Trophic interactions, the consumption of one organism, or a part of it, by another, are a fundamental component of all ecosystems. The vast majority of net primary productivity is eventually consumed, either by herbivores if the tissue is still alive, or by decomposers if the tissue has died (e.g. Cebrian, 2004). Similarly, these primary consumers are themselves consumed either by predators, parasites or decomposers (secondary consumers). Thus, trophic interactions form the pathways through which carbon flows through an ecosystem and, to a large extent, these interactions control ecosystem carbon dynamics, either directly (via consumption of another organism) or indirectly (e.g. altering competition between the prey individual/population and other organisms).
In this chapter we consider the principal ways by which trophic interactions influence soil carbon fluxes (Fig. 10.1). Firstly, we discuss the impacts of both above- and below-ground herbivores on carbon flux into, and out of, the soil and the interactions between herbivores, plants and soil organisms (dashed box in Fig. 10.1). Secondly, we investigate the role of soil fauna in organic matter decomposition, either directly via the consumption of litter, or indirectly via feeding on saprotrophs or the movement of organic matter (dotted box in Fig. 10.1). Thirdly, we examine the role of resource availability versus predation in structuring soil food webs, followed by the linkages between soil biodiversity and a range of ecosystem processes, including plant growth, litter decomposition and carbon mineralization (solid box in Fig. 10.1).
We use a historical context to examine the accomplishments of soil biodiversity and ecosystem research. These accomplishments provide a framework for future research, for enhancing and driving ecological theory, and for incorporating knowledge into sustainable management of soils and ecosystems.
A soil ecologist's view of the world differs from that of a terrestrial ecologist who focuses research primarily on above-ground organisms. We offer ‘ten tenets of soil ecology’ that illustrate the perspectives of a soil ecologist.
Challenges for the future are many and never has research in soil ecology been more exciting or more relevant. We highlight our view of ‘challenges in soil ecology’, in the hope of intensifying interactions among ecologists and other scientists, and stimulating the integration of soils research into the science of terrestrial ecology.
We conclude with the vision that healthy soils are the basis of global sustainability. As scientists, we cannot achieve our future goals of ecological sustainability without placing emphasis on the role of soil in terrestrial ecology.
Despite the visionary appeals of an earlier generation of soil scientists, soil biologists and others (Jacks & Whyte 1939; Hyams 1952), above-ground ecologists have hitherto shown insufficient awareness of the significance and fragility of soils and the need to understand how life in soils relates to sustaining our global environment. However, many scientists, including microbial ecologists, atmospheric scientists, biogeochemists and agronomists, as well as economists and policy makers, are now starting to take heed of the multiple issues involving soils and their biota, on both local and global scales.
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