Many Louisiana swamps have a long legacy of anthropogenic disturbance due to hydrologic changes. Though permanent flooding as a consequence of levee construction is known to adversely affect trees in bald cypress swamps, little is known about the response of associated herbaceous communities to these conditions. We asked whether a change from a free flowing to a permanently flooded hydrologic regime due to impoundment would lead to changes in species richness and diversity. Swamps were studied with either seasonally flooded (Bayou Capuchin or Cat Island) or permanently flooded conditions (Lake Martin and Henderson Lake). The standing vegetation and seed banks were studied in five 100 m² plots. 

Results/Conclusions

Species richness was higher in the standing vegetation of Lake Martin and Henderson Lake. The relatively low species richness of Bayou Capuchin and Cat Island may be explained by an unusually long flooded season in 2008. The late drawdown may have affected seedling recruitment. The seed banks of both Bayou Capuchin and Cat Island showed a higher species richness and Shannon-Wiener index of diversity scores when compared to both the permanently flooded sites. Lake Martin had higher species diversity for standing vegetation than the other locations, which all received similar scores. This study is important to understanding changes in herbaceous vegetation associated with impoundment and may help predict impacts to bald cypress habitats.