Candace Kosmala, 2013 Acknowledgements One cannot write a dissertation without the support and help of others, and I am indebted to many people who have supported me over the past six years. Thank you to my committee – Dave Tilman, Craig Packer, George Heimpel, and Elizabeth Borer – for helpful suggestions that improved this dissertation. Likewise, I am grateful for the insightful reviews and comments I have received on various proposals and papers from Liza Comita, Justin Becknell, Tom Giarla, Andrew Simons, Sarah Hobbie, Corinna Riginos, Jennifer Schmidt, Mark Bee, Megan Strauss, Meggan Craft, and Scott Lanyon. Several individuals have served as unofficial advisors and mentors during my time as a graduate student. I thank Sarah Hobbie for on-going advice, Mathew Leibold for adopting me into his lab during my “grad student sabbatical,” Norma Fowler for inviting me into her discussion section, and Scott Miller for hosting me at the Smithsonian’s National Museum of Natural History. Holly Sigler, who worked with me as an undergraduate, greatly facilitated much of my work with long hours in the lab. Thank you to Colleen Satyshur for sharing her knowledge of entomology with me, and to Clarence Lehman and Nick Haddad for stimulating conversations about science, computing, and careers. I am grateful for the support of the EEB office staff, especially that of Lisa Wiggins and Sue Wenker, and of the Cedar Creek staff. Thanks to Steve Polasky and Jason Hill for discussions of beef production (Chapter 2) and for sending references my way. Alfredo DiCostanzo spent time helping me understand the U.S. industrial beef system. Mike Messman assisted with cattle rations, and Cheryl Baldwin provided unpublished data on restaurant facilities. I could not have conducted the biological control experiment (Chapter 3) without the expert oversight of Troy Mielke. Thanks to Emily Mohl for discussions about experimental design. Jonathan Dregni designed and built a prototype mesh covering for the soybean cages and reared aphids to put on the soybean plants. (Acknowledgements are continued in Appendix 7). i for Ben Hardt, my friend, partner, and teammate in life ii Table of Contents List of Tables ..................................................................................................................... vi List of Figures ................................................................................................................... vii Chapter 1 : Introduction ...................................................................................................... 1 Chapter 2 : Environmental impacts of beef production ...................................................... 4 Introduction ..................................................................................................................... 4 Methods ........................................................................................................................... 6 Impacts Calculations and Functional Units ................................................................. 7 Byproduct calculations ................................................................................................ 8 Green-Label Beef ........................................................................................................ 9 LCA Survey ................................................................................................................. 9 Results & Discussion .................................................................................................... 10 Impacts of U.S. Industrial Beef Production ............................................................... 10 Green-Label Beef ...................................................................................................... 11 Literature Survey of Beef LCAs ................................................................................ 12 Trade-offs and best practices for beef production ..................................................... 14 Underestimation of environmental impacts ............................................................... 16 Tables and Figures ........................................................................................................ 19 Chapter 3 : Local plant diversity does not enhance biological control of soybean aphid in a field experiment ............................................................................................................. 24 Introduction ................................................................................................................... 24 Methods ......................................................................................................................... 28 Site location and preparation ..................................................................................... 28 Soybeans and Soybean Aphids .................................................................................. 28 Natural Enemy Exclusion .......................................................................................... 29 Ant Exclusion ............................................................................................................ 30 Root Biomass ............................................................................................................. 30 Data Analyses ............................................................................................................ 31 Soybeans ................................................................................................................ 31 iii Aphids .................................................................................................................... 31 Natural Enemies ..................................................................................................... 32 Natural enemy exclusion........................................................................................ 34 Non-aphid herbivores............................................................................................. 35 Results ........................................................................................................................... 36 Soybeans .................................................................................................................... 36 Aphids ........................................................................................................................ 37 Natural enemies ......................................................................................................... 38 Natural enemy exclusion ........................................................................................... 39 Non-aphid herbivores ................................................................................................ 40 Ants ............................................................................................................................ 40 Discussion ..................................................................................................................... 40 Tables and Figures ........................................................................................................ 46 Chapter 4 : Local competition and dispersal limitation affect community dynamics over twenty years in a seed addition experiment ...................................................................... 61 Introduction ................................................................................................................... 61 Methods ......................................................................................................................... 63 Results ........................................................................................................................... 65 Discussion ..................................................................................................................... 68 Tables and Figures ........................................................................................................ 73 Chapter 5 : Estimating wildlife disease dynamics in complex systems using approximate Bayesian computation models .......................................................................................... 83 Introduction ................................................................................................................... 83 Methods ......................................................................................................................... 86 Lion demographic simulation .................................................................................... 87 Disease model ............................................................................................................ 88 Observed field data .................................................................................................... 89 ABC-SMC algorithm ................................................................................................. 90 Results ........................................................................................................................... 93 Discussion ....................................................................................................................