VEGETATION DYNAMICS AND THE EFFICACY OF PRESCRIBED FIRES IN RESTORING OAK- DOMINATED ECOSYSTEMS IN SOUTHERN OHIO by SHERYL M. PETERSEN Submitted in partial fulfillment of the requirements For the degree of Doctor of Philosophy Department of Biology CASE WESTERN RESERVE UNIVERSITY January, 2012 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the thesis/dissertation of Sheryl M. Petersen ______________________________________________________ Doctor of Philosophy candidate for the ________________________________degree *. Roy Ritzman (signed)_______________________________________________ (chair of the committee) Joseph F. Koonce ________________________________________________ Robin Snyder ________________________________________________ David Burke ________________________________________________ Michael Benard ________________________________________________ Matthew Dickinson ________________________________________________ September 2, 2011 (date) _______________________ *We also certify that written approval has been obtained for any proprietary material contained therein. Copyright © 2011 by Sheryl M. Petersen All rights reserved Table of contents Table of contents ........................................................................................................ i List of Tables ............................................................................................................. iv List of Figures ........................................................................................................... viii Acknowledgments .................................................................................................... xiii Abstract 1 Chapter 1: Introduction .............................................................................................. 3 1.1. Disturbance ecology and restoration of disturbance-dependent plant communities ....................................................................................................... 4 1.2. The effects of fire suppression ................................................................................ 6 1.3. Prescribed fire as a restoration tool ....................................................................... 7 1.4. Fire ecology of oak-dominated ecosystems in southern Ohio’s Bluegrass Region .......................................................................................................................... 11 1.4.1. Regional vegetation history .......................................................................... 11 1.4.2. Mixed-oak forests .......................................................................................... 13 1.4.3. Barrens .......................................................................................................... 15 1.4.4. Fire regime .................................................................................................... 16 1.4.5. Current burn prescriptions ............................................................................ 21 1.5. General experimental approach ........................................................................... 21 1.6. Study sites ............................................................................................................. 23 1.6.1. Location and region ....................................................................................... 23 1.6.2. Barrens study sties ........................................................................................ 25 1.6.3. Forest study sites ........................................................................................... 26 1.7. Organization of dissertation.................................................................................. 30 Chapter 2: Effects of biennial fire and clipping on woody and herbaceous ground layer vegetation in oak barrens of southern Ohio .............................................. 31 2.1. Abstract ................................................................................................................. 31 2.2. Introduction .......................................................................................................... 32 2.3. Methods ................................................................................................................ 35 2.3.1. Study sites ..................................................................................................... 35 2.3.2. Experimental design and data collection ...................................................... 37 2.3.3. Response variables ........................................................................................ 40 2.3.4. Data analysis .................................................................................................. 42 2.4. Results ................................................................................................................... 45 2.4.1. Fire behavior.................................................................................................. 45 2.4.2. Treatment effects on plant functional groups .............................................. 45 2.4.3. Effects of treatment on competitive interactions between woody and herbaceous groundcover plants over time ................................................. 56 2.5. Discussion .............................................................................................................. 60 2.5.1. Potential for fire to reduce shrub encroachment ......................................... 60 i 2.5.2. Potential for fire to foster herb abundance and diversity ............................ 63 2.5.3. Conclusions and management implications ................................................. 65 2.6. Appendices ............................................................................................................ 67 2.6.1. Appendix A: Full ANCOVA model results. ..................................................... 67 2.6.2. Appendix B: Full ANOVA model results. ........................................................ 71 2.6.3. Appendix C: Linear contrasts for effect of treatment over time. ................. 72 2.6.4. Appendix D: Changes in the relationship between herbaceous and woody groundcover plants between the first and last census by treatment and site. .............................................................................................................. 73 Chapter 3: Vegetation-environment relationships among the ground layers of four southern Ohio mixed oak forests .............................................................. 75 3.1. Abstract ................................................................................................................. 75 3.2. Introduction .......................................................................................................... 76 3.3. Methods ................................................................................................................ 79 3.3.1. Study sites ..................................................................................................... 79 3.3.2. Study design and data collection .................................................................. 82 3.3.3. Statistical analyses......................................................................................... 85 3.4. Results ................................................................................................................... 90 3.4.1. Differences in community pattern, structure, and diversity between sites. 90 3.4.2. Differences in environmental characteristics between sites. ....................... 95 3.4.3. Vegetation-environment relationships within individual sites and differences in ground layer assemblages between future burn management units. ... 99 3.5. Discussion ............................................................................................................ 109 3.5.1. Patterns in community pattern, structure, and diversity across sites. ....... 109 3.5.2. Differences in study site environmental characteristics. ............................ 111 3.5.3. Within-site vegetation-environment relationships patterns ...................... 113 3.5.4. Differences in ground layer assemblages between future burn management units within sites. ...................................................................................... 116 3.5.5. Conclusions and management implications ............................................... 117 3.6. Appendix ............................................................................................................. 119 Chapter 4: Composition and structure of oak-dominated forests of the Bluegrass Region in southern Ohio. ........................................................................ 127 4.1. Abstract ............................................................................................................... 127 4.2. Introduction ........................................................................................................ 128 4.3. Methods .............................................................................................................. 130 4.3.1. Study sites ................................................................................................... 130 4.3.2. Vegetation sampling and analysis ............................................................... 130 4.4. Results ................................................................................................................