Availability of Electron Acceptors with Higher Reduction Potentials

4 Availability of Electron Acceptors with Higher Reduction Potentials 

In wetland soils, organic matter decomposition is frequently limited by electron acceptor availability, rather than carbon availability as in upland ecosystems. The concentration and type of electron acceptors available in soils determine the types of microbial communities involved and the rate of decomposition process. Much of the detrital matter produced in wetlands is deposited on the soil surface. It is unlikely that there is enough oxygen in this matrix to decompose this material. Therefore, the decomposition of detrital matter is also dependent on the activity of anaerobic microorganisms using alternate electron acceptors. Similarly, the rate of organic matter decomposition in soils is dependent on the availability of electron acceptors (see for discussion in Chapters 3 and 4). 

It is evident that oxygen-, nitrate-, sulfate-reducing and methanogenic conditions have a profound effect on various biogeochemical properties regulating organic matter decomposition in wetland soils (Table 5.14). A review on the comparison of microbial dynamics in marine and freshwater system as influenced by the availability of electron acceptors is presented by Capone and Kiene 

FIGURE 5.47 Effect of wet and dry cycles on decomposition of organic matter (Reddy and Patrick, 1975). 

Selected Biogeochemical Properties Related to Soil Organic Matter Decomposition in Wetland Soils Incubated under Various Redox Conditions 

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Availability of electron acceptors with higher reduction potentials... 

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