Missouri Ozark Province fens are relatively rare wetland ecosystems in the unglaciated mid-continent USA. Soils from 30 study fens were described, sampled, analyzed for physical and chemical parameters, and classified in order to better understand these groundwater seepage communities and their carbon accumulating substrates. The organic carbon (OC) and clay content were used along with nutrient levels to separate soil materials into four groups: organic, mucky-mineral, mineral, and marly. This information was combined with field observations of soil horizon expression and thickness in order to classify the soils.

Results/Conclusions

Fens typically form mosaics of different soils types, vegetation zones, and surface hydrologic features. The study fen soils typically have thin (< 40 cm) organic soil materials, or mucky-mineral soil materials at the surface, and mineral substrates. The most common diagnostic soil horizons in the fens are histic and mollic epipedons. All of the fen soils have redoximorphic features within and beneath the epipedons. Few fen soils have a thick enough histic epipedon to be classified as Histosols. Most fen soils are classified as Histic, Cumulic, or Typic Endoaquolls depending on the OC content and thickness of the epipedon. Subgroup distinctions are nearly impossible without the OC and clay content data. Longer periods of saturation appear to correlate with greater organic carbon content, and thicker epipedons. Generally, fens dominated by mineral soil materials at the surface appear to only have seasonal saturation, including episaturation. Marly fens, with a few exceptions, are mostly shallow with visible deposition of carbonate minerals on the ground surface and scattered patches of calciphitic vegetation. Marly soils are distinguished by an alkaline pH, high calcium levels, and are classified as Lithic and Typic Endoaquents.