Louisiana Department of Wildlife and Fisheries, New Iberia Field Office, 2415 Darnell Road, New Iberia, Louisiana 70560, U.S.A.
Erosion rather than plant dieback as the mechanism of marsh loss in an estuarine marsh
Version of Record online: 26 JUL 2006
Copyright © 1994 John Wiley & Sons, Ltd
Earth Surface Processes and Landforms
Volume 19, Issue 1, pages 69–84, February 1994
How to Cite
Nyman, J. A., Carloss, M., Delaune, R. D. and Patrick, W. H. (1994), Erosion rather than plant dieback as the mechanism of marsh loss in an estuarine marsh. Earth Surf. Process. Landforms, 19: 69–84. doi: 10.1002/esp.3290190106
- Issue online: 26 JUL 2006
- Version of Record online: 26 JUL 2006
- Manuscript Revised: 6 JUN 1993
- Manuscript Received: 27 APR 1992
- United States Geological Survey. Grant Number: 14-08-0001-23320
- Louisiana Department of Wildlife and Fisheries
- Estuarine marsh;
Coastal marsh loss in Louisiana is attributed to plane dieback caused by processes that stress vegetation, and a common landscape pattern is broken marsh that expands at the expense of surrounding unbroken marsh. We tested the hypothesis that vegetation is more stressed in broken marsh than in adjacent unbroken marsh, as indicated by vegetation aboveground biomass, species diversity and soil Eh, on transects that extended from broken marsh to unbroken marsh at Marsh Island, Louisiana. Soil Eh, vegetation above-ground biomass and species diversity did not differ between broken marsh and unbroken marsh, and above-ground biomass was similar to that reported from other marshes. Thus, we rejected the hypothesis that marsh loss is related to vegetation stress. Two factors were related to vegetation vigour: soil drainage and soil bulk density. Surprisingly, significant soil drainage occurred in broken marsh but not in unbroken marsh. Above-ground biomass of the dominant plant, Spartina patens (Aiton) Muhl., was lowest where soil bulk density was less than 0-08 gcm−3, which illustrated the importance of mineral matter accumulation in submerging coastal marshes. The mechanism of marsh loss appeared to be erosion below the living root zone, as indicated by the vertical and often undercut marsh-water interface, and by the separation of sod clasts. This is different from more rapid marsh loss associated with plant stress which we observed in other Louisiana marshes only 135 km away, indicating that marsh loss mechanisms can vary spatially even within a relatively small region.