Forest vegetation was studied in relation to hydrogeomorphology on a large fluvial island in the meandering section of the Lower Mississippi River. The island has a relatively wide topographic gradient, including a former channel of the Mississippi River. Vegetation patterns were related to geomorphologic features, elevation, flood duration, and characteristics of surficial sediment. Overstory vegetation was species rich for the island as a whole and dominated by the pioneer taxa Populus deltoides (eastern cottonwood) and Salix nigra (black willow). Both pioneer species dominated the old channel. Vegetation at higher elevations was characterized by tree species from later successional stages such as Celtis laevigata (sugarberry), Acer saccharinum (silver maple), Liquidambar styraciflua (sweetgum) and Ulmus spp. (elm). Seedlings and saplings were dominated by sugarberry and other later successional species, whereas cottonwood was infrequent. Our results suggest that on the Lower Mississippi River, coexistence in the floodplain of pioneer stages and later successional stages will not be perpetuated under the prevailing hydrologic and geomorphologic regimes.