Gaseous Forms of Carbon

Carbon dioxide and methane are two gaseous end products of decomposition of organic matter under anaerobic conditions, whereas only carbon dioxide is produced under aerobic conditions. Carbon dioxide readily dissolves in water and is partitioned into H2CO3, HCO , and CO as follows  

The balance between dissolved and gaseous inorganic carbon depends on the pH of the water column and soil pore water. In wetlands, pH of soil may be buffered between 6 and 7, depending on the rate of reduction of various electron acceptors (see Chapter 4 for a detailed discussion). Water column pH may fluctuate between day and night depending on the photosynthetic activities of algae and submerged macrophytes. 

Atmospheric carbon dioxide is fixed during photosynthesis, and organic carbon is produced. As plants age, older tissue is converted into detrital tissue and is subjected to fragmentation, leaching, and decomposition while attached to living plants. Some of this detrital matter may be above the floodwater surface. 

Detrital plant tissue is detached from original plant and deposited on the soil surface. Various macro- and microscale processes (as discussed in the latter part of this chapter) are involved in the breakdown of this material. 

FIGURE 5.7 Decay continuum of organic matter decomposition and accretion in wetlands. 

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