Indicators hydric soil

In upland/drained soils, oxidized forms of chemical species dominate the system, whereas in wetland soils reduced forms dominate the system (Figure 3.6). During flooding or in the absence of molecular oxygen, the oxidized forms are converted into reduced forms, through several microbially mediated catabolic processes. Under drained conditions, many of the reduced forms are converted into oxidized forms through chemical and biological processes. Presence of reduced forms indicates soil wetness or anaerobic soil conditions, which are used as indicators of hydric soil identification. 

Many of the hydric soil indicators were developed for delineation purposes. During the development of these hydric soil indicators, observations were concentrated near the edge of the wetlands and in the interior of wetlands therefore, there are wetlands that lack any of the approved hydric soil indicators in their wettest portions. Delineators and other users of the hydric soil indicators should concentrate their observation efforts at the wetland edge when these conditions are suspect. 

The following list of indicators was obtained from the USDA NRCS (2006) report on field indicators of hydric soils. Field indicators of hydric soils are grouped as follows ... 

List some important field indicators used in the identification of hydric soils. 

Richardson, J. L. and M. J. Vepraskas. 2001. Wetland Soils. Lewis Publishers, Boca Raton, FL. 417 pp. USDA NRCS. 2006. In G. W. Hurt and L. M. Vasilas (eds.) Field Indicators of Hydric Soils in the United States, Version 6.0. USDA NRCS in cooperation with the National Technical Committee for Hydric Soils, Ft. Worth, TX. 

Canse mottling and gleying, which serve as indicators of hydric soils Oxidizes toxic organic contaminants... 

Unique characteristics of ferromanganese nodules and associated oxidation-reduction reactions have been used by soil scientists as morphological indicators to help identify hydric soils (see Chapter 3). These characteristics are termed by soil scientists as redoximorphic features however, various terms such as redox concentrations, redox depletions, and reduced matrix are synonymously used for the oxidation-reduction of iron and manganese and their respective concentrations. We prefer not to define these characteristics as redoximorphic features because oxidation-reduction reactions not only involve iron and manganese but also a range of elements that support biotic communities in the biosphere. 

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