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

Plant community development and phytosociology on mudflats on two inner deltaic splays in the Mississippi River delta, Louisiana, are described. The splays supported three communities based upon plant species occurrence, soil, and plant biomass data collected over seven growing seasons. About 77% of the vegetated land on the splays became dominated by Scirpus deltarum Schuyler three growing seasons after mudflat emergence. 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 Scirpus deltarum dominated mudflats, Salix nigra Marshall became the dominant plant. This woody community occupies 21% of the land area on the splays. Backwater substrates (2% of land area) just below the Scirpus community became a community dominated by Colocasia esculenta (L.) Schott. From analysis of substrate grain size, each community can be described by proportions of sand, silt, and clay. The Scirpus community had the coarsest sediment with the greatest amount of sand and the Colocasia community had the finest sediment with greatest amount of clay and silt. Each community differed also in total organic material, the Colocasia community having twice as much as the other two communities. These communities are maintained by the hydrology and associated factors, especially influxes of sediment during spring floods.