Dataset: Effect of soil organic matter content and nutrient loading on productivity of Spartina patens (v.0.10)

River sediment diversions in the Mississippi River Delta have been planned
as a keystone strategy for wetland restoration in coastal Louisiana. The
introduction of mineral sediment and dissolved nutrients present in
Mississippi River water could drastically alter the abiotic environment of
the surrounding wetlands, and the effects on wetland vegetation are
unclear. In this study, 50 sods were transplanted from a Spartina
patens-dominated brackish marsh into a greenhouse and grown in either
mineral or organic soil in combination with one of five levels of nutrient
enrichment. The primary component of the mineral soil was silt collected
from the bank of the Mississippi River, while that of the organic soil was
peat collected from the aforementioned S. patens marsh. Nutrient
treatments were based on a range of Mississippi River diversion discharge
rates of nitrate, phosphate, sulfate, potassium, and iron as well as a
control with no nutrient addition. After one summer, we found that total
porewater conductivity increased with nutrient loading under both soil
types. Under higher nutrient treatments the concentrations of porewater
sulfide were elevated to phytotoxic levels, but this effect was only
observed in the organic soil treatment. Nitrate and ammonium porewater
concentrations were affected by both nutrient loading and soil type;
however, nitrate was higher in the mineral soil while ammonium was higher
in the organic soil. Porewater phosphorous and potassium concentrations
were elevated in organic soil conditions and higher nutrient loading,
while porewater iron was higher under mineral soil and lower nutrient
loading. Aboveground standing crop, belowground biomass accumulation
(i.e., ingrowth), and soil shear strength were also sampled at the end of
the growing season with the goal of examining their relationships with
nutrient and sediment enrichment and porewater chemistry.