XVI International Botanical Congess

Methane emissions were measured using the eddy covariance technique in a prairie wetland in north-central Nebraska, USA. The wetland was dominated by Phragmites australis and Scirpus acutus. Methane emissions during midseason exhibited a pronounced diel pattern with a mid- to late morning peak. Concurrent field measurements of pressures in culms of Phragmites showed similar diel variations. Isotopic signatures of methane extracted from live and dead Phragmites culms also exhibited a diel pattern. Results are consistent with a major role of convective throughflow in Phragmites in determining daytime methane emissions from this wetland. At night, diffusion and ebullition appear to be the dominant mechanisms of methane transport to the atmosphere.