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American Chestnut Restoration in Eastern Hemlock-Dominated Forests of Southeast

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American Chestnut Restoration in Eastern Hemlock-Dominated Forests of Southeast American Chestnut Restoration in Eastern Hemlock-Dominated Forests of Southeast Ohio A thesis presented to the faculty of the College of Arts and Sciences of Ohio University In partial fulfillment of the requirements for the degree Master of Science Nathan A. Daniel June 2012 © 2012 Nathan A. Daniel. All Rights Reserved. 2 This thesis titled American Chestnut Restoration in Eastern Hemlock-Dominated Forests of Southeast Ohio by NATHAN A. DANIEL has been approved for the Program of Environmental Studies and the College of Arts and Sciences by James M. Dyer Professor of Geography Brian C. McCarthy Professor of Environmental and Plant Biology Howard Dewald Interim Dean, College of Arts and Sciences 3 ABSTRACT DANIEL NATHAN A., M.S., June 2012, Environmental Studies American Chestnut Restoration in Eastern Hemlock-Dominated Forests of Southeast Ohio (51 pp.) Directors of Thesis: James M. Dyer and Brian C. McCarthy Restoration of American chestnut (Castanea dentata (Marsh.) Borkh.) is currently underway in eastern North American forests. American chestnut and eastern hemlock (Tsuga canadensis (L.) Carr.) trees historically co-occurred in these forests. Today, hemlock-dominated forests are in decline due to hemlock wooly adelgid (Adelges tsugae Annand) infestation, and as such, may serve as appropriate habitat for chestnut reestablishment. To investigate this notion, I evaluated the performance of American chestnut seedlings planted under healthy eastern hemlock-dominated canopies. Two process-oriented greenhouse experiments were also performed to study the response of American chestnut to drought stress and to test the competitive performance of chestnut against red maple (Acer rubrum (L.)), the most abundant hardwood found in the understory of regional hemlock-dominated forests. After two growing seasons, mean chestnut seedling survival in the field experiment was 6.6%. Seedling survival was significantly higher among trees that lacked a protective tree tube, suggesting low light levels played a major role in seedling mortality. In the drought stress experiment, American chestnut exhibited significantly higher mortality under a severe drought treatment compared to the control group. The moderate stress treatment also responded poorly to drought; however, results did not differ significantly with the control group. In 4 the competition experiment, American chestnut grew significantly taller than red maple. The results of this study caution against the underplanting of bare-root chestnut seedlings in low light conditions or where moisture may be limiting to establishing seedlings. Approved: _____________________________________________________________ James M. Dyer Professor of Geography _____________________________________________________________ Brian C. McCarthy Professor of Environmental & Plant Biology 5 DEDICATION To my wife, Kimberly W. Daniel 6 ACKNOWLEDGMENTS I would like to thank Kimberly Daniel, Keith Gilland, Joseph Moosbrugger, Lindsay Scott, Justin Schwalenburg, and Gideon Daniel for their assistance in the field. I would also like to thank my thesis committee, Dr. Brian C. McCarthy, Dr. James M. Dyer, and Dr. Jared L. Deforest for their invaluable suggestions and guidance on this project. I thank the Southern Appalachian Botanical Society, Ohio University Graduate Student Senate, Voinovich School of Leadership and Public Affairs, and Department of Environmental and Plant Biology for financial support. The American Chestnut Foundation kindly provided seedlings for this study. I am grateful to both the Ohio Department of Natural Resources Divisions of Forestry and State Parks for granting permits to conduct this experiment. 7 TABLE OF CONTENTS Page ABSTRACT........................................................................................................................ 3 DEDICATION.................................................................................................................... 5 ACKNOWLEDGMENTS .................................................................................................. 6 LIST OF TABLES.............................................................................................................. 8 LIST OF FIGURES ............................................................................................................ 9 INTRODUCTION ............................................................................................................ 10 MATERIALS AND METHODS...................................................................................... 18 American Chestnut Performance in Eastern Hemlock-Dominated Forests.................. 18 American Chestnut Drought Stress Experiment........................................................... 24 Competitive Ability of American Chestnut and Red Maple......................................... 26 Statistical Analysis........................................................................................................ 29 RESULTS ......................................................................................................................... 31 American Chestnut Performance in Eastern Hemlock-Dominated Forests.................. 31 American Chestnut Drought Stress Experiment........................................................... 34 Competitive Ability of American Chestnut and Red Maple......................................... 36 DISCUSSION................................................................................................................... 39 CONCLUSIONS .............................................................................................................. 44 LITERATURE CITED ..................................................................................................... 46 8 LIST OF TABLES Page Table 1. Site characteristics and soil properties of eastern hemlock-dominated study plots in the Hocking Hills region of southeast Ohio........................................23 Table 2. Analysis of variance results for height of American chestnut and red maple grown in mixtures of varying proportions and densities under two light treatments.........................................................................................................36 Table 3. Overall mean height (cm) ± standard error (SE) for American chestnut and red maple grown under two light treatments ...................................................37 Table 4. Mean height ± standard error (SE) for American chestnut and red maple grown across mixtures of five proportions and three densities........................37 9 LIST OF FIGURES Page Figure 1. Native range of American chestnut (left) and eastern hemlock (right) (USGS 1999).................................................................................................11 Figure 2. Hocking Hills region of southeast Ohio........................................................19 Figure 3. Hocking Hills field site design diagram........................................................20 Figure 4. Monthly rainfall (mm) and temperature (°C) measurements for the Jackson, Ohio weather observing station......................................................24 Figure 5. Size-class analysis of the five most important hardwood species found in eastern hemlock-dominated forests in the Hocking Hills.........................27 Figure 6. Multiple deWit replacement design for competition study between American chestnut and red maple.................................................................28 Figure 7. Monthly survival (%) of American chestnut seedlings protected and unprotected by tree tubes. .............................................................................32 Figure 8. Boxplot of annual height increase (cm yr-1) in American chestnut seedlings unprotected by tree tubes. .............................................................32 Figure 9. After two growing seasons, no significant correlation was found between American chestnut seedling survival (%) and any of the environmental variables tested......................................................................33 Figure 10. Monthly survival (%) of American chestnut seedlings based on drought treatment. ......................................................................................................34 Figure 11. Boxplot showing growth of American chestnut seedlings subjected to three watering regimes over a 120 day experiment. .....................................35 Figure 12. Mean height growth of American chestnut and red maple grown at five proportions, three densities, and two light treatments. .................................38 10 INTRODUCTION Until its functional extirpation from the overstory during the mid 20th century, American chestnut (Castanea dentata (Marsh.) Borkh.) was a dominant foundation species in the forests of eastern North America (Braun 1950, Ellison et al. 2005). In 1904, the introduction of chestnut blight (Cryphonectria parasitica (Murr.) Barr.), an exotic invasive fungal pathogen accidentally imported from Asia, forced a precipitous decline in both abundance and ecosystem function of American chestnut (Ellison et al. 2005). Although the pandemic struck before the advent of modern ecological record keeping, it is estimated that upwards of 4 billion trees or 99.9% were killed (Griffin et al. 2004). Today, from Maine to Alabama, American chestnut persists in the forest understory through a process of resprout and dieback as the trees are repeatedly infected by chestnut blight (Paillet 1988,
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