Biodiversity and Ecosystem Function

The biota of the earth is being altered at an unprecedented rate. We are witnessing wholesale exchanges of organisms among geographic areas that were once totally biologically isolated. We are seeing massive changes in landscape use that are creating even more abundant succes­ sional patches, reductions in population sizes, and in the worst cases, losses of species. There are many reasons for concern about these trends. One is that we unfortunately do not know in detail the conse­ quences of these massive alterations in terms of how the biosphere as a whole operates or even, for that matter, the functioning of localized ecosystems. We do know that the biosphere interacts strongly with the atmospheric composition, contributing to potential climate change. We also know that changes in vegetative cover greatly influence the hydrology and biochemistry ofa site or region. Our knowledge is weak in important details, however. How are the many services that ecosystems provide to humanity altered by modifications of ecosystem composition? Stated in another way, what is the role of individual species in ecosystem function? We are observing the selective as well as wholesale alteration in the composition of ecosystems. Do these alterations matter in respect to how ecosystems operate and provide services? This book represents the initial probing of this central ques­ tion. It will be followed by other volumes in this series examining in depth the functional role of biodiversity in various ecosystems of the world.

Section A: Ecosystem Function.- 1 Biological Diversity and Terrestrial Ecosystem Biogeochemistry.- 1.1 Introduction.- 1.2 Semantics.- 1.3 Biological Diversity and Biogeochemistry.- 1.3.1 Experimental Tests.- 1.3.2 Biogeographic Patterns.- 1.4 Other Potential Effects of Plant Diversity on Biogeochemistry.- 1.5 Conclusions.- References.- 2 Biodiversity and Ecosystem Function in Agricultural Systems.- 2.1 Introduction.- 2.2 Characteristics of Agricultural Ecosystems.- 2.2.1 Diversity and Complexity.- 2.2.2 Classification in Relation to Diversity and Complexity.- 2.2.3 Sustainability.- 2.3 Productive Attributes of Low Number Multiple Cropping Systems.- 2.4 Biodiversity and the Function of the Decomposer Subsystem.- 2.4.1 Biodiversity in Relation to Function.- 2.4.2 Decomposer Diversity and Function in Agricultural Systems.- 2.4.3 Interactions Between Plants and the Soil Biota.- 2.5 Biodiversity and the Function of the Herbivore Subsystem.- 2.6 Conclusions.- 2.6.1 A Hypothesis of the Importance of Plant Diversity in Ecosystem Regulation.- 2.6.2 The Importance of Increasing Plant Species Number.- 2.6.3 The Importance of Plant Species Composition.- 2.6.4 Assessment of Long-Term Trends.- References.- 3 Biodiversity and Interactions Within Pelagic Nutrient Cycling and Productivity.- 3.1 Introduction: Explanations to the Paradox of the Plankton.- 3.2 Further Determinants of Biodiversity.- 3.2.1 Plasticity and Cell Shape.- 3.2.2 Turbulence.- 3.3 Selection and Succession.- 3.3.1 Descriptive Model of Plankton Succession.- 3.4 Microbial Loop: Structure and Function.- 3.4.1 Structure.- 3.5 Structural Diversity Indices.- 3.6 Ataxonomic Approach to Assess Ecosystem Stability.- 3.7 Conclusions.- References.- Section B: Functional Groups.- 4 Functional Groups of Microorganisms.- 4.1 Introduction.- 4.2 Free-Living Components of the Soil Microbiota.- 4.3 Metabolic Types of Bacteria.- 4.4 The Role of Microorganisms in the Decomposition of Organic Material.- 4.4.1 Cellulose.- 4.4.2 Lignin.- 4.4.3 Proteins, Peptides, and Amino Acids.- 4.4.4 Pectin.- 4.5 The Role of Microorganisms in the Biogeochemical Cycle of Nitrogen.- 4.5.1 Nitrification.- 4.5.2 Denitrification.- 4.5.3 N2 Fixation.- 4.6 The Role of Microorganisms in the Biogeochemical Cycle of Sulfur.- 4.6.1 The Oxidation of Reduced Sulfur Compounds.- 4.6.2 Desulfurication.- 4.7 Conclusions.- References.- 5 Plant Traits and Adaptive Strategies: Their Role in Ecosystem Function.- 5.1 Introduction.- 5.2 Schemes to Classify Plants on the Basis of Their Ecological Traits.- 5.2.1 Single-Character Functional Classification of Vascular Plants.- 5.2.2 Attempts to Classify Species Based on Their Overall Ecological Adaptability.- 5.3 Adaptive Strategies.- 5.3.1 Optimization.- 5.3.2 Plant Adaptive Strategies.- 5.3.3 Why Optimally Criteria Are Not Always Sufficient.- 5.4 Definition of Ecosystem Functional Properties.- 5.5 The Meaning of Adaptive Strategy in a Complex, Nonlinear World.- 5.6 Conclusions: The Importance of Diversity in a Nonequilibrium Situation.- References.- 6 Scaling from Species to Vegetation: The Usefulness of Functional Groups.- 6.1 Introduction: What Are Functional Groups and Why Use Them?.- 6.2 Selecting Functional Groups.- 6.3 Narrow or Wide Grouping: The Dilemma of Experimental Safety and Ecological Applicability.- 6.4 Grouping of Plant Species with Respect to Their Structural, Physiological, and Life Strategy Characteristics.- 6.4.1 Life-Forms and Structures: The Morphotype.- 6.4.2 Dry Matter Partitioning: Investment Type.- 6.4.3 The Physiotype.- 6.4.4 The Physiomorphotype.- 6.4.5 Life Strategies.- 6.5 The Spatial Definition of Functional Groups within Plant Communities.- 6.6 Ecosystems: The Largest Functional Group.- 6.7 Integration of Contrasting Levels of Complexity: A Compromise.- 6.8 A Promising Tool: Using Functional Groups in Controlled Ecosystems.- 6.9 Conclusions.- References.- Section C: Species Interaction.- 7 Evolution of Functional Groups in Basidiomycetes (Fungi).- 7.1 Introduction.- 7.2 What Are Fungi?.- 7.2.1 Yeasts and Dimorphic Fungi.- 7.3 Functional Fungal Groups.- 7.4 Evolution of Fungal Parasites of Plants.- 7.5 Evolution in Diverse Wood-Decaying Fungi.- 7.5.1 Saprobic Fungi.- 7.6 Evolution in Symbiontic Basidiomycetes.- 7.6.1 Basidiolichens.- 7.6.2 Mycorrhizae.- 7.7 Diversity and Coevolutionary Trends in Septobasidiales.- 7.8 Conclusions.- References.- 8 The Role of Parasites in Plant Populations and Communities.- 8.1 Introduction.- 8.2 The Diversity and Specialization of Parasites and Their Effects on the Fitness of the Host Plant.- 8.2.1 Parasitic Plants.- 8.2.2 Fungal and Viral Pathogens.- 8.3 The Hidden Effects of Parasite Attack — Changes in the Genetic Structure of Plant Populations.- 8.4 Parasite Attack as a Determinant of Ecosystem Structure.- 8.4.1 Lessons from Exotic Pathogens and Severely Disturbed Natural Systems.- 8.4.2 Evidence from Natural Parasite-Host Associations.- 8.5 Conclusions.- References.- 9 Plant-Microbe Mutualisms and Community Structure.- 9.1 Introduction.- 9.2 Plant-Microbe Mutualisms in Grassland Communities.- 9.3 Plant-Microbe Mutualisms in Savanna and Tropical Forest Communities.- 9.4 Plant-Microbe Mutualisms in Boreal and Temperate Forest Communities.- 9.5 Plant-Microbe Mutualisms in Heathland and Related Wetland Ecosystems.- 9.6 The Role of Mutualisms in Successional Processes.- 9.7 Conclusions.- References.- 10 The Evolution of Interactions and Diversity in Plant- Insect Systems: The Urophora-Eurytoma Food Web in Galls on Palearctic Cardueae.- 10.1 Introduction.- 10.2 The Urophora Food Web.- 10.2.1 General Ecological Characteristics of the Urophora-Eurytoma System.- 10.2.2 Structure and Evolution of the Urophora Gall.- 10.2.3 The Effect of the Gall Size on the Two Eurytoma spp..- 10.3 Resource Exploitation, Interactions, and Evolution.- 10.3.1 The Evolution of Diversity at the Herbivore Level of Plant-Insect Systems.- 10.3.2 Host Plants as Underexploited Resources.- 10.3.3 Exploitation Strategies in the Urophora-Eurytoma System.- 10.3.4 Interaction Patterns at the Second and Third Trophic Level: Evolutionary Adjustments in Food Webs.- 10.4 Conclusions.- References.- Section D: Community Interactions.- 11 Keystone Species.- 11.1 Introduction.- 11.2 History of the Concept.- 11.3 The Different Kinds of Keystone Species.- 11.3.1 Keystone Predators.- 11.3.2 Keystone Herbivores.- 11.3.3 Keystone Pathogens.- 11.3.4 Keystone Competitors.- 11.3.5 Keystone Mutualists.- 11.3.6 Earth-movers.- 11.3.7 System Processes.- 11.3.8 Abiotic Processes.- 11.3.9 Summary of Types of Keystone Species.- 11.4 Identifying Keystone Species.- 11.4.1 Towards a General Protocol.- 11.5 Which Keystone Species Are Vulnerable?.- 11.6 Conclusions.- References.- 12 Redundancy in Ecosystems.- 12.1 Introduction.- 12.2 Evidence from the Fossil Record.- 12.3 Patterns of Energy Flow, Biomass and the Structure of Food Webs.- 12.3.1 Productivity and Biomass.- 12.3.2 Food Webs.- 12.4 Theoretical Models of Ecosystem Stability and Resilience.- 12.4.1 Species Deletion Stability.- 12.4.2 Possible Modelling Approaches.- 12.5 Observations and Experiments on Real Systems.- 12.5.1 Species Richness and Population Fluctuations.- 12.5.2 Keystone Species.- 12.5.3 Manipulation Experiments: General Considerations.- 12.5.4 Manipulation Experiments: Examples.- 12.6 Conclusions.- References.- 13 How Many Species Are Required for a Functional Ecosystem?.- 13.1 Introduction.- 13.1.1 Ecosystems.- 13.2 Species Diversity and Ecosystem Properties.- 13.2.1 Introduction.- 13.2.2 Species Enumerations and Ecosystem Functions.- 13.2.3 The Inequality of Species in Ecosystem Function.- 13.2.4 Species Diversity and Ecosystem Stability.- 13.2.5 Species Numbers and Dynamics: Year-to-Year Averaging.- 13.2.6 Species Numbers and Dynamics: Species Feedbacks.- 13.3 Species Diversity and Ecosystem Dynamics.- 13.3.1 Introduction.- 13.3.2 Experiments.- 13.3.3 Modelling.- 13.4 Conclusions.- References.- 14 Rare and Common Plants in Ecosy