Utah State University DigitalCommons@USU All Graduate Theses and Dissertations Graduate Studies 5-2017 Impact of Climate Variability on the Frequency and Severity of Ecological Disturbances in Great Basin Bristlecone Pine Sky Island Ecosystems Curtis A. Gray Utah State University Follow this and additional works at: https://digitalcommons.usu.edu/etd Part of the Forest Sciences Commons Recommended Citation Gray, Curtis A., "Impact of Climate Variability on the Frequency and Severity of Ecological Disturbances in Great Basin Bristlecone Pine Sky Island Ecosystems" (2017). All Graduate Theses and Dissertations. 6529. https://digitalcommons.usu.edu/etd/6529 This Dissertation is brought to you for free and open access by the Graduate Studies at DigitalCommons@USU. It has been accepted for inclusion in All Graduate Theses and Dissertations by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. IMPACT OF CLIMATE VARIABILITY ON THE FREQUENCY AND SEVERITY OF ECOLOGICAL DISTURBANCES IN GREAT BASIN BRISTLECONE PINE SKY ISLAND ECOSYSTEMS by Curtis A. Gray A dissertation submitted in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY in Ecology Approved: __________________________ __________________________ Michael Jenkins, Ph.D. Thomas C. Edwards, Jr., Ph.D. Major Professor Committee Member __________________________ __________________________ Peter Howe, Ph.D. R. Douglas Ramsey, Ph.D. Committee Member Committee Member __________________________ __________________________ Justin Runyon, Ph.D. Mark R. McLellan, Ph.D. Committee Member Vice President for Research and Dean of the School of Graduate Studies UTAH STATE UNIVERSITY Logan, UT 2017 ii Copyright © Curtis A. Gray 2017 All Rights Reserved iii ABSTRACT Impact of Climate Variability on the Frequency and Severity of Ecological Disturbances in Great Basin Bristlecone Pine Sky Island Ecosystems by Curtis A. Gray, Doctor of Philosophy Utah State University, 2017 Major Professor: Dr. Michael Jenkins Department: Wildland Resources Great Basin bristlecone pine (GBBP) (Pinus longaeva Bailey) is one of the longest-lived organisms on Earth, and is one of the most highly fragmented high elevation conifer species. Throughout the Great Basin of the Intermountain West, GBBP are being impacted by changing disturbance regimes, invasive species, and climate change. To better understand the effects of climate variability and ecological disturbances in GBBP systems, three studies were designed and implemented. The first characterized the distribution of forest fuel in stands of GBBP and predicted how fuels may change under future climate scenarios. Using the Forest Inventory Analysis (FIA) plot variables of tree species, height, diameter at breast height (DBH), canopy base height (CBH), coarse (CWD) and fine (FWD) woody debris across elevational gradients, this study examined the effects of changes to fuel loading on predicted changes in fire behavior and severity. All classes of FWD decreased with elevation, and only 1000-hr fuels remained constant across elevational transects. This, combined with lower CBH and foliar moisture iv and increasing temperatures due to climate change, suggested increased fire potential at the GBBP treeline. The second study examined the role of volatile organic compounds (VOCs) and tree chemistry and their response to the environment. VOCs and within needle chemistry were collected and analyzed along elevational gradients near the northern and southern limits of GBBP. Random Forest analysis distinguished elevation using VOCs, with 83% accuracy, and identified the compounds most important for classification. Ordination revealed that temperature, heat load index, and relative humidity were each significantly correlated with VOCs. Within-needle chemistry provided less predictive value in classifying elevation (68% accuracy) and was correlated only with heat load index. These findings suggest that GBBP VOCs are highly sensitive to the environment. The final study explored the role of VOCs in host selection of mountain pine beetle (MPB). Mountain pine beetles oriented toward VOCs from host limber pine (Pinus flexilis James) and away from VOCs of non-host GBBP using a Y- tube olfactometer. When presented with VOCs of both trees, females overwhelmingly chose limber pine over GBBP. While there were only a few notable differences in VOCs collected from co-occurring GBBP and limber pine, 3-carene and D-limonene were produced in greater amounts by limber pine. There was no evidence that 3-carene is important for beetles when selecting trees, however, addition of D-limonene to GBBP VOCs disrupted the ability of beetles to distinguish between tree species. Climate change will impact how forests are managed and this research could provide insight into the mechanisms underlying the incredible longevity of this iconic tree species. (160 Pages) v PUBLIC ABSTRACT Impact of Climate Variability on the Frequency and Severity of Ecological Disturbances in Great Basin Bristlecone Pine Sky Island Ecosystems Curtis A. Gray Many high elevation conifer species, including high elevation five needle pines, are declining throughout western North America. Warming temperatures, mountain pine beetle, white pine blister rust and alteration of naturally occurring fire regimes represent an interactive set of circumstances leading to greater risk. The loss of these treeline pines can detrimentally impact biodiversity and valuable ecosystem services including wildlife habitat, watershed and soil protection, aesthetics and recreation. Great Basin bristlecone pine ecosystems are naturally highly fragmented because of their elevational requirements. However, they may become even more fragmented due to combined impacts of warming temperature, insects and diseases listed above. This study increased the knowledge of Great Basin bristlecone pine ecology by examining response to climate change with respect to fire, fuels and tree chemistry. The first study examined alteration of the fire regime and showed that fuels in Great Basin bristlecone pine decreased with elevation. Yet, canopy fuels that are more susceptible to fire, suggested fire potential may increase at higher elevations with warming air temperatures, which could threaten the oldest individuals of this iconic species. Examination of tree chemistry to environmental gradients (like elevation and temperature) demonstrated a clear response to climate induced environmental stress. This has the potential to alter flammability and the effectiveness of tree defenses to mountain pine beetle. Lastly, this research determined vi that volatile organic compounds emitted from Great Basin bristlecone pine foliage influence host selection for mountain pine beetle. All three of these studies will aid in developing unique forest management practices to increase forest resilience of treeline species and could provide insight into the mechanisms underlying the incredible longevity of Great Basin bristlecone pine. vii ACKNOWLEDGMENTS I would like to express my gratitude to my Ph.D. advisor, Dr. Michael Jenkins. Mike has been a great mentor and without his guidance this research would not have been possible. I would like to thank the USFS EM Project INT-EM-F-10-02, the Ecology Center at Utah State University, the Utah Agricultural Experiment Station (UAES), and a USDA National Needs Graduate Fellowship Competitive NIFA Grant for providing the funding for this project. Additionally, I would also like to thank my committee members, Dr. Thomas Edwards, Dr. Peter Howe, Dr. R. Douglas Ramsey, and Dr. Justin Runyon, who provided constructive and critical feedback on this research. Additionally, I am grateful to Danielle Malesky who helped collect volatiles and read drafts of my manuscripts. Matthew Blakeley-Smith, Chelsea Toone, and Andrew Guinta who helped install field plots, collect, and enter field data. Their long days helped accelerate this project’s completion. I also wish to acknowledge Barbara Bentz, Matt Hansen, and Jim Vandygriff of the USFS Rocky Mountain Research Station in Logan, UT for help in acquiring, and rearing, mountain pine beetles. The staff at Cave Lake State Park, NV and Great Basin National Park, NV for providing site access and camping. I wish to acknowledge the help of the Department of Wildland Resources administration staff, Marsha Bailey and Lana Barr, who were always willing to laugh at my jokes. Finally, I want to express my love and appreciation to Dr Sarah Null for taking on an unofficial graduate student, and providing embarrassingly large amounts of help with preparing manuscripts. Curtis Gray viii CONTENTS Page ABSTRACT ....................................................................................................................... iii PUBLIC ABSTRACT .........................................................................................................v ACKNOWLEDGMENTS ................................................................................................ vii LIST OF TABLES ...............................................................................................................x LIST OF FIGURES .......................................................................................................... xii CHAPTER 1. INTRODUCTION .......................................................................................1 References ..............................................................................................3 2. USING MULTIVARIATE