Invasion of Smooth Brome Into North American Tall-Grass Prairies: Impact on Native Plant/Herbivore Species and Mechanisms Responsible for Successful Invasion
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INVASION OF SMOOTH BROME INTO NORTH AMERICAN TALL-GRASS PRAIRIES: IMPACT ON NATIVE PLANT/HERBIVORE SPECIES AND MECHANISMS RESPONSIBLE FOR SUCCESSFUL INVASION A Dissertation Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy in The Department of Biological Sciences By Forrest Paul Dillemuth B.S. 2003, Louisiana State University Fish and Wildlife Conservation May 2012 ACKNOWLEDGMENTS This dissertation project was completed with the help and support of many people. I would like to first thank my advisor, Jim Cronin, for providing me with a wide breadth of academic and scientific training and for being available whenever I needed advice. I am also very grateful for his willingness and intense effort to review my manuscripts. I also thank my graduate committee Ken Brown, Kyle Harms, Richard Stevens and Hallie Dozier for their willingness to help and support me with difficulties that arose during my manuscript preparations. I would like to extend a special thanks to Kurt Tompkins of the United States Fish and Wildlife Service (Devils Lake District), The Nature Conservancy and The Minnesota Department of Natural Resources for providing me with access to their land in order to conduct my work. I also extend a very special thanks to Casey Wedin and his family for helping me find places to live during my field seasons far away from home and for being a second family to me while I was conducting my field research. My work would have never had been finished if it were not for the hard work and long hours put in by many undergraduates Erick Rietscher, Amanuel Zeccarias, Bryan Thompkins, Brian Anderson. Erick Rietscher and Bryan Anderson also became friends beyond measure during my dissertation and for that, I am forever grateful. Funding for my dissertation project was provided by NSF grants DEB 0211359, DEB-0515764, DEB-1020867 and DEB DEB-1020867, Seed Money Grant from the Center of Invasive Plant Management, Louisiana State University (LSU) Biograds, plus 3 Research Experience for Undergraduate Supplements to J. T. Cronin. My labmates were a huge asset to me professionally and personally during my tenure at LSU. Heather Jackson was not only a good friend and an open ear to toss ideas around but she also provided critical insight into helping me design my experiments and analyze my data. I ii thank Alyssa Hakes and Amanda Accamando for their upbeat disposition, coffee making skills and laughter that helped keep me going during the day. I thank Ganesh Bhattarai for his critical thinking whenever I ran a question by him. I also want to give a special thanks to Kyle Haynes and Kristen Baum for mentoring me and getting me started as a graduate student. Without their guidance, graduate school would have been a lot more difficult. I also thank Barry Aronhime for helping get through the last phases of my dissertation, without him finishing would have been a lot more difficult. Finally, I thank my family Bob and Paula Dillemuth for their support during through life, even if I did not become a real “Doctor”. I also thank my lovely fiancée, Amber Lodrigues, for putting up with the long hours of work and the long months while I was away conducting field research. Nicholas Roy and Frank Du were always there for me when I needed a break and help me find some sanity during intense moments. iii TABLE OF CONTENTS Acknowledgments….……………………………………………………………………………..ii List of Tables....…………………………………………………………………………………..vi List of Figures...………………………………………...…………………………………….....viii Abstract....………………………………………………………………………………………....x Chapter 1: Introduction....….……………………………………………………………………...1 Chapter 2: Patch Dynamics of a Native Grass in Relation to the Spread of Invasive Smooth Brome (Bromus inermis)...……………………………………….……………………………….5 Introduction....……...…………………………………….………………………...……..5 Methods........……………………………………………...……………………………....7 Invasive Smooth Brome...……..………………………………………….............7 Study System....…………............………………………………………………..8 Vegetation Mapping…..……………………...…………......................................9 Establishment and Extinction of Cordgrass Patches.............................................13 Results...............................................................................................................................14 Discussion.........................................................................................................................16 Brome Management..............................................................................................20 Chapter 3: Seedling Emergence and Interspecific Competition of an Invasive Species in the Tallgrass Prairies of North America..................................................................................22 Introduction........................................................................................................................22 Methods..............................................................................................................................24 Invasive Smooth Brome History and Biology.......................................................24 Research Site..........................................................................................................25 Germination and Competition Experiment............................................................25 Smooth Brome Germination and Disturbance.......................................................28 Statistical Analysis.................................................................................................29 Results................................................................................................................................32 Germination Success..............................................................................................32 Species Composition and Its Effect on Plant Performance Following Germination...........................................................................................................35 Discussion..........................................................................................................................37 Management Implications......................................................................................41 Chapter 4: Multi-Scale Impact of an Invasive Plant on Native Herbivore Communities............43 Introduction.......................................................................................................................43 Methods.............................................................................................................................46 Study System.........................................................................................................46 Sampling Design....................................................................................................47 Herbivore Identification.........................................................................................49 iv Statistical Analysis................................................................................................50 Results...............................................................................................................................51 Discussion.........................................................................................................................55 Chapter 5: Summary and Conclusions..........................................................................................63 Smooth Brome Management.............................................................................................65 Literature Cited..............................................................................................................................68 Appendix – Copyright Permission for Chapter 2..........................................................................80 Vita................................................................................................................................................81 v LIST OF TABLES Table 2.1 Summary statistics for the three field sites, Site 104, LimeHouse and North Kelly. Data are divided among 3 time periods (2000, 2004, and 2006)……………………………………...10 Table 2.2 Results from separate Kruskall–Wallis tests for the effect of percent brome surrounding a cordgrass patch (<25%, 25–50%, 50–75%, and >75%) on the percent change in cordgrass area……………………………………………………………………….…………....15 Table 3.1 Mixed model results for percent germination of seeds. Type III test for fixed effects indicate if significance was met for fixed factors (e.g. habitat, single/mixed species subplots, species and all interactions) and prediction of random effects indicate significance and slope for abiotic soil (salinity, % moisture and elevation) effects for species within each habitat……...…33 Table 3.2 Mixed model results for mean plant height. Type III test for fixed effects indicate if significance was met for fixed factors (e.g. habitat, single/mixed species subplots, species and all interactions) and prediction of random effects indicate significance and slope for abiotic soil (salinity, % moisture and elevation) effects for species within each habitat…………………….35 Table 3.3 Mixed model results for number of stems per numbers of seeds released. Type III test for fixed effects indicate if significance was met for fixed factors (e.g. habitat, single/mixed species subplots, species and all interactions) and