A Geostatistical Analysis of Soil Properties in the Davis Pond Mississippi Freshwater Diversion

Land loss has been a major concern in the Mississippi River Delta as the levees constructed along the river caused a severe drop in sediment and nutrient loads for the adjacent wetland areas. Several freshwater diversions along the lower reach of the Mississippi River were built to resolve this. This study represents the first spatial survey of one such diversion, Davis Pond, with the objective to understand the current nutrient status and to determine a baseline of key soil properties. We also expect that the processes driving wetland accretion are scale dependent, and present the scale dependency in the spatial relationships of those properties which are key to accretion. These soil properties are: soil moisture (MOIST), bulk density (BD), pH, organic matter content (OM), total phosphorus (TP), nitrogen (TN), and carbon (TC) sampled 142 stations (0-10 and 10-20-cm depth). Maps of soil properties in the recently accreted 0- to 10-cm interval were produced using kriging. From the spatial correlation analysis we observed that TN, TC, and OM, in the 0- to 10-cm depth interval, had similar spatial properties and were closely related to BD. The spatial relationship between TP or pH with any other variable was weak. We also inferred that processes driving dynamics of TP in the Davis Pond act on a finer spatial scale than processes affecting TN, TC, and OM. We can identify where there are different deposition processes affecting the spatial patterns in this wetland, that is, C deposition by the plants vs. mineral river sediment deposition.