List of Contributors xv Foreword xvii Preface xix A Note on the Text xx 1 Introduction 1 Value of Trees Globally 1 Value of Urban Trees 2 Managing Trees 5 References 11 2 The Woody Skeleton: Trunk and Branches 15 What is a Tree? 15 How Does a Tree Grow? 15 Tree Design 18 How Shoots Grow 19 Building Blocks: Meristems and Buds 19 New Shoots From Buds 22 Apical Dominance and Apical Control 25 Epicormic Shoots and Sprouting 26 Epicormic Shoots (Sprouts) 27 Basal Sprouts 29 Branch and Trunk Sprouts 30 Opportunistic Sprouts 31 Sprouts Originating Underground 32 Practical Considerations of Sprouting 33 Sprouting in Response to Mechanical Injury 34 Sprouting in Response to Disturbance 34 Secondary Growth 34 The Vascular Cambium 35 Thickening of Woody Cell Walls 38 Programmed Cell Death 40 Bark and Secondary Phloem 40 How Bark Grows 41 Variation in Bark 43 Secondary Xylem - Wood 44 Different Cell Types Found in Wood 46 Living Cells in the Wood - Parenchyma 47 Non?Living Cells in the Wood - Vessels, Tracheids and Fibres 49 Variation in Wood Structure 52 Gymnosperm Wood 52 Dicotyledonous Wood 53 Sapwood and Heartwood 56 Sapwood and Water Movement 57 Heartwood 59 Sapwood and Heartwood - Considerations for Pruning Operations 62 Trade?offs in Wood Design 62 Trade?offs and the Movement of Water 63 Freezing?Induced Cavitation 66 Drought?Induced Cavitation 67 Moving Water Around a Tree - Vascular Sectorality 71 References 72 3 Leaves and Crowns 77 Angiosperm Leaves 78 Angiosperm Leaf Anatomy 82 Gymnosperm Leaves 83 Gymnosperm Leaf Anatomy 85 Juvenile Leaves 86 Sun and Shade Leaves 87 Leaf Arrangement 90 Compound Leaves 91 Evergreen and Deciduous Leaves 93 Value of Evergreen and Deciduous Leaves 94 Leaf Phenology 97 Tree Crowns 101 Shape of Tree Crowns 104 Role of Branches in Tree Crowns 107 Biomechanical Design of Tree Crowns 108 Reaction Wood 122 Branch Shedding as a Natural Process 124 Tree Pruning 126 Pruning Practices 129 Tree Crown Support 133 References 135 4 Tree Roots 141 Root Growth and Development 141 Root Systems 146 Secondary Root Growth 148 Root Architecture 150 Tree Anchorage 153 Extent of Root Systems 154 When Do Roots Grow? 157 Soil Compaction 161 Soil Resistance to Root Development 163 Management of Soil Compaction 165 Mulching 168 Decompaction 168 Estimating Appropriate Soil Volumes for Tree Roots 171 Improving Soil Volumes in Urban Environments 179 References 183 5 The Next Generation of Trees: From Seeds to Planting 187 Flowers, Seeds and Fruits 187 Variation in Flowers and Pollination 189 Not All Seeds Require Pollination 191 Cost of Reproduction 193 Numbers Involved 195 Flowering and Fruiting in Urban Landscapes 196 Tree Crops 198 Vegetative Reproduction 199 Growing Trees 203 Seeds and Their Origins 203 Storing Seeds 205 Seed Dormancy 205 Germination 207 Seedlings 208 Tree Establishment - From Production to the Landscape 210 Momentum of Tree Establishment 211 Tree Species Selection 212 Tree Quality 219 Nursery Production 219 Rooting Environment 225 Arboricultural Practices 227 References 231 6 Tree Water Relations 239 Water is Fundamental to Tree Development 239 Importance of Water Potential 240 Trees Experience Soil Water Potential, Not Soil Water Content 241 Managing Soil Water Availability 243 Fine Roots are Critical for Water Absorption 249 Hydraulic Redistribution 251 Ascent of Sap from Roots to Shoots 253 Transpiration 255 Resistance to Water Loss 255 References 258 7 Tree Carbon Relations 261 Carbon Moves from Source to Sink via the Phloem 262 Light and Other Environmental Variables That Influence Photosynthesis 263 Coping With Low Light 266 Coping With Too Much Light 268 Practical Implications of the Light Environment and Shade Tolerance 269 Other Key Factors Influencing Photosynthesis - Temperature, Nutrition and Water 270 Species Differ Widely in Their Leaf Photosynthetic Capacity 271 The Big Picture - Carbon Gain Over the Years 273 Carbon Dynamics in Trees: Production, Use and Storage 275 How Do Trees Die? 278 Improving the Carbon Balance in Landscape Trees 280 Annual Carbon Dynamics of the Tree and the Timing of Arboricultural Work 280 References 281 8 Tree Nutrition 285 Essential Nutrients 287 Nutrient Uptake 287 Symbiotic Relationships That Help Nutrient Acquisition 289 Other Factors That Influence Nutrient Availability -pH, Moisture, Aeration, Temperature 292 Nutrient Cycling 294 Managing Tree Nutrition 298 References 301 9 Interactions With Other Organisms 303 Trees as Habitats and Hosts 303 Plants and Epiphytes 303 Microorganisms 306 Symbiotic Fungi 306 Commercial Inoculants 308 Pathogenic Fungi 309 Defence of Stems 315 Historical Context of Stem Defence 316 Stem Defence 316 Effect of Wounding to the Bark 318 Effect of Wounding to the Sapwood 320 Pruning and Wounding 323 Decay in Stems 324 Bacteria 326 Insects 328 Pollinators and Defenders 328 Sap Suckers and Defoliators 328 Wood and Bark Borers 330 Synergy of Pests, Diseases and Environmental Stress 332 Mammals and Birds 333 Seed Dispersers 333 Injury by Birds and Mammals 334 Managing Trees as Habitats 334 Deadwood 342 References 346 10 Environmental Challenges for Trees 351 Avoidance and Tolerance of Plant Stress 351 Acclimation and Adaptation 352 Cold?Hardiness 353 Acquiring Cold?Hardiness 353 Cold?Hardiness Maps 354 Cold Injury to Trees 356 Avoiding Freezing in Below?Zero Temperatures 357 Ice Formation Outside of the Cell Protoplast 357 Frost Injury 358 High Temperatures 361 Coping with High Temperatures 362 Drought and Water Deficits 364 Water Deficits and Tree Development 365 Resistance of Water Deficits Using Avoidance and Tolerance Strategies 369 Drought Tolerance for Difficult Urban Sites 372 Flooding and Waterlogging Tolerance 376 Flooding Injury 377 Flooding and Soils 378 Variation in Tolerance to Flooding 378 Structural Adaptations to Flooding 378 Physiological Adaptations to Flooding 381 Riparian Trees Adapted to Urban Environments 382 Salt Tolerance 382 Dehydration and Toxicity Injuries in Saline Soils 383 Managing Saline Soils in Amenity Tree Planting 384 References 385 Index 391
ANDREW D. HIRONS is a Senior Lecturer in Arboriculture at University Centre Myerscough, UK. He has international experience as a climbing arborist and a plant health care practitioner. As well as lecturing on a range of arboricultural courses he is also actively involved in research. His current research activity is motivated by the need to create resilience in our urban forests, and is focused on using plant traits to inform species selection for urban environments. PETER A. THOMAS is a Reader in Plant Ecology at Keele University, UK. He has more than 30 years of experience in ecological aspects of trees and forests in the UK, Europe, North & Central America, Africa, Russia, Asia and Australasia.
"Overall this is very well written and beautifully presented book on applied tree biology that completely meets its declared objectives and is an excellent resource for all those engaged in the care and management of amenity trees, parks and other urban landscapes. It also fills an important and neglected niche in the scientific literature and so it is highly recommended reading for all interested in the management of trees - especially urban trees." - Prof RRB Leakey, Forest Trees and Livelihood, March 2018 "This is an ambitious book that bridges the gap between basic plant biology and practical arboriculture. Books have attempted this before but not in such a comprehensive way. Arborists, in common with other professions, sometimes too easily accept and follow practices based on unquestioning assumption rather than evidence. This book will help ground modern arboriculture in sound science."- The Plantsman, June 2018