An Introduction to Agroforestry: Four Decades of Scientific Developments

Description

Agroforestry – the practice of growing trees and crops in interacting combinations – is recognized the world over as an integrated approach to sustainable land-use. Agroforestry systems, being multifunctional, facilitate not only the production of food and wood products but also provide a variety of ecosystem services such as climate-change mitigation, biodiversity conservation, and soil quality improvement. Agroforestry research has made rapid strides since organized efforts started in the late 1970s. Today, a vast body of scientific knowledge and an impressive array of publications on agroforestry are available. Four World Congresses on Agroforestry conducted once every five years since 2004 have brought together the global community of agroforestry professionals and practitioners to share and discuss the emerging trends and paradigm shifts in this field. The fifth Congress is scheduled to be held in Québec, Canada.  However, a comprehensive college-level textbook incorporating these research findings did not exist until this book was first published. The first edition of this book in 1993 (Nair, P. K. R., 1993) is out of print and somewhat dated. This revised edition, with emphasis on the scientific developments during the past more than four decades, addresses this long-felt need.    Preface Acknowledgments Contents Section I: Introduction Chapter 1: Historical Developments: The Coming of Age of Agroforestry 1.1 Introduction 1.2 Cultivating Trees and Crops Together: An Age-Old Practice 1.3 Developments in the Agriculture Sector 1.3.1 The Green Revolution 1.3.2 The International Agricultural Research Centers (IARCs) 1.4 Developments in the Forestry Sector 1.4.1 The General Pattern of Forest Resource Utilization Over Time 1.4.2 Major Forestry Research and Development Initiatives Since the 1950s 1.4.3 Deforestation 1.4.4 People-Oriented Forestry Programs 1.5 Formation of ICRAF and the Institutionalization of Agroforestry References Chapter 2: Definition and Concepts of Agroforestry 2.1 Introduction 2.2 Evolution of Definitions of Agroforestry 2.3 Definitions Galore 2.4 Concepts, Principles, and Attributes of Agroforestry 2.5 Other Agroforestry-Related Land-Use Systems References Chapter 3: Classification of Agroforestry Systems 3.1 Introduction 3.2 Early Efforts in Classification 3.3 Classification Based on the Structure of the System 3.3.1 Nature of Components 3.3.2 Arrangement of Components 3.4 Based on the Function of the System 3.5 Based on Ecological Characteristics 3.6 Based on Socioeconomic Criteria 3.7 Other Approaches to Classification of Tropical Agroforestry Systems 3.8 Agroforestry Systems and Practices 3.9 Classification of Agroforestry Practices in the Temperate Regions 3.10 Concluding remarks: A Framework for Classification of Agroforestry Systems References Chapter 4: Global Distribution of Agroforestry Systems 4.1 Introduction 4.2 The Tropical Environment 4.3 Distribution of Tropical Agroforestry Systems 4.3.1 Lowland Humid and Sub-humid Tropics 4.3.2 Semiarid and Arid Tropics 4.3.3 Tropical Highlands 4.4 Agroecological Spread of Tropical Agroforestry Systems 4.5 The Temperate Environment and Land Use Systems 4.6 Temperate Agroforestry Practices 4.7 Temperate vs. Tropical Agroforestry 4.8 Geographical Distribution and Area Under Agroforestry Systems References Section II: Agroforestry Systems and Practices Chapter 5: Shifting Cultivation and Taungya 5.1 Introduction 5.2 Shifting Cultivation 5.2.1 System Overview 5.2.2 The Common Activities in the Practice of Shifting Cultivation 5.2.3 Soil Management Under Shifting Cultivation 5.3 Taungya: An Agroforestry Practice for Forest Plantation Establishment 5.3.1 An Overview of the Taungya Practice 5.3.2 Alternatives/Improvements to Taungya 5.4 Agroforestry Pathways to Improving Shifting Cultivation: Planted Fallows 5.4.1 Fallow Intensification Pathways 5.4.2 Planted Fallows 5.5 Concluding Remarks References Chapter 6: Tropical Alley Cropping and Improved Fallows 6.1 Introduction 6.2 Tropical Alley Cropping 6.2.1 Hedgerow Species 6.2.2 Nutrient (Nitrogen) Yield from Tree Species and Soil Fertility 6.2.3 Soil Properties and Soil Conservation 6.2.4 Crop Yields Under Alley Cropping 6.2.5 The Rise and Fall of Alley Cropping 6.3 Improved (Shrub and Tree) Fallows 6.3.1 Improved Fallow: The Practice and Terminology 6.3.2 Improved-Fallow Species 6.3.3 Soil Fertility and Crop Yields Under Improved Fallows 6.3.4 The Rise and Fall of Improved Fallows 6.4 Concluding Remarks References Chapter 7: Tropical Homegardens 7.1 Introduction 7.2 Global Distribution of Homegardens 7.3 History, Evolution, and Distribution of Homegardens 7.4 Types of Homegardens 7.5 Ecology and Structure 7.5.1 Floristic Diversity 7.5.2 Vegetation Structure 7.5.3 Ecosystem Services 7.6 Commercialization of Homegardens 7.7 Major Tropical Homegarden Systems 7.7.1 Homegardens of Kerala (India) 7.7.2 Javanese Homegardens of Indonesia 7.7.3 Polynesian Homegardens 7.7.4 The Shamba and Chagga Gardens of East Africa 7.7.5 The Sri Lankan Homegardens 7.7.6 Central American Homegardens 7.7.7 Homegardens in the Brazilian Amazon 7.8 Research on Homegarden Systems 7.9 Concluding Remarks References Chapter 8: Shaded Perennial Agroforestry Systems 8.1 Introduction 8.2 Tropical Tree Crops: An Overview 8.2.1 Abundance and Distribution of Species 8.2.2 The Scale of Operations: Commercial Plantations and Smallholder Systems 8.2.3 Research and Development Efforts 8.3 Integrated, Smallholder Land-Use Systems with Shaded Perennial (Plantation) Crops 8.4 Coconut-Based Smallholder Systems: A Notable Example of Integrated Agroforestry 8.4.1 Common Land-Use Features of Coconut-Based Ecosystems 8.4.2 Growth Habits of the Coconut Palm Concerning Multispecies Systems 8.4.3 Intercropping Under Coconuts 8.4.4 Special Forms of Integrated Production Systems with Coconuts 8.4.5 Prospects of Land-Use Intensification with Coconuts 8.5 Shaded Coffee and Cacao Systems 8.5.1 Shaded Coffee Systems 8.5.2 Cacao Production Systems 8.5.3 Shade Trees for Coffee and Cacao 8.6 Other Agroforestry Systems Involving Tropical Tree Crops 8.6.1 Tropical Palms 8.6.2 Multistory Tree Gardens 8.7 Concluding Remarks References Chapter 9: Silvopastoral Systems (SPS) in the Tropics and Subtropics 9.1 Introduction 9.2 Tropical and Subtropical SPS: An Introduction 9.3 Common Forms and Terms of Silvopasture 9.4 Common Silvopastoral Grazing Systems in the Drylands 9.4.1 The Parkland System of West Africa 9.4.2 SPS in the Semiarid Brazilian Tropics 9.4.3 SPS in the Arid and Semiarid Parts of India 9.4.4 Other SPS in the Semiarid Regions Worldwide 9.5 The Browsing Systems: Tree Fodder and Fodder Trees 9.5.1 The Cut-and-Carry System 9.5.2 Fodder Banks 9.5.3 Boundary Planting 9.6 Research in Tropical Silvopastoral Systems 9.7 Integrated Crop Livestock Forestry Systems: New Wine in Old Bottles? 9.8 Outlook on Tropical Silvopastoral Systems References Chapter 10: Agroforestry Systems in The Temperate Zone 10.1 Introduction 10.2 Historical Perspectives 10.3 Agroforestry Systems in North America 10.3.1 Alley Cropping 10.3.2 Silvopastoral Systems 10.3.3 Windbreak Practices 10.3.4 Riparian and Upland Buffers 10.3.5 Forest Farming 10.4 Agroforestry in Europe 10.4.1 Traditional Practices: The Dehesa System 10.4.2 Traditional Practices: Integrated Fruit-Orchard Agroforestry in Europe 10.4.3 Recent European Initiatives in Agroforestry 10.4.4 Current Status of Agroforestry Systems in Europe 10.5 Agroforestry in Other Temperate/Industrialized Regions 10.5.1 Australia 10.5.2 New Zealand 10.5.3 China 10.5.4 Southern Parts of Latin America 10.6 Concluding Remarks References Chapter 11: Other Agroforestry Systems and Practices 11.1 Introduction 11.2 Cinderella Agroforestry Systems 11.3 Agroforestry Systems for Production of Subsidiary Commodities 11.3.1 Fuelwood Trees in AFS 11.3.2 Fodder Trees in AFS 11.3.3 Medicinal and Aromatic Plants in AFS 11.4 Agroforestry for Ecosystem Protection 11.5 Other Agroforestry-Related Land-Use Systems 11.5.1 Social Forestry 11.5.2 Farm Forestry 11.5.3 Community Forestry 11.5.4 Urban Forestry and Urban Food Forestry 11.5.5 Permaculture 11.5.6 Trees Outside Forests 11.5.7 Carbon Farming 11.5.8 Satoyama: The Socio-Ecological Production Landscape of Japan 11.5.9 The Damar Agroforests of Indonesia 11.6 Concluding Remarks References Section III: Biophysical Foundations of Agroforestry: Plant Productivity Chapter 12: General Principles of Plant Productivity 12.1 Introduction 12.2 Photosynthesis and Respiration: The Basics 12.3 Plant and Ecosystem Productivity 12.3.1 Plant Productivity 12.3.2 Ecosystems and Their Productivity 12.3.3 Productivity Measurements and Evaluation in Agroecosystems 12.4 Manipulation of Photosynthesis in Agroforestry 12.4.1 Choice of Species 12.4.2 Shade Management 12.5 Conclusion References Chapter 13: Multipurpose Trees (MPTs) and Other Agroforestry Species 13.1 Introduction 13.2 Agroforestry Species 13.3 Multipurpose Trees (MPTs) 13.3.1 Fodder Trees 13.3.2 Fuelwood Trees 13.3.3 Fruit Trees (see also Chapter 23, Section 23.3.1) 13.3.4 Other Underexploited Woody Perennials 13.3.5 MPT Databases 13.3.6 MPT Species Profiles 13.4 Lesser-Known Agroforestry Species 13.4.1 Shade-Tolerant Specialty Crops and Medicinal & Aromatic Plants 13.4.2 Agronomic and Horticultural Species in Agroforestry Systems 13.4.3 Overexploited (Endangered) Species 13.5 Tree Improvement in Agroforestry 13.5.1 A Brief Account of Accomplishments 13.5.2 Ideotypes of Agroforestry Trees? 13.6 Concluding Remarks Appendices Appendix I: Short Descriptions of Multipurpose Trees and Shrubs (MPTs) Commonly Used in Agroforestry Systems Appendix II Shade-Tolerant Specialty Species Black pepper (Piper nigrum, Family: Piperaceae) Vanilla (Vanilla planifolia, Family: Orchidaceae) Cardamom (Elettaria cardamomum, Family: Zingiberaceae) Large Cardamom (Amomum subulatum, A. aromaticum, Family: Zingiberaceae) Ginger (Zingiber officinale, Family: Zingiberaceae) Turmeric (Curcuma longa, Family: Zingiberaceae) Ginseng: Panax ginseng (Korean ginseng); P. quinquefolium (American ginseng), Family: Aralioideae Allspice (Pimenta dioica, Family: Myrtaceae) Cinnamon (Cinnamomum zeylanicum) Nutmeg (Myristica fragrans, Myristicaceae) References Chapter 14: Plant-to-Plant (Tree-Crop) Interactions in Agroforestry Systems 14.1 Introduction 14.2 Tree-Crop Interactions: Shifting Paradigms 14.3 The Complexity of Tree-Crop Interactions 14.3.1 Different Ways of Looking at Interactions 14.3.2 Root Plasticity and Belowground Interactions 14.3.3 Multiple Factors and Processes of Interactions 14.4 Measurement of Tree-Crop Interactions 14.4.1 Crop Yields as Indicators 14.4.2 Land Equivalent Ratio 14.4.3 Tree-Crop Interaction Models 14.5 Management of Tree-Crop Interactions 14.6 Concluding Remarks References Section IV: Biophysical Foundations of Agroforestry: Soil Productivity and Protection Chapter 15: Soils and Agroforestry: General Principles 15.1 Introduction 15.2 Soils and Agroforestry 15.3 Soil Formation 15.3.1 How is the Soil Formed? 15.3.2 Soil Horizon and Soil Profile 15.4 Soil Properties 15.4.1 Physical Properties How heavy is a soil? 15.4.2 Chemical Properties 15.4.3 Biological Properties 15.5 Soil Types and Soil Classification 15.5.1 The USDA Soil Classification (Soil Taxonomy) 15.5.2 The US Soil Taxonomy and UN (FAO/UNESCO) Soil Classification 15.6 Plant Nutrients in Soils 15.7 Tropical Soils 15.8 Soil Health References Chapter 16: Soil Organic Matter (SOM) and Nutrient Cycling 16.1 Introduction 16.2 Soil Organic Matter 16.3 Organic Matter Decomposition 16.3.1 Rates of Organic Matter Decomposition 16.3.2 Litter Quality 16.3.3 Synchronizing Nutrient Release with Plant Uptake 16.4 Nutrient Cycling 16.4.1 The General Concept of Nutrient Cycling 16.4.2 Nutrient Cycling in Agroforestry Systems 16.4.3 Management of Litter Decomposition for Nutrient Use Efficiency 16.5 Soil Fertility Improvement through Trees in Agroforestry Systems 16.5.1 Tree Biomass and Its Decomposition 16.5.2 Tree Roots 16.5.3 Deep Capture of Nutrients 16.6 Concluding Remarks References Chapter 17: Biological Nitrogen Fixation and Nitrogen Fixing Trees 17.1 Introduction 17.2 Dinitrogen Fixation 17.3 Rhizobia and the Root-Nodule 17.3.1 Rhizobia 17.3.2 The Root Nodule 17.4 Nitrogen-Fixing Plants 17.4.1 The Family Leguminosae (Fabaceae) 17.4.2 Actinorhizal Plants 17.5 Symbiotic Nitrogen Fixation (SNF) in Woody Perennials 17.5.1 Estimates of SNF by Trees 17.5.2 Factors Affecting SNF by Woody Perennials 17.5.3 Mycorrhizal Infection of Legume Roots to Stimulate Nodulation 17.6 Measurement of Symbiotic Nitrogen Fixation 17.6.1 Acetylene Reduction Assay (ARA) 17.6.2 The Difference Method 17.6.3 The 15N Isotopic Methods 17.6.4 Xylem-Solute Method 17.6.5 Other Methods for Comparing Nitrogen Fixation 17.7 Transfer of Symbiotically Fixed Nitrogen 17.7.1 Nitrogen Transfer Pathways 17.7.2 Factors Affecting Nitrogen Transfer 17.7.3 Methodological Considerations 17.7.4 Nitrogen Gains of Non-NFTs in Mixed-Species Plantations with NFTs 17.8 Managing the Microsymbionts in Agroforestry 17.8.1 Legume Inoculation 17.8.2 Establishment of the Microsymbiont 17.9 Concluding Remarks References Chapter 18: Soil Conservation and Control of Land-Degradation 18.1 Introduction 18.2 Soil Conservation 18.3 Historical Developments in Soil Erosion 18.4 Water Erosion 18.4.1 General Principles and Considerations 18.4.2 Measurement of Soil Erosion by Water 18.4.3 Effect of Agroforestry Systems on USLE Soil Erosion Factors 18.4.4 Agronomic Approaches to Water Erosion Control 18.5 Wind Erosion 18.5.1 Wind Erosion: Nature and Measurement 18.5.2 Windbreaks and Shelterbelts (in the Tropics) 18.5.3 Soil Erosion Rates Under Agroforestry Systems 18.6 Land Degradation 18.6.1 Definitions and Characteristics of Land Degradation 18.6.2 The Nature and Extent of Land Degradation 18.7 Agroforestry for the Control of Soil Erosion and Land Degradation: Some Notable Large-Scale Field Projects in the Tropics 18.7.1 Country-Specific Projects (Before 2000) 18.7.2 Multi-country Projects (Current: Post 2015) 18.7.3 ``Biodrainage´´ and Agroforestry for Reclamation of Saline Soils 18.8 Concluding Remarks References Section V: Ecosystem Services of Agroforestry Chapter 19: Ecosystem Services of Agroforestry: An Introduction 19.1 Introduction 19.2 Global Assessments of Ecosystem Services 19.3 Ecosystem Services of Agroforestry References Chapter 20: Carbon Sequestration and Climate Change Mitigation 20.1 Introduction 20.2 Climate Change: The Language, Extent, Causes, and Consequences 20.2.1 Definition 20.2.2 Causes of Climate Change: The Greenhouse Gases 20.2.3 The Extent and Impact of Climate Change 20.2.4 Global Initiatives for Combating Climate Change 20.2.5 Climate Change Mitigation and Adaptation 20.3 Carbon Sequestration 20.3.1 Definition and Concepts 20.3.2 Aboveground (Vegetation) Carbon Sequestration 20.3.3 Belowground (Soil) Carbon Sequestration 20.3.4 Mechanisms of Soil Carbon Sequestration 20.3.5 Soil Aggregates and Their Importance in Soil Carbon Sequestration 20.4 Measurement and Estimation of Carbon Sequestration in Agroforestry Systems 20.4.1 Vegetation 20.4.2 Belowground (Soils) 20.4.3 Methodological Difficulties 20.5 Reported Data on Carbon Sequestration Under Agroforestry Systems 20.5.1 Soil Carbon Sequestration: Results from a Set of Multi-locational Studies 20.5.2 Meta-analyses 20.5.3 Carbon Saturation in Soils 20.5.4 Carbon Sequestration Potential of Agroforestry Systems: Summary 20.6 Agroforestry Management for Carbon Storage and Climate-Change Mitigation 20.6.1 Biochar Use in Agroforestry 20.6.2 Tree Selection and Management 20.6.3 Mitigation and Adaptation Strategies 20.6.4 Development Agendas and Paradigms 20.7 Concluding Remarks References Chapter 21: Agroforestry for Biodiversity Conservation 21.1 Introduction 21.2 Biodiversity Conservation: A Major Global Environmental Issue 21.3 What is Biodiversity? 21.3.1 Biodiversity: Definitions Galore 21.3.2 Measuring Biodiversity 21.4 Agrobiodiversity or Farmland Biodiversity 21.5 Other Subsets of Biodiversity 21.6 Agroforestry for Biodiversity Conservation 21.6.1 Biodiversity Hotspots and ``Coldspots´´ 21.6.2 Agroforestry for Offsetting Threats to Agrobiodiversity 21.6.3 Species Diversity in Agroforestry 21.6.4 Habitat Diversity: Some Empirical Aspects 21.6.5 Pathways for Conservation of Tree Diversity in Smallholder Agroforestry Systems 21.6.6 Land Sharing Strategy for Biodiversity Conservation in Agricultural Landscapes 21.7 Ecosystem Resilience 21.8 Concluding Remarks References Chapter 22: Other Ecosystem Services of Agroforestry 22.1 Introduction 22.2 Hydrological Characteristics and Soil Water Storage 22.3 Water Quality Enhancement 22.4 Cultural Ecosystem Services (CES) 22.4.1 Traditional Ecological Knowledge 22.4.2 Ethnoforestry and Tropical Homegardens as Providers of CES 22.5 Plant Health: Control of Pests, Diseases, and Weeds 22.6 Opportunities for Agroforestry Hot Spots as Biodiversity and Ecotourism Attractions References Section VI: Sustainable Development, Agroforestry, and Land Management in the Future Chapter 23: Food Security, Agroforestry, and Sustainable Development Goals 23.1 Introduction 23.2 Agroforestry and Food Security 23.3 Direct Role of Agroforestry in Food Security 23.3.1 Fruit Trees 23.3.2 Nutritional Security 23.4 Indirect Role of Agroforestry in Food Security 23.5 The Way Forward Annexure I U. N. Sustainable Development Goals (2015) (https://www.un.org/sustainabledevelopment/sustainable-development-goals) References Chapter 24: Agroforestry and Land Management in the Future 24.1 Introduction 24.2 The Past 24.3 The Present 24.4 The Future References Acronyms and Abbreviations Glossary Appendix SI Units and Conversion Factors 1 SI Units 1.1 The SI Base Units 1.2 SI Derived Units 1.3 SI Prefixes 1.4 Non-SI Units 1.5 SI Conventions 1.5.1 Unit Symbols 1.5.2 Unit Names 1.5.3 Formatting the Value of a Quantity 1.5.4 Formatting Numbers, and the Decimal Marker 1.5.5 Multiplying or Dividing Quantity Symbols, the Values of Quantities, or Numbers 1.5.6 Stating Quantity Values Being Pure Numbers 2 Conversion Factors 2.1 Basic Conversion Factors 2.2 Conversion Factors for SI and Non-SI Units (Source: ASA, CSSA, and SSSA, 2020) References Subject Index