The University of Maine DigitalCommons@UMaine Electronic Theses and Dissertations Fogler Library Fall 12-21-2019 Spruce Budworm Defoliation Dynamics and its Influence on the Acadian Forest Cen Chen university of maine, [email protected] Follow this and additional works at: https://digitalcommons.library.umaine.edu/etd Part of the Forest Biology Commons, and the Forest Management Commons Recommended Citation Chen, Cen, "Spruce Budworm Defoliation Dynamics and its Influence on the Acadian orF est" (2019). Electronic Theses and Dissertations. 3081. https://digitalcommons.library.umaine.edu/etd/3081 This Open-Access Thesis is brought to you for free and open access by DigitalCommons@UMaine. It has been accepted for inclusion in Electronic Theses and Dissertations by an authorized administrator of DigitalCommons@UMaine. For more information, please contact [email protected]. SPRUCE BUDWORM DEFOLIATION DYNAMICS AND ITS INFLUENCE ON THE ACADIAN FOREST By Cen Chen B.A. South China Agricultural University, 2000 M.S. Swedish University of Agricultural Sciences, 2012 A DISSERTATION Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy (in Forest Sciences and Biology) The Graduate School The University of Maine December 2019 Advisory Committee: Aaron Weiskittel, Professor of Forest Biometrics and Modeling, Advisor Mohammad Bataineh, Assistant Professor David MacLean, Professor of Forest Ecology Mindy Crandall, Assistant Professor of Forest Landscape Management & Economics Erin Simons-Legaard, Assistant Research Professor in Forest Landscape Modeling Copyright 2019 Cen Chen ii SPRUCE BUDWORM DEFOLIATION DYNAMICS AND ITS INFLUENCE ON THE ACADIAN FOREST By Cen Chen Dissertation Advisor: Dr. Aaron Weiskittel An Abstract of the Dissertation Presented in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy (in Forest Sciences and Biology) December 2019 Spruce budworm (SBW; Choristoneura fumiferana (Clem.)) is the primary forest defoliator in North America. SBW defoliation has affected tens of millions ha of forests during its periodic outbreaks and caused severe growth reduction and mortality of spruce-fir (Picea-Abies) species. Evaluating these damaging effects of SBW defoliation requires understandings of the variation and dynamics of defoliation, as well as trees' variable responses to defoliation in consideration of various tree- stand-, and site-level factors. In this dissertation, we developed statistical models to 1) evaluate influences of SBW defoliation on spruce-fir stand dynamics of annual volume net growth, mortality, and ingrowth, 2) quantify effects of SBW defoliation on annualized diameter and height increment, crown recession, and mortality, and 3) assess patterns and temporal development of SBW defoliation on individual trees. Measurements of individual trees and their defoliation collected from 560 permanent sample plots in Maine and New Brunswick during the last SBW outbreak in the 1970s-1980s, which covered > 40 000 km2 as well as 10 years of varying ranges of defoliation and forest conditions were used in the analyses. Our results strongly demonstrated that 1) even relatively low levels of cumulative defoliation were significantly related to stand-level mortality and ingrowth, while net growth was more competition driven, 2) effects of defoliation on diameter increment, crown recession, and mortality were highly significant but relatively moderate depending on species, and 3) variation in individual tree defoliation was predominantly dependent on species. In addition, defoliation of each host species analyzed developed towards their respective converged trajectories. Based on these findings, we developed annualized modifiers for the Acadian variant of the Forest Vegetation Simulator (FVS-ACD) to account for effects of SBW defoliation on forest development, which consistently had smaller biases and prediction errors than FVS-ACD refined by STAMAN (a Canadian growth model) SBW modifiers. Overall, our findings highlight the high variability in SBW defoliation and trees' responses to defoliation, which were consistent between Maine and New Brunswick despite varying forest management history and species composition. We believe the developed modeling framework should also be extendable to analyzing other forms of defoliation in broader regions. ACKNOWLEDGEMENTS I would like to thank my advisor, Dr. Aaron Weiskittel, for guiding me through my study, thank Drs. Mohammad Bataineh, David MacLean, Mindy Crandall, Erin Simons-Legaard, and Christian Kuehne for their inputs into this dissertation and serving on my advisory Committee, thank Dr. Thomas Brann, the University of Maine Cooperative Forestry Research Unit, and the Canadian Forest Service for providing data used in this dissertation, and thank the Northeastern States Research Cooperative, the University of Maine School of Forest Resources, and the Maine Agricultural and Forest Experiment Station for providing funding for my study. Special thanks to Drs. Robert Seymour, Greg Reams, Chris Hennigar, and many editors as well as anonymous reviewers for reviewing and providing feedback on drafts of chapters of this dissertation. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS ................................................................................................................................ iii LIST OF TABLES ........................................................................................................................................... viii LIST OF FIGURES ............................................................................................................................................ x Chapter 1. THE ACADIAN FOREST AND THE SPRUCE BUDWORM: A PROLOGUE ................................................... 1 1.1. The Acadian Forest ...................................................................................................................... 1 1.2. The Spruce Budworm and its Outbreaks ..................................................................................... 3 1.3. Structure of This Dissertation ...................................................................................................... 6 2. EVEN LOW LEVELS OF SPRUCE BUDWORM DEFOLIATION AFFECT MORTALITY AND INGROWTH BUT NET GROWTH IS MORE DRIVEN BY COMPETITION .................................................... 9 2.1. Introduction ................................................................................................................................. 9 2.2. Material and Method ................................................................................................................ 13 2.2.1. Study Area .................................................................................................................... 13 2.2.2. Data .............................................................................................................................. 14 2.2.2.1. Growth Impact Study of Maine ....................................................................... 15 2.2.2.2. Permanent Sample Plots of New Brunswick.................................................... 15 2.2.2.3. Data Compilation ............................................................................................. 16 2.2.3. Analysis ........................................................................................................................ 19 2.2.3.1. Net Growth ...................................................................................................... 19 2.2.3.2. Mortality .......................................................................................................... 20 2.2.3.3. Ingrowth........................................................................................................... 21 iv 2.3. Results ....................................................................................................................................... 22 2.3.1. Net Growth .................................................................................................................. 22 2.3.2. Mortality ...................................................................................................................... 26 2.3.3. Ingrowth ...................................................................................................................... 28 2.4. Discussion .................................................................................................................................. 31 3. EVALUATING THE INFLUENCE OF VARYING LEVELS OF SPRUCE BUDWORM DEFOLIATION ON ANNUALIZED INDIVIDUAL TREE GROWTH AND MORTALITY IN MAINE, USA AND NEW BRUNSWICK, CANADA ......................................................................................................................... 36 3.1. Introduction ............................................................................................................................... 36 3.2. Material and Method ................................................................................................................ 39 3.2.1. Study Area .................................................................................................................... 39 3.2.2. Data .............................................................................................................................. 41 3.2.2.1. Growth Impact Study of Maine ....................................................................... 41 3.2.2.2. Permanent