Although coastal wetlands are valued for their storm protection and erosion abatement functions, the ability of restored wetlands to provide these services is dependent upon the stability and resilience of these wetlands to chronic environmental stressors and acute disturbances. Soil shear strength, defined as the maximum resistance of a soil to shearing, can be used as an indicator of the ability of a restored marsh to resist erosion due to wind or wave energy. A field study conducted on one natural and two restored salt marshes was employed to examine differences in shear strength in relation to soil properties, plant community composition, elevation, and marsh age following restoration. A complimentary experiment in a controlled greenhouse setting was used to further refine our understanding of the influence of soil properties, elevation, and nitrogen levels on the growth of two salt marsh species, Spartina alterniflora and Avicennia germinans, and the resultant effects on soil shear strength. Plant development did not occur as predicted in the field study, with the younger restoration site experiencing severely limited vegetation development and the absence of a high marsh plant community at the older restoration site. Results of the field study suggest that the factors affecting soil shear strength in restored back-barrier salt marshes may change as the marsh ages and soil development progresses. In the greenhouse, S. alterniflora was more flood tolerant and had faster growth, while A. germinans was more resilient to the initial stress of transplantation. Despite their differential responses to environmental conditions, shear strength was significantly greater in experimental units that were planted with either species as compared to unvegetated soil. Results from this study provide essential information on the suite of characteristics that both optimizes the growth of salt marsh vegetation and in turn, produces the most resilient and stable restored marsh.
|Advisor:||Hester, Mark W.|
|Commitee:||Duke-Sylvester, Scott, Hasenstein, Karl H.|
|School:||University of Louisiana at Lafayette|
|School Location:||United States -- Louisiana|
|Source:||MAI 55/03M(E), Masters Abstracts International|
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