To Sedum or Not to Sedum: Improving Extensive Green Roof Functioning Using Invasion Theory as a Management Tool by Chih Julie Wang A thesis submitteD in conformity with the requirements for the Degree of Master of Science Department of Ecology anD Evolution University of Toronto © Copyright by Chih Julie Wang 2020 To Sedum or Not to Sedum: Improving Extensive Green Roof Functioning Using Invasion Theory as a Management Tool Chih Julie Wang Master of Science Department of Ecology and Evolution University of Toronto 2020 Abstract Green roofs have become increasingly popular to mitigate the negative impacts of urbanization and to restore key ecosystem functions in cities. In this thesis, I evaluate green roof functioning in two ways, using a meta-analysis of existing literature and a field-based manipulation experiment. The meta-analysis showed that Sedum survived better than non-Sedum, but there was no pattern of roof cooling and stormwater management. In the field, I conducted a factorial experiment using invasion theory as a management tool to increase native species diversity on extensive green roofs and evaluate green roof functioning. I hypothesized that resource addition via irrigation and disturbance treatments will enhance native species success and increase roof cooling and stormwater management. Results show plants aid in roof cooling and increase moisture retention, however evidence supporting diversity enhancing green roof functioning is lacking. Diversity effects on function theoretically require co-existence mechanisms, thus requiring observation over longer temporal scale. ii AcknowleDgments I would like to express my sincere gratitude to everyone who has helped me throughout this project; this would not have been possible without them. First and foremost, I would like to thank my supervisors Dr. Marc Cadotte and Dr. Scott MacIvor for their insight, support, and guidance throughout this project. Second, I would like to extend my thanks to my supervisory committee members Dr. Eliana Gonzales-Vigil and Dr. Roberta Fulthorpe, for their invaluable comments, time, and encouragement. I would also like to thank my examination committee members, Dr. Peter Kotanen and Dr. Kenneth Welch for agreeing to supervise my examination despite having busy schedules. Third, I would like to thank the Cadotte lab members, Dr. Marta Carboni, Dr. Carlos Alberto Arnillas, Dr. Deyi Yin, Adriano Roberto, Antonio Lorenzo, Chung Chui, Menilek Beyene, Rachel Rigden, and Weihan (Bill) Liu, the MacIvor lab members, Nicholas Sookhan, Garland Xie, Miranda Klymiuk, Praveen Jayarajan, and Stephen Grabinsky, work study students, Kelly Ray, Natasha Klasios, Nigarsan Kokilathasan, Raisa Chowdhury, Rebecca Morris, Shannon Underwood, Tony Li, and Waqqas Khalid, and the numerous dedicated and hardworking volunteers who have all together made this project possible. Fourth, I would like to thank my family and friends for being supportive and encouraging throughout my project. Finally, I would like to thank the Department of Ecology and Evolutionary Biology at the University of Toronto for its resources and research opportunities that allow this project to be successful. iii Table of Contents Acknowledgments .......................................................................................................................... iii Table of Contents ........................................................................................................................... iv List of Tables ................................................................................................................................. vi List of Figures ............................................................................................................................... vii List of Appendices ....................................................................................................................... viii Chapter 1 Introduction .................................................................................................................... 1 Introduction ............................................................................................................................. 1 1.1 Consequences of urbanization ........................................................................................ 1 1.2 Green roofs can mitigate the negative impacts of urbanization ...................................... 2 1.3 Thesis overview .............................................................................................................. 3 1.3.1 Chapter 2: To Sedum or not to Sedum: Evaluating Sedum relative to Non-Sedum performance on extensive green roofs .................................................................................... 3 1.3.2 Chapter 3: Improving extensive green roof functioning using invasion theory as a management tool ..................................................................................................................... 4 References ....................................................................................................................................... 5 Chapter 2 To Sedum or not to Sedum: Evaluating Sedum relative to Non-Sedum performance on extensive green roofs ...................................................................................................................... 8 To Sedum or not to Sedum: Evaluating Sedum relative to Non-Sedum performance on extensive green roofs ...................................................................................................................... 8 2.1 Introduction ..................................................................................................................... 8 2.2 Materials and Methods .................................................................................................. 10 2.2.1 Literature search ........................................................................................................ 10 2.2.2 Meta-analysis ............................................................................................................ 11 2.3 Results ........................................................................................................................... 12 2.3.1 Green roof research trends ........................................................................................ 12 2.3.2 Sedum verses non-Sedum survival ............................................................................ 12 2.3.3 Sedum verses non-Sedum roof cooling performance ................................................ 12 2.3.4 Sedum verses non-Sedum stormwater management ................................................. 13 2.4 Discussion ..................................................................................................................... 13 2.4.1 Opportunities for future research .............................................................................. 16 References ..................................................................................................................................... 17 Figures........................................................................................................................................... 21 Appendix ....................................................................................................................................... 25 iv Chapter 3 Improving extensive green roof functioning using invasion theory as a management tool ................................................................................................................................................ 40 Improving extensive green roof functioning using invasion theory as a management tool . 40 3.1 Introduction ................................................................................................................... 40 3.2 Materials and methods .................................................................................................. 42 3.2.1 Experimental set up ................................................................................................... 42 3.2.2 Data collection .......................................................................................................... 44 3.2.3 Statistical analysis ..................................................................................................... 45 3.3 Results ........................................................................................................................... 46 3.3.1 Native invader success .............................................................................................. 46 3.3.2 Green roof functioning .............................................................................................. 46 3.4 Discussion ..................................................................................................................... 47 3.4.1 Native invader success .............................................................................................. 47 3.4.2 Green roof functioning .............................................................................................. 48 3.4.3 Conclusion ................................................................................................................ 50 3.4.4 Future directions ....................................................................................................... 51 References ....................................................................................................................................