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Autogenic and allogenic controls on carbon dynamics in peatlands from Alaska and Patagonia by Julie Loisel A Dissertation Presented to the Graduate and Research Committee of Lehigh University in Candidacy for the Degree of Doctor of Philosophy in Earth and Environmental Sciences Lehigh University April 2012 i © 2012 Copyright JULIE LOISEL ii Approved and recommended for acceptance as a dissertation in partial fulfillment of the requirements for the degree of Doctor of Philosophy Julie Loisel Autogenic and allogenic controls on carbon dynamics in peatlands from Alaska and Patagonia Defense Date Zicheng Yu, Dissertation Director Approved Date Committee Members: Robert K. Booth Frank J. Pazzaglia Nigel T. Roulet (Name of Committee Member) iii ACKNOWLEDGMENTS I first wish to acknowledge the prominent role that my advisor, Zicheng Yu, has played in my professional development over the past four years. The generous gift of his time, experience, energy, and advice is much appreciated. Zic has thought me how to develop solvable hypotheses, how to foster new ideas through sharing and discussing, and how to become a respected scientist and colleague that one can always count on. His hard work and dedication have inspired me, and his encouragements have helped me move forward and made me crave for more challenges. Begin a student and employee of Robert Booth and Frank Pazzaglia has also been detrimental in my professional development and overall appreciation of my Lehigh experience. Bob‟s exceptionally thorough work inculcated me with a (much needed) need for slowing down to think through every idea, and to pursue high-quality work at all times. I‟ve always been impressed by Frank‟s sincere devotion for everybody‟s well- being, endless motivation, positive attitude, and great knowledge. He has been a role model both as a teacher and group leader. I would also like to acknowledge the wisdom of Nigel Roulet. Saying that his knowledge of peatland dynamics is comprehensive would be an understatement, and the detailed and insightful comments he provided on my work kindled exciting research hypotheses and ideas. While at Lehigh, I had the opportunity to get to know Miriam Jones, Alex Ireland, Chris Bochicchio, and Daniel Minguez, four unusually driven, talented, and intelligent young people with whom I shared many moments of contentment, joy, and enlightenment. Their company in the field, in classrooms, in the lab, and in life is beyond iv appreciation. I also wish to thank Eric Klein, Michael Clifford, Travis Andrews and Steph Hunt from the paleoecology lab for their help, support, and friendship. The Department of Earth and Environmental Sciences has become my family over the past four years, and I am grateful to my office mates, comrades, colleagues, and professors for making this department an Institution where sharing occupies a central place. Finally, the long-distance support and love from my parents, sister, grand-mother, family, and close friends are indisputably a large component of my success here in the United States. The research in Alaska was funded by US-NSF grants (ATM-0628455 and EAR- 0819717) and a Kerry Kelts Research Award from the Limnogeology Division of the Geological Society of America. The research in Patagonia was funded by a Faculty Innovation Grant from Lehigh University (2009), a US-NSF grant (AGS-0628455), a US-NSF Doctoral Dissertation Improvement Grant (DEB-1110665) and the Department of Earth and Environmental Sciences at Lehigh University. Tuition and stipend were paid for by an NSERC Canada Postgraduate Scholarship (BESC-D3-362645-2008) and a Dean‟s Fellowship from the College of Arts and Sciences at Lehigh University. Thanks to Bob Booth, Chris Bochicchio, Dan Brosseau, Andrew Gonyo, Miriam Jones, Eric Klein, Bryan Mark, Erin Markel, Jay Nolan, Nathan Stansell and Zic Yu for their help in the field; Bassam Ghaleb, Jake Kleinknecht, Molly O‟Neill, Greg Sills, Ginger Somerville and Kristi Wallace for their assistance in the lab; Chris Bochicchio, Dan Brosseau, Chris Burke, Angela Gallego-Sala, Daniel Minguez, Jay Nolan and Andy Parsekian for computer assistance; and Bob Booth, Michael Clifford, Angela Gallego- Sala, Alex Ireland, Tim Moore, Robert McCulloch, Patricio Moreno, Andy Parsekian, Frank Pazzaglia, Nigel Roulet, Lee Slater and Zic Yu for discussions. v TABLE OF CONTENTS List of Figures x List of Tables xiii Abstract 1 Preface 2 Chapter 1: Recent acceleration of carbon accumulation in a Boreal peatland, south-central Alaska 5 Abstract 6 1.1: Introduction 7 1.2: Materials and Methods 10 1.2.1: Study site 10 1.2.2: Peat-core sampling and analyses 13 1.2.3: Peat accumulation and decomposition models 15 1.3: Results 18 1.3.1: Age-depth models and chronology 18 1.3.2: Paleoecological reconstructions 21 1.3.3: Peat geochemical properties 23 1.3.4: Apparent peat-C accumulation rates 24 1.3.5: Modeled litter input and peat loss patterns 24 1.4: Discussion 27 1.4.1: Recent vegetation shift, oligotrophication, and fen-bog transition at Petersville peatland 27 1.4.2: Causes of the rapid increase in peat-C accumulation rates over the last century 30 1.4.3: Impact of warmer climate on peatland structure and functioning 34 1.5: Conclusions and Implications 36 vi 1.6: Acknowledgements 38 1.7: References 39 Chapter 2: Global-scale pattern of peatland Sphagnum growth driven by photosynthetically active radiation and growing season length 53 Abstract 54 2.1: Introduction 55 2.1.1: Research question and rationale 59 2.2: Methods 59 2.2.1: Sphagnum growth 59 2.2.2: Bioclimatic variables 63 2.2.3: Statistical analysis 64 2.3: Results 65 2.3.1: Effect of species, peatland type, microform, and continentality on Sphagnum productivity 65 2.3.2: Relationships between Sphagnum productivity and bioclimatic parameters 65 2.4: Discussion 68 2.4.1: Species, peatland type, and microform effects 68 2.4.2: Climatic controls 69 2.4.3: Role of Sphagnum growth in regulating peat-C accumulation in northern peatlands 73 2.5: Conclusions and Implications 74 2.6: Acknowledgements 76 2.7: References 77 2.8: Appendix 84 Chapter 3: Quantifying landscape morphology influence on peatland lateral expansion using ground penetrating radar and peat core analysis 93 vii Abstract 94 3.1: Introduction 95 3.2: Materials and Methods 99 3.2.1: Study site 99 3.2.2: General approach and study design 101 3.2.3: Field survey and sampling 102 3.2.4: Peat core analysis 103 3.2.5: Tephra analysis 104 3.2.6: Water table depth monitoring 104 3.3: Results 106 3.3.1: Identifying the tephra layer using ground penetrating radar 106 3.3.2: Changes in topography, slope, and lateral expansion rates 106 3.3.3: Changes in peat stratigraphy, thickness, and bulk density 109 3.3.4: Water table depth and variability along the transect 109 3.4: Discussion 111 3.4.1: Peatland basin development and lateral expansion process 111 3.4.2: Self-regulated surface slope shallowing and slope threshold for lateral expansion 113 3.5: Conclusions and Implications 119 3.6: Acknowledgements 120 3.7: References 121 Chapter 4: Holocene peatland carbon dynamics in Patagonia 129 Abstract 130 4.1: Introduction 132 4.2: Patagonian peatlands 134 4.2.1: Distribution, ecology, and ecosystem dynamics 134 4.2.2: Holocene boundary conditions and climate history 139 4.3: Materials and Methods 141 viii 4.3.1: Climate envelope analysis 141 4.3.2: New study sites and field sampling 142 4.3.3: Laboratory analysis of new peat cores 146 4.3.4: Data synthesis of published peat records 151 4.3.5: Calculating and modeling Holocene peat accumulation 151 4.4: Results 152 4.4.1: Climate domain for Patagonian peatlands 152 4.4.2: Peat types, bulk density, and organic matter content 155 4.4.3: Peat accumulation dynamics 158 4.5: Discussion 164 4.5.1: Patagonian peatlands: a distinct climate envelope 164 4.5.2: Unusually high rates of peat addition during the Holocene 166 4.5.3: Controls of carbon accumulation in Patagonian peatlands 168 4.6: Conclusions and Future Research 171 4.7: Acknowledgements 173 4.8: References 174 Conclusions 188 Appendix I: Peatland dynamics in Patagonia: abrupt mid-Holocene fen-to-bog transition and carbon sequestration implications 192 Appendix II: Patagonian testate amoebae transfer function for paleohydrological reconstructions in ombrotrophic peatlands 203 Appendix III: Climate control of carbon sequestration in peatlands mediated by local-scale ecohydrological feedbacks 206 Curriculum Vitae 218 ix LIST OF FIGURES Figure 1.1: Location maps and study site 12 Figure 1.2: Exponential decay modeling results from Petersville peatland in south-central Alaska 21 Figure 1.3: Paleoecological reconstructions for cores PE08-S and PE08- A25 at Petersville peatland in south-central Alaska 22 Figure 1.4: Late-Holocene peat-carbon fluxes for core PE08-S, as modeled using the super peatland approach 26 Figure 1.5: Recent peat decomposition modeling results for core PE08-S at Petersville peatland 26 Figure 1.6: Correlations of recent climate warming, vegetation shift, and carbon accumulation 30 Figure 1.7: Conceptual model linking the ongoing climate warming and peatland C sequestration 32