Soil Teeming with Life: New Frontiers for Soil Science - Sustainable Management of Soil Organic Matter - page 388

Continuum of Biological Organization

Ecosystem Community Organism Protein Nucleic acid

Function Cell Molecular

Environmental regulators
O 2
carbon
geochemistry
Stresses
temperature
drought
salt
Landscape
slope
drainage

Growth kinetics
K s , µ max
Tolerances
nutritional
requirements,
cross-feeding
Motility
Interactions,
quorum sensing
Morphological
adaptations,
spores, adhesions,
size, shape
Versatility of
pathways,
energy generation

Gene regulation
expression level
coordination
specificity
Kinetics
response time
K m
K cat
K I
Enzyme activity,
turnover
Active site
specificity
Isozymes

plants
fauna
cultivation

Fig. 6.1. The traits that control microbiological activity and can exhibit variation at different levels
of biological organization.

reflect biodiversity that can be important to function. In the past, soil sci-
ence research typically has stopped at the level of function, but in the future
we argue that we should take the lead in extending the continuum, not
stopping artificially at the level of function. This model provides a wealth of
opportunity for research in the future, a true frontier.
While a biologist may identify more easily with the model in Fig. 6.1
than a soil chemist physicist, mineralogist or taxonomist, it is extremely
important that the latter provide their expertise in understanding the
environmental conditions so that environmental control of these processes
can be understood at the organismal and molecular levels. Understanding
this complexity at a mechanistic level demands a multidisciplinary effort.
Some of the basic questions to be addressed include:

1. Biological diversity is much greater in soil than elsewhere; why? This
observation suggests that basic features of the soil matrix promote and
sustain diversification. What are the soil features which are most important,
does soil management alter these features, and hence diversification?
2. Are there microbial patterns that can be explained by soil taxonomy or
by vegetative history? Are current soil taxonomic traits appropriate for
mapping microbial biogeography? Microbial communities are selected by
growth of the successful competitors; the outcome reflects the primary