ABSTRACT BEAVER (CASTOR CANADENSIS) ELECTIVITY FOR AMUR HONEYSUCKLE (LONICERA MAACKII) COMPARED TO OTHER WOODY SPECIES by Janet L. Deardorff The North American beaver is a keystone riparian obligate which creates and maintains riparian areas by building dams. In much of the eastern U.S., invasive shrubs are common in riparian zones, but we do not know if beavers promote or inhibit these invasions. I investigated whether beavers use the invasive shrub, Amur honeysuckle (Lonicera maackii), preferentially compared to other woody species and the causes of differences in L. maackii electivity among sites. At eight sites, I identified woody stems on transects, recording stem diameter, distance to the water’s edge, and whether the stem was cut by beaver. To determine predictors of cutting by beaver, I conducted binomial generalized regressions, using distance from the water’s edge, diameter, and plant genus as fixed factors and site as a random factor. To quantify beaver preference, I calculated an electivity index (Ei) for each genus at each site. Lonicera maackii was only preferred at two of the eight sites though it comprised 41% of the total cut stems. Stems that were closer to the water’s edge and with a smaller diameter had a higher probability of being cut. Among sites, L. maackii electivity was negatively associated with the density of stems of preferred genera. BEAVER (CASTOR CANADENSIS) ELECTIVITY FOR AMUR HONEYSUCKLE (LONICERA MAACKII) COMPARED TO OTHER WOODY SPECIES A Thesis Submitted to the Faculty of Miami University in partial fulfillment of the requirements for the degree of Master of Science by Janet L. Deardorff Miami University Oxford, Ohio 2019 Advisor: Dr. David Gorchov Reader: Dr. Susan Hoffman Reader: Dr. Bartosz Grudzinski ©2019 Janet L. Deardorff This thesis titled BEAVER (CASTOR CANADENSIS) ELECTIVITY FOR AMUR HONEYSUCKLE (LONICERA MAACKII) COMPARED TO OTHER WOODY SPECIES by Janet L. Deardorff has been approved for publication by The College of Arts and Sciences and Department of Biology ____________________________________________________ Dr. David Gorchov ______________________________________________________ Dr. Susan Hoffman _______________________________________________________ Dr. Bartosz Grudzinski Table of Contents LIST OF TABLES……………………………………………………………………………....IV LIST OF FIGURES……………………………………………………………………………....V LIST OF APPENDEXES………………………………………………………………………..VI ACKNOWLEDGEMENTS…………………………………………………………………….VII INTRODUCTION………………………………………………………………………………...1 Beaver Foraging Behavior………………………………………………………………...1 Herbivore/Plant Interactions………………………………………………………………2 Amur honeysuckle, Lonicera maackii…………………………………………………….2 Beaver Abundance in Ohio……………………………………………………………......3 Potential Importance of Beaver-Lonicera Interactions in Riparian Zones……………......3 Study Questions…………………………………………………………………………...3 METHODS……………………………………………………………………………………......4 Transect Configuration……………………………………………………………………4 Woody Plant Sampling……………………………………………………………………5 Canopy Openness………………………………………………………………………….5 Beaver Residency Time…………………………………………………………………...5 Density of Preferred Stems……………………………………………………………......5 Photos of Beavers Cutting………………………………………………………………...6 STATISTICAL ANALYSIS……………………………………………………………………...6 Probability of a Stem Being Cut………………………..…………………………………6 Electivity…………………………………………………………………………………..6 Linear Regressions…………………………………………………………………….......7 RESULTS…………………………………………………………………………………………7 Factors Influencing Stem Cutting…………………………………………………………7 Electivities…………………………………………………………………………………8 Differences in L. maackii Electivity Among Sites………………………………………..8 DISCUSSION……………………………………………………………………………………..8 Difference Among Sites………………………………………………………………….10 Few Cut Stems in Spring Census………………………………………………………...10 Future Research………………………………………………………………………….11 CONCLUSION…………………………………………………………………………………..11 REFERENCES……...…………………………………………………………………………...13 TABLES…………………………………………………………………………………………17 FIGURES………………………………………………………………………………………...23 APPENDIX 1 ……………………………………………………………………………………37 APPENDIX 2…………………………………………………………………………………….41 APPENDIX 3…………………………………………………………………………………….48 iii List of Tables Table 1. The location, city, beaver residency time, management entity, aquatic system, and transect type, and field notes from spring/summer 2018 at each site. ….……………………….17 Table 2. Analysis of Deviance table (Type III Wald chisquare tests) for generalized binomial regression on whether a stem was cut or uncut, using stems from all genera…………………...18 Table 3. Analysis of Deviance table (Type III Wald chisquare tests) for generalized binomial regression on whether a stem was cut or uncut using stems from genera found in five or more sites……………………………………...……………………………………………………….19 Table 4. Analysis of Deviance table (Type III Wald chisquare tests) for generalized binomial regression on whether a stem was cut or uncut using stems from L. maackii…………………...20 Table 5. The number of browsed stems for each genus and each diameter class at each site during the fall census……...……………………………………………………………………………..21 Table 6. The number of cut and browsed stems during the spring re-census in each genus and each diameter class.………………..………………………………………………………….....22 iv List of Figures Figure 1. First survey of beaver in Ohio 1949 after extermination in 1830. The author inferred beaver colonies in the northwest came from Michigan and the eastern colonies came from Pennsylvania. Figure from Chapman (1947)……………………………..……………………...23 Figure 2. Map describing the distribution and abundance of beavers in Ohio in 2012. Image taken from http://wildlife.ohiodnr.gov/species-and-habitats/species-guide-index/mammals/beaver ………………………………………………………………………………………...………….24 Figure 3. Beaver population estimates in Ohio from 1980-2011. Image taken from http://wildlife. ohiodnr.gov/species-and-habitats/species-guide-index/mammals/beaver ..………………...…...25 Figure 4. Locations of study sites in southwest Ohio…………………………………………....26 Figure 5. Schematic of transect designs………………………………………………………………….27 Figure 6. Photos taken during summer 2018 from Browning (Model BTC-5HDE) trail cameras placed at Bachelor Pond (Oxford, Oh)…………………………………………………………..28 Figure 7. Barplot of proportion of stems cut out of all stems within each distance class………..29 Figure 8. Barplot of proportion of stems cut out of all stems within each diameter class………30 Figure 9. Barplot of proportion of L. maackii stems cut out of all L. maackii stems within each distance class……………………………………………………………………………………..31 Figure 10. Barplot of proportion of L. maackii stems cut out of all L. maackii stems within each diameter class…………………………………………………………………………………….32 Figure 11. Barplot of proportion of cut stems belonging to each genus………………………....33 Figure 12. Electivity values (Ei) for all genera found within this study..………………………...34 Figure 13. Electivity values (Ei) for genera found within five or more sites……………………..35 Figure 14. Regressions of L. maackii electivity on average canopy openness, beaver residency time (years) per site, and density of preferred stems among the eight sites……………………..36 v List of Appendices Appendix 1. The total number of stems, stems cut, proportion cut, proportion of total stems cut and electivity (Ei) for each genus at each site…………………………………………………..37 Appendix 2. R code and output for binomial generalized regressions and linear regressions….41 Appendix 3. Barplot of the proportion of L. maackii stems cut within each size class for stems close to the water’s edge and stems far from the water’s edge………………………………….48 vi Acknowledgements I would first like to thank Dr. David Gorchov for his invaluable insight and attentiveness throughout this entire project. I would like to thank Zoey Armstrong, Zoey Scancarello, Kelly Benoit, Courtney Dvorsky, Anna Bowen, Nicole Berry, and Jake Godfrey for their assistance in the field, Mike Mahon for his help with statistics, and the Gorchov and Stevens labs for providing helpful feedback on study design and presentations. I also thank Dr. Bartosz Grudzinski and Dr. Susan Hoffman for serving on my committee and providing insightful feedback as well as access to labs and field equipment. I am grateful for financial support from the John L. Vankat Student Grant Fund for Field Research in Terrestrial Plant Ecology. Lastly, I would like to thank the staff at Great Parks of Hamilton County, Five Rivers Metroparks, the Ohio Department of Natural Resources, the Oxford Department of Service and Engineering, and the Miami University Natural Areas for answering all my questions and giving me permission to conduct research at their sites. vii INTRODUCTION Throughout the United States, riparian zones, interfaces between waterways and land, have become a conservation concern for land managers. Riparian zones have large ecological importance because they maintain the thermal regulation of water and establish microclimates, supply coarse organic matter to aquatic systems, provide large woody debris that affects the channel shape and water flow, provide refugia to fish and substrate for aquatic invertebrates, purify water and regulate nutrient inputs into streams and lakes, dampen floods and droughts by decreasing surface runoff and replenishing groundwater, and stabilize stream banks and stream- bed sediments (Naiman et al. 2005). The management goals for riparian areas increasingly include conservation of both terrestrial and aquatic wildlife because riparian zones have been found to support high levels of biodiversity on small areas of the landscape