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Created Environments Voluntarily Colonized by Spartina Alterniflora in Coastal Louisiana

by Xu, Han

Abstract (Summary)
The coastal wetlands play a central role in maintaining productivity of the Gulf of Mexico while protecting coastal regions during severe storms. To help offset the loss of coastal marsh, there is growing interest in the beneficial use of dredge spoil for reconstruction of eroded areas. Hydraulic dredges are routinely employed to maintain navigation and the unconsolidated sediments can be pumped considerable distances to create gently sloping wetland areas. Some areas of these reconstructed wetlands are rapidly colonized by Spartina alterniflora, the dominant vegetative species in saline areas under tidal influence. Some areas, however, fail to colonize despite favorable positions near the tidal zone. Even where volunteer colonization succeeds, marked differences in vegetative growth are commonly observed. A study was conducted to assess the impact of landscape and edaphic features on volunteer colonization along five transects (40 sites) located in a reconstructed wetland near Port Fourchon LA. Volunteer stands were observed growing 8 cm below to 45.3 cm above mean tide level (MTL). Six of the more productive sites were located at elevations above the mean high water line and the elevation of one of the most productive sites was 30.1 cm above MTL. N deficiency appears to be the primary determinant of overall productivity of S. alterniflora in this marsh, and is more acute in areas receiving lower accumulations of organic matter. The organic C and total N contents of sediments in optimal environments were 11 g C kg-1 and 0.44 g N kg-1, respectively. Concentrations of >11 g N kg-1 in either uppermost leaves or standing biomass were sufficient for optimum productivity. Highly productive plants also contained higher amounts of P and K and substantially lower amounts of Fe and Al than severely stressed plants. The failure of low-lying areas to colonize appears to be due primarily to an excessive accumulation of salts. These persistently barren areas currently or may have once served as drainage ways with insufficient flow to flush salts to open water, and therefore salts accumulated to a level where colonization is no longer possible
Bibliographical Information:

Advisor:Jing Wang; Stephen A. Harrison; Jim J. Wang; Gary A. Breitenbeck

School:Louisiana State University in Shreveport

School Location:USA - Louisiana

Source Type:Master's Thesis

Keywords:agronomy environmental management

ISBN:

Date of Publication:01/19/2006

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