Responses of Aquatic Plant Communities to Stream and Riparian Restoration and Management

Responses of Aquatic Plant Communities to Stream and Riparian Restoration and Management By EMILY PEFFER ZEFFERMAN B.S (Florida State University) 2007 DISSERTATION Submitted in partial satisfaction of the requirements for the degree of DOCTOR OF PHILOSOPHY in Ecology in the OFFICE OF GRADUATE STUDIES of the UNIVERSITY OF CALIFORNIA DAVIS Approved: ________________________________________________________ Truman P. Young, Chair ________________________________________________________ Eliška Rejmánková ________________________________________________________ Peter B. Moyle Committee in Charge 2014 i UMI Number: 3685316 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. UMI 3685316 Published by ProQuest LLC (2015). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, MI 48106 - 1346 Acknowledgements I owe a debt of gratitude to a large number of people without whom this dissertation would not have been possible. The following words cannot express the full magnitude of all the ways in which I have been helped and humbled by my amazing colleagues, friends, and family throughout this journey. Nor can they include every individual who has helped me along the way. With these words, I merely hope to skim the surface of the deep pool of gratitude I feel for the many wonderful people who have been, and will hopefully continue to be, in my life. First, I am grateful to my family, especially my parents Claire and Steve Peffer, for never failing to support and believe in my ambitions. I thank my advisor, Truman Young, for his eternal encouragement, constant willingness to provide ideas and advice, and his unabashed use of the word ‘audacious’ when describing my PhD work. I thank my other committee members, Peter Moyle and Eliška Rejmánková, for their feedback and advice on my dissertation, and for being role models as scientists who are making a difference in conservation and restoration policy and practice. Thank you to the students of the Young Lab (who over my years in Davis included Kurt Vaughn, Lauren Porensky, Kevin Welch, Marit Wilkerson, Jen Balachowski, Kelly Gravuer, Mila Dunbar-Irwin, Steve Fick, Laura Morales, Kristina Wolf, Derek Young, and Grace Charles) for their ideas, feedback, friendship, and logistical help. I would not have been able to complete my dissertation work were it not for their help, and that of many other kind souls who helped me in the field, most notably Elaine Chow and Karen Askeland. At multiple times, Neil Willits provided valuable statistical advice. I am especially grateful to Andrew Fulks and J.P. Marie of the Putah Creek Riparian Reserve for creating an artificial channel system for my shade experiments twice, and to the UC Davis Center for Aquatic Biology and Aquaculture for providing the water for these ii experiments. I also thank the staff at the Sierra Nevada Aquatic Research Laboratory and the University of California Natural Reserve System. I thank Rich Marovich, Putah Creek Streamkeeper, for suggesting that I submit a grant to the Solano County Water Agency for studying their aquatic vegetation management issues. And I thank SCWA, especially Alex Rabidoux, for funding said study and for being open and enthusiastic about working with me. I am greatly appreciative to the University entities that provided funding for my graduate education: the Graduate Group in Ecology (for several Block Grants), the Plant Sciences Department (several scholarships and a multi-year research fellowship), and the Center for Aquatic Biology and Aquaculture (scholarship). I also thank the benefactors of these funding sources and their awards committees. I am grateful for the academic peer review process that has led to improvements to my first two dissertation chapters (and other publications), and that will lead to improvements in future manuscripts. I also thank the many wonderful professors and researchers at UC Davis who have taught fantastic classes, and/or opened their doors to answer my questions and provide advice on a variety of topics. While completing my PhD, my psychological health was preserved by the many amazing friends I have made during my time in Davis, and I cannot thank them enough for all they have taught me about science, life, love, and costumery. I am continually humbled by their greatness, both personally and academically. Last but not least, I thank my husband Matthew Zefferman for continually agreeing to help me in the field despite enduring many hours of exceedingly boring work, for editing and providing feedback on my papers, for providing emotional support when needed, and for co- creating an awesome last name. iii Responses of Aquatic Plant Communities to Stream and Riparian Restoration and Management Abstract Submersed macrophytes (plants that grow underwater) are important components of freshwater ecosystems, providing food and habitat for a variety of invertebrates, fish, and other wildlife, and influencing key chemical and physical processes. In moderate abundance, native submersed macrophytes contribute positively to overall stream health, but excessive proliferation of submersed macrophytes, particularly non-native invasive species, can cause ecological harm and create management difficulties. My dissertation examines how management actions can affect submersed macrophyte communities, and thus, the ecological integrity of stream ecosystems. This work incorporates and contributes to ecological theory from the disciplines of restoration ecology, invasion ecology, and plant community ecology, but also addresses sustainable management of streams and riparian areas. My first chapter asks how riparian restoration, through the alteration of canopy shading, might influence the ability of a native and a non-native invasive submersed macrophyte species—elodea (Elodea nuttallii) and Eurasian watermilfoil (Myriophyllum spicatum), respectively— to establish and grow. I conducted separate experiments in artificial stream channels in two locations in California, USA, using shade cloth as a proxy for four different levels of overstory canopy shading. I found that increasing shade decreased the growth rates of both species but had no effect on establishment: both species had high survival in 0- 90% shade. For my second chapter, I built on the work from chapter one and conducted a similar experiment in an artificial stream channel system in Davis, CA. I examined how shade levels could affect competitive dynamics between Eurasian watermilfoil and elodea. I also asked 1 whether giving the native elodea a temporal priority (i.e., planting it several weeks earlier than the non-native watermilfoil) could reduce the growth rates or survival of the non-native, and whether this priority effect would interact with shade level. Similar to my earlier findings, the growth rates of both species decreased with greater shade, but I found no significant effect of priority on the growth rates of the non-native species in any shade level. For my third chapter, I examined the abiotic factors influencing the prolific submersed macrophyte growth in the Interdam Reach of Putah Creek in CA. In this stream reach, huge quantities of aquatic vegetation pose significant management challenges for the water resource agency in charge of regulating water flow and delivery in this area. I surveyed macrophyte cover and a suite of environmental factors throughout the Interdam Reach and, with a collaborator, created boosted regression tree models to identify the most important factors related to macrophyte cover. I found that factors associate with light availability and water velocity had the greatest influence on nuisance submersed macrophyte abundance in the models. 2 Chapter 1 Increasing canopy shading reduces growth but not establishment of Elodea nuttallii and Myriophyllum spicatum in stream channels Summary Submersed macrophytes are often important drivers of instream structure and function, but can be problematic when overabundant. The establishment success, growth rates, and morphology of submersed macrophytes could be affected by alteration of instream light levels during riparian restoration (via removing or planting canopy-forming vegetation), potentially influencing the success of riparian restoration projects aimed at improving aquatic habitats. To examine the effects of canopy shading on two common submersed macrophytes—Elodea nuttallii (native) and Myriophyllum spicatum (non-native)—I conducted experiments in artificial stream channels in two locations in California, USA. Initial establishment of stem fragments of both species was close to 100% in all shade levels, including shade that reduced incident light by 94%. Growth rates of the two species were similar across shade levels, and lowest in the highest shade. Full light appeared to have a photoinhibitory effect on E. nuttallii at the higher elevation site. Higher shade increased the length:biomass ratio and decreased the branching of E. nuttallii. My findings suggest that altering canopy cover during riparian restoration is unlikely to affect the ability of these species to establish,

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