CLASSIFICATION, VEGETATION-ENVIRONMENT RELATIONSHIPS, AND DISTRIBUTION OF PLANT COMMUNITIES ON SOUTHEAST FARALLON ISLAND, CALIFORNIA A Thesis submitted to the faculty of A 6 San Francisco State University 3G In partial fulfillment of 2-01$ the requirements for the Degree Master of Arts In Geography: Resource Management and Environmental Planning by Jamie Lee Hawk San Francisco, California May 2015 Copyright by Jamie Lee Hawk 2015 CERTIFICATION OF APPROVAL I certify that I have read Classification, Vegetation-Environment Relationships, and Distribution of Plant Communities on Southeast Farallon Island, California by Jamie Lee Hawk, and that in my opinion this work meets the criteria for approving a thesis submitted in partial fulfillment of the requirement for the degree Master of Arts in Geography: Resource Management and Environmental Planning at San Francisco State University. Professor Jaime Jahncke, Ph.D. California Current Director, Point Blue Conservation Science CLASSIFICATION, VEGETATION-ENVIRONMENT RELATIONSHIPS, AND DISTRIBUTION OF PLANT COMMUNITIES ON SOUTHEAST FARALLON ISLAND, CALIFORNIA Jamie Lee Hawk San Francisco, California 2015 We present the plant communities of Southeast Farallon Island and describe their relationships to environmental variables and disturbance factors. We sampled a total of 42 vegetation plots containing 26 taxa with a stratified design across the 29-hectare (72- acre) island. To classify the herbaceous communities we applied agglomerative hierarchical clustering, while the influence of site parameters was obtained using Nonmetric Multidimensional Scaling (NMDS) ordination. A total of five plant communities were classified, including two native plant assemblages (Spergularia macrotheca type and Lasthenia maritima type) and three invaded communities (Tetragonia tetragonioides type, Plantago coronopus type, and Mixed vegetation type). The strongest gradients in vegetation composition can be explained by solar heat load, dominance of substrate type, and edaphic factors (soil pH, salinity, depth). Physical disturbance and proximity to anthropogenic land use also influence plant community composition. A map of the classified vegetation types and additional mapping units were created to better understand current patterns in vegetation and assist in long-term management of the island’s resources. Southeast Farallon Island is the largest seabird breeding colony south of Alaska and the U.S. Fish & Wildlife Service is planning for intensive habitat restoration, therefore, a clear understanding of native and invaded plant communities and vegetation-environment relationships is required. I certify that the Abstract is a correct representatior of the content of this thesis. Chair, Thesis Committee /} Date ACKNOWLEDGEMENTS It is a sincere pleasure to express my deep sense of thanks and gratitude to my primary advisor and mentor Dr. Barbara A. Holzman. Her dedication and keen interest in the subject had been a primary driver in the completion of this work. Immense thanks are also owed to Drs. Ellen Hines and Jaime Jahncke for timely advice and candid communication. I thank profusely all the staff and interns at Point Blue Conservation Science and the U.S. Fish & Wildlife Service for making this research possible, with special recognition of Russ Bradley, Pete Warzybok, Ryan Berger, Gerry McChesney, and Jonathan Shore for their input and support in all phases of this work. I owe a deep sense of gratitude to the field crewmembers for their assistance in data collection and overall good humor: Dan Adams, Richard Chasey. Patrick Daly, Josh Nuzzo, Owen Parker, Brian Peterson, Thad Shelton, and David Zimmerman. This research was supported in part by the SFSU Department of Geography & Environment Steven Pease Memorial Award. The U.S. Fish & Wildlife Service and Point Blue Conservation Science provided logistical support, vessel transportation, and lodging. Dr. Holzman and the SFSU Department of Geography & Environment afforded food and field equipment throughout the study period. Lastly, I am extremely thankful to my parents, Michael and Sue Hawk, and my partner, Owen Parker, for their encouragement and support over the years. TABLE OF CONTENTS List of Tables.......................................................................................................................... vii List of Figures........................................................................................................................ viii List of Appendices................................................................................................................... ix Introduction................................................................................................................................ 1 Methods........................................................................................................................................ Study area.......................................................................................................................8 Vegetation survey.......................................................................................................12 Environmental variables.............................................................................................14 Data analysis................................................................................................................17 Type description key...................................................................................................19 Mapping techniques................................................................................................... 20 Accuracy assessment................................................................................................. 21 Spatial data attribution and metadata........................................................................ 22 Results.......................................................................................................................................... Taxonomic overview .......................................................................................24 Classification............................................................................................................... 25 Ordination................................................................................................................... 28 Vegetation types..........................................................................................................30 Vegetation map...........................................................................................................35 Map accuracy.............................................................................................................. 38 Invasive species modifier........................................................................................... 41 Disturbance and invasive species.............................................................................. 43 Discussion................................................................................................................................47 Conclusion...............................................................................................................................58 References................................................................................................................................ 59 Appendices............................................................................................................................... 71 LIST OF TABLES Table Page 1. Soil salinity classes.................................................................................................... 15 2. Soil pH classes........................................................................................................... 15 3. Anthropogenic disturbance categories..................................................................... 15 4. Seabird burrow density classes................................................................................. 15 5. Synoptic table of classified vegetation types.......................................................... 26 6. Diagnostic species of classified vegetation types................................................... 27 7. Correlation between axes and environmental variables......................................... 29 8. Summary table of mapping units..............................................................................36 9. Error matrix of user and producer accuracies..................................................38 10. Summary table of Tetragonia tetragonioides modifier..........................................41 LIST OF FIGURES Figures Page 1. Map of study area......................................................................................................9 2. Map of vegetation sampling plots locations............................................................13 3. Dendrogram of classified vegetation types............................................................. 25 4. NMDS ordination diagrams........................................................................................29 5. Vegetation map of Southeast Farallon Island......................................................... 37 6. Map of accuracy assessment points................................................................... 40 7. Herbicide treatment effect within Tetragonia tetragonioides type.......................42 8. Map of non-native vegetative cover within classified