Soil as a Support of Biodiversity and Functions - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 149

should be possible to establish: (i) a statis-
tical link between the different parameters
of soil microbial diversity (i.e. synthetic
diversity index/species richness/evenness)
and the intensity of the microbial processes
involved in the major biogeochemical cycles,
this being a prerequisite to determining the
importance of microbial diversity in the
provision of ecosystem services by the soil
environment; and (ii) the relative import-
ance of the environmental filters controlling
the functionality of soil microbial commu-
nities. Large-scale sampling, as in national
soil survey networks, offers unique oppor-
tunities to implement this strategy (Gardi
et al ., 2009).

when biodiversity increases, which there-
fore would be expected to be favourable to
plant productivity (Baumann et al ., 2012).
However, a possible trade-off has to be con-
sidered. Indeed, the enhancement of SOM
mineralization contributes to decreasing
soil C stock and increasing CO 2 emission,
when C storage in soils represents a major
issue in the context of global change. In con-
trast, decreased SOM mineralization would
be favourable to C storage and would con-
tribute to decreased CO 2 emission, which
would favour the control of global change.
However, as indicated above, this would
impair plant productivity and therefore the
incorporation of organic matter from pri-
mary production, and thus would decrease
C storage in soils. Thus, proper agroecologi-
cal practices have to be developed in order
to minimize these trade-offs by monitoring
soil biodiversity. One of them, proposed by
Fontaine et al . (2011), would be to modulate
organic mineralization to match the nutri-
tional requirement of the plants in order to
avoid the flush of mineralization which
would lead to C loss and possible leaching
of N. Further research needs to be carried
out in order to test hypotheses on the rela-
tions between soil biodiversity and func-
tioning with regards to the C status in soil.
This research represents a major challenge
not only in microbial ecology but also in
agroecology in the context of global change.

Conclusions

Organic matter is essential for soil proper-
ties and functioning. It contributes to soil
aggregation, structure stability and porosity
(Duchicela et al ., 2012). These impact water
regulation, and therefore plant productivity.
More generally, organic matter supports life
in soils, since most soilborne organisms are
heterotrophic. Their activities lead to the
decomposition and mineralization of SOM,
making nutrients available to plants and
again contributing to primary productivity.
Studies reported in this chapter report that
the rate of SOM mineralization is promoted

References

Adrén, O., Brussaard, L. and Clarholm, M. (1999) Soil organism influence on ecosystem-level process -
bypassing the ecological hierarchy? Applied Soil Ecology 11, 177-188.
Arrouays, D., Deslais, W. and Badeau, V. (2001) The carbon content of topsoil and its geographical distribution
in France. Soil Use and Management 17, 7-11.
Bååth, E. and Anderson, T.H. (2003) Comparisons of soil fungal/bacterial ratios in a pH gradient using
physiological and PLFA-based techniques. Soil Biology and Biochemistry 35, 955-963.
Balvanera, P., Pfisterer, A.B., Buchmann, N., He, J.S., Nakashizuka, T., Raffaelli, D. and Schmid, B. (2006)
Quantifying the evidence for biodiversity effects on ecosystem functioning and services. Ecology Letters
9, 1146-1156.
Bates, S.T., Berg-Lyons, D., Caporaso, J.G., Walters, W.A., Knight, R. and Fierer, N. (2011) Examining the
global distribution of dominant archaeal populations in soil. The ISME Journal 5, 908-917.
Baumann, K., Dignac, M.F., Rumpel, C., Bardoux, G., Sarr, A., Steffens, M. and Maron, P.A. (2012) Soil
microbial diversity affects soil organic matter decomposition in a silty grassland soil. Biogeochemistry
doi:10.1007/s10533- 012- 9800- 6.
Beijerinck, M.W. (1913) De infusies en de ontdekking der backterien. In: Jaarboek van de Knoniklijke Akademie
van Wetenschappen . Muller, Amsterdam.