Identifier

etd-10212016-115651

Degree

Doctor of Philosophy (PhD)

Department

Oceanography and Coastal Sciences

Document Type

Dissertation

Abstract

Deltas are globally important locations of diverse ecosystems, human settlement and economic activity that are threatened by reduced sediment delivery, accelerated sea level rise, and subsidence. In this dissertation I investigated a number of aspects of the ecosystem development over time within an actively prograding river dominated delta along the northern Gulf of Mexico coast. I outlined a conceptual model of deltaic floodplain wetland establishment and succession focused on the vegetated deltaic floodplain ecosystem, which includes subtidal, intertidal and supratidal zones. This was used to guide the experimental design and statistically driven hypothesis testing in order to ascertain the validity of the processes outlined therein. I attempted to determine how sediment surface elevation of delta floodplain wetlands changed in a prograding delta as a result of flooding, hurricanes, and cold front passage, and to compare the patterns of change between years. I also investigated the patterns in island edge cross-sectional morphology over time within a chronosequence framework which encompassed the entire period of subaerial expression of the Wax Lake Delta (WLD) in Louisiana, USA. The zonation and patterns of the herbaceous vegetation community were also investigated in response the elevation as well as hurricane storm surge passage. The forest structure of Salix nigra (black willow) on deltaic floodplain islands, was investigated in response to the estimated age of the stand, (i.e. time since establishment) and the major river floods, using both the chronosequence map and aerial imagery analysis of willow stands. Based on these finding I suggest refinements and expansion of the conceptual model to allow for inclusion of the temporal aspect of the ecosystem as a whole, which at any one time consists of numerous phases of ecological development. The findings of this dissertation and the proposed refinements of the conceptual model add to a better understanding of the deltaic floodplain ecosystem and provide a framework on which to investigate further questions of ecological development.

Date

2016

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Twilley, Robert

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