A comparative study of surface energy fluxes of three communities (Phragmites australis, Scirpus acutus, and open water) in a prairie wetland ecosystem

Components of the surface energy balance were measured using the Bowen ratio-energy balance method in three different communities (Phragmites australis, Scirpus acutus, and open water) in a wetland located in north-central Nebraska during the growing season of 1994. During daytime, the heat storage term (S) was a considerably larger sink of energy in open water as compared to the vegetated communities (Phragmites and Scirpus). During nighttime, S was a significant source of energy in all three communities. As compared to the evapotranspiration (ET) from Phragmites and Scirpus, the evaporation (E) from open water (averaged over the measurement period) was about 25% smaller during daytime and three times larger during the night. The diurnal pattern of ET in Phragmites and Scirpus generally followed that of R-n The diurnal pattern of the open water E, however., did not follow R-n; rather, it seemed to depend on thermal stability conditions and air dryness. For the overall measurement period, the daily integrated (24-hour) evaporation from the open water area was 8% more than the evapotranspiration from the Phragmites-dominated part of the wetland and 17% more than the evapotranspiration from the Scirpus-dominated part of the wetland.