UC San Diego UC San Diego Electronic Theses and Dissertations Title How a landscape responds to changes in the world around it: The Dynamic Critical Zone in the Luquillo Mountains, Puerto Rico Permalink https://escholarship.org/uc/item/7wt9d72j Author Harrison, Emma Jayne Publication Date 2020 Peer reviewed|Thesis/dissertation eScholarship.org Powered by the California Digital Library University of California UNIVERSITY OF CALIFORNIA SAN DIEGO How a landscape responds to changes in the world around it: The Dynamic Critical Zone in the Luquillo Mountains, Puerto Rico A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Earth Sciences by Emma Jayne Harrison Committee in charge: Professor Jane K. Willenbring, Chair Professor Adrian Borsa Professor Elsa Cleland Professor Neal Driscoll Professor Isabel Rivera-Collazo 2020 The Dissertation of Emma Jayne Harrison is approved, and it is acceptable in quality and form for publication on microfilm and electronically: __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ __________________________________________________ Chair University of California San Diego 2020 iii DEDICATION The nights I spent in the rivers with the fireflies and the coquis made everything worth it. iv TABLE OF CONTENTS Signature page ................................................................................................................................ iii Dedication ...................................................................................................................................... iv Table of Contents ............................................................................................................................ v List of Figures ................................................................................................................................ ix List of Tables ................................................................................................................................. xi Acknowledgements ....................................................................................................................... xii Vita ............................................................................................................................................... xiv Abstract of the Dissertation .......................................................................................................... xv CHAPTER 1. Introduction.............................................................................................................. 1 1. Background ............................................................................................................................. 1 1.1. Geomorphology and the Critical Zone ............................................................................. 1 1.2. The Luquillo Mountains ................................................................................................... 3 1.3. Cosmogenic 10Be .............................................................................................................. 5 2. Research focus ......................................................................................................................... 9 3. Research significance .............................................................................................................. 9 4. Statement on content and organization ................................................................................. 10 5. Research objectives and design ............................................................................................. 11 5.1. Water .............................................................................................................................. 11 5.2. Ecosystems and erosion .................................................................................................. 13 5.3. Soils ................................................................................................................................ 15 Glossary of terms ...................................................................................................................... 21 CHAPTER 2. Dynamic Critical Zone architecture driven by subsurface flow in the Luquillo Mountains, Puerto Rico ................................................................................................................ 22 v Abstract ..................................................................................................................................... 22 1. Introduction ........................................................................................................................... 23 1.1. Field Setting .................................................................................................................... 25 1.2. Site Hydrology ................................................................................................................ 27 2. Methods ................................................................................................................................. 29 2.1. Field campaigns and digital terrain analysis ................................................................... 29 2.2. Baseflow discharge measurements ................................................................................. 31 2.3. Bedload grain size analysis ............................................................................................. 32 2.4. 10Be derived erosion rates ............................................................................................... 32 3. Results ................................................................................................................................... 34 3.1. Field campaigns and digital terrain analysis ................................................................... 34 3.2. Baseflow discharge measurements ................................................................................. 35 3.3. Bedload grain size analysis ............................................................................................. 37 3.4. 10Be derived erosion rates ............................................................................................... 37 4. Discussion ............................................................................................................................. 38 4.1. Channel incision and seepage ......................................................................................... 38 4.2. Landscape (dis)equilibrium and seepage ........................................................................ 42 5. Conclusions ........................................................................................................................... 44 Acknowledgments ..................................................................................................................... 45 CHAPTER 3. Quaternary record of terrestrial environmental change in response to climatic forcing and anthropogenic perturbations ...................................................................................... 46 Abstract ..................................................................................................................................... 46 1. Introduction ........................................................................................................................... 47 1.1. Sedimentary archives of ecogeomorphology.................................................................. 49 2. Field setting ........................................................................................................................... 51 vi 3. Methods ................................................................................................................................. 54 3.1. Radiocarbon dating ......................................................................................................... 54 3.2. Stable carbon isotopes .................................................................................................... 54 3.3. Meteoric 10Be concentrations ......................................................................................... 55 3.4. Grain size and geochemistry ........................................................................................... 56 4. Results ................................................................................................................................... 56 4.1. Stratigraphy and Chronology .......................................................................................... 56 4.2. Grain size and geochemistry ........................................................................................... 59 4.3. Erosion rates from 10Be .................................................................................................. 60 4.4. Stable carbon isotope ratios ............................................................................................ 62 5. Discussion ............................................................................................................................. 63 5.1. Paleo-erosion record ....................................................................................................... 63 5.2. Carbon sources and evidence for ecological succession ...............................................