Semester of Graduation

Summer 2021


Master of Science (MS)


Biological Sciences

Document Type



Since 2016, there has been widespread dieback of P. australis in the Lower Mississippi River Delta (hereafter referred to as Lower MRD, which is defined as the Birds Foot Delta) with relatively little to no signs of recovery. The cause of the current dieback is not fully understood. This thesis explores P. australis with emphasis on chemical profile characterization of different soil types and its effects on plant growth and the potential for restoration in the Lower MRD.

In chapter 2, I characterized the chemical profiles of soils collected from healthy and dieback stands of Phragmites, and from newly created dredge sites. To assess restoration potential in dieback and dredge sites, we experimentally tested whether these different soil types impact P. australis aboveground biomass. Dieback soils were characterized by higher % organic matter, % carbon, % nitrogen, and higher S and Fe concentrations, whereas healthy soils had higher Cu, Al, P and Zn. Whereas, dredge sites were low in nutrients and organic matter compared to healthy soils. Biomass was 16-23% and 44% lower in dieback and dredge soils, respectively, than in healthy soils. Dieback soils most negatively affected Delta followed by EU and Gulf lineages. Plants grown in dredge soils had the lowest mean biomass compared to healthy and dieback soils.

Subsequently, I provide preliminary findings from a restoration field trial to assess the potential of three lineages of P. australis (Delta, EU and Gulf) and common wetland plant species including S. californicus, S. alterniflora, S. patens and Z. miliacia to revegetate marsh habitats in the Lower MRD. After 6-months, plant survival of Delta and Gulf had high survival of 72.4% and 76.9%, respectively, whereas EU lineage had approximately 43% lower survival. Delta had high survival regardless of having the greatest scale abundance after one year. After 2.5 years, only 4 of 9 sites had surviving plantings which consisted of only Delta, EU, Gulf and S. californicus. Area cover was the greatest for Delta among the lineages, thus I conclude that Delta lineage would be the most optimal for restoration success in the Lower MRD.

Committee Chair

Cronin, James T.