Restoration of wetland vegetation on the Kissimmee River floodplain: Potential role of seed banks

The composition of seed banks of areas on the drained Kissimmee River flood plain (Florida, USA) that are currently pasture and formerly had been wet p rairie, broadleaf marsh, and wetland shrub communities was compared to that of seed banks of areas that have extant stands of these communities. The s pecies composition of the seed banks of existing wet prairie and former wet prairie sites were the most similar, with a Jaccard index of similarity of 55. Existing and former broadleaf marsh and wetland shrub communities had Jaccard indices of 38 and 19, respectively. Although existing and former we t prairie seed banks had nearly the same species richness, species richness at former broadleaf marsh and wetland shrub sites was higher than at exist ing sites. Mean total seed densities were similar in existing and former we t prairies (700 to 800 seeds m(2)). However, seed densities in former broad leaf marsh and wetland shrub sites were significantly greater than in compa rable existing communities (>4,900 seeds m(2) at former sites versus 200 to 300 in existing communities). The higher seed densities in former broadlea f marsh and wetland shrub sites was due to over 4,000 seeds m(2) of Juncus effusus in their seed banks. Half of the species that characterize wet prai ries were found in the seed banks at former and existing wet prairie sites. At existing broadleaf marsh and wetland shrub sites, most of the character istic species were found in their seed banks. However, only one characteris tic broadleaf species was found in the seed banks of the former broadleaf m arsh sites, and no characteristic wetland shrub species were found in the s eed banks of the former wetland shrub sites. The seeds of only two non-indi genous species were found in the seed banks of former wetland communities a t very low densities. For all three vegetation types, but particularly for the broadleaf marsh and wetland shrub sites, re-establishment of the former vegetation on the restored floodplain will require propagule dispersal fro m off-site sources.