Many arborists learn tree work practices without fully understanding the biological and physiological principles behind them. However, outcomes for the health and longevity of trees are greatly improved when an arborist understands the science behind the care of tree root systems and crowns. In Applied Tree Biology, Drs. Hirons and Thomas draw upon their decades of experience in the laboratory, classroom, and the field – as well as the expertise of distinguished contributors to this volume – to provide those responsible for tree care with the scientific information that informs best practices for planting, pruning, soil decompaction, irrigation, and much more.
- Takes a multidisciplinary approach, integrating knowledge from plant biology, physiology, arboriculture, ecology, and more
- Provides a systematic presentation of fundamental tree biology and the scientific principles informing high quality tree care
- Presents accessible scientific information and best practices that help promote the health and longevity of trees
- Reflects the authors’ decades of experience as tree biology researchers and educators, as well as their years of professional experience across the globe
Applied Tree Biology is an indispensable source of practical, succinct information on tree biology, physiology, and ecology for professionals and interested amateurs involved with the care of trees. Arborists, foresters, and horticulturists at all stages of their careers will find this text particularly useful.
Table of Contents
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
