| The effects of anthropogenic modifications of stream systems on in situ plant community composition and seed bank composition were examined at five riparian sites in the Yazoo River watershed in northern Mississippi. This analysis was performed to determine if the soil seed bank can provide a means for the restoration of riparian floodplain plant communities. The study sites represented five different kinds of hydrological alteration: a highly incised riparian terrace isolated from the stream channel, a deforested original stream with reduced flow due to channelization and standing water due to levees, a forested original stream with reduced flow due to channelization, a stream above a reservoir, and a stream below an embankment dam. The study of the in situ community revealed that functional group richness and species richness were strongly correlated, that wetland functional groups were outnumbered by facultative functional groups at all sites except for one site managed as a marsh, that canopy openings were related to increased wetland species richness, and that laterally expanded floodplains created high species richness of wetland, facultative, and upland species. The seed bank analysis revealed that when the aboveground species assemblages were dominated by upland species the functional group and species richness in the seed banks of riparian floodplains were reduced, seed banks were composed of species adapted to conditions not currently at a site, and wetland species were more abundant in seed banks at drier sites. This study found an assemblage of species in the seed bank that would most successfully contribute to restoration projects in conjunction with restoration of some level of flood hydrology and selective clearing. |
