Clemson University TigerPrints All Dissertations Dissertations 5-2016 Impacts of Laurel Wilt Disease on Native Persea of the Southeastern United States Timothy M. Shearman Clemson University, [email protected] Follow this and additional works at: https://tigerprints.clemson.edu/all_dissertations Recommended Citation Shearman, Timothy M., "Impacts of Laurel Wilt Disease on Native Persea of the Southeastern United States" (2016). All Dissertations. 1656. https://tigerprints.clemson.edu/all_dissertations/1656 This Dissertation is brought to you for free and open access by the Dissertations at TigerPrints. It has been accepted for inclusion in All Dissertations by an authorized administrator of TigerPrints. For more information, please contact [email protected]. IMPACTS OF LAUREL WILT DISEASE ON NATIVE PERSEA OF THE SOUTHEASTERN UNITED STATES A Dissertation Presented to the Graduate School of Clemson University In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Forest Resources by Timothy M. Shearman May 2016 Accepted by: Dr. G. Geoff Wang, Committee Chair Dr. Saara J. DeWalt Dr. Donald L. Hagan Dr. Julia L. Kerrigan Dr. William C. Bridges ABSTRACT Laurel Wilt Disease (LWD) has caused severe mortality in native Persea species of the southeastern United States since it was first detected in 2003. This study was designed to document the range-wide population impacts to LWD, as well as the patterns of mortality and regeneration in Persea ecosystems. I used Forest Inventory and Analysis (FIA) data from the U.S. Forest Service to estimate Persea borbonia (red bay) populations from 2003 to 2011 to see if any decline could be observed since the introduction of LWD causal agents. Population estimates from 2003 to 2011 suggest that the population is declining. The population in Georgia significantly decreased from ca. 241.1 ± 11.9 million stems in 2003 to ca. 150.3 ± 7.9 million in 2011. Red bay densities decreased significantly in plots surveyed before and after the reported infection by an average of 89.6 live red bay stems/ha. I developed a logistic regression model to predict the probability of red bay mortality due to LWD. Number of years since LWD infection was the most significant variable, with every increase in 1 year resulting in a 153.7 % increase in odds of death. Diameter was also a significant predictor, with an increase of 1 cm DBH resulting in a 5.0 % increase in odds of death. To document the stand characteristics of red bay and swamp bay (Persea palustris) communities, I analyzed data collected from 1988–2012 by the Carolina Vegetation Survey. We used cluster analyses and species indicator analyses to group 388 plots into distinct communities. Red bay and swamp bay communities were significantly different in species composition. In addition, red bay was almost exclusively limited to ii maritime coastal forests, whereas swamp bay had a significantly larger geographical range, extending from near coastal setting inland through the fall-line sandhills. I surveyed plots from 1 to 10 years post LWD in South Carolina and Georgia. We did not find evidence of invasive species abundance increasing after LWD. Nearly all Persea in a plot are killed within the first two years of LWD, with the exception of smaller stems under 2.5 cm in diameter. After 10 years, Persea has regained much of the basal area prior to infection, however the structure of the stand is predominantly composed of small diameter stems (1 – 5 cm DBH). Seedling densities remain relatively the same throughout all recovery years. Contrary to initial fears, this study suggests that the native Persea species in the U.S. are not on the immediate verge of extinction from LWD at this time. However, it is still too early to say whether these species will fully recover from the disease. iii DEDICATION This dissertation is dedicated to my family. To my parents, Richard and Patricia Shearman, for their unconditional love and support, making me into the person that I am today. To Laura, Kennedy, and Jocelyn, for always believing in me. iv ACKNOWLEDGMENTS This dissertation would not have been possible without Dr. Geoff Wang, who provided me with the opportunity and guidance to work on this project. The U.S. Forest Health Monitoring Program provided the funding (grant SO-EM-B-12-05) for this dissertation. I would like to thank my committee, Drs. William Bridges, Don Hagan, Julia Kerrigan, and Saara DeWalt, for their helpful advice and edits to the manuscript. Special thanks to everyone that helped in finding plot locations and acquiring necessary permits: Laurie Reid, Stan Hutto, Scott Cameron, George Chastain, William Conner, Skip Van Bloem, Doug Hoffman, Ben Carswell, and Joel Wells. Thanks to Dr. Robert Peet and Michael Lee and for providing data from the Carolina Vegetation Survey, as well as all of the researchers who participated in collecting data over the years. Thanks to John Bowers and Carson Barefoot for their assistance in the field. Lastly, I would like to thank Laura Dunn, Kennedy Dunn, and Jocelyn Houghmaster for supporting the decision to get my Ph.D. and for their encouragement throughout my program. I could not have made it without them. Thank you all very much. v TABLE OF CONTENTS Page TITLE PAGE .................................................................................................................... i ABSTRACT ..................................................................................................................... ii DEDICATION ................................................................................................................ iv ACKNOWLEDGMENTS ............................................................................................... v LIST OF TABLES ........................................................................................................ viii LIST OF FIGURES ...................................................................................................... xiii CHAPTER I. INTRODUCTION ......................................................................................... 1 Forest Diseases and Pathogens ................................................................ 1 Dissemination of fungal pathogens by beetles......................................... 4 Laurel Wilt Disease.................................................................................. 6 Disease Cycle ........................................................................................... 7 Lauraceae ............................................................................................... 10 Dissertation format................................................................................. 17 Literature Cited ...................................................................................... 18 II. POPULATION DYNAMICS OF RED BAY (PERSEA BORBONIA) AFTER LAUREL WILT DISEASE: AN ASSESSMENT BASED ON FOREST INVENTORY AND ANALYSIS DATA .............................................. 25 Introduction ............................................................................................ 25 Materials and Methods ........................................................................... 29 Results .................................................................................................... 34 Discussion .............................................................................................. 45 Literature Cited ...................................................................................... 50 vi Table of Contents (Continued) Page III. A COMMUNITY ANALYSIS FOR FOREST ECOSYSTEMS WITH NATURAL GROWTH OF PERSEA IN THE SOUTHEASTERN UNITESD STATES .............................................. 55 Introduction ............................................................................................ 55 Materials and Methods ........................................................................... 58 Results .................................................................................................... 62 Discussion .............................................................................................. 80 Literature Cited ...................................................................................... 84 IV. RECOVERY OR EXTINCTION? INSIGHT FROM PERSEA RESPONSE TO LAUREL WILT DISEASE DURING THE FIRST 10 YEARS ........................................................ 89 Introduction ............................................................................................ 89 Materials and Methods ........................................................................... 91 Results .................................................................................................... 98 Discussion ............................................................................................ 104 Literature Cited .................................................................................... 110 V. MODELING FIRE BEHAVIOR AFTER LAUREL WILT DISEASE .................................................................................. 113 Introduction .......................................................................................... 113 Materials and Methods ......................................................................... 115 Results .................................................................................................. 118 Discussion ............................................................................................ 122