Wetland Soils
Types and Definitions
Hydric soils: formed under conditions of saturation long enough to develop anaerobic conditions.
Mineral soils: less than 20-35% OM.
Organic soils have a specific definition dependent upon degree of saturation and soil texture.
Organic soils differ from mineral soils in these categories:
Bulk density and porosity (lower bulk density)
Hydraulic conductivity (depends on degree of decomposition)
Nutrient availability (more nutrients are tied up in unavailable organic forms)
Cation exchange capacity (greater cation exchange capacity)
Organic Wetland Soils
Characteristics depend on botanical origin
1. mosses
2. herbaceous material
3. wood and leaf litter
Decomposition: as OM decomposes, it becomes more dense and less permeable
Organic soil types: saprists (muck), fibrists (peat), hemists (mucky peat), folists (tropical and boreal montane soils)
Mineral Wetland Soils
Flooded mineral soils develop redoximorphic features. These are caused by the reduction, translocation and/or oxidation of iron and manganese oxides. Redoximorphic features are developed by biological processes. Also required are sustained anoxia, soil temperatures above 5oC, and organic matter to serve as a microbial substrate.
Gleying. Flooded soils will develop black, grey, bluish or greenish color as a result of the reduction of iron. Oxidized iron is reddish; oxidized manganese is black. When reduced they become colorless and can be leached out leaving the natural grey or black color of the parent material.
Oxidized Rhizosphere. Oxidized iron is left along the traces of small roots.
Mottles and concretions. Wetted and dried soils develop spots of highly oxidized materials. They are reddish-brown and relatively insoluble, enabling them to remain in the soil long after it has been drained.