Carbon Gas Emissions and Organic Matter Characteristics in Coastal Wetland Soils.

Wetlands constitute as much as 25% of the total terrestrial soil carbon and play a major role in global C cycle. These wetland soils release appreciable amounts of CO₂ and CH₄ into the atmosphere. Fluxes of carbon gas emissions from a given soil are controlled by a variety of factors including temperature, water table, type and number of microorganisms and soil organic matter characteristics. In the present study, direct measurements of CO₂ and CH₄ fluxes were made in forested swamp, and freshwater, brackish, and saline marshes located in Barataria basin of Louisiana Coast. Vertical flux of CO₂ and CH₄ from selected wetlands were measured using chamber method for a period of two years. In addition, soil organic matter from the top 0 – 50 cm from each sampling site was characterized using pyrolysis- GC/MS technique. Estimated average total annual release of CO₂ and CH₄ were highest for forested swamp followed by freshwater, brackish and salt marsh soils. Decreasing CH₄ emissions with the increasing salinity shows the inhibitory effect of increasing levels of sulfate in the system. Further, multiple regression analysis were conducted between the total carbon gas emissions and different carbon fractions of soil organic carbon. The implication of these results will be further discussed.