Adaptive Geometry of Trees PDF
Preview Adaptive Geometry of Trees
THE ADAPTIVE GEOMETRY OF Trees MONOGRAPHS IN POPULATION BIOLOGY EDITED BY ROBERT M. MAY 1. The Theory of Island Biogeography, by Robert H. Mac- Arthur and Edward O. Wilson 2. Evolution in Changing Environments: Some Theoretical Ex- plorations, by Richard Levins 3. Adaptive Geometry of Trees, by Henry S. Horn 4. Theoretical Aspects of Population Genetics, by Motoo Ki- mura and Tomoko Ohta 5. Populations in a Seasonal Environment, by Stephen D. Fret- well 6. Stability and Complexity in Model Ecosystems, by Robert M. May 7. Competition and the Structure of Bird Communities, by Mar- tin L. Cody 8. Sex and Evolution, by George C. Williams 9. Group Selection in Predator-Prey Communities, by Michael E. Gilpin 10. Geographic Variation, Speciation, and Clines, by John A. Endler 11. Food Webs and Niche Space, by Joel E. Cohen 12. Caste and Ecology in the Social Insects, by George F. Oster and Edward O. Wilson 13. The Dynamics of Arthropod Predator-Prey Systems, by Mi- chael P. Hassell 14. Some Adaptations of Marsh-Nesting Blackbirds, by Gordon H. Orians 15. Evolutionary Biology of Parasites, by Peter W. Price 16. Cultural Transmission and Evolution: A Quantitative Ap- proach, by L. L. Cavalli-Sforza and M. W. Feldman 17. Resource Competition and Community Structure, by David Tilman 18. The Theory of Sex Allocation, by Eric L. Charnov 19. Mate Choice in Plants: Tactics, Mechanisms, and Conse- quences, by Mary F. Willson and Nancy Burley THE ADAPTIVE GEOMETRY OF Trees BY HENRY S. HORN PRINCETON, NEW JERSEY PRINCETON UNIVERSITY PRESS Copyright © 1971 by Princeton University Press ALL RIGHTS RESERVED L. C. Card: 70-140279 ISBN: 0-691-08089-5 ISBN: 0-691-02355-7 (pbk.) This book has been composed in Linofilm Baskerville Printed in the United States of America Contents Preface vii Preface to the Second Printing ix Symbols Used xii 1. Introduction 3 2. Measurement of Light Intensity 8 3. Analysis of a Forest Succession 19 4. Theoretical Strategies of Leaf Distribution 45 5. Photosynthetic Response of the Strategies 64 6. Measurement of Actual Strategies 89 7. Speculations on the Shapes of Tree Crowns 104 8. On the Relation between Theory and Reality 118 Nomenclature 131 Bibliography 135 Index 141 Preface I started this project almost by accident three years ago. Robert MacArthur and I had been trying to find mechani- cal ways to measure foliage profiles, which he had found to be accurate predictors of the variety of birds in a habitat. One of our machines was an adjustable- light meter that I shall describe in Chapter 2. While testing it in the woods on a Sunday afternoon, I recorded the meter readings above various saplings, and I was struck by a general pat- tern. Trees that typically invade old fields were never found under a canopy. The familiar species of young forests were found beneath openings in the canopy, and denizens of virgin forests were found in deep shade. An accumulation of many more measurements eventually gave strong support to the foresters' axiom that species which tolerate a canopy become progressively more dominant as succession proceeds —a result that was more gratifying than surprising. However, the analysis raised new questions and cast new light on some old ones. I sub- sequently invented a theory to explore these questions. The theory led to new kinds of measurements, which led to changes in the theory, and so on. The result to date is this book, in which I simultaneously commit the sins of vitalism and mechanism. Indeed, thinking of trees as crafty green strategists has given me many new insights, and simplified assumptions have allowed me to test these in- sights. I have organized my ideas around the traditional problem of plant succession, but my basic interest is the prediction and testing of patterns of adaptive strategies among trees. I sincerely hope that my ideas will not be viewed as a contribution to past and current controversies about the appropriateness of successional terminologies. v 11 PREFACE Rather, I am much more interested in the way that nature shapes theory than in the constraints that theory imposes on nature. The greatest homage that can be paid to an em- pirical theory is the constructive criticism that makes it obsolete at an early age. Throughout this study I have had continual discussions with Robert MacArthur and Egbert Leigh. I am indebted to them for elegant improvements in the theory and for critical empirical observations. I have also had very helpful comments and observations from John Bonner, Gordon Orians, Daniel Janzen, Christopher Smith, Woodruff Ben- son, and J. Merritt Emlen. For permission to work on their land, or for tolerating my presence without permission, I am grateful to those in charge of the Institute Woods, Herrontown Woods County Park, and the Stony Ford Field Station at Princeton, N.J.; Mammoth Cave National Park, Ky.; Calaveras County Big Tree Park, Calif.; and Finca las Cruces, San Vito de Java, Puntarenas Prov., Costa Rica. For help in the field and in the lab, I am indebted to my wife, Elizabeth, to Thomas Gibson, to Robert Millaway, and to several students in the August 1969 O.T.S. Advanced Population Biology group. The funds for this study were scrounged from many sources. My wife allowed me to use part of the family budget that she earned. The Eugene Higgens Trust Fund of the Princeton Department of Biology provided pin money. I had free use of electronic gadgets provided and maintained by the Whitehall Foundation. The Organiza- tion for Tropical Studies paid my way to and in Costa Rica in return for a series of lectures on theoretical forestry. Although they don't know it yet, the Princeton University Computer Center provided free computer time, charged to a grant from the National Science Foundation. For reading the entire manuscript and tendering valu- vl I i
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