Spatial Distributions of Soil Biogeochemical Properties in Stormwater Treatment Area 3/4 CELLS 3A and 3B.

Investigation of spatial distributions of edaphic properties has been utilized successfully to assess ecosystem condition throughout the Everglades. We utilize spatial analyses to identify processes and trends in soil components (litter, floc, recently accreted soil (RAS) and pre-STA soils) of Cells 3A and 3B of STA-3/4. Cell 3A being in the front end of treatment flow path, received inflow waters with relatively higher P concentration than Cell 3B which received treated water with lower TP concentration. Cell 3A is dominated by emergent aquatic vegetation (EAV) while Cell 3B is dominated by submerged aquatic vegetation (SAV). We were able to assess the effects of variable P loading rates (1.32 +/- 0.18 g P m^-2yr^-1in 3A; 0.83 +/- 0.14 g P m^-2yr^-1in 3B) and dissimilar vegetation communities on soil processes in these treatment cells.

Spatial mapping was conducted on data from a spatial sampling effort (Cell 3A-65 soil cores; Cell 3b 56 cores) conducted in fall of 2015. The geostatistical wizard extension of Arc GIS V. 10.4 was used to create Kriging models and DOT maps (for trend validation) of total carbon (TC), total nitrogen (TN), total phosphorus (TP), total sulfur (TS) and total calcium (TCa). Phosphorus storage was calculated utilizing P concentration, bulk density, and depth for each soil component.

Floc TP exhibited trends of highest enrichment proximal to inflows in Cell 3A with concentrations diminishing towards the south (outflows) in Cell 3B. Spatial patterns of enrichment of floc in Cell 3A were substantially higher than Cell 3B. Trends in floc TP in southern portion of Cell 3A and northern portion of Cell 3B suggest an established breakpoint in floc concentration at the change point in vegetation. Trends in RAS TP were very similar to those of floc in Cell 3A and 3B exhibited steady declines in TP from inflows to the outflows. Likewise, spatial trends suggest a break point at the levee between 3A and 3B which also demarcates the change in vegetation from EAV to SAV dominance. Although TP trends in floc and RAS were similar, the RAS TP concentration as a whole was lower than the floc component directly above it in the soil profile. Pre-STA soils were found to be much more homogenous with spatial trends suggesting enrichment of this soil profile with P from inflows. Overall, TP model trends suggest strong gradients from inflows to outflows in litter, floc, RAS and pre-STA soils and a strong break point at the back end of Cell 3A and front end of Cell 3B. Phosphorus storages were typically higher in Cell 3A in comparison to SAV cell (Cell 3B). This was in contrast to STA-2 Cell 3 and Cell 1, where SAV cells had higher TP storages. Concentrations of TP, TC, TN and TS were lower in all soil sections in SAV (Cell 3B) but TCa concentration were higher. Mass storages of macronutrients and TCa were higher in floc layer of STA-3/4 Cell 3B, but for RAS and pre-STA soil layer, TP, TC, TN, TS and TCa storages were higher in EAV Cell 3A suggesting differences in the influence of vegetation type across soil components.