Methane flux from Mississippi River deltaic plain wetlands

Methane emissions from three wetland habitats in the Mississippi River deltaic plain were measured over a three year period. Flux data collected indicate that each habitat was a net source of methane to the atmosphere throughout the year. Average emission from a Taxodium distichum / Nyssa aquatica (bald cypress / water tupelo) swamp forest was 146 +/- 199 mg CH4 m(-2)d(-1) while emissions from a Sagittaria lancifolia (bulltongue) freshwater marsh averaged 251 +/- 188 mg CH4 m(-2)d(-1). Methane flux from a Spartina patens / Sagittaria lancifolia intermediate marsh was significantly higher, 912 +/- 923 mg CH4 m(-2)d(-1). Seasonal variation was significant with emissions being higher in the late summer and early fall. Significant diurnal emissions were observed from the Sagittaria lancifolia marsh site. Soil temperature (5 and 10 cm depths) was found to be significantly correlated with methane emission from the three sites.