Agriculture Reference
In-Depth Information
CHAPTER IV
FUNCTIONING OF THE SOIL SYSTEM
As discussed in the introduction to this work, three of the major integrated functions
of soils are the provision of physical and nutritive support for plant production and
the decomposition of dead organic materials. In addition to their ecosystem roles, these
functions implicate soils in such major global processes as the hydrological cycle,
climatic and stratospheric ozone regulation through the medium of greenhouse and trace
gas emissions. Decomposition of organic residues and the maintenance of soil structure
are largely complementary processes in most soils. This is because organic matter has
important effects on soil structure both in colloidal form (cement) and as larger particles,
(see Chapter I). Secondly, the energy released through decomposition processes is used
by organisms for bioturbation, an important process in the creation and maintenance
of soil structure, and in soil formation (see Chapter II) (Figure IV.1).
Soil organisms acting as functional interactive units - referred to as biological systems
of regulation (BSR) - are the main mediators of soil functioning at micro- and meso-scales.
Ecosystem engineers largely determine the activities of the other organisms‚ smaller
invertebrates and micro-organisms; microbial activity is regularly stimulated in
microsites where BSR's are active through the production of readily assimilable
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