Insights into the Dynamics of Methane In Flooded and Flood-Protected Riparian Forests.

Insights into the dynamics of methane in flooded and flood-protected riparian forests. 

Methane (CH₄) dynamics in riparian forests is not well understood and the contribution of these ecosystems to regional greenhouse gas budget is thus poorly quantified.  This situation stems largely on a lack of field data and the variability associated with delivery of sediment and nutrients during flooding events.  In this study, CH₄ fluxes were monitored in flood-protected (FP) and regularly-flooded (FL) sections of three riparian forests (age: 7, 45 and 80 years) along the White River in Central Indiana. Physical (texture, bulk density) and biochemical (CH₄ oxidation potential, mineralizable C, microbial diversity index, and methanotrophic community analysis) properties of soils were also determined.  Results showed that the FP sections of the riparian forests were net CH₄ sinks (-1.1 to -3.1 mg CH₄-C m^-2 d^-1) with uptake rates increasing linearly with forest age.  In the FL sections, two of the sites were net sinks but rates were 28 % lower compared to FP.  The FL section of the third site was a net CH₄ source (+0.6 mg CH₄-C m² d^-1) and this was ascribed to the unique geomorphology of that section which is favorable to the deposition of fine-grained slack-water sediments during flooding events. These results will be examined along with data on soil physical properties and microbial community characteristics in FP and FL sections of the riparian forests.