University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Masters Theses Graduate School 5-2007 Century-Scale Trends in Climatic Variability for the Pacific Northwest from Western Juniper (Juniperus occidentalis Hook. ssp. occidentalis) Tree-Ring Data Christopher Aaron Underwood University of Tennessee, Knoxville Follow this and additional works at: https://trace.tennessee.edu/utk_gradthes Part of the Geography Commons Recommended Citation Underwood, Christopher Aaron, "Century-Scale Trends in Climatic Variability for the Pacific Northwest from Western Juniper (Juniperus occidentalis Hook. ssp. occidentalis) Tree-Ring Data. " Master's Thesis, University of Tennessee, 2007. https://trace.tennessee.edu/utk_gradthes/4440 This Thesis is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Masters Theses by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a thesis written by Christopher Aaron Underwood entitled "Century- Scale Trends in Climatic Variability for the Pacific Northwest from Western Juniper (Juniperus occidentalis Hook. ssp. occidentalis) Tree-Ring Data." I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Master of Science, with a major in Geography. Henri D. Grissino-Mayer, Major Professor We have read this thesis and recommend its acceptance: Carol P. Harden, Roger Tankersley, Jr. Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) To the Graduate Council: I am submitting herewith a thesis written by Christopher Aaron Underwood entitled "Century-Scale Trends in Climatic Variability for the PacificNorthwest from Western Juniper (Juniperus occidentalis Hook. ssp. occidentalis) Tree-Ring Data." I have examined the finalpaper copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the requirements forthe degree of Master of Science, with a major in Geography. A:enriD.Grissino-Mayer,��Major Professor We have read this thesis and recommend its acceptance: Carol P. Harden Roger Tankersley, Jr. Accepted for the Council: Carolyn ges, Vice Provost and Dean of the Graduate School -rhtsiS :)007 . U'13 Century-Scale Trends in Climatic Variability for the Pacific Northwest from Western Juniper (Juniperus occidentalis Hook. ssp. occidentalis) Tree-Ring Data A Thesis Presented for the Master of Science Degree The Universityof Tennessee, Knoxville Christopher Aaron Underwood May 2007 Dedication This work is dedicated to my family. I lost my father during the course of this project. He was always my rock, my biggest supporter, and the one I sought for assistance when no one else could help. Losing him has created a void in my lifethat is still being bridged, yet only through God's grace and the love and support offered by my family. Even though you have not sanded a single sample, counted a lone ring, or written a solitary word of this thesis, you are the foundationon which this project rests. Thank you. lll Acknowledgments This project was conducted under the guidance of Dr. Henri D. Grissino-Mayer. I owe him a debt of gratitude fortaking me in when I was searching foran academic home. Henri's expertise, teaching, assistance, friendship, and critiques have been invaluable throughout the duration of this research. I also thank my other committee members, Drs. Carol P. Harden and Roger Tankersley, Jr. fortheir support, knowledge, and reviews during this project. Dr. Kenneth H. Orvis provided additional expertise and comments during the review process. I wish to thank Daniel Lewis, who, along with Dr. Grissino-Mayer, collected the samples formy project. Central Oregon in early August can be brutally hot with almost no shade, and temperatures were well above 30 °C during sample collection in the High Desert. Guys, I am still indebted to you for this. The Bureau of Land Management is also owed a great deal of thanks for allowing the collection of these samples. I am furtherindebted to Justin Hart, Jessica Brogdon, and Lisa Laforest fortheir thorough reviews of my manuscripts. Many thanks to the three of you for making my writing better. The personnel in the Laboratory of Tree-Ring Science have been instrumental in conveying to me their knowledge of dendrochronology. I thank you all foryour assistance and friendship during the past two years. I am gratefulto Will Fontanez and the staffat the University of Tennessee Cartographic Services forthe two very nice maps they provided forthis thesis. Randy Heise of the High Desert Museum, Bend, Oregon, provided some very helpfulinformation that only an Oregonian would know. Thanks, Randy. I would also like to recognize the editorial staffin Graduate Student Services for their great job of technical editing. V I thank my parents fortheir unconditional love and support. I want to especially thank my mother, Mary, and my high school science teacher, John Jones, forinstilling in me a love of nature, science, and the environment. Finally, my loving wife, Sherri, has been a grounding spirit throughout this experience. She gives me motivation to better myself and to push ahead in my academic career. I will be forever thankfulto her. Vl Abstract The history of the Earth's climate shows many fluctuations, and there is reason to believe that climatic fluctuationswill continue to occur in the future. Climatic shifts related to processes such as the PacificDecadal Oscillation (PDO) initiate many environmental anomalies, including interruptions in traditional storm tracks, average precipitation, fire regimes, streamflow, and animal behavior. Our historical climatic records are too short to fully illustrate climatic fluctuations over long time scales. Proxy records are oftenused to extend these historical climatic records. In this dendroclimatological study, I used westernjuniper (Juniperus occidentalis Hook. ssp. occidentalis) fromcentral Oregon as a climatic proxy. Westernjuniper is the tree species most suitable forthis project because of its extensive range, longevity, high sensitivity to moisture, and low sensitivity to temperature. Twenty-fivewestern juniper cross sections wereprepared and measured using standard dendrochronological techniques. A master chronology that extends from A.D. 797-2000 was established using the 25 westernjuniper cross sections. Pearsons's product-moment correlation analyses were conducted using regional precipitation data, the PDO index, and the Nifio 3 index. The correlation between regional precipitation and radial tree growth wasthe strongest, suggesting that moisture is the most influential limiting factorof growth in central Oregon. Significantpositive relationships, however, were also discovered between radial tree growthand the other climatic variables. Regression analyses were performedand climatic variables were reconstructed forthe entire length of the tree-ring chronology. Vll Many climatic episodes are evident in the reconstructions. The most prominent featuresof the tree-ring chronology include sustained periods of suppressed radial tree growthduring A.D. 13 51-13 90 and 1917-194 7, as well as a long-term period of above­ average growthduring A.D. 1948-1999. These new data provide a better understanding of the strength and periodicity of past climatic change in the PacificNorthwest, and strengthens our predictive capabilities of potential futureclimatic shifts. vm Table of Contents 1. Introduction ..........................................................................................................1 1.1 Background ..................................................................................................1 1.2 Climatic Reconstructions fromProxy Data ................................................. 2 1.3 Major Climatic Oscillations that Affect the PacificNorthwest ...................7 1.3.1 El Nino-Southern Oscillation (ENSO)............................................. 7 1.3.2 The PacificDecadal Oscillation (PDQ) .........................................11 1.4 Problem Statement ..................................................................................... 14 1.5 Objectives of the Study ..............................................................................18 2. Literature Review ..............................................................................................19 2.1 Dendroclimatology in the PacificNorthwest.. ........................................... 19 2.1.1 Keen (1937) ...................................................................................19 2.1.2 Knapp et al. (2002) ........................................................................ 21 2.1.3 Pohl et al. (2002)............................................................................ 25 2.1.4 Knappet al. (2004) ........................................................................26 2.2 The PacificDecadal Oscillation (PDQ) ..................................................... 28 2.2.1 Mantua et al. (1997) .......................................................................28 2.2.2 Minobe (1997) ...............................................................................29 2.2.3 Biondi et al. (2001) ........................................................................31