Identifier

etd-01222008-160333

Degree

Doctor of Philosophy (PhD)

Department

Oceanography and Coastal Sciences

Document Type

Dissertation

Abstract

Increased flooding, nutrient and sediment deprivation, and saltwater intrusion have been implicated as probable causes of coastal swamp deterioration in the Mississippi Delta. An understanding of the interactive effects of these factors is required to enable successful planning of wetland restoration activities. I used field data collected from 2000 till 2005 at forty study sites to characterize the baseline conditions of the Maurepas swamp. I used a cluster analysis to identify four swamp habitat clusters, and characterized the clusters on the basis of soil properties, salinity, basal area, stem density, and other tree-related variables. ANOVA and related statistical techniques showed that three of the four habitat clusters exhibited tree biomass and densities indicative of flooding stress, and one cluster showed high tree mortality in response to salt-water intrusion. I then developed a two-species individual-based forest succession model (IBM) of a coastal swamp. The IBM followed the weekly growth, mortality, and reproduction of individuals of Taxodium distichum and Nyssa aquatica trees in a 1-km2 spatial grid, using historical time-series of stage and salinity data as inputs. IBM simulations predicted that increased flooding leads to swamps with reduced basal areas and stem densities, while increased salinity (~1-3 psu) resulted in lower basal areas. The IBM showed a tendency to overestimate wood production and the dominance of T. distichum in comparison to field data. Lastly, I compared the predictions of the IBM and a widely-used landscape model. I used salinity and flooding conditions simulated by the landscape model in eight of its 1-km2 cells as input to the IBM, and compared both models’ predictions of habitat change over 100 years. The models showed good agreement in their predictions of marsh persistence and swamp to marsh conversion. The IBM, however, showed higher sensitivity to changes in both salinity and flooding than the landscape model, and never predicted swamp persistence. The next generation of models for forecasting coastal habitat change in the Mississippi Delta will likely be a combination of the individual-based and landscape models used in this dissertation.

Date

2008

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Kenneth A. Rose

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