Soil Teeming with Life: New Frontiers for Soil Science - Sustainable Management of Soil Organic Matter - page 386

quality, including safety from the emerging water-borne pathogens;
discovery of new biotechnological products, including new pharma-
ceuticals, pesticides and enzymes from the undiscovered microbial diversity
of soil; and optimizing recycling of soil nutrients, soil texture and water
content for sustainable agricultural and forestry. The terrestrial (soil)
environment hosts almost all of the world's human population and provides
much of its basic resources. The biology of soil and its control by the soil's
chemical and physical features play a daily role in sustaining those
resources. Hence, there should be no question about the importance of soil
science in the 21st century.
Biology at the current level of understanding is recognized as complex,
i.e. the interactions at the molecular, organismal and environmental
level are multiple and often non-linear, making predictability difficult.
Understanding this complexity will require expertise from most scientific
disciplines including the geosciences, chemistry, physics, computational
sciences and even the social sciences. The soil environment is arguably
the most complex biological community because of the extremely high
diversity at small scales and a chemical environment of complex and
changing gradients housed in a heterogeneous physical environment. These
features are influenced further by larger scale effects such as climate,
geological history and human activity. Several basic facts are important
in appreciating the complexity of this community, including:
1. Soil harbours high population density . Fertile surface soils typically
contain a few billion prokaryotes (bacteria and archaea) per gram and often
an equivalent amount of fungal biomass. While soil particle surfaces are not
crowded with life at this density, it nonetheless means that the potential for
diverse biological activity resides at virtually every microsite.
2. Soil harbours enormous microbial diversity . This diversity is exhibited
as metabolic, genetic, kinetic, morphological and life history variation.
Furthermore, and most significant, it appears that only 0.1% or so of the
soil microorganisms have been cultured and hence their metabolic role
understood. One of the greatest frontiers in biology remains the discovery
and characterization of the particularly novel organisms that reside in soil.
Understanding complexity requires knowledge about its component parts;
hence novel approaches are needed to understand better the undiscovered
diversity.
3. Soil harbours a tremendous range of physical and chemical conditions . Life
in soil experiences a complexity of gradients of nutrients, oxygen, carbon
and other salts which are rarely held constant. Furthermore, the types of
carbon compounds are numerous, an important point in understanding a
heterotroph-dominated community such as soil. Different mineral surfaces,
organic coatings of different ages and composition and the extent and depth
of organic surfaces add further to the microbe's complex environment.
Also, the physical environment, especially as it influences moisture and the