Floral Enhancement of Turfgrass Lawns for the Benefit of Bee Pollinators in Minneapolis, Minnesota a Thesis SUBMITTED to the FA
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Floral Enhancement of Turfgrass Lawns for the Benefit of Bee Pollinators in Minneapolis, Minnesota A Thesis SUBMITTED TO THE FACULTY OF UNIVERSITY OF MINNESOTA BY James Ithan Wolfin IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE Dr. Marla Spivak and Dr. Eric Watkins January, 2020 © James Ithan Wolfin 2019 Acknowledgements I would like to thank everyone who helped me on this journey. I have been lucky to have two fantastic, supportive advisors, Drs. Marla Spivak and Eric Watkins, who have provided me with invaluable guidance, expertise, and, when needed, encouragement as I’ve worked on this project. The members of the Bee Lab and Turfgrass Science Lab have provided me with the tools to become a true bee expert and turfgrass scientist. I can say with absolute certainty that I would not be in this position without the expertise of Ian Lane, Andrew Hollman, Zach Portman, Sam Bauer, Elaine Evans, Jon Trappe, and countless others in the Bee Lab and Turfgrass Science labs. I was fortunate enough to have the assistance of fantastic technicians, Rachel Urick and Maddie Bergum, who shared my passion for bees and conservation, and consistently exceeded my expectations with the quality of work they produced. My parents, Steve and Madelyn Wolfin, have been my earliest teachers, my greatest cheerleaders, and have provided me the emotional support and encouragement I’ve needed to succeed as a student, a professional, and as a man. My brother Michael is my best friend, my mentor, and has been and will continue to be an inspiration to me throughout my life. My friends from home, college, and graduate school have eased the burden that is graduate school, and I am forever grateful to them as they not only accept me and my peculiar love of bees, they even do their best to embrace my passion. Finally, shoutout my fantastic pets Lexi, Pookie, and Sami (Cat), and the constant smiles they bring to my face. i Dedication I dedicate this work to my mother, who has provided me with the foundation needed to succeed every step of the way throughout my academic journey. From an early age, earlier than I can even remember, you’ve imparted so much wisdom onto me that set the foundation for my success. You taught me how to study, you taught me the value of diligence, and you’ve believed in me through all my successes and failures, even when I failed to believe in myself. You’re the first person I turn to when I need support, and the only person who can lift me up in times of doubt. While this is likely my last academic venture, it is the life lessons that I have learned from you that have carried me to this point, and that will continue to guide me every step of the way as I grow as a professional and as a man. This may mark the end of my academic career, but because of you, I will never stop being a student. Thank you. ii Abstract The turfgrass lawn is a common feature of urban and suburban communities, often accounting for the largest green spaces by area in these landscapes. Flowering species within turfgrass lawns have the potential to serve as a source of forage for bee pollinators in urban and suburban areas. We intentionally introduced low-growing flowers to turfgrass lawns to promote bee diversity and reduce inputs, while maintaining the traditional aesthetics and recreational uses associated with lawns. We compared bee communities on lawns with naturally-occurring blooms of Trifolium repens to bee communities on florally enhanced lawns that contained Prunella vulgaris ssp. lanceolata and Thymus serpyllum in addition to T. repens. T. repens supported both wild bee communities and A. mellifera colonies, as 56 species of bees were observed on T. repens, with A. mellifera as the most common species observed. We found that florally enhanced lawns supported more diverse bee communities than lawns with just T. repens. Furthermore, the bee communities supported by florally enhanced lawns were significantly different from the bee communities supported by lawns containing just T. repens based on presence-absence (Jaccard’s dissimilarity index). Our research indicates that A. mellifera colonies and wild bee communities can be supported by allowing T. repens to bloom in turfgrass lawns, and that further steps to promote the conservation of bees can be taken by land managers by intentionally introducing low-growing flowers to lawns. iii Table of Contents Acknowledgements ...................................................................................................................... i Dedication .................................................................................................................................. ii Abstract ..................................................................................................................................... iii Table of Contents ....................................................................................................................... iv List of Tables .............................................................................................................................. vi List of Figures ............................................................................................................................ vii Chapter 1: Thesis introduction .................................................................................................... 1 Importance of bees ................................................................................................................. 1 Overview of bee pollination ................................................................................................. 1 Apis mellifera: Value in agriculture and stressors ................................................................. 3 Wild bees: Value in agriculture and stressors ....................................................................... 4 Land use changes and habitat conversion ................................................................................ 6 Overview of land use changes and effects on bees .............................................................. 6 Urbanization and urban conservation efforts ....................................................................... 8 The turf lawn and other green spaces .................................................................................... 11 Overview of the turf lawn and lawn inputs ........................................................................ 11 Pollinator conservation within urban landscapes and the turf lawn ................................... 13 Candidates for floral enhancement within turf lawns ......................................................... 15 The value of T. repens and potential for floral enhancement in turf lawns ......................... 19 Chapter 2: Floral Enhancement of Turfgrass Lawns for the Benefit of Bee Pollinators in Minneapolis, Minnesota ............................................................................................................ 21 Introduction .......................................................................................................................... 21 General Methods .................................................................................................................. 26 Study area ......................................................................................................................... 26 Floral enhancements ......................................................................................................... 26 Floral selection .................................................................................................................. 27 Site preparation................................................................................................................. 28 Vegetation surveys ............................................................................................................ 29 iv Bee surveys on T. repens ................................................................................................... 30 Bee surveys on clover-only vs. florally enhanced plots ....................................................... 31 Bee identification .............................................................................................................. 32 Data analysis ......................................................................................................................... 33 Parks with T. repens only ................................................................................................... 33 Results .................................................................................................................................. 36 Floral abundance in Minneapolis public parks .................................................................... 36 Bee communities on T. repens ........................................................................................... 36 Functional traits of bees on T. repens ................................................................................ 37 Predicting floral visitors on T. repens ................................................................................. 38 Bee species composition at paired parks ........................................................................... 38 Bees collected on Enhanced Vs Clover-only Parks .............................................................. 39 Bees collected by host plant .............................................................................................