Applied Tree Biology

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

• List of Contributors xvForeword xviiPreface xixA Note on the Text xx1 Introduction 1Value of Trees Globally 1Value of Urban Trees 2Managing Trees 5References 112 The Woody Skeleton: Trunk and Branches 15What is a Tree? 15How Does a Tree Grow? 15Tree Design 18How Shoots Grow 19Building Blocks: Meristems and Buds 19New Shoots From Buds 22Apical Dominance and Apical Control 25Epicormic Shoots and Sprouting 26Epicormic Shoots (Sprouts) 27Basal Sprouts 29Branch and Trunk Sprouts 30Opportunistic Sprouts 31Sprouts Originating Underground 32Practical Considerations of Sprouting 33Sprouting in Response to Mechanical Injury 34Sprouting in Response to Disturbance 34Secondary Growth 34The Vascular Cambium 35Thickening of Woody Cell Walls 38Programmed Cell Death 40Bark and Secondary Phloem 40How Bark Grows 41Variation in Bark 43Secondary Xylem – Wood 44Different Cell Types Found in Wood 46Living Cells in the Wood – Parenchyma 47Non‐Living Cells in the Wood – Vessels, Tracheids and Fibres 49Variation in Wood Structure 52Gymnosperm Wood 52Dicotyledonous Wood 53Sapwood and Heartwood 56Sapwood and Water Movement 57Heartwood 59Sapwood and Heartwood – Considerations for Pruning Operations 62Trade‐offs in Wood Design 62Trade‐offs and the Movement of Water 63Freezing‐Induced Cavitation 66Drought‐Induced Cavitation 67Moving Water Around a Tree – Vascular Sectorality 71References 723 Leaves and Crowns 77Angiosperm Leaves 78Angiosperm Leaf Anatomy 82Gymnosperm Leaves 83Gymnosperm Leaf Anatomy 85Juvenile Leaves 86Sun and Shade Leaves 87Leaf Arrangement 90Compound Leaves 91Evergreen and Deciduous Leaves 93Value of Evergreen and Deciduous Leaves 94Leaf Phenology 97Tree Crowns 101Shape of Tree Crowns 104Role of Branches in Tree Crowns 107Biomechanical Design of Tree Crowns 108Reaction Wood 122Branch Shedding as a Natural Process 124Tree Pruning 126Pruning Practices 129Tree Crown Support 133References 1354 Tree Roots 141Root Growth and Development 141Root Systems 146Secondary Root Growth 148Root Architecture 150Tree Anchorage 153Extent of Root Systems 154When Do Roots Grow? 157Soil Compaction 161Soil Resistance to Root Development 163Management of Soil Compaction 165Mulching 168Decompaction 168Estimating Appropriate Soil Volumes for Tree Roots 171Improving Soil Volumes in Urban Environments 179References 1835 The Next Generation of Trees: From Seeds to Planting 187Flowers, Seeds and Fruits 187Variation in Flowers and Pollination 189Not All Seeds Require Pollination 191Cost of Reproduction 193Numbers Involved 195Flowering and Fruiting in Urban Landscapes 196Tree Crops 198Vegetative Reproduction 199Growing Trees 203Seeds and Their Origins 203Storing Seeds 205Seed Dormancy 205Germination 207Seedlings 208Tree Establishment – From Production to the Landscape 210Momentum of Tree Establishment 211Tree Species Selection 212Tree Quality 219Nursery Production 219Rooting Environment 225Arboricultural Practices 227References 2316 Tree Water Relations 239Water is Fundamental to Tree Development 239Importance of Water Potential 240Trees Experience Soil Water Potential, Not Soil Water Content 241Managing Soil Water Availability 243Fine Roots are Critical for Water Absorption 249Hydraulic Redistribution 251Ascent of Sap from Roots to Shoots 253Transpiration 255Resistance to Water Loss 255References 2587 Tree Carbon Relations 261Carbon Moves from Source to Sink via the Phloem 262Light and Other Environmental Variables That Influence Photosynthesis 263Coping With Low Light 266Coping With Too Much Light 268Practical Implications of the Light Environment and Shade Tolerance 269Other Key Factors Influencing Photosynthesis – Temperature, Nutrition and Water 270Species Differ Widely in Their Leaf Photosynthetic Capacity 271The Big Picture – Carbon Gain Over the Years 273Carbon Dynamics in Trees: Production, Use and Storage 275How Do Trees Die? 278Improving the Carbon Balance in Landscape Trees 280Annual Carbon Dynamics of the Tree and the Timing of Arboricultural Work 280References 2818 Tree Nutrition 285Essential Nutrients 287Nutrient Uptake 287Symbiotic Relationships That Help Nutrient Acquisition 289Other Factors That Influence Nutrient Availability –pH, Moisture, Aeration, Temperature 292Nutrient Cycling 294Managing Tree Nutrition 298References 3019 Interactions With Other Organisms 303Trees as Habitats and Hosts 303Plants and Epiphytes 303Microorganisms 306Symbiotic Fungi 306Commercial Inoculants 308Pathogenic Fungi 309Defence of Stems 315Historical Context of Stem Defence 316Stem Defence 316Effect of Wounding to the Bark 318Effect of Wounding to the Sapwood 320Pruning and Wounding 323Decay in Stems 324Bacteria 326Insects 328Pollinators and Defenders 328Sap Suckers and Defoliators 328Wood and Bark Borers 330Synergy of Pests, Diseases and Environmental Stress 332Mammals and Birds 333Seed Dispersers 333Injury by Birds and Mammals 334Managing Trees as Habitats 334Deadwood 342References 34610 Environmental Challenges for Trees 351Avoidance and Tolerance of Plant Stress 351Acclimation and Adaptation 352Cold‐Hardiness 353Acquiring Cold‐Hardiness 353Cold‐Hardiness Maps 354Cold Injury to Trees 356Avoiding Freezing in Below‐Zero Temperatures 357Ice Formation Outside of the Cell Protoplast 357Frost Injury 358High Temperatures 361Coping with High Temperatures 362Drought and Water Deficits 364Water Deficits and Tree Development 365Resistance of Water Deficits Using Avoidance and Tolerance Strategies 369Drought Tolerance for Difficult Urban Sites 372Flooding and Waterlogging Tolerance 376Flooding Injury 377Flooding and Soils 378Variation in Tolerance to Flooding 378Structural Adaptations to Flooding 378Physiological Adaptations to Flooding 381Riparian Trees Adapted to Urban Environments 382Salt Tolerance 382Dehydration and Toxicity Injuries in Saline Soils 383Managing Saline Soils in Amenity Tree Planting 384References 385Index 391