Gentianopsis Crinita in NEW YORK STATE
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A LIFE HISTORY APPROACH TO THE STUDY OF PLANT SPECIES RARITY: Gentianopsis crinita IN NEW YORK STATE A Dissertation Presented to the Faculty of the Graduate School of Cornell University in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy by Heather Jane Robertson August 1992 1 © Heather Jane Robertson 1992 ALL RIGHTS RESERVED Author’s note: The content of this digital version of my thesis is the same as the original paper version but the text has been re-formatted to reduce the size of the document and, as a consequence, the thesis has been re-paginated. 2 A LIFE HISTORY APPROACH TO THE STUDY OF PLANT SPECIES RARITY: Gentianopsis crinita IN NEW YORK STATE Heather Jane Robertson, Ph.D. Cornell University, 1992 Gentianopsis crinita (Froel.) Ma, (fringed gentian), is a rare biennial plant, native to eastern North America. Generalizations about the life history characteristics of biennials, and the habitats where these plants occur, provided a framework for examining the critical factors affecting the rarity of Gentianopsis crinita in New York State. The relative significance of these factors was assessed by comparing Gentianopsis crinita's responses to those of Daucus carota L. (wild carrot), a common biennial that occurs in the same localities as Gentianopsis crinita. The principal study sites were two old fields near Ithaca in Tompkins County, and a landslide at Letchworth State Park in Livingston County. In one old field, seeds were sown in experimental treatments that represented successional habitats ranging from bare ground to scrub more than 3 m tall. Survival and reproduction of both species were enhanced where interspecific competition was reduced by ground disturbance and clipping of vegetation, but both species also persisted among tall herbs and low woody shrubs less than 1 m high. Neither species survived in tall scrub. Experiments indicated that Gentianopsis crinita may lack a persistent buried seed bank, and according to previous studies, so does Daucus carota. Flowering individuals of Gentianopsis crinita had a higher seed output on average than Daucus carota despite greater losses to herbivores. Although Gentianopsis crinita performed at least as well as Daucus carota in all these ways, observations and experiments revealed that the distribution and abundance of Gentianopsis crinita were more limited by its narrower tolerance of edaphic conditions. In contrast to Daucus carota, survival and growth required relatively high soil moisture levels and circumneutral to alkaline soils. The results also demonstrated that the optimal ecological conditions for Gentianopsis crinita, where survival, growth and reproductive output are greatest, can shift spatially over time, because patches of more fertile soils sometimes have inadequate moisture. Recommended conservation action includes permanent prevention of scrub encroachment on preserves and the selection of preserves containing refuge areas that are wet enough to maintain populations even in dry years. 3 BIOGRAPHICAL SKETCH Heather Robertson spent her childhood travelling abroad and in Britain with her parents, who were in the British Army. She lived in Singapore and Aden and was lucky enough to visit the National Parks of Kenya. She graduated from Durham University, England in 1974 with a First Class Honours degree in Botany and Geography. She pursued her developing interest in ecology and conservation by completing a M.Sc. degree in Conservation, with Distinction, at University College London in 1977. After graduating, she lived in the English Lake District for over 8 years and obtained practical experience in nature conservation by working as the Ecologist for the Lake District National Park and as an Assistant Regional Officer for the Nature Conservancy Council, the British government's advisory agency. In 1985 she was given leave by the Nature Conservancy Council to study for a Ph.D. in plant ecology at Cornell University, to increase her scientific expertise. In 1990 she returned to the Nature Conservancy Council in England and joined its team of national specialists in the Science Directorate as a grassland ecologist. 4 To Catharine, Joy and Deborah 5 ACKNOWLEDGEMENTS My thanks go to my committee members, Dr. Robert Cook, Dr. Peter Marks, and Dr. Charlie Smith, for all their help during my time as a graduate student. Bob Cook not only gave me the chance to carry out research in plant ecology, but also, in his role as Director of Cornell Plantations, enabled me to gain direct experience of nature conservation in the United States. I greatly valued this opportunity to be involved in the Plantations' important work of conserving the University's Natural Areas. Two ecologists whose research I found particularly inspiring during my project deserve special mention: Dr. Peter Grubb of Cambridge University, United Kingdom, and the late Dr. Deborah Rabinowitz. Deborah was a member of my committee, but unfortunately I knew her for only for a brief period before her untimely death in 1987. Staff at Cornell Plantations and the members of the University's Natural Areas Committee were all extremely helpful about my thesis project, and I hope that my work will in turn assist them in their efforts to conserve the fringed gentian. Dr. Nancy Ostman, Hal Martin, Dr. William Hamilton, Jr., Dr. William Dress and Robert Dirig gave freely of their time and experience. F. Robert Wesley not only provided information on past and present gentian localities but was also endlessly patient in helping me to identify American plants. Douglas Bassett, the Naturalist at Letchworth State Park, gave me a great deal of valuable information and assistance. Other naturalists also made very useful contributions to my project including Greenleaf Chase, Bonnie Glickman, Dorothy McIlroy, Mary Kelsey, Bente King, Dr. Pat Martin, Ron Pappert, Kenneth Paul and Edith Schroott. Permission to visit various gentian sites in New York State was kindly given by the landowners, including Mr. and Mrs. Robert B. Jones, the Kelly family, Robert Otter, the Bergen Swamp Preservation Society and the Burroughs-Audubon Nature Club. State Heritage Program staff across the northeastern United States and the government conservation staff in Canada provided much useful information on the status and distribution of the fringed gentian. Many of Cornell's faculty, research associates and staff gave me help and guidance. In particular I thank Dr. Karl Niklas, for investigating seed dispersal of the fringed gentian with me, Dr. Susan Riha, Dr. David Bouldin, Dr. Ray Bryant and his assistant Emmy Lucas for their help with soil analyses, Dr. Keith Eggleston for climate information, Dr. John Franclemont for identifying insects, Dr. Tom Weiler for advice about growing gentians in the greenhouse, Dr. David Winkler for discussions about life history models and dispersal experiments, and Dr. Chuck McCulloch, Dr. Hugh Gauch and Dr. Philip Dixon for advice on statistics. People from other organizations who gave me advice and assistance included Dr. Hugh Iltis from the University of Wisconsin, Dr. Norton Miller of the State Museum of New York, Dr. Ferguson of the USDA's Systematic Entomology Lab, Dr. Klaus Satler of the British Museum of Natural History and Dr. Robert Young of SUNY Geneseo. Essential funding was provided by an International Fellowship from the American Association of University Women, a fellowship given to me by the Josephine De Karman Trust, grants from the Cornell and national chapters of Sigma Xi and from the Rabinowitz Graduate Student Research Fund and the Robert H. Whittaker Memorial Fund. I am very grateful to the Nature Conservancy Council of Britain, for giving me special leave to undertake my Ph.D. degree at Cornell, and to staff from NCC's successor body, English Nature (NCC England), for all their support, in particular Dr. Keith Kirby, Dr. Rick Keymer and Dr. John Hopkins. Special thanks go to my fellow graduate students at Cornell, for their willingness to discuss ideas and for their immediate response when I needed volunteer labor! Steve Anderson, Sana Gardescu, Laura Jackson, Felix Sperling, Mark Witmer, and research associates Dr. Aaron Ellison and Dr. Robert 6 Muller combined their efforts to make an extremely effective "bulldozer," which cleared scrub from the Fringed Gentian Natural Area in a matter of minutes. John Andersland, Curtis Bohlen, Cynthia Jensen, Beate Nürnberger, John Saponara and Sara Tjøssem were among other grad students who gave me ready assistance during my project. Between 1988 and 1990 I was also lucky to have three cheerful and enthusiastic research assistants, Jim Murray, Carolyn Tomaino and Laurie Isenberg. Family and friends helped me along too, especially Debbie Joseph, who managed the transition from librarian to plant ecologist with ease. Among all the many people who contributed to my project, I owe my greatest debt of thanks to Sana Gardescu. She helped me in innumerable ways throughout my time at Cornell and held together the American side of my thesis production when I returned to England. I simply could not have completed my thesis without her constant and unstinting encouragement and support. 7 TABLE OF CONTENTS Chapter 1 INTRODUCTION 14 Chapter 2 BIOLOGY OF Gentianopsis crinita AND DESCRIPTIONS OF THE STUDY SITES 20 INTRODUCTION 20 BIOLOGY OF Gentianopsis crinita (Froel.) Ma 21 Taxonomy 21 Historical background 21 Distribution, abundance and conservation status of G. crinita 22 Life cycle and morphology of G. crinita 26 Floral biology