ABSTRACT
Diversity Measurements .........................................................................................................90 5.7 The Impact of Agriculture on Soil Prokaryotic Diversity: A View on Functional
Diversity in the Nitrogen Cycle .............................................................................................91 5.8 Conclusions ............................................................................................................................93 Acknowledgments ............................................................................................................................93 References ........................................................................................................................................93
Prokaryotes are the most successful organisms on our planet, as they outnumber every other group of organisms. The total amount of carbon and nitrogen stored in the prokaryotes is in the same range of the amount that is located in plant biomass above Earth;140 and prokaryotes are active: for soil, it has been estimated that the average turnover of elements within this prokaryotic biomass is 2.5 years.140 The driving force for this turnover on the global scale is the input of energy that initially comes from sunlight and photosynthesis, and that is ultimately lost by heat radiation. The primary and major source of carbon and energy for all soil-inhabiting organisms comes from the plants. The energy is first captured chemically by the synthesis of high energy compounds, mainly ATP (adenosine triphosphate) and this synthesis is driven by redox-reactions in which electrons are transferred from an electron donor to an electron acceptor. The flow of energy in soil supports the development of the highest diversity of life that we find on Earth, and most of this soil biodiversity is represented by prokaryotes.
