GRASSES AND GRASSLAND ECOLOGY This page intentionally left blank Grasses and Grassland Ecology David J. Gibson Southern Illinois University, Carbondale 1 3 Great Clarendon Street, Oxford OX2 6DP Oxford University Press is a department of the University of Oxford. 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Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, at the address above You must not circulate this book in any other binding or cover and you must impose the same condition on any acquirer British Library Cataloguing in Publication Data Data available Library of Congress Cataloging in Publication Data Data available Typeset by Newgen Imaging Systems (P) Ltd., Chennai, India Printed in Great Britain on acid-free paper by CPI Antony Rowe, Chippenham, Wiltshire ISBN 978–0–19–852918–7 978–0–19–852919–4 (Pbk) 10 9 8 7 6 5 4 3 2 1 Preface . a vast expanse of level ground unbroken save by one My own experience in grasslands results from thin line of trees which scarcely amounted to a scratch an early and abiding love of the chalk grasslands upon the great blank; until it met the glowing sky of southern England. The dune grasslands of wherein it seemed to dip . There it lay, a tranquil sea Newborough Warren, Anglesey and the montane or lake without water . with the day going down upon grasslands of Snowdonia, Wales have also been it . it was lovely and wild, but oppressive in its barren important to me ever since my days as a doctoral monotony. student at the University College of North Wales Charles Dickens (American Notes for General Circulation, (now the University of Bangor). My research in 1842) describing Looking Glass Prairie grasslands has been inspired by many mentors and near Lebanon, Illinois colleagues, but I must mention in particular Paul Risser (formerly of the University of Oklahoma), Grasslands evoke emotion, they are the largest the late Lloyd Hulbert (Kansas State University), biome on Earth, they represent a tremendous source and the Long Term Ecological Research group at of biodiversity, they provide important goods and Konza Prairie during the late 1980s as having a services, and they are the place where as a species, large and enduring influence on my understand- we first stood up and walked. As a result, grasses ing of the North American prairie. The writing of and grasslands are widely studied. However, after this book follows from the start that they gave me. teaching an upper level/postgraduate course on It takes a long time to write a book, but I am grassland ecology for several years, I realized that a grateful to Southern Illinois University Carbondale suitable textbook was needed. Hence, I have written for providing a sabbatical leave in Spring 2006 this book in the hope that it will be useful not just that allowed time to write several chapters. Many, for the students taking my grassland course, but many people helped me write this book. In par- researchers, land managers, and anyone who has ticular, I thank colleagues who answered my an interest in grasslands anywhere in the world. questions and read drafts of various chapters The book brings together a huge literature from including Roger Anderson (Chapter 10), Elizabeth ecological, natural history, and agricultural disci- Bach (Chapter 1), Sara Baer (Chapters 7 and 10), plines. The nomenclature for plant names is syno- Ray Callaway (Chapter 6), Ryan Campbell (Index), nymized according to the USDA Plants National Gregg Cheplick (Chapter 5), Keith Clay (Chapter Database (http://plants.usda.gov/index.html) as 5), Jim Detling (Chapter 9), Stephen Ebbs (Chapter of May 2008, or, for species not in the database, 4), Don Faber-Langendoen (Chapter 8), Richard the name used in the original source. As a result, Groves (Chapter 8), Trevor Hodkinson (Chapter 2), names are changed from the original source when a Allison Lambert (Chapters 1, 2, 3, 4, and 8), Susana more up-to-date name is provided in the database. Perelman (Chapter 8), Wayne Polley (Chapter 4), Some familiar plants have new names: for exam- David Pyke (Chapter 10), Steve Renvoize (Chapter ple, where I talk about tall fescue I use Schedonorus 3), Paul Risser (Chapter 1), Tim Seastedt (Chapter 7), phoenix in place of the older Festuca arundinacea. Rob Soreng (Chapter 2), and Dale Vitt (Chapter 8). Older names are included in the index with a ref- Thanks to Daniel Nickrent, Hongyan Liu, Gervasio erence to the new name. Piñeiro, Sam NcNaughton, Dale Vitt, Steve Wilson, v vi PREFACE and Zicheng Yu for allowing me to reproduce their tirelessly helpful in ensuring that this book was excellent photographs. John Briggs kindly supplied actually published. Finally, grateful thanks to my the satellite image for Plate 13 and Howard Epstein wife Lisa and our children Lacey and Dylan for an original for Fig 4.3. Cheryl Broadie and Steve providing the love and emotional support neces- Mueller of the SIUC IMAGE facility were a tremen- sary for the marathon of writing a book. dous help in preparing several of the photographs Carbondale, Illinois D.J.G and figures. Helen Eaton, Ian Sherman, and the May 2008 staff at Oxford University Press have always been Contents Preface v 1 Introduction 1 1.1 Grasslands: a tautological problem of defi nition 1 1.2 Extent of the world’s grasslands 2 1.3 Grassland loss 4 1.4 Grassland goods and services 12 1.5 Early grassland ecologists 18 2 Systematics and evolution 21 2.1 Characteristics of the Poaceae 21 2.2 Traditional vs modern views of grass classifi cation 22 2.3 Subfamily characteristics 24 2.4 Fossil history and evolution 29 3 Ecological morphology and anatomy 35 3.1 Developmental morphology—the phytomer 35 3.2 Structure of the common oat Avena sativa 36 3.3 Culms 36 3.4 Leaves 43 3.5 Roots 46 3.6 Infl orescence and the spikelet 49 3.7 The grass seed and seedling development 51 3.8 Anatomy 54 4 Physiology 58 4.1 C3 and C4 photosynthesis 58 4.2 Forage quality 68 4.3 Secondary compounds: anti-herbivore defences and allelochemicals 73 4.4 Silicon 78 4.5 Physiological integration of clonal grasses and mechanisms of ramet regulation 79 5 Population ecology 81 5.1 Reproduction and population dynamics 81 5.2 Fungal relationships 94 5.3 Genecology 102 vii viii CONTENTS 6 Community ecology 110 6.1 Vegetation–environment relationships 110 6.2 Succession 113 6.3 Species interactions 115 6.4 Models of grassland community structure 121 6.5 Summary: an issue of scale 128 7 Ecosystem ecology 129 7.1 Energy and productivity 129 7.2 Nutrient cycling 141 7.3 Decomposition 149 7.4 Grassland soils 153 8 World grasslands 160 8.1 Ways of describing vegetation 160 8.2 General description of world grasslands 162 8.3 Examples of regional grassland classifi cations 179 9 Disturbance 184 9.1 The concept of disturbance 185 9.2 Fire 187 9.3 Herbivory 194 9.4 Drought 207 10 Management and restoration 211 10.1 Management techniques and goals 211 10.2 Range assessment 221 10.3 Restoration 235 References 243 Plant index 289 Animal index 297 Subject index 299 CHAPTER 1 Introduction Each grass-covered hillside is an open book for those The main points that these varied definitions have who care to read. Upon its pages are written the condi- in common are the prevalence of grasses (members tions of the present, the events of the past, and a forecast of the Poaceae), an infrequent or a low abundance of those of the future. Some see without understand- of woody vegetation, and a generally arid climate. ing; but let us look closely and understandingly, and act Risser’s (1988) definition is perhaps the most com- wisely, and in time bring our methods of land use and prehensive as it encompasses these ideas. Other conservation activities into close harmony with the dic- factors that are important and which together help tates of Nature. characterize natural grasslands in many parts of John E. Weaver (1954) the world include deep, fertile, organic-rich soils (frequently Chernozems—see Chapter 7), frequent The purpose of this first chapter is to introduce the natural fire (Chapter 9), and large herds of graz- grassland biome. Grasslands are the most extensive, ing mammals (Chapter 9). Semi-natural or seeded arguably the most useful to human society, yet the grasslands (e.g. amenity grasslands: Chapter 8) most threatened biome on the planet. Nevertheless, may lack some of these features, especially natural it is surprisingly difficult to unambiguously define disturbance.