Semester of Graduation
Spring 2024
Degree
Master of Biological Science (MBioSci)
Department
Biological Science
Document Type
Thesis
Abstract
ABSTRACT
Plant productivity in wetland ecosystems is necessary to maintain a healthy habitat and to respond to sea level rise. The Mississippi River Delta (MRD), following intensive die-back during the previous decade, experienced important changes in the vegetational community, particularly the increase in abundance of less desirable species. The dominant species, Phragmites australis, has two lineages in the MRD: European (EU), the well-known invasive lineage found throughout the United States but sparely distributed throughout the MRD, and Delta, the most common vegetation type in the MRD. Owing to environmental pressures and herbivory from a specialized scale insect, Delta has exhibited extensive dieback since at least 2016. The increase in coverage of shallow-rooted Colocasia esculenta in the MRD and within Delta patches raised concerns about possible negative interactions between these two species, either via competition for resources or mediated by pathogenic soil microbes that create soil legacy effects (i.e., the microbes left behind by C. esculenta may have pathogenic effects on P. australis). To investigate the interactions between these two species within the Mississippi River Delta's wetland ecosystems, my research focused on the competitive dynamics and soil microbial effects C. esculenta and the two lineages of P. australis, EU and Delta. In a common-garden experiment, these three plant types were grown alone or in pairs to provide the first test of whether they compete with each other for resources. Plants were also subjected to a C. esculenta soil microbe treatment to assess whether these microbes negatively affected plant biomass. Overall, a general reduction in total biomass for all lineages/species in the presence of competitors and soil microbes. The EU lineage exhibited greater tolerance when subjected to these treatments relative to the Delta lineage. However, Delta experienced significant reductions in biomass, especially in the presence of the EU and C. esculenta soil microbes. This study provides insight into the dynamic wetland environment of the MRD, revealing the intricate interplay between plant competition and soil microbes in affecting plant productivity. These findings highlight potential challenges for Delta lineage recovery, restoration, and expansion, raising concerns about the fate of the Mississippi River Delta.
Date
4-15-2024
Recommended Citation
Johnston, Joseph R. III, "Competition and soil-microbe mediated interactions between Phragmites australis and Colocasia esculenta in the Mississippi River Delta" (2024). LSU Master's Theses. 5964.
https://repository.lsu.edu/gradschool_theses/5964
Committee Chair
James Cronin