Now let s examine nutrients and carbon cycle in wetlands when oxygen becomes limiting. When we talked about N transformations in upland soils, we saw that chemoautotrophy was a major microbial metabolism, where the energy released from the oxidation of NH4 to NO3 and then to N2 was coupled to carbon fixation. On pages 226-231, Schlesinger provides a lot of background about the chemistry of redox reactions. The voltmeter measures the strength of electrons moving into or out of the soil, and you can think of the voltage as the energy needed to stop the flow of electrons. As you can see, the voltage is small compared to a 9 or 12V battery.
More energy allows microorganisms to grow faster and survive on less food.
There are large differences in the energy available to heterotrophic microbes based on the kinds of chamical species found in the soil. We see that the reduction of O2 leads to the greatest release of energy. There is a large difference in oxidation between organic matter and O2, which means that there is a large amount of potential energy to be released by breaking down organic matter when using O2 as the terminal electron acceptor. As soil redox potential declines, there is less energy released from heterotrophic respiration of organic matter . These differences in energy are responsible for a cascade of reactions seen in wetlands .