Louisiana State University LSU Digital Commons LSU Doctoral Dissertations Graduate School 2006 Nutrient constraints on plant community production and organic matter accumulation of subtropical floating marshes Guerry O., Jr. Holm Jr. Louisiana State University and Agricultural and Mechanical College, [email protected] Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_dissertations Part of the Oceanography and Atmospheric Sciences and Meteorology Commons Recommended Citation Holm, Guerry O., Jr. Jr., "Nutrient constraints on plant community production and organic matter accumulation of subtropical floating marshes" (2006). LSU Doctoral Dissertations. 273. https://digitalcommons.lsu.edu/gradschool_dissertations/273 This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Doctoral Dissertations by an authorized graduate school editor of LSU Digital Commons. For more information, please [email protected]. NUTRIENT CONSTRAINTS ON PLANT COMMUNITY PRODUCTION AND ORGANIC MATTER ACCUMULATION OF SUBTROPICAL FLOATING MARSHES 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 Oceanography and Coastal Sciences by Guerry O. Holm, Jr. B.S., University of Georgia, 1993 M.S., Louisiana State University, 1998 December 2006 ACKNOWLEDGEMENTS During my years of graduate school, I learned scientists are human, and science is not exclusive of personality despite what the purists say. I have been fortunate to know how some successful scientists think, make a living, and work toward understanding. My committee has helped me see these things in unique ways. My full gratitude goes to Dr. Charles E. Sasser. Not just for his guidance as professor, but he showed me a model for living that I thoroughly respect. Charles is a mentor who teaches by example and encourages individual thinking. I am fortunate for the opportunity of working and knowing such a remarkable naturalist, scientist, and above all, genuine person. I count him among my lifelong friends. My other committee members played unique roles in my development, mostly through their tacit wisdoms. Dr. Irving A. Mendelssohn made time to answer questions about wetland plant biology, greenhouse plant cultivation, and nutrient solution preparation. By example, Irv showed me the importance of objectivity and the disarming value of admitting the limits of your knowledge. Another member of my committee, Dr. Dubravko Justic, has a passion for big questions, and although a discussion may begin with science, it always comes to rest with something personal. Dubravko sees the questions of science and people as inseparable. I admire his ability to see how it all fits together. Dr. Jaye E. Cable is among the brightest and most energetic faculty in our department—a positive role model for new students who want to find success in science. She gave me a glimpse into how a young investigator can balance her family life and still have an extraordinary research program. My dean’s representative, Dr. Kurt Svoboda, ii made my job simple: he was approachable and supportive. Looking back, my committee could not have been more professional and refreshingly devoid of ego issues. Mike Francis made it possible for me to get my fieldwork done in comfort by offering his camp, Maison Misere—thank you Mike. I appreciate Roger Vincent for giving me access to Miami Corporation land. I am grateful to Elaine Evers (GIS expertise) and Erick Swenson (gage guru) for making my work easier. Charlie Milan and Tom Oswald helped me with water and soil chemistry. Dr. James Gosselink always showed interest in my development and helped in practical ways. Fieldwork was made more enjoyable by the hard work of my friends Jay Gore and Lee Stanton. The sanity keepers included: Brian Perez (chef extraordinaire) and Saturday college ball (you too, Angie); the Piazza’s and ‘ienda’ (where true stories, half-truths, and damned lies are perpetuated, alongside good food and malt). Hilary Collis always gave me a laugh, smile, or hug at the right times. At a young age, my mom gave me comfort, showed me nature, and released me. My sister is my best friend (save the Wet-Willie’s), and I could not imagine life without her. Today, most dearly, I think of my father. Pop showed me that life must be lived with great humor, for how else can we bear life’s tragedies? I will always adore our memories together among the woods and waters. iii TABLE OF CONTENTS ACKNOWLEDGEMENTS................................................................................................ ii LIST OF TABLES............................................................................................................ vii LIST OF FIGURES ........................................................................................................... ix ABSTRACT....................................................................................................................... xi CHAPTER 1. WETLAND ORGANIC MATTER ACCUMULATION AND FLOATING MARSHES OF LOUISIANA............................................................................................. 1 Introduction..................................................................................................................... 1 Wetland Nutrient Enrichment......................................................................................... 2 Plant Competition ........................................................................................................... 2 Wetland Organic Matter Formation................................................................................ 3 Floating Marshes in Louisiana........................................................................................ 4 Research Objectives........................................................................................................ 8 Literature Cited ............................................................................................................... 8 CHAPTER 2. THE ECOLOGY AND MANAGEMENT OF THE WETLAND GRASS, PANICUM HEMITOMON OR MAIDENCANE ............................................................. 12 Introduction................................................................................................................... 12 Description and General Characteristics....................................................................... 12 Distribution, Habitats, and Assemblages...................................................................... 14 Reproduction................................................................................................................. 16 Growth Factors.............................................................................................................. 17 Sediment Type and Nutrient Chemistry ................................................................... 17 Fire ............................................................................................................................ 18 Flooding .................................................................................................................... 20 Grazing...................................................................................................................... 21 Salt Tolerance ........................................................................................................... 21 Uses for Soil and Water Remediation........................................................................... 22 Wildlife Habitat Use and Value.................................................................................... 25 Planting and Management............................................................................................. 26 Ecotypes.................................................................................................................... 26 Propagation and Field Establishment........................................................................ 26 Methods of Control................................................................................................... 28 Synthesis ....................................................................................................................... 28 Literature Cited ............................................................................................................. 29 CHAPTER 3. THE EFFECTS OF NUTRIENT-ENRICHMENT ON BELOWGROUND ORGANIC MATTER ACCUMULATION OF SUBTROPICAL FLOATING MARSHES........................................................................................................................ 39 Introduction................................................................................................................... 39 Materials and Methods.................................................................................................. 42 iv Study Sites ................................................................................................................ 42 Water and Soil Nutrients........................................................................................... 43 Hydrologic Variables................................................................................................ 44 Belowground Accumulation ..................................................................................... 44 Belowground