Agriculture Reference
In-Depth Information
K. Ritz and B.S. Griffiths
Implications of SoilBiodiversityforSOMManagement
5
Implications of Soil
Biodiversity for Sustainable
Organic Matter Management
K. R
ITZ AND
B.S. G
RIFFITHS
Soil Plant Dynamics Unit, Scottish Crop Research Institute,
Invergowrie, Dundee DD2 5DA, UK
Introduction
Organic matter (OM) plays a pivotal role in the effective functioning of soil
systems. It underpins their structural integrity and provides a fundamental
basis to soil fertility in that it acts as an energy and nutrient source to
soil organisms. The basis of sustainable management of soil OM is one of
balance: inputs must be balanced against losses, but there is a need for
appropriate dynamics as well, to ensure that nutrient elements are cycled
within and between ecosystems. Soil organisms and OM dynamics are
inextricably linked, since collectively the biota is the primary agent
responsible for the myriad of biochemical transformations that drive
elemental cycles and plays an important role in modulating soil structure.
Defining biodiversity is not as straightforward as the mass media would
wish. It is essentially a concept, and not an entity in its own right, that aims
to rationalize a complex set of factors that encompass the basic genetic,
taxonomic, trophic and functional components of community and their
spatio-temporal dynamics. It should also include the number of different
biological forms, entities or units from each of these perspectives, their
relative abundance and the degree of interconnectedness between them.
Gaston (1996) paraphrases it succinctly and elegantly as 'a biology of
numbers and difference'.
Below-ground biodiversity usually exceeds that which prevails above
ground by orders of magnitude. From virtually any perspective, the soil
biota is exceptionally diverse. Numerically, 100 g of a typical temperate
grassland soil contains in the order of 10
11
prokaryotes, 10
4
m of fungal
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