Salt marshes play a big role in global carbon (C) storage, and C stock estimates are used to predict future changes. However, spatial and temporal gradients in C burial rates over the landscape exist due to variations in water inundation, dominant plant species and stage of growth, and tidal action. We quantified soil C concentrations in soil cores across time and space beside several porewater biogeochemical variables and discussed the controls on variability in soil C in salt marsh ecosystems.