DECOMPOSITION OF EMERGENT MACROPHYTE ROOTS AND RHIZOMES IN A NORTHERNPRAIRIE MARSH

Dry mass, nitrogen and phosphorus content in belowground litter of fou r emergent macrophytes (Typha glauca Godr., Phragmites australis (Cav. ) Trin., Scolochloa feslucacea (Willd.) Link and Scirpus lacustris L.) were followed for 1.2 years in a series of experimental marshes, Delt a Marsh, Manitoba. Litter bags containing roots and rhizome materials of each species were buried in unflooded soil, or soil flooded at thre e water depths (1-30, 31-60, > 60 cm). There were few differences in d ry mass loss in unflooded or flooded soils, and depth of flooding also had little effect on decomposition rates. In the flooded sites, Scolo chloa and Phragmites roots lost more mass (48.9-63.8% and 59.2-85.5%, respectively) after 112 days than Typha and Scirpus (36.3-43.6 and 37. 0-47.2%, respectively). These differences continued through to the end of the study, except in the shallow sites where Scirpus roots lost mo re mass and had comparable mass remaining as Scolochloa and Phragmites . In the unflooded sites, there was little difference between species. All litters lost nitrogen (22.9-90.0%) and phosphorus (46.3-92.7%) du ring the first 112 days, then levels tended to remain constant. Decay rates for our belowground root and rhizome litters were comparable to published literature values for aboveground shoot litter of the same s pecies, except for Phragmites roots and rhizomes which decomposed at a faster rate (-k = 0.0014-0.0032) than shoots (-k = 0.0003-0.0007, [va n der Valk, A.G., Rhymer, J.M., Murkin, H.R., 1991. Flooding and the d ecomposition of litter of four emergent plant species in a prairie wet land. Wetlands 11, 1-16]). (C) 1997 Elsevier Science B.V.