Date of Award
Doctor of Philosophy (PhD)
Plant, Enviromental and Soil Sciences
Wayne H. Hudnall
This dissertation is a part of the Louisiana NASA/EPSCoR (Experimental Program to Stimulate Competitive Research) global change research, which studied the fate of carbon and sediments within the Barataria Bay Basin, Louisiana. It studied water composition to assess seawater influence within the marsh. Ion exchange resin strips were used to study the effect of salinity and Chloride (Cl) on sulfate (SO4) reduction and their potential for water and soil analysis. Chloride dominated the water system and the Cl/SO 4 ratio can be used to assess the seawater influence. Resin extractable sulfur (S) predicted non-pyritic S fraction for the marsh soils. High salinity reduced the affinity of target ions onto the resin. Limited affinity of SO 4 to resin indicates SO4 accumulation within root zone, which promotes sulfate reduction and pyrite formation. This project mainly studied landscape position and salinity effects on pyrite accumulation and the spatial variability of soil characteristics within a saline and a brackish marsh. Salinity, pyrite, and non-pyritic iron (Fe) and S varied between streamside and inland. Depressions in mineral layer, accretion variations and associated hydrology caused the field-scale variability. When the inland site is landlocked, salinity and pyrite content within the surface horizon varied. Non-pyritic S, pH, and pyrite profiles were different in different marsh types. Mineralogical evidence also found for presence of pyrite framboids. These soils should be reclassified to indicate accumulations of reduced sulfur. Thickness of subsurface horizons was highly spatially variable. Variation in depth to mineral layer (DML) can be due to the presence of depressions in the mineral layer surface. Typic Medisaprists occurred mostly toward inland areas and away from waterways at the saline marsh. The DML was shallower for the degrading marsh within the saline marsh type. Typic Medisaprists within the brackish marsh had thick organic layers due to presence of thick subhorizons. Spatial variability is evident for pH and organic/mineral ratio (OMR) within organic subhorizons. The OMR data varied widely for the brackish marsh compared to saline marsh. Organic soil characteristics vary spatially due to variations in associated processes, therefore, spatial variability should be considered for soil sampling schemes.
Dharmasri, L. Cecil, "Spatial Variability of Coastal Organic Soil Characteristics." (1998). LSU Historical Dissertations and Theses. 6824.