Degradation of Baldcypress–Water Tupelo Swamp to Marsh and Open Water in Southeastern Louisiana, U.S.A.: An Irreversible Trajectory?

Decline of the Maurepas Swamp, Pontchartrain Basin, Louisiana, and Approaches to Restoration

“…Shaffer et al [10] initiated a study in 2000 in which 20 sites in the Maurepas swamp were established with paired 625-m 2 stations to capture three habitat types characterized by different hydrological regimes: (1) Relict-stagnant, nearly permanently flooded interior sites, characterized by trees with broken canopies, few mid-story species, a well-defined herbaceous community, and a complete lack of natural regeneration; (2) Degraded-sites near Lake Pontchartrain or the margin of Lake Maurepas that are prone to severe saltwater intrusion events characterized by dead trees, sparsely dotted with baldcypress, and dominated by herbaceous species and open water; and (3) Throughput-sites receiving reliable nonpoint sources of freshwater runoff, characterized by mature overstory and midstory stands and little herbaceous cover ( Figure 2). The Relict, Degraded, and Throughput sites characterize an area roughly 828 km 2 and were replicated to reflect the relative proportion of each habitat type.…”

“…Plant material was clipped at the soil surface, placed in a labeled bag, and transported to the lab, where it remained in cold storage until it could be oven-dried and weighed. Annual aboveground herbaceous production was estimated by summing the summer and fall biomass estimates [10]. …”

“…Periodic droughts can raise salinity in western Lake Pontchartrain and parts of Lake Maurepas above 10 ppt for extended periods [12]. As a result of these impacts, tree mortality rates are high and much of the swamp is transitioning to marsh and open water [10]. There is very little closed canopy left and most of the trees in the swamp will not naturally regenerate due to semi-permanent to permanent flooding [9][10][11][19][20][21][22][23][24].…”

“…As a result of these impacts, tree mortality rates are high and much of the swamp is transitioning to marsh and open water [10]. There is very little closed canopy left and most of the trees in the swamp will not naturally regenerate due to semi-permanent to permanent flooding [9][10][11][19][20][21][22][23][24]. The vegetation under the swamp canopy is mostly weakly rooted marsh and shrub species or open water [10].…”

“…There is very little closed canopy left and most of the trees in the swamp will not naturally regenerate due to semi-permanent to permanent flooding [9][10][11][19][20][21][22][23][24]. The vegetation under the swamp canopy is mostly weakly rooted marsh and shrub species or open water [10]. Without the forest in place, the understory vegetation is very susceptible to hurricane disturbance [25,26].…”