Two Post-Glacial Sagebrush Steppe Fire Records at the Wildland-Urban Interface, Eastern Cascades, Washington" (2018)
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Central Washington University ScholarWorks@CWU All Master's Theses Master's Theses Fall 2018 Two Post-Glacial Sagebrush Steppe Fire Records at the Wildland- Urban Interface, Eastern Cascades, Washington Dusty Pilkington Central Washington University, [email protected] Follow this and additional works at: https://digitalcommons.cwu.edu/etd Part of the Forest Management Commons, Natural Resources Management and Policy Commons, and the Paleobiology Commons Recommended Citation Pilkington, Dusty, "Two Post-Glacial Sagebrush Steppe Fire Records at the Wildland-Urban Interface, Eastern Cascades, Washington" (2018). All Master's Theses. 1097. https://digitalcommons.cwu.edu/etd/1097 This Thesis is brought to you for free and open access by the Master's Theses at ScholarWorks@CWU. It has been accepted for inclusion in All Master's Theses by an authorized administrator of ScholarWorks@CWU. For more information, please contact [email protected]. TWO POST-GLACIAL SAGEBRUSH STEPPE FIRE RECORDS AT THE WILDLAND-URBAN INTERFACE, EASTERN CASCADES, WASHINGTON __________________________________ A Thesis Presented to The Graduate Faculty Central Washington University ___________________________________ In Partial Fulfillment of the Requirements for the Degree Master of Science Resource Management ___________________________________ by Dusty Joel Pilkington November 2018 CENTRAL WASHINGTON UNIVERSITY Graduate Studies We hereby approve the thesis of Dusty Joel Pilkington Candidate for the degree of Master of Science APPROVED FOR THE GRADUATE FACULTY ______________ _________________________________________ Dr. Megan Walsh, Committee Chair ______________ _________________________________________ Dr. Michael Pease ______________ _________________________________________ Dr. Steve Hackenberger ______________ _________________________________________ Dean of Graduate Studies ii ABSTRACT TWO POST-GLACIAL SAGEBRUSH FIRE RECORDS AT THE WILDLAND- URBAN INTERFACE, EASTERN CASCADES, WASHINGTON by Dusty Joel Pilkington November 2018 Recent increases in large fires in the rapidly developing wildland-urban interface (WUI) areas of central Washington, where development intermixes with wildland fuels, contribute to federal firefighting costs exceeding of $1 billion annually. In addition, cheatgrass (Bromus tectorum) invasion and anthropogenic-caused warming shorten fire return intervals while lengthening fire seasons. These climatic, ecological, economic, and social factors combine with fuel accumulation resulting from historic fire suppression to threaten lives and property in the WUI. To plan for safe growth in WUI areas, long-term fire histories are needed to expand understanding of past fire regimes in an understudied ecosystem, sagebrush steppe. In this thesis, two ca. 15,000-year-old fire histories were developed from study sites in Okanogan County, Washington. Lake sediment cores were analyzed using macroscopic charcoal analysis and CharAnalysis software. Relationships between past fire, vegetation, human activities, and climatic drivers, such as the Early Holocene Warm Period, the Medieval Climate Anomaly, the Little Ice Age, and El-Niño Southern Oscillation, were considered. Results suggest that although climate influences eastern Cascades sagebrush steppe environments over millennial timescales, fuel availability represents a limiting factor over shorter intervals, with wet years allowing sagebrush and other fine fuels to proliferate, and fires occurring in subsequent dry intervals. The performance of CharAnalysis in sagebrush environments suggests that constant charcoal influx from frequent, low-severity fire events renders individual fire difficult to resolve from macroscopic charcoal records. The record analyzed here can inform decision makers in setting policies consistent with the long-term fire regime of the Methow Valley. iii ACKNOWLEDGEMENTS Many thanks to my thesis committee, Dr. Megan Walsh, Dr. Michael Pease, and Dr. Steven Hackenberger for their patience with my disorganized drafts, and their assistance in cobbling them into an organized narrative. I would also like to recognize the Kittitas Audubon Society, along with Central Washington University’s Graduate Studies and Research for their generous grants. Special thanks to Zoe Rushton, Kevan Ferrier, Dr. Craig Revels, Hailey Duke, Sarah Jenson, Forest Beard, Megan Cline, and Kylie Ishimitsu for their generous laboratory and field assistance. I would like to acknowledge my family: my mom, my dads Eddie Pilkington and James Larson, both Dans: Hernandez and Ralph, my sisters Erica and Jessica, and my aunt Joni for coming to my thesis defense. My Utah friends for the encouragement: Tim and Jessi Done, Ty Norton, Dustin Booker, Ryan Baldwin, Justin Olson, Katie Maloney, and the Poulsen brothers. Washington friends: Lynn and Patience, Nic Crosby, Robert Moser, James Brown, Chazidy Norton and the whole clan in Spokane, along with Lucas Norton and Joseph Whisler. Special regards to Dr. Karl Lilliquist for all the support, and to Dr. Elvin Delgado for pushing me to put together a top-notch thesis proposal. I also thank the faculty at Weber State University who helped me get to where I am: Dr. Julie Rich, Dr. Dan Bedford, and Dr. Carla Trentelman. And most importantly, to my wife Liz. Your constant reminders that the best thesis is a completed thesis were indispensable in completing this work. iv TABLE OF CONTENTS Chapter Page I INTRODUCTION ........................................................................................ 1 II LITERATURE REVIEW ............................................................................. 9 III STUDY AREA ........................................................................................... 38 IV METHODS ................................................................................................. 57 V RESULTS .................................................................................................... 63 VI DISCUSSION .............................................................................................. 89 VII CONCLUSIONS ....................................................................................... 107 REFERENCES CITED ............................................................................................. 114 v LIST OF TABLES Table Page 2.1: Fire Regime Condition Classes ........................................................................... 12 5.1: Age determinations for Green Lake core GL15B ............................................... 65 5.2: Summary of charcoal data for GL15B ................................................................ 66 5.3: Age determinations for Campbell Lake core CBL15C....................................... 78 5.4: Summary of charcoal data for Campbell Lake ................................................... 85 vi LIST OF FIGURES Figure Page 1.1: The Carlton and Okanogan Complex burn areas .................................................. 3 2.1: Historic return intervals and Fire Regime Condition Classes ............................. 11 2.2: Acres burned, wildfire count, and acres burned from 1960 – 2014. ................... 23 2.3: Forest Service wildfire suppression expenditure from 1985-2015 ...................... 24 2.4: Climax series of Washington and Oregon .......................................................... 29 2.5: Map of ponderosa pine distribution in North America ....................................... 31 2.6: Big Sagebrush extent in North America .............................................................. 33 3.1: Study area ........................................................................................................... 38 3.2: The Northern Okanogan Plateau ......................................................................... 43 3.3: Southern Okanogan Plateau ................................................................................ 44 3.4: Map showing the Green Lake study site ............................................................. 47 3.5: General vicinity of Green Lake........................................................................... 48 3.6: Elevation map of the Green Lake watershed ...................................................... 49 3.7: Green Lake temperature and precipitation .......................................................... 50 3.8: Aerial view of the Campbell Lake study site ...................................................... 52 3.9: Elevation map of the Campbell Lake watershed ................................................ 53 3.10: General Campbell Lake area ............................................................................. 54 3.11: Campbell Lake climate information ................................................................. 55 4.1: Coring platform ................................................................................................... 57 4.2: Charcoal fragments ............................................................................................. 61 5.1: Examples of Green Lake sediment cores ............................................................ 64 5.2: Green Lake (GL15B) age-depth model .............................................................. 66 vii LIST OF FIGURES (CONTINUED) Figure Page 5.3: Green Lake (GL15B) sedimentation rate ............................................................ 67 5.4: Green Lake (GL15B) charcoal, LOI, and magnetic susceptibility ..................... 69 5.5: Green Lake SNI, peak magnitude, episode frequency,