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Communities and Ecosystems

Communities and Ecosystems: Linking the Aboveground and Belowground Components (MPB-34)

Copyright Date: 2002
Pages: 400
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  • Book Info
    Communities and Ecosystems
    Book Description:

    Most of the earth's terrestrial species live in the soil. These organisms, which include many thousands of species of fungi and nematodes, shape aboveground plant and animal life as well as our climate and atmosphere. Indeed, all terrestrial ecosystems consist of interdependent aboveground and belowground compartments. Despite this, aboveground and belowground ecology have been conducted largely in isolation. This book represents the first major synthesis to focus explicitly on the connections between aboveground and belowground subsystems--and their importance for community structure and ecosystem functioning.

    David Wardle integrates a vast body of literature from numerous fields--including population ecology, ecosystem ecology, ecophysiology, ecological theory, soil science, and global-change biology--to explain the key conceptual issues relating to how aboveground and belowground communities affect one another and the processes that each component carries out. He then applies these concepts to a host of critical questions, including the regulation and function of biodiversity as well as the consequences of human-induced global change in the form of biological invasions, extinctions, atmospheric carbon-dioxide enrichment, nitrogen deposition, land-use change, and global warming.

    Through ambitious theoretical synthesis and a tremendous range of examples, Wardle shows that the key biotic drivers of community and ecosystem properties involve linkages between aboveground and belowground food webs, biotic interaction, the spatial and temporal dynamics of component organisms, and, ultimately, the ecophysiological traits of those organisms that emerge as ecological drivers. His conclusions will propel theoretical and empirical work throughout ecology.

    eISBN: 978-1-4008-4729-7
    Subjects: Biological Sciences

Table of Contents

  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-vi)
  3. Acknowledgments
    (pp. vii-viii)
  4. CHAPTER ONE Introduction
    (pp. 1-6)

    All terrestrial ecosystems consist of a producer subsystem and a decomposer subsystem. These components are obligately dependent upon one another, with the producers acting as the primary source of organic carbon for the system, and the decomposers being responsible for the breakdown of organic matter and the release and cycling of nutrients. Any approach to better understanding ecosystem functioning therefore requires explicit consideration of both these subsystems. Further, both the producer and decomposer subsystems involve consumer organisms, and as a result ecosystems include both a herbivore-focused food web (located largely, though not entirely, aboveground), and a detritus-based food web. The...

  5. CHAPTER TWO The Soil Food Web: Biotic Interactions and Regulators
    (pp. 7-55)

    In any food web, the primary drivers are the autotrophs, which are responsible for determining the amounts of carbon that enter the system. However, in the case of the decomposer food web, the heterotrophic organisms are ultimately responsible for governing the availability of nutrients required for plant productivity. As a result, the plant and decomposer subsystems are in an obligate mutualism with one another, with each of the two components carrying out processes required for the long-term maintenance of the other.

    Those organisms that comprise the decomposer food web span several orders of magnitude in terms of body size, and...

  6. CHAPTER THREE Plant Species Control of Soil Biota and Processes
    (pp. 56-104)

    In chapter 2 I considered how NPP and basal resource inputs may influence soil food webs and how this could in turn affect soil processes that ultimately determine plant growth. However, plant species differ tremendously with regard to the quality of organic matter that they return to the soil, and this in itself has important consequences for both the soil biota and the processes that it regulates. Although trophic dynamic theories (including those discussed in chapter 2) frequently consider the magnitude of NPP as the main means of bottom-up control of consumer trophic levels, it may be that the quality...

  7. CHAPTER FOUR Belowground Consequences of Aboveground Food Web Interactions
    (pp. 105-137)

    It is apparent from the previous two chapters that the soil food web and the processes that it regulates are influenced both by the productivity of the plant community and by the quality of the resources that the plant community produces. However, in addition to driving the belowground subsystem, primary producers also represent the basal trophic level of the aboveground food web. The primary consumers of the aboveground food web, i.e., the foliar herbivores, frequently have important effects on both the ecophysiology of individual plants and the structure of the plant community; these effects may in turn influence the quantity...

  8. CHAPTER FIVE Completing the Circle: How Soil Food Web Effects Are Manifested Aboveground
    (pp. 138-182)

    It is clear from the material that I have presented so far that the soil biota is responsive to the amounts of plant material returned to the soil (chapter 2), the quality of resource input and the composition of the plant community (chapter 3), and the composition of the aboveground food web and nature of aboveground trophic interactions (chapter 4). For feedbacks to exist between the aboveground and belowground biota it is required that soil organisms also influence what is observed aboveground.

    The interaction between plants and the decomposer food web is ultimately mutualistic because the two components are usually...

  9. CHAPTER SIX The Regulation and Function of Biological Diversity
    (pp. 183-238)

    The previous four chapters of this book have focused on biotic interactions among organisms, with an emphasis on associations between aboveground and belowground organisms, and the consequences of these for community and ecosystem properties. However, the conceptual basis of these chapters is also relevant to understanding what regulates biological diversity and the ecological consequences of this. Traditionally the study of mechanisms that determine diversity has had a predominantly aboveground focus, although the issue of belowground diversity or “soil biodiversity” has emerged rather suddenly as an area of considerable topicality. That notwithstanding, there have been few serious attempts to develop general...

  10. CHAPTER SEVEN Global Change Phenomena in an Aboveground-Belowground Context
    (pp. 239-294)

    The rapid growth of the human population over the past few centuries has had a major effect on the Earth’s ecosystems. Over a third of the Earth’s land surface, including most of that which is fertile and capable of supporting high NPP, has been transformed by human activity (Vitousek et al. 1997a). Colonization of new land surfaces by humans appears to have coincided with rapid extinctions of most of the larger vertebrate species in Australia, New Zealand, and North America. Further, current extinction rates of species are probably around 100 to 1000 times their prehuman levels (Pimm et al. 1995)....

  11. CHAPTER EIGHT Underlying Themes
    (pp. 295-308)

    A dominating theme throughout this book has been the significance of biotic interactions. Traditionally, ecology has focused on interactions involving competition and predation, and indeed the ecological literature is replete with examples of these sorts of interactions. As outlined in this book, top-down regulation by predators and bottom-up regulation involving competition are clearly important regulatory forces for many groups of biota both above-and belowground. In the decomposer subsystem this is especially apparent in the microfood-web subsystem involving microorganisms, nematodes, and protozoa. However, there are a variety of other types of interaction between organisms that, while not featured as prominently in...

  12. References
    (pp. 309-386)
  13. Index
    (pp. 387-392)