INVASIVENESS OF YELLOW TOADFLAX ( LINARIA VULGARIS ) RESULTING FROM DISTURBANCE AND ENVIRONMENTAL CONDITIONS by Erik Adam Lehnhoff A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Ecology and Environmental Sciences MONTANA STATE UNIVERSITY Bozeman, Montana April 2008 © COPYRIGHT by Erik Adam Lehnhoff 2008 All Rights Reserved ii APPROVAL of a dissertation submitted by Erik Adam Lehnhoff This dissertation has been read by each member of the dissertation committee and has been found to be satisfactory regarding content, English usage, format, citations, bibliographic style, and consistency, and is ready for submission to the Division of Graduate Education. Dr. Lisa J. Rew Approved for the Department of Land Resources and Environmental Sciences Dr. Jon Wraith Approved for the Division of Graduate Education Dr. Carl A. Fox iii STATEMENT OF PERMISSION TO USE In presenting this dissertation in partial fulfillment of the requirements for a doctoral degree at Montana State University, I agree that the Library shall make it available to borrowers under rules of the Library. I further agree that copying of this dissertation is allowable only for scholarly purposes, consistent with “fair use” as prescribed in the U.S. Copyright Law. Requests for extensive copying or reproduction of this dissertation should be referred to ProQuest Information and Learning, 300 North Zeeb Road, Ann Arbor, Michigan 48106, to whom I have granted “the exclusive right to reproduce and distribute my dissertation in and from microform along with the non- exclusive right to reproduce and distribute my abstract in any format in whole or in part.” Erik Adam Lehnhoff April 2008 iv ACKNOWLEDGEMENTS I owe endless gratitude to Dr. Lisa Rew for her support on all phases of this dissertation including project establishment, experimental design, data analysis, and editing and polishing the final document. Dr. Bruce Maxwell has been a source of inspiration, and from him I have learned to never stop asking questions about the systems in which we work and to seek new ways of understanding them through empirical models. I am also grateful for the support of Drs. Cliff Montagne, Cathy Zabinski and Steve Sutherland for their input on the research and this dissertation, and Dr. Mark Taper for assistance with statistical analysis and programming in R. I thank Susan Lamont and her crew from the Gallatin National Forest, Hebgen Lake Ranger District for assistance with locating suitable research sites and with burning select plots. I also thank Marie Jasieniuk and Charles Repath for the use of data from their prior experiment. Other data were collected with the help of numerous friends and colleagues, including Tim Seipel, Karin Neff, Brad Bauer, Tyler Brummer, Frank Dougher, Fred Pollnac, Brenda Sanchez, Jerad Corbin and Amanda Morrison. Additional gratitude is expressed to Tim for lending his expertise in plant identification and to Frank for solving all of my computer problems and providing GIS support. The Montana State University Big Sky Institute, the Center for Invasive Plant Management and the U.S. Forest Service Rocky Mountain Research Station, Fire Sciences Laboratory are gratefully acknowledged for providing funding. Finally, I would like to thank my family. I am forever indebted to my parents for instilling within me a deep appreciation of, and interest in, the natural world, and for supporting my academic pursuits. To my wife, Kris Evans, I owe eternal gratitude for the endless love and support she has provided throughout the past five years. v TABLE OF CONTENTS PROLOGUE: A SHIFT TOWARD ECOLOGICAL BASED MANAGEMENT OF NON-INDIGENOUS PLANT SPECIES ................................................................1 1. INTRODUCTION AND REVIEW OF LITERATURE ...............................................5 Introduction....................................................................................................................5 Plant Invasions...............................................................................................................7 Community Assembly Theory..............................................................................8 Niche Assembly Theory ..............................................................................9 Dispersal Assembly Theory.......................................................................10 Unified Neutral Theory..............................................................................10 Competition Theory...................................................................................11 Disturbance ................................................................................................12 Other Factors Shaping Plant Community ..................................................13 Plant Invasion Theory.........................................................................................13 Impacts of NIS ....................................................................................................17 Impact of Weed Management.............................................................................20 Linaria vulgaris ...........................................................................................................20 Origin and Distribution.......................................................................................21 Reason for Concern.............................................................................................22 Historical and Beneficial Uses............................................................................23 Habitat.................................................................................................................24 Morphology.........................................................................................................24 Comparison and Possible Hybridization with Linaria dalmatica ......................25 Floral Biology and Seed Production...................................................................26 Seed Dispersal.....................................................................................................26 Germination and Seedling Establishment...........................................................27 Vegetative Reproduction ....................................................................................27 Phenology ...........................................................................................................29 Invasive Potential................................................................................................30 Impacts................................................................................................................31 Ecological ..................................................................................................31 Economic ...................................................................................................31 Response to Disturbance.....................................................................................33 Fire .............................................................................................................33 Soil Disturbance.........................................................................................34 Grazing.......................................................................................................34 Management.................................................................................................................35 Biological...................................................................................................35 Chemical ....................................................................................................38 Physical/Mechanical/Cultural.............................................................................39 Fire .............................................................................................................41 vi TABLE OF CONTENTS – CONTINUED Grazing.......................................................................................................41 Integrated Management .............................................................................41 Primary Objectives of Research...................................................................................42 Objective 1: Effects of Size of Soil Disturbance and Propagule Pressure On L. vulgaris Colonization.......................................................................43 Objective 2: Population Dynamics and Invasiveness ........................................44 Objective 3: Effects of Disturbance and Habitat on L. vulgaris Population Invasiveness.............................................................................46 Objective 4: Impacts of Disturbance and L. vulgaris on Native Vegetation .....46 2. EFFECTS OF DISTURBANCE SIZE AND PROPAGULE PRESSURE ON LINARIA VULGARIS COLONIZATION SUCCESS..................................48 Introduction..................................................................................................................48 Materials and Methods.................................................................................................50 Site Descriptions .................................................................................................50 Clearcut Sites .............................................................................................51 Wildfire Site...............................................................................................52