VASCULAR PLANT COMMUNITY-DEVELOPMENT ON MUDFLATS IN THE MISSISSIPPI RIVER DELTA, LOUISIANA, USA

Plant community development and phytosociology on mudflats on two inne r deltaic splays in the Mississippi River delta, Louisiana, are descri bed. The splays supported three communities based upon plant species o ccurrence, soil, and plant biomass data collected over seven growing s easons. About 77% of the vegetated land on the splays became dominated by Scirpus deltarum Schuyler three growing seasons after mudflat emer gence. Net primary production of these marshes was 523 g dry weight m- 2 year-1. On the highest mudflats, i.e. more than 11 cm above the Scir pus deltarum dominated mudflats, Salix nigra Marshall became the domin ant plant. This woody community occupies 21% of the land area on the s plays. Backwater substrates (2% of land area) just below the Scirpus c ommunity became a community dominated by Colocasia esculenta (L.) Scho tt. From analysis of substrate grain size, each community can be descr ibed by proportions of sand, silt, and clay. The Scirpus community had the coarsest sediment with the greatest amount of sand and the Coloca sia community had the finest sediment with greatest amount of clay and silt. Each community differed also in total organic material, the Col ocasia community having twice as much as the other two communities. Th ese communities are maintained by the hydrology and associated factors , especially influxes of sediment during spring floods.