1 Towards Ecological Relevance Progress and Pitfalls in the Path Towards an Understanding of Mycorrhizal Functions in Nature... 3 D.J.

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1 Contents Section A: Introduction 1 Towards Ecological Relevance Progress and Pitfalls in the Path Towards an Understanding of Mycorrhizal Functions in Nature... 3 D.J. Read 1.1 Summary Introduction The Platform Provided by Reductionist Approaches Approaches to Examination of Mycorrhizal Function at the Community Level The Microcosm Approach The Field Approach Conclusion References Section B: Ecophysiology, Ecosystems Effects and Global Change 2 Carbon and Nutrient Fluxes Within and Between Mycorrhizal Plants S.W. Simard, D. Durall, M. Jones 2.1 Summary Introduction Ecto-mycorrhiza and Nutrient Uptake Quantitative Effects of Ecto-mycorrhiza on Nutrient Uptake by Plants Mechanisms of Increased Nutrient Uptake Transport of Nutrients Within the Ecto-mycorrhizal Fungal Mycelium Carbon Flux in Ecto-mycorrhizal Plants

2 X Contents Mechanism of Carbon Exchange Between Symbionts Quantification of Belowground C Partitioning Biological and Physical Effects on Belowground Carbon Partitioning Carbon and Nutrient Transfers Between Plants Hyphal Links Between Plants Carbon and Nutrient Transfer Between Plants Factors Regulating Carbon and Nutrient Transfer Conclusions on the Ecological Significance of Interplant Transfer References Function and Diversity of Arbuscular Mycorrhizae in Carbon and Mineral Nutrition I. Jakobsen, S.E. Smith, F.A. Smith 3.1 Summary Introduction Carbon Nutrition and Growth of the Fungus Mineral Nutrition of the Fungus Nutrition of the Plant: The Autotrophic Symbiont Mycorrhizal Responsiveness From Individual Symbioses to Plant Communities References Foraging and Resource Allocation Strategies of Mycorrhizal Fungi in a Patchy Environment P.A. Olsson,I.Jakobsen,H.Wallander 4.1 Summary Introduction The Mycorrhizal Mycelium Structures and Growth Rates Density of the Mycelium Front Energy Storage Foraging of the Ecto-mycorrhizal Mycelium Response to Inorganic Nutrients Response to Organic Nutrient Sources Response to Plant Roots Foraging of the Arbuscular Mycorrhizal Mycelium Response to Inorganic Nutrients

3 Contents Response to Organic Material and Compounds Response to Plant Roots Differences in Foraging Strategies Between Arbuscular Mycorhizal and Ecto-mycorrhizal Fungi Models and Theories on the Foraging of Mycorrhizal Fungi Conclusions and Future Perspectives References XI 5 The Role of Various Types of Mycorrhizal Fungi in Nutrient Cycling and Plant Competition R. Aerts 5.1 Summary Introduction Soil Nutrient Sources Different Mycorrhizal Types Can Tap Different Soil Nutrient Sources Vascular Plant 15 N Natural Abundance as an Indicator for the Type of Mycorrhiza-Mediated Plant Nutrition? A Conceptual Model for Mycorrhizal Impacts on Plant Competition and Coexistence Effects of Increased Nitrogen Deposition Plant-Soil Feedbacks: Mineralization or Organicisation? Future Challenges References Global Change and Mycorrhizal Fungi M. Rillig, K.K. Treseder, M.F. Allen 6.1 Summary Introduction What Is Global Change? Rationale for Considering Mycorrhizae in Global Change Biology Global Change: Multiple Factors Elevated Atmospheric CO Nitrogen Deposition Altered Precipitation and Temperature Ozone UV Radiation Global Change Factor Interactions

4 XII Contents 6.5 Long-Term Versus Short-Term Responses Global Change and Effects on Symbionts Conclusions References Section C: Biodiversity, Plant and Fungal Communities 7 Diversity of Ecto-mycorrhizal Fungal Communities in Relation to the Abiotic Environment S. Erland, A.F.S. Taylor 7.1 Summary Introduction Natural Abiotic Factors Influencing Ecto-mycorrhizal Community Structure Edaphic Factors Soil Organic Matter and Spatial Heterogeneity Moisture ph Temperature Wildfire Effects of Pollution and Forest Management Practices on Ecto-mycorrhizal Fungal Communities Elevated CO Ozone Heavy Metals N-Deposition and Fertilisation Acidification Liming Wood Ash Application and Vitality Fertilisation Conclusions Future Progress References

5 Contents XIII 8 Genetic Studies of the Structure and Diversity of Arbuscular Mycorrhizal Fungal Communities J.P. Clapp, T. Helgason, T.J. Daniell, J.P.W. Young 8.1 Summary Introduction The Importance of Community Structure in Arbuscular Mycorrhizal Fungi Molecular Identification of Arbuscular Mycorrhizal Fungi Strategies for Identifying Arbuscular Mycorrhizal Fungi Using Molecular Markers Methods Available Primers Developed for Analysis of Arbuscular Mycorrhizal Fungal Ribosomal Genes: A Short History Investigations of Arbuscular Mycorrhizal Fungal Communities Primers that Target Single Families or Species Primers Intended to Target all Glomalean Fungi Alternative Approaches to Molecular Characterisation of Arbuscular Mycorrhizal Fungi Comparison of Molecular and Morphological Data Phylogeny and Taxonomy Field Data The Genetic Organisation of Arbuscular Mycorrhizal Fungi Heterogeneous Sequences in Spores and Cultures Contaminant Sequences in Spores and Cultures How Is the Sequence Heterogeneity Organised? How Is Sequence Heterogeneity Maintained? How Does This Affect Analysis of Field Sequences? Future Prospects References Diversity of Arbuscular Mycorrhizal Fungi and Ecosystem Functioning M. Hart, J.N. Klironomos 9.1 Summary Introduction Linking Biodiversity and Ecosystem Function Arbuscular Mycorrhizal Fungal Diversity and Ecosystem Functioning Arbuscular Mycorrhizal Fungal Networks

6 XIV Contents Functional Specificity Differential Effects Community Effects Succession of Arbuscular Mycorrhizal Fungi Conclusions References Arbuscular Mycorrhizal Fungi as a Determinant of Plant Diversity: In Search for Underlying Mechanisms and General Principles M.G.A. van der Heijden 10.1 Summary Introduction Arbuscular Mycorrhizal Fungi as a Determinant of Plant Diversity Importance of Plant Species Composition and Nutrient Availability Mycorrhizal Dependency Underlying Mechanisms and Explaining Models Ecological Significance of Arbuscular Mycorrhizal Fungal Diversity Influence on Plants and Plant Communities Thoughts on Underlying Mechanisms Mycorrhizal Species Sensitivity Conclusions References Dynamics Within the Plant Arbuscular Mycorrhizal Fungal Mutualism: Testing the Nature of Community Feedback J.D. Bever,A. Pringle, P.A. Schultz 11.1 Summary Introduction Mutual Interdependence of Plant and Arbuscular Mycorrhizal Fungal Growth Rates Cause Feedback Dynamics Positive Feedback Negative Feedback Identifying Positive Versus Negative Feedback: Complimentary Approaches

7 Contents Interdependence of Plant and Fungal Population Growth Rates: A Mechanistic Approach Plant Response to Manipulated Arbuscular Mycorrhizal Fungal Communities: A Phenomenological Approach Evidence for Interdependence of Plant and Fungal Population Growth Rates Specificity of Plant Response to Arbuscular Mycorrhizal Fungal Species Specificity of Arbuscular Mycorrhizal Fungal Response to Plant Species Testing Feedback Between Plant and Arbuscular Mycorrhizal Fungal Communities Evaluation of Feedback Using the Mechanistic Approach Evaluation of Feedback Using the Phenomenological Approach A Comparison of Mechanistic and Phenomenological Approaches to Testing Feedback Implications and an Extension of the Feedback Framework Negative Feedbacks and the Evolutionary Maintenance of Mutualism Spatial Structure and the Dynamics of Feedback Conclusion References XV Section D: Multitrophic Interactions 12 Mycorrhizae-Herbivore Interactions: Population and Community Consequences G.A. Gehring, T.G. Whitham 12.1 Summary Introduction Effects of Aboveground Herbivory on Mycorrhizal Fungi Population Level Responses Community Level Responses Carbon Limitation as a Mechanism of Herbivore Impacts on Mycorrhizae Conditionality in Mycorrhizal Responses to Herbivory Effects of Mycorrhizal Fungi on the Performance of Herbivores

8 XVI Contents Patterns of Interaction Mechanisms of Mycorrhizal Impacts on Herbivores Not All Mycorrhizae Are Equal Ecological and Evolutionary Implications Herbivore Effects on Mycorrhizae Mycorrhizae Effects on Herbivores Combined Effects Suggestions for Future Research References Actions and Interactions of Soil Invertebrates and Arbuscular Mycorrhizal Fungi in Affecting the Structure of Plant Communities A.C. Gange,V.K. Brown 13.1 Summary Introduction Soil Invertebrate Groups Earthworms Nematodes Mites Insects Other Invertebrates Field Studies Conclusions References Interactions Between Ecto-mycorrhizal Fungi and Saprotrophic Fungi J.R. Leake, D.P.Donnelly, L. Boddy 14.1 Summary Introduction The Importance of Ecto-mycorrhizal and Saprotrophic Fungi in Forest Soils Structural and Functional Similarities Between Mycelia of Saprotrophic and Ecto-mycorrhizal Fungi Competition for Nutrients Between Ecto-mycorrhizal and Saprotrophic Fungi

9 Contents XVII Evidence of Saprotrophic Nutrient Mobilising Activities of Ecto-mycorrhizal Fungi The Effect of Short-Circuiting of the N and P Cycles by Ecto-mycorrhizal Fungi on the Activities of Saprotrophic Fungi Interactions Between Ecto-mycorrhizal and Saprotrophic Fungi Observed in Microcosms Containing Natural Soil Transfers of P Between Interacting Mycelia of Ecto-mycorrhizal and Saprotrophic Fungi The Effect of Interaction with Saprotrophic Fungi on Growth and Carbon Allocation in Ecto-mycorhizal Mycelium The Effect of Interaction with Ecto-mycorrhizal Mycelium on the Growth and Morphology of Mycelial Cords of the Saprotrophic Fungus Phanerochaete velutina Conclusions References Section E: Host Specificity and Co-evolution 15 Mycorrhizal Specificity and Function in Myco-heterotrophic Plants D.L. Taylor,T.D.Bruns,J.R.Leake,D.J.Read 15.1 Summary Introduction Evidence for Specificity in Myco-heterotrophs Overview of Specificity in the Orchidaceae Overview of Specificity in the Monotropoideae Influences on Specificity Local Distribution of Fungi Habitat and Genetic Influences on Specificity Ontogenetic Influences on Specificity Evolution of Specificity Fungal Trophic Niches and Mycorrhizal Carbon Dynamics Conclusions and Future Goals References

10 XVIII Contents 16 Specificity in the Arbuscular Mycorrhizal Symbiosis I.R. Sanders 16.1 Summary Introduction Definitions of Specificity Why Is Specificity in the Mycorrhizal Symbiosis Ecologically Interesting? Theoretical Considerations on the Evolution of Specificity in Mutualistic Symbioses Why Do We Not Already Know Whether Specificity Exists? Evidence Supporting a Lack of Specificity Arbuscular Mycorrhizal Fungi Have a Broad Host Range A Systematic Perspective Repeatable Patterns of Arbuscular Mycorrhizal Fungal Community Structure Physiological Evidence Evidence Supporting Specificity Arbuscular Mycorrhizal Fungal Effects on Plant Fitness Plant Species Effects on Fungal Fitness What Information Is Missing and Which Experiments Are Needed? Arbuscular Mycorrhizal Fungal Benefit from Specific Hosts Reciprocal Benefit Between Plant Species and Fungal Species A Genetic Basis for Specificity in Plants A Genetic Basis for Specificity in Arbuscular Mycorrhizal Fungi The Importance of the Hyphal Network for Understanding Specificity Conclusions References Section F: Conclusions 17 Mycorrhizal Ecology: Synthesis and Perspectives M.G.A. van der Heijden,I.R.Sanders 17.1 Introduction Ecophysiology, Ecosystem Effects and Global Change

11 Contents XIX 17.3 Biodiversity, Plant and Fungal Communities Multitrophic Interactions Host Specificity and Co-evolution Conclusions References Subject Index Taxonomic Index

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