Semester of Graduation

Summer 2020

Degree

Master of Science (MS)

Department

Renewable Natural Resources

Document Type

Thesis

Abstract

Phragmites australis is cosmopolitan plant species with an invasive variety present throughout most of North America. In the Balize Delta, Louisiana, USA, P. australis plays an important role in combatting subsidence, maintaining navigation channels, and protecting interior fish and wildlife habitat from waves and storm surge. In 2016 a dieback of P. australis was reported by wetland managers, coinciding with the appearance of an invasive Asian scale insect (Nipponaclerda biwakoensis), though the specific cause is still unknown. Two previous efforts attempted to identify the onset of dieback conditions met with limited success. Using Landsat images from 1985 to 2019 we classified P. australis. That classification was ground-truthed with information from five helicopter surveys made between 1988 and 2013. P. australis was stable from 2010 until 2014 but then decreased in area in 2015 and decreased in NDVI from 2014 to 2016. Area of total marsh vegetation and P. australis varied in similar patterns from the 1980s until the 2000s; since then, they vary in different ways. I concluded that detectable dieback conditions in the area began as early as 2014 and started recovery post 2016. Spatial patterns of decline is consistent with multiple stressors inducing dieback conditions such as eutrophication, salinity, or water level.

Committee Chair

Nyman, John

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