Table 3. Examples of the responses of coastal wetland communities to altered hydrologic regimes. 



Experiment 



Purpose 



Result 



Source 



1. Streamside plants 

 moved to lower 

 elevation in the 

 marsh (in pots; 

 LA) 



2. Inland plants 

 moved to higher 

 elevation in the 

 marsh (LA) 



3. Drainage tiles 

 added to inland 

 marsh (GA) 



4. Belowground water 

 movement blocked 

 (LA) 



5. Aboveground water 

 movement blocked 

 (LA) 



6. Above- and 



belowground water 

 movement blocked 

 (LA) 



7. Above- and 

 belowground water 

 movement blocked 

 (NC) 



8. Impoundment levee 

 broken (FLA) 



Increase flood 

 height and 

 duration 



Decrease flood 

 height and 

 duration 



Increase 

 belowground 

 water movement 



Reduce 

 belowground 

 horizontal flow, 

 increase soil 

 flooding 



Greatly reduce 

 sheet flow and 

 increased 

 flooding 



Greatly reduce 

 waterflow and 

 increased 

 belowground 

 flooding 



Greatly reduce 

 sheetflow and 

 increase below- 

 ground flooding 



Increase above 

 and belowground 

 waterflow 



Lower standing 

 crop, plant height, 

 and density 



Higher plant 

 biomass, height, 

 and density 



Higher plant 

 biomass, lower 

 sulfide, higher iron 



Reduced Eh and 

 flower density 



Mendelssohn et al. 1982 



Variable Eh 

 change; negligible 

 sedimentation 



Reduced Eh, 

 sedimentation rate, 

 and tasseling 



Reduced Eh, plant 

 growth, and 

 sedimentation rate 



Dying vegetation 

 recovered 



Mendelssohn et al. 1982 



King et al. 1982; 

 Wiegert et al. 1983 



Turner et al. 1985 



Turner et al. 1985 



Turner et al., 1985 



Mendelssohn and 

 Seneca 1980 



Gilmore et al. 1981 



9. Ditched marshes 

 filled in (DEL) 



Re-establish 



original 



hydrology 



Vegetation 

 recovered, soil 

 subsidence reversed 



Stearns et al. 1940 



159 



