FIRE REGIMES OF THE SOUTHERN APPALACHIAN MOUNTAINS: TEMPORAL AND SPATIAL VARIABILITY AND IMPLICATIONS FOR VEGETATION DYNAMICS A Dissertation by WILLIAM TREUTLEN FLATLEY Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved by: Chair of Committee, Charles W. Lafon Committee Members, David M. Cairns Andrew C. Millington X. Ben Wu Head of Department, Vatche P. Tchakerian December Choose an item. Major Subject: Geography Copyright 2012 ABSTRACT Ecologists continue to debate the role of fire in forests of the southern Appalachian Mountains. How does climate influence fire in these humid, temperate forests? Did fire regimes change during the transition from Native American settlement to Euro-American settlement? Are fire regime changes resulting in broad vegetation changes in the forests of eastern North America? I used several approaches to address these questions. First, I used digitized fire perimeter maps from Great Smoky Mountains National Park and Shenandoah National Park for 1930-2009 to characterize spatial and temporal patterns of wildfire by aspect, elevation, and landform. Results demonstrate that fuel moisture is a primary control, with fire occurring most frequently during dry years, in dry regions, and at dry topographic positions. Climate also modifies topographic control, with weaker topographic patterns under drier conditions. Second, I used dendroecological methods to reconstruct historical fire frequency in yellow pine (Pinus, subgenus Diploxylon Koehne) stands at three field sites in the southern Appalachian Mountains. The fire history reconstructions extend from 1700 to 2009, with composite fire return intervals ranging from 2-4 years prior to the fire protection period. The two longest reconstructions record frequent fire during periods of Native American land use. Except for the recent fire protection period, temporal changes in land use did not have a significant impact on fire frequency and there was little discernible influence of climate on past fire occurrence. ii Third, I sampled vegetation composition in four different stand types along a topographic moisture gradient, including mesic cove, sub-mesic white pine (Pinus strobus L.)-hardwood, sub-xeric oak (Quercus L.), and xeric pine forests in an unlogged watershed with a reconstructed fire history. Stand age structures demonstrate changes in establishment following fire exclusion in xeric pine stands, sub-xeric oak stands, and sub-mesic white pine-hardwood stands. Fire-tolerant yellow pines and oaks are being replaced by shade-tolerant, fire sensitive species such as red maple (Acer rubrum L.) and hemlock (Tsuga canadensis L. Carr.). Classification analysis and ordination of species composition in different age classes suggest a trend of successional convergence in the absence of fire with a shift from four to two forest communities. iii ACKNOWLEDGEMENTS There are many people who deserve credit for the completion of this project. First and foremost, I would like to thank my wife Jennifer for her support and encouragement. She has never lost faith in me during this long process. I couldn’t have done it without you. I would also like to thank my family for their continued support during my educational journey. You have always encouraged and enabled me to pursue my interests, no matter how far off the beaten path. Thank you and I love you all. I would also like to thank my committee chair Dr. Charles Wilber Lafon, for invaluable guidance in the art of field work, research, writing, teaching, and punnery. I can only hope that I have absorbed a small portion of the knowledge that you impart on a daily basis. I would also like to thank my committee members Dr. David Cairns, Dr. Andrew Millington, and Dr. X. Ben Wu. In particular, I thank Dr. Cairns for guidance in the analysis of the vegetation dynamics section. I also owe a debt of gratitude to Serena Aldrich for blazing a trail as the original dendrochronology guru at Texas A&M University. Your work made everything easier for me. Thank you for leading the way. This project was made possible by the National Interagency Joint Fire Science Project Grant # 06-3-1-05 issued to Dr. Charles Lafon, Dr. Henri Grissino-Mayer, and Dr. Sally Horn. Additional funding during my graduate studies was generously provided by the Texas A&M University Department of Geography, the Office of Graduate Studies Phil Gramm Fellowship, and the Biogeography Specialty Group of the Association of American Geographers. iv During this project I was aided by many professionals in the National Park Service and U.S. Forest Service. In particular, I would like to thank Rob Klein and the fire effects monitoring crew for help in the field and logistical guidance during field work in GSMNP. A number of other people deserve thanks for providing guidance in my search for fire history sites including, Beth Buchannan, Gary Kaufmann, Greg Salansky, Steve Croy, guy in Nantahallah office. I would also like to thank House Mountain State Natural Area, Great Smoky Mountains National Park, Pisgah National Forest, Nantahala National Forests and Cherokee National Forest for granting permission to collect samples. Finally, thank you to Great Smoky Mountains National Park and Shenandoah National Park for providing me with the fire perimeter maps. Finally, this project would not have been possible without an army of helpers in the field and the laboratory. Thank you Dr. Charles Lafon, Dr. Henri Grissino-Mayer, Lisa LaForest, Amanda Young, Jennifer Flatley, Ashley Pipkin, Sandra Metoyer, Illiyana Dobreva, Ralph Baker, Brandon Wilcox, David Sitting Bear, Beth Munoz, Tyler Pruett, Martina Antonia, Andrew Nidoh, Rob Klein, Ian Feathers, Grant Harley, Phillip White, Nelson Lafon, and Griff the hound dog. The collection of 250 pine cross sections and 1500 tree cores could not have been accomplished without all of your help. My days in the field are my favorite memories from this process. Thank you for sharing them with me. v NOMENCLATURE AF All Fires AWF Area Wide Fire AWI Area Wide Fire Interval CART Classification and Regression Tree CFI Composite Fire Interval DBH Diameter at Breast Height DEM Digital Elevation Model EP Exclusion Period FFI Filtered Fire Interval FP Fire Period GSMNP Great Smoky Mountains National Park ISA Indicator Species Anlaysis LEI Lower Exceedance Interval MCFI Mean Composite Fire Interval MF Major Fire MFI Mean Fire Interval vi MRPP Multi-Response Permutation Procedure NCDC National Climatic Data Center NMS Non-metric Multidimensional Scaling OS Origin to Scar PDSI Palmer Drought Severity Index PFI Point Fire Interval PP Post-fire Period RF Regional Fire RFI Regional Fire Interval SD Standard Deviation SEA Superposed Epoch Analysis SNP Shenandoah National Park UEI Upper Exceedance Interval WFI Weibull Median Fire Interval vii TABLE OF CONTENTS Page ABSTRACT ....................................................................................................................... ii ACKNOWLEDGEMENTS .............................................................................................. iv NOMENCLATURE ......................................................................................................... vi TABLE OF CONTENTS ................................................................................................ viii LIST OF FIGURES ........................................................................................................ xiii LIST OF TABLES ........................................................................................................ xviii INTRODUCTION ............................................................................................................. 1 Purpose of the Study ...................................................................................................... 6 Contemporary Landscape Patterns of Fire ................................................................. 6 Fire History ................................................................................................................. 9 Vegetation Dynamics ............................................................................................... 12 LITERATURE REVIEW ................................................................................................ 15 Fire Regimes in the Southern Appalachian Mountains ................................................ 15 Models of Fire and Vegetation Development in Eastern Forest .............................. 16 Pre-Euro-American Settlement Fire Regimes .......................................................... 17 Post Euro-American Settlement Fire Regimes ......................................................... 21 Fire Atlases ................................................................................................................... 23 Characterizing Fire Regimes .................................................................................... 23 Assessing Modern Changes in Fire Regimes ........................................................... 24 Identification of Controls on Fire Regimes .............................................................. 26 Combining Fire Atlases with Other Techniques ...................................................... 28 Issues of Bias within Fire Atlas Data ....................................................................... 29 Fire History Reconstructions ........................................................................................ 32 Methods for Using Fire Scars to Characterize Fire Regimes ................................... 32 Individual-Tree Fire Interval .................................................................................... 33 viii The Mean Composite Fire Interval ........................................................................... 34 Origin-to-Scar Interval ............................................................................................. 36 Sample Size .............................................................................................................. 39 Targeted Sampling .................................................................................................... 40 Vegetation Dynamics ................................................................................................... 42 Community vs. Individualistic Concepts of Vegetation Association ....................... 42 Vegetation Disturbance ............................................................................................ 43 Characterizations of Disturbance .............................................................................. 44 Disturbance as regressive succession ....................................................................... 45 Disturbance mediated accelerated succession .......................................................... 45 Disturbance as a fundamental alteration in the successional sequence .................... 46 Disturbance and Vegetation Diversity ...................................................................... 47 METHODS* ..................................................................................................................... 49 Study Area .................................................................................................................... 49 Topography and Soils ............................................................................................... 49 Climate...................................................................................................................... 51 Vegetation ................................................................................................................. 52 Land Use History ......................................................................................................... 54 Native American ....................................................................................................... 54 Early Euro-American Settlement .............................................................................. 60 Period of Extractive Industry .................................................................................... 63 Era of Fire Protection and Suppression .................................................................... 63 Landscape Patters of Fire ............................................................................................. 65 Study Areas............................................................................................................... 65 Great Smoky Mountains National Park ................................................................ 65 Shenandoah National Park .................................................................................... 67 Spatial Data............................................................................................................... 67 Fire Perimeter Maps .............................................................................................. 67 Climate Data ......................................................................................................... 70 Topographic Data.................................................................................................. 70 Data Analysis ............................................................................................................ 71 Fire History .................................................................................................................. 75 ix Study Sites ................................................................................................................ 75 House Mountain .................................................................................................... 75 Licklog Ridge........................................................................................................ 77 Linville Mountain ................................................................................................. 80 Field Methods ........................................................................................................... 82 Laboratory Methods ................................................................................................. 82 Data Analysis ............................................................................................................ 84 Fire Frequency ...................................................................................................... 84 Temporal Variations in Fire Activity .................................................................... 86 Fire-climate Relationships .................................................................................... 87 Vegetation Dynamics ................................................................................................... 89 Study Site .................................................................................................................. 89 Field Methods ........................................................................................................... 89 Laboratory Methods ................................................................................................. 90 Data Analysis ............................................................................................................ 91 RESULTS ........................................................................................................................ 95 Contemporary Landscape Patterns of Fire ................................................................... 95 Fire-climate Relationship ......................................................................................... 95 Fire-topography Relationships ............................................................................... 100 Climate-topography Interaction .............................................................................. 104 Fire History ................................................................................................................ 108 Fire Frequency ........................................................................................................ 109 Temporal Variations in Fire Activity ..................................................................... 124 Fire-climate Relationships ...................................................................................... 126 Vegetation Dynamics ................................................................................................. 131 Pine Stands ............................................................................................................. 131 Oak Stands .............................................................................................................. 131 White Pine-Hardwood Stands ................................................................................ 132 North Cove Stands .................................................................................................. 133 South Cove Stands .................................................................................................. 133 Classification of Forest Communities .................................................................... 143 Successional Change and Community Diversity .................................................... 147 x