The links between microbial diversity and soil functions

The relationship between microbial diversity and soil functions is largely unclear not only for the complexity of soil as a microhabitat but also for the limits of the present assays used to determine the composition of soil microflora and rates of microbe-mediated reactions. For example, in spite of the development of molecular techniques, which have allowed the detection of unculturable microorganisms, it is still problematic to determine composition of soil microbial communities. Present assays for determining microbial activities in soil do not detect microbial species really involved in the measured parameter. Soil seems to be characterised by a redundancy of functions. Processes like organic matter degradation are not related to microbial diversity and a reduction in any group of species has little effect on the overall process. A better quantification of soil functions does not require the determination of the structure of microbial communities in soil. The holistic approach, based on the division of the system in pools and measurements of fluxes among these pools is still the best approach to quantify nutrient cycling in soil. However, further advances require determining new pools, which are important in nutrient cycling in soil. Recently the combined use of 13C labelled compounds and molecular techniques has allowed determining the active microbial biomass involved in the oxidation of the organic compound.