Exploring correlation between redox potential and other edaphic factors infield and laboratory conditions in relation to methane efflux

Methane is primarily a biogenic gas, which is implicated in global warming. Although its production in the anoxic conditions is regulated by several e daphic factors, aquatic macrophytes also influence methane emission by prov iding aerenchyma to act as chimney for CH4 transport from the sediment to t roposphere, by releasing root exudates to the sediment to serve as substrat e for methanogenic bacteria and by transporting atmospheric O-2 to rhizosph ere, which stimulates CH4 consumption. Among the edaphic factors, redox pot ential (Eh) is the most important, which largely determines the action of m ethanogenic bacteria. Hence, a study was undertaken first to find out the c orrelation between CH4 emission and edaphic factors in the field conditions and then to understand the relationship between Eh and other edaphic facto rs. The field studies revealed that natural wetlands were the major source of CH4 emission, and the vegetation plays an important role in CH4 emission from the water bodies. However, it was very difficult to establish a stron g relationship between the CH4 emission and the edaphic factors in the fiel d conditions due to other limiting factors and their constant fluctuations. In this connection, the laboratory experiments exhibited that soil tempera ture, pH, moisture regime and incubation period were negatively correlated with Eh, which determines the initiation of methanogenic process. However, organic carbon and the water regime over the soil surface did not show any impact on Eh in this study. (C) 2001 Elsevier Science Ltd. All rights reser ved.