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LAND USE AND LAND COVER CHANGE: THE EFFECTS OF WOODY PLANT ENCROACHMENT AND PRESCRIBED FIRE ON BIODIVERSITY AND ECOSYSTEM CARBON DYNAMICS IN A SOUTHERN GREAT PLAINS MIXED GRASS SAVANNA A Dissertation by EMILY BROOKE HOLLISTER Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY May 2008 Major Subject: Molecular and Environmental Plant Sciences LAND USE AND LAND COVER CHANGE: THE EFFECTS OF WOODY PLANT ENCROACHMENT AND PRESCRIBED FIRE ON BIODIVERSITY AND ECOSYSTEM CARBON DYNAMICS IN A SOUTHERN GREAT PLAINS MIXED GRASS SAVANNA A Dissertation by EMILY BROOKE HOLLISTER Submitted to the Office of Graduate Studies of Texas A&M University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Approved by: Chair of Committee, Thomas W. Boutton Committee Members, R. James Ansley David D. Briske Christopher W. Schadt David A. Zuberer Chair of the Molecular and Environmental Plant Sciences Faculty, Jean H. Gould May 2008 Major Subject: Molecular and Environmental Plant Sciences iii ABSTRACT Land Use and Land Cover Change: The Effects of Woody Plant Encroachment and Prescribed Fire on Biodiversity and Ecosystem Carbon Dynamics in a Southern Great Plains Mixed Grass Savanna. (May 2008) Emily Brooke Hollister, B.A., Wells College Chair of Advisory Committee: Dr. Thomas W. Boutton In the southern Great Plains, the encroachment of grassland ecosystems by mesquite (Prosopis glandulosa), is widespread, and prescribed fire is commonly used in its control. Despite this, substantial quantitative information concerning their influences on the community composition, functional dynamics, and soil organic carbon (SOC) storage potential of grassland ecosystems is lacking. The objectives of this study were to: a) quantify the effects of seasonal prescribed fire treatments and mesquite encroachment on aboveground net primary productivity (ANPP) and herbaceous community composition; b) characterize SOC pool sizes, turnover, and storage potential relative to vegetation type and fire treatment; c) evaluate the structure and diversity of soil microbial communities relative to vegetation type; and d) characterize the functional diversity of these same microbes using the GeoChip functional gene microarray. Repeated winter and summer fires led to increased ANPP rates (average, 434 and 313 g m-2 y-1, respectively), relative to unburned controls (average, 238 g m-2 y-1), altered herbaceous community composition, and increased the storage of resistant forms of SOC, but did not affect overall SOC storage. Herbaceous ANPP rates did not differ significantly as a result of mesquite encroachment, but herbaceous community composition and SOC storage did. Mesquite soils contained significantly more total, slow-turnover, and resistant forms of SOC than those that occurred beneath C3 or C4 grasses. Similarity among the soil bacterial and fungal communities associated with the major vegetation types in this system was low to moderate. Significant differences were detected among soil fungi, with the mesquite-associated fungi harboring significant iv differences in community structure relative to the fungal communities associated with each of the other vegetation types examined. Despite this result, few significant differences were detected with respect to the functional diversity of these communities, suggesting either a high degree of functional redundancy, or that the functional differences harbored by these communities are beyond the scope of the GeoChip. The results of this study demonstrate that both fire and mesquite encroachment have the potential to alter ecosystem components and processes significantly, providing new insight regarding the effects of these widespread land use and land cover changes on ecosystem structure and function. v ACKNOWLEDGEMENTS I would like to acknowledge the members of my graduate committee, Drs. Tom Boutton, Jim Ansley, Dave Briske, David Zuberer, and Chris Schadt, for their patience, guidance, and support through this process, as well as Wylie Harris, Julia Liao, E Bai, Feng Liu, Lori Biederman, Ilsa Kantola, and the other members of the Boutton lab for their friendship, humor, encouragement, and thorough editing skills. This work would not have been possible without the help of Lisa Alexander, Kirk Jessup, and Darrin Moore, whose patience for repetitive tasks and long days in the field were greater than I ever could have imagined. I would like to thank Frank Hons, Michael Thon, Terry Gentry, and the members of their research groups for allowing me to use their lab space and equipment, as well as the Environmental Sciences Division and Microbial Ecology and Physiology Research Group of Oak Ridge National Laboratory for allowing me to spend time in their laboratories learning new techniques and utilizing their functional gene array. Additional thanks are extended to the faculty and staff at the Texas AgriLife Research Station at Vernon who helped to ensure smooth field campaigns under difficult conditions and provided assistance when things didn’t go quite as smoothly as anticipated. Words are not adequate to express my gratitude for the love and support provided by my family and friends throughout this process, but I acknowledge this large and varied, crazy, loving, group fully, knowing that I wouldn’t have made it through without them. This research was supported in part by the USDA/CASMGS Program, the U.S. DOE Global Change Education Program’s Graduate Research Environmental Fellowship, NASA’s Earth Systems Science Fellowship (EFFS-03-0000-0022), and an NSF Doctoral Dissertation Improvement grant (DEB/DDIG-0608465). vi TABLE OF CONTENTS Page ABSTRACT.............................................................................................................. iii ACKNOWLEDGEMENTS ...................................................................................... v TABLE OF CONTENTS.......................................................................................... vi LIST OF FIGURES................................................................................................... viii LIST OF TABLES .................................................................................................... ix CHAPTER I INTRODUCTION................................................................................ 1 II PRESCRIBED FIRE AND WOODY ENCROACHMENT ALTER ABOVEGROUND NET PRIMARY PRODUCTIVITY IN A SOUTHERN GREAT PLAINS MIXED GRASS SAVANNA........... 6 Introduction .................................................................................... 6 Materials and Methods................................................................... 8 Results ............................................................................................ 12 Discussion ...................................................................................... 27 Conclusions .................................................................................... 37 III EFFECTS OF PRESCRIBED FIRE AND WOODY ENCROACHMENT ON SOIL ORGANIC CARBON POOL SIZES AND TURNOVER RATES................................................................. 38 Introduction .................................................................................... 38 Materials and Methods................................................................... 41 Results ............................................................................................ 45 Discussion ...................................................................................... 50 Conclusions .................................................................................... 57 vii CHAPTER Page IV SOIL MICROBIAL COMMUNITY COMPOSITION IN A SOUTHERN GREAT PLAINS MIXED GRASS SAVANNA: INFLUENCE OF PLANT FUNCTIONAL TYPES............................ 58 Introduction .................................................................................... 58 Materials and Methods................................................................... 60 Results ............................................................................................ 69 Discussion ...................................................................................... 73 V EVALUATION OF THE FUNCTIONAL GENE DIVERSITY OF SOIL COMMUNITIES IN A SOUTHERN GREAT PLAINS MIXED GRASS SAVANNA USING THE GEOCHIP, A FUNCTIONAL GENE MICROARRAY............................................. 79 Introduction .................................................................................... 79 Materials and Methods................................................................... 81 Results ............................................................................................ 89 Discussion ...................................................................................... 94 Conclusions .................................................................................... 96 VI SUMMARY AND CONCLUSIONS................................................... 97 LITERATURE CITED ............................................................................................. 102 APPENDIX A ........................................................................................................... 123 VITA ......................................................................................................................... 147 viii LIST OF FIGURES FIGURE Page 1 Monthly precipitation and temperature patterns for Vernon, TX. ............. 13

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