Identifier

etd-04082016-141120

Degree

Master of Science (MS)

Department

Plant, Enviromental and Soil Sciences

Document Type

Thesis

Abstract

Recent studies have revealed that the deterioration of Louisiana coastal wetlands with the loss of soil organic matter could be one of the main reasons leading to the hypoxia in the northern Gulf of Mexico. In this study, Atchafalaya basin undergoing land building and Barataria basin experiencing land loss were evaluated for soil organic matter (SOM) chemistry and relation to carbon source and degradation dynamics. Both lignin biomarkers and SOM molecular compositions from wetland soil profiles up to 50 cm depth of the two contrasting basins were characterized and compared. Lignin monomers were determined using alkaline CuO oxidation followed by gas chromatography-mass spectrometry (GC/MS) detection and SOM compositions were measured directly by pyrolysis-GC/MS. Results showed that Barataria basin wetland soil profiles were dominated by nonwoody angiosperms, whereas Atchafalaya basin wetland soil profiles were dominated by both nonwoody gymnosperms and nonwoody angiosperms. The SOM degradation of the two basin wetland soils was influenced by different factors. Soil acidity had a strong negative effect on the SOM degradation in the Atchafalaya basin, whereas high N contents inhibited lignin degradation in the Barataria basin. Soil electrical conductivity (EC) negatively affected organic matter degradation in the profiles of low salinity wetlands but positively influenced SOM decomposition in higher salinity wetlands. Wetland ecosystems along an increasing salinity gradient of Louisiana coast also exhibited a large variation in SOM composition. Freshwater marsh conditions influenced the amount of N-containing compounds of SOM, whereas brackish and saline marshes exerted more influence on the presence of lignin and aliphatic compounds in SOM, respectively. Overall, coastal wetland SOM compositions were mainly influenced by vegetation sources of specific ecosystems with different salinity tolerance and degradation status that was facilitated by specific environmental factors.

Date

2016

Document Availability at the Time of Submission

Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.

Committee Chair

Wang, Jim Jian

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