Balancing Biodiversity and Human Land Use
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BALANCING BIODIVERSITY AND HUMAN LAND USE: EFFECTS OF FIRE, GRAZING AND HARVEST ON PLANT INDIVIDUALS, POPULATIONS AND COMMUNITIES IN THE WESTERN GHATS, INDIA A DISSERTATION SUBMITTED TO THE GRADUATE DIVISION OF THE UNIVERSITY OF HAWAI‘I AT MᾹNOA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY IN BOTANY (ECOLOGY, EVOLUTION AND CONSERVATION BIOLOGY) MAY 2012 By Lisa Mandle Dissertation Committee: Tamara Ticktin, Chairperson Curtis C. Daehler David C. Duffy Rebecca Ostertag Andrew D. Taylor Keywords: ecosystem services, functional diversity, integral projection model, non- timber forest product, Phoenix loureiri, savanna woodland ACKNOWLEDGEMENTS I am grateful for the many people who helped in the development and completion of this work and who made my time as a graduate student a wonderful adventure. I am especially indebted to my adviser Tamara Ticktin for her endless encouragement, advice and enthusiasm. I don’t think there could ever be a more supportive and caring adviser! Thank you to my committee – Andy Taylor, Becky Ostertag, Curt Daehler and Dave Duffy – for valuable feedback and ideas from beginning to end. This work would not have been possible without the knowledge, skills and dedication of my collaborators at Keystone Foundation and the Ashoka Trust for Ecology and the Environment (ATREE). I am particularly grateful for the assistance I received from Anita Varghese, Snehlata Nath, Pratim Roy, Sumin George Thomas, Siddappa Setty, R. Ganesan and Ankila Hiremath. Thank you to everyone who helped with data collection, especially B. Mahadesh, Basavanna, Mahadevan, K. Sudhakar, T. Aradukuttan, Kumbegowda, Kettegowda and Javanna, and to local community members who shared their knowledge and many cups of tea with me. Thank you also to the Karnataka and Tamil Nadu Forest Departments and the Palaniappa Estate for permission to conduct fieldwork. I feel incredibly fortunate to have been part of such an inspiring and talented lab group at University of Hawaiʻi and am grateful for the support of Ticktin lab members past and present, especially Isabel Schmidt, Orou Gaoue, Anita Varghese, Vandana Krishnamurthy, Georgia Hart, Tamara Wong, Shimona Quazi, Katie Kamelamela, Heather McMillen, Leyla Cabugos and Clay Trauernicht. Plant identification by R. Ganesan, Shiny Rehel and L. Rasingam was critical to completing this work. Brian Chrysler processed camera trap photos with astonishing, and appreciated, speed. My dissertation was much improved by guidance and feedback on analyses and interpretation from Andy Taylor and the mixed-effects modeling group, as well as Orou Gaoue and the IPM group. I thank Eileen Herring for assistance researching the history of mountain date palm harvest. For invaluable help with paperwork and logistics, I owe many, many thank yous to Patty Bedoya, Kori-Ann Phillips, Lucy Kida, Rena Duhl and Gerry Nakamoto, as well as Graduate Division Deans Patricia Cooper and Peter Garrod. Thank you to Gretchen Daily and her lab group for providing a stimulating place from which to work in California. Thank you to the many people whose generosity and hospitality (and delicious food!) have made me feel at home around the world, including Isabel Schmidt and Alexandre Sampaio, Henrietta and Dave Whitcomb, Cliff and Sharon Hu, Anita and Merab Varghese, Vandana Krishnamurthy, Vishnu Ramaprasad and the Krishnamurthy family, Leyla Cabugos, Helen Felsing and Wayne Watkins, SamitaVasudevan and Kunal Sharma, Renuka, Samira Agnihotri, K. Sudhakar and Mageshwari, Dave Elliott and Daniela Dutra Elliott, Nat Bletter and Abby Cuttriss, Courtney Angelo, Jennifer Bufford, Marian Chau and Matt Lurie. I am grateful to my family for their unwavering support for what I do, even when I don’t always succeed in making it clear what exactly that is. And to Chris for sticking with me and being a source of sanity throughout. This work was supported by funding from the National Science Foundation in the form of a Graduate Research Fellowship (grant no. 0822443) and an International Dissertation Enhancement Award (grant no. OISE-1104989); the Society for Economic Botany; the W.T. Yoshimoto Foundation; Maybelle Roth and Sarah Ann Martin scholarships from ARCS Foundation; as well as several sources within the University of Hawaiʻi including Beatrice Krauss and Charles H. Lamoureux awards from the Botany Department; the Ecology, Evolution and Conservation Biology Program (National Science Foundation grant DGE05-38550 to K.Y. Kaneshiro); the Arts and Sciences Advisory Council; and the Graduate Student Organization. ii ABSTRACT Effective conservation of the world’s remaining diversity requires determining to what degree preservation of biodiversity is compatible with meeting human needs. However, there is still a limited scientific understanding of the compatibility and trade- offs between biodiversity conservation and human land use. I used the case study of wild mountain date palm (Phoenix loureiri Kunth) in savanna woodland ecosystems of India’s Western Ghats biodiversity hotspot to investigate the ecological effects and conservation implications of fire, grazing and palm leaf harvest – three widespread and commonly co- occurring forms of land management activities in the tropics. I integrated results from a manipulative experiment, a regional observational study and mathematical models to determine how the effects of and interactions among these activities scale from palm individuals to populations to plant communities. I found that mountain date palm populations exhibited resilience to fire and low intensities of harvest and grazing, indicating a high potential for sustainable harvest. Individual-level compensatory growth, vegetative reproduction and density-dependent survival contributed to palm population resilience to disturbance. At the community level, areas managed for palm leaf harvest and livestock grazing retained similar levels of plant species and functional diversity to areas protected from these activities. However, the combined effects of fire, wild plant harvest and livestock grazing were associated with reduced tree cover and diversity and increased understory diversity. I also found evidence for a trade-off between maximizing the growth of mountain date palm populations and maximizing tree species diversity, mediated by the relationship between fire and canopy openness. Overall, my results suggest that human-managed savanna woodlands can both support mountain date palm iii leaf harvest and contribute to conservation objectives. Promoting a mosaic of land management practices would be an effective way to balance the need to preserve plant diversity with the potential for these ecosystems to contribute to the livelihoods of local people. Protected areas with reduced human land use may more effectively conserve tree cover and tree diversity, while areas managed for plant harvest and livestock grazing could still maintain substantial overall plant diversity and provide connectivity between protected areas, while additionally providing benefits to local people. iv TABLE OF CONTENTS ACKNOWLEDGEMENTS ............................................................................................. ii ABSTRACT ...................................................................................................................... iii LIST OF TABLES ......................................................................................................... viii LIST OF FIGURES ......................................................................................................... ix CHAPTER 1. INTRODUCTION .....................................................................................1 Biodiversity and human land use in the Western Ghats, India ........................................2 Land use and conservation in seasonally dry tropical ecosystems ..................................3 Fire, grazing and non-timber forest product harvest are widespread, often co-occurring, land management activities ..............................................................................................4 Palms in multi-use landscapes .........................................................................................6 Importance of understanding interactions among disturbances for plant demography ...7 Importance of understanding effects of human land use at multiple ecological levels ...7 Research questions and dissertation outline ....................................................................8 CHAPTER 2. THE IMPORTANCE OF CONSIDERING THE BROAD ECOLOGICAL CONTEXT OF HARVEST FOR COMMON PLANT SPECIES: MOUNTAIN DATE PALM (PHOENIX LOUREIRI) LEAF HARVEST IN SOUTH INDIA .................................................................................11 Abstract ..........................................................................................................................11 Introduction ....................................................................................................................11 Methods..........................................................................................................................13 Results and discussion ...................................................................................................15 Conclusions ....................................................................................................................19 CHAPTER 3. INTERACTIONS AMONG FIRE, GRAZING, HARVEST AND ABIOTIC CONDITIONS SHAPE PALM DEMOGRAPHIC RESPONSES TO DISTURBANCE