Semester of Graduation

Summer 2019

Degree

Master of Biological Science (MBioSci)

Department

Biological Sciences

Document Type

Thesis

Abstract

Cogongrass (Imperata cylindrica (L.) Beauv.), an invasive species from East Asia, is found worldwide and is problematic in several countries. In the United States, it grows primarily in the Southeast, reducing biodiversity by growing in dense patches and potentially causing mortality and reducing value of native and planted pinelands due to a high burning temperature. Using Lee Memorial Forest, a Louisiana State University AgCenter property in Washington Parish as a study site, this thesis explores cogongrass in Louisiana with emphasis on soil microbes and soil legacy effects on native plant species. Cogongrass populations at Lee Memorial Forest were more likely to occur in management units with a prescribed burn, found primarily in evergreen forest on both soil types on the property and have a clustered distribution.

Soil microbial community effects on cogongrass growth were compared in soil collected from the native range in Japan and in soil collected from Louisiana. There was an initial release from soil microbial pathogens with 1.4 times more aboveground biomass in live versus sterile soil from the invaded range. In the native-range soil, 1.4 times more aboveground biomass was produced in sterile soil than in live soil, indicating the presence of pathogens. Live soils were reused to test how cogongrass induced alterations in microbial community affected subsequent cogongrass growth. Aboveground biomass production in sterile soil was always greater than in live soil, 1.2 times in Japanese soil and 2.2 times in Louisiana soil, indicating increased pathogens. Cogongrass from two Louisiana populations responded similarly in aboveground biomass production, however there were differences in the allocation of that biomass to leaves or additional height, indicating variable invasive potential.

The second study investigated the cogongrass legacy remaining in soil after its removal and the impact on subsequent plants. Two native plants, Schizachyrium scoparium and Arnoglossum ovatum, were grown in soil either previously containing cogongrass or having no previous plant growth. Schizachyrium scoparium accumulated 2.9 times and A. ovatum 1.3 times more total biomass in cogon-free soil compared to cogon-exposed soil. Soil mitigation techniques due to cogongrass soil legacy may be needed for optimal restoration success.

Date

6-19-2019

Committee Chair

Cronin, James

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