AN ABSTRACT OF THE DISSERTATION OF Robert J. Smith for the degree of Doctor of Philosophy in Botany and Plant Pathology presented on May 1, 2017. Title: Realized and Potential Climate Responses of Lichen and Bryophyte Communities in a National Forest Inventory Abstract approved: Bruce McCune Climate and terrestrial vegetation have had mutual feedbacks for nearly five hundred million years, yet both are now departing from recent historical norms, with uncertain implications for forest ecosystems. This dissertation outlines the current and potential future climate responses of lichen and bryophyte communities in the United States as part of a national forest inventory. The first task was to identify influences on carbon and nitrogen storage of moss and lichen “ground layers” in subarctic interior Alaska. Nutrient stores were more sensitive to local vegetation and topography than regional macroclimate. Nutrients and biomass were greatest among apparently less-disturbed stands. This suggests that climatic changes could diminish ground layer nutrient storage indirectly if they promote intensifying wildfire regimes or expansions of competitive vascular vegetation. Turning to focus on species diversity, the next task was to quantify the strength of relationship between epiphytic lichen community composition and macroclimate across the 4,000 km-long swath of the U.S. Pacific coastal states. The strongest fitting lichen response gradients involved precipitation, temperature, and a heat-moisture index. Lichen indicator species (diagnostic of ten defined climate zones) emerged as useful monitoring tools because their abundance changes could signal shifting climate zone boundaries. After establishing key present-day climatic relationships, the next task was to pinpoint nationwide locations where epiphytic lichen communities will be most vulnerable to species losses under current and future warming scenarios. Novel niche-based metrics revealed greatest vulnerability among supposedly “warm-adapted” communities in southern/lowland locations, contrary to usual assumptions centering on cooler northern/montane habitats. Vulnerability analyses can steer conservation and monitoring attention to specific locations where warming is most expected to affect ecological communities. The final task, to anticipate how warming will impact individual lichen performance, was addressed by quantifying how experimental climate treatments (whole-ecosystem warming and CO2 additions) affected growth of the boreal epiphytic lichen species Evernia mesomorpha. Over just one year, incremental warming and concurrent drying caused progressive growth declines and biomass losses among individual transplants. Such warming-induced biomass losses of epiphytic lichens could precede local population extinctions and regional range contractions. Overall, this dissertation weaves together multiple lines of evidence from nutrient, diversity and growth responses to indicate the ecological effects of climate and climatic changes on vegetation in a national forest inventory context. This work suggests a pathway for integrating lichen and bryophyte responses into nationwide climate monitoring to address emergent interactions between humans, vegetation, and the global climate commons. © Copyright by Robert J. Smith May 1, 2017 All Rights Reserved Realized and Potential Climate Responses of Lichen and Bryophyte Communities in a National Forest Inventory by Robert J. Smith A DISSERTATION submitted to Oregon State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy Presented May 1, 2017 Commencement June 2017 Doctor of Philosophy dissertation of Robert J. Smith presented on May 1, 2017 APPROVED: Major Professor, representing Botany and Plant Pathology Head of the Department of Botany and Plant Pathology Dean of the Graduate School I understand that my dissertation will become part of the permanent collection of Oregon State University libraries. My signature below authorizes release of my dissertation to any reader upon request. Robert J. Smith, Author ACKNOWLEDGEMENTS I am deeply grateful to Bruce McCune for guidance, inspiration, and for setting an unparalleled example – I cannot repay the mentorship, but I vow to pay it forward. I am grateful to my committee members: Sarah Jovan, who championed my work and facilitated its growth, and Andy Jones, Lisa Ganio and Dominique Bachelet, for kindly giving their time and expertise, for challenging me with high standards, and for helping shape the course of my work and thought. I thank Pat Muir for hospitality and encouragement throughout, as well as past and present members of the McCune family: Peter Nelson, Heather Root, Ricardo Miranda Gonzalez, Kaleigh Spickerman, Nijmah Ali, Abby Glauser, Amanda Hardman, Elisa DiMeglio, Joe DiMeglio, Daphne Stone, and others. For assistance and hospitality in Alaska, I thank Nick Lisuzzo, Trish Wurtz, Knut Kielland, Jamie and Teresa Hollingsworth, Beth Schulz, and Shalane Frost. For helping develop the Alaskan moss mat project I thank Juan Benavides and Mike Amacher, and I am grateful for constructive input from Andy Gray, Robert Pattison, Ken Winterberger, Amy Miller, Tina Boucher, and Rob DeVelice. I gratefully acknowledge USFS and FIA data collection staff at Anchorage and Portland. Thanks also to pilot Jan Gunderson for safe, skillful flights. For facilitating field work at Marcell Experimental Forest, I thank Paul Hanson, Randy Kolka, Steve Sebestyen, Deacon Kyllander and Peggy Muir Marshall. I also thank all who were involved in Minnesota data collection including Bruce McCune, Pat Muir, Peter Nelson, Kaleigh Spickerman, Elisa DiMeglio, Courtney Kerns, and Bobby Henderson. I thank Cheri Carr and Scott Clippinger for hospitality in Madison, Wisconsin. For contributions and development of the coastal Alaskan epiphytic lichens work, I thank Karen Dillman, Rob DeVelice, Mike Bower, Amy Miller, James Walton, Heather Root and Linda Geiser. I gratefully acknowledge funding from Cooperative Agreement PNW 12-JV-11261979-047 between the US Forest Service and Oregon State University, and Task Agreement P14AC01637 between the US National Park Service and Oregon State University. This work could not have been possible without the support of Ruddy Johnson, Joe Rausch, Nate, Anna and Nolan James, Ian and Caitlin Batch, Guy and Kathy Stephenson, and all other friends and family who kindly supported my wanderings. My gratitude to them all for support and positive encouragement. Most importantly I thank my wife Anna James, the moon in my sky, for her compassion and perspective, and for motivating me beyond what I ever thought possible. Tusen takk! CONTRIBUTION OF AUTHORS Sarah Jovan contributed to study design for all chapters, contributed to all aspects of the research and writing, and helped obtain funding. Andrew Gray made contributions to analyses for Chapter Two. Peter Nelson and Paul Hanson made contributions to study design for Chapter Five. All authors reviewed the manuscripts and revisions. TABLE OF CONTENTS Page CHAPTER 1. INTRODUCTION ............................................................................................. 1 CHAPTER 2. SENSITIVITY OF CARBON STORES IN BOREAL FOREST MOSS MATS: EFFECTS OF VEGETATION, TOPOGRAPHY AND CLIMATE ............................ 4 Abstract ................................................................................................................................. 5 Introduction .......................................................................................................................... 5 Materials and Methods ......................................................................................................... 7 Study area and sampling design ......................................................................................... 7 Ground layer attributes ...................................................................................................... 8 Environmental predictors ................................................................................................... 8 Results .................................................................................................................................. 9 Ground layer attributes ...................................................................................................... 9 Environmental predictors ................................................................................................. 10 Discussion ........................................................................................................................... 10 Biomass, carbon and nitrogen stores in boreal ground layers .......................................... 10 Environmental sensitivity and consequences ................................................................... 11 Estimating carbon distributions ....................................................................................... 13 Acknowledgements............................................................................................................. 13 References .......................................................................................................................... 13 Tables .................................................................................................................................. 18 Figures ................................................................................................................................ 22 CHAPTER 3. SENSITIVITY