SOIL AND LITTER LEGACY EFFECTS OF INVASIVE FLOWERING RUSH (BUTOMUS UMBELLATUS) ON LAKE ERIE WETLAND RESTORATION Alyssa Dietz A Thesis Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August 2015 Committee: Helen Michaels, Advisor Enrique Gomezdelcampo C. Eric Hellquist Jeffrey Miner ii ABSTRACT Helen Michaels, Advisor The Great Lakes region has been impacted by the invasion of over 180 different alien species. As invasives have reduced wetland habitat availability and altered community structure, managers have developed extensive eradication programs. However, even following the removal of dense monocultures, invasive plants can influence native ecosystems through long-term chemical and biological changes, known as legacy effects. My research investigates the potential for these legacy effects following the removal of Flowering Rush (Butomus umbellatus), an understudied emergent in Lake Erie wetlands. This research focuses on how legacy effects of B. umbellatus may influence restoration of native communities and investigates whether the presence of remnant stands of B. umbellatus propagules or litter alters the success of native reestablishment. A seed mix of 25 native species was sown into flats with soil from either native dominated soils, areas with formerly moderate invasions, or areas with persistent Butomus monocultures. These sown plant communities were then subjected to single and combined treatments of living B. umbellatus vegetative propagules and litter alongside unsown flats that examined the response of seedbank communities. The presence of propagules greatly reduced the growth of native seedlings developing in experimental plantings by 69%. While there was no difference in biomass between native seedlings grown in univaded soils and those from areas of B. umbellatus monocultures, native diversity and community evenness were lower. Contrary to initial predictions, B. umbellatus litter increased native biomass and taxon diversity. Planted propagules also reduced applied iii invasive litter decomposition. Nutrient analysis of soils from sites of monocultures had elevated levels of phosphorus and nitrogen release. This work documents specific negative impacts of this understudied invasive emergent plant on Great Lakes wetland communities. My results demonstrate the importance of controlling vegetative propagules and emphasizes their potential role in inhibiting restoration efforts that are costly and time consuming endeavors for management partners. This work also suggests that there may be possible changes to microbial communities and related ecosystem nutrient cycles once monocultures have developed. My research suggests the presence of legacy effects of B. umbellatus that alter community composition and soil conditions that warrant further investigation. iv ACKNOWLEDGMENTS First and foremost I would like to thank my advisor Dr. Helen Michaels for her help and guidance on my thesis. I would also like to thank my committee members Dr. Jeffrey Miner, Dr. Enrique Gomezdelcampo, and Dr. C. Eric Hellquist for their help and willingness to answer endless questions throughout my project. I also thank Ron and Kathy Huffman of US Fish and Wildlife who provided key background information about ONWR and whose discussions played a central part in the creation of my thesis. Many thanks go to my labmates Paige Arnold and Jacob Sublett for not only their help in hours upon hours of harvesting but also their friendship and support every day in the office. I’m also thankful for the help that I received from the graduated members of the lab Mike Plenzler, Jennifer Shimola, and Ryan Walsh in their guidance and advice in the development of my thesis. My research could have never been accomplished without the help of multiple people in the field. I am extremely grateful for the help I received from the Miner lab (Jake Miller, Dani McNeil, Jamie Russell, Kevin Bland, Jordan Pharris) for their help in collecting soils and the setup of my mesocosms. I’m also thankful for the help of Rachel Schirra, without whom the native species mix may have never been finished. I am eternally grateful for the help of Dylan Jacobs, who not only labored away at the collection of my field soils and harvest but who also served as a great friend and supporter throughout my masters. Last, and certainly not least I would also like to thank my family and friends for their kind words and support throughout not only my research but my whole college career. I want to thank my parents for encouraging me to take on projects that challenged me and for helping me in my times of need including hours spent looking at the radar. To my friends Ashlee Thomas, Mike Fashinpaur, Addie Bagford, Jessica LaHurd, and Meredith Barnes, thank you for being the much needed escape from the lab and for always getting me through even the toughest times. v TABLE OF CONTENTS Page INTRODUCTION... .............................................................................................................. 1 MATERIALS AND METHODS ........................................................................................... 5 Site Description .......................................................................................................... 5 Experimental Design .................................................................................................. 5 Environmental Factors ............................................................................................... 9 Soil, Leaf Tissue, and Litter Collection ..................................................................... 10 Statistical Analyses .................................................................................................... 11 Environmental Variables ............................................................................... 11 Native Seedling Response Measures ............................................................. 12 B. umbellatus Growth and Litter Decomposition .......................................... 12 RESULTS ............................................................................................................ 14 Environmental Conditions ......................................................................................... 14 Seed Bank Community ............................................................................................. 15 Native Monocultures .................................................................................................. 16 Taxon Richness of Seeded Treatments ...................................................................... 16 Total Biomass ........................................................................................................... 17 Community Attributes: Diversity, Evenness, and Similarity .................................... 18 B. umbellatus Responses .......................................................................................... 19 Litter Decomposition and Tissue Quality .................................................................. 19 DISCUSSION ............................................................................................................ 21 Implications for Managers and Further Areas of Research ....................................... 26 vi REFERENCES ...................................................................................................................... 28 APPENDIX A. STATISTICAL TABLES ............................................................................ 49 vii LIST OF TABLES Table Page 1 Applied Seed Mix Composition ................................................................................. 33 2 Average Recorded Nutrients of Soils ........................................................................ 34 3 Common Emerged Species and Responses to Applied B. umbellatus Treatments ... 35 4 Ungerminated Applied Seed Species ......................................................................... 36 viii LIST OF FIGURES Figure Page 1 National Distribution of B. umbellatus ...................................................................... 37 2 Map of Ottawa National Wildlife Refuge .................................................................. 38 3 Butomus umbellatus nodules ..................................................................................... 39 4 Vegetation of Common Seedbank Taxa .................................................................... 40 5 Effect of Soil Invasion History on Native Response Measures ................................. 42 6 Effect of Applied Nodules and Litter on Native Response Measures ...................... 44 7 B. umbellatus Litter and Nodule Responses to Soil Invasion History ....................... 45 8 Effect of Nodules on the Decomposition of Litter..................................................... 46 9 Effect of Soil and Nodule Interactions on the Decomposition of Litter .................... 47 10 B. umbellatus Tissue Nutrients .................................................................................. 48 1 INTRODUCTION Although wetlands provide nearly 40% of renewable ecosystem services (Costanza et al. 1997, Zedler 2000), the United States is annually losing 60,000 acres (24,281 hectares) of these important ecosystems (EPA 2015). Given that less than 5% of the original wetlands of some Great Lakes states still remain (Zedler 2003), understanding major causes of destruction and hindrances