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93 The general conclusion of wetland water budget studies is that the hydrologic system of which the wetland is a part is sufficiently complex that alterations to one part of the system may have far reaching effects upon the other components (Carter et al. 1979). Soil SOU is one of the lIIO.t important physical cOlllponelnts of wetlands. It exercises a strong influence over the type of vegetatioll able to survive and the species of organi81l8 that dwell on and within it. ,According to the U.S. Soil Conservation Service, soil is lilllited to terrestri.ll situations and shallow waters: "Areai,'.re oot conSidered to have soil if the surface is permanently covered' by water deep enough that only floating plants are present . . ." Soil is limited to terrestrial situatiolns and shallow waters. The emergent plants associated with freshwater wetlands do not grow beyond a depth of about two meters, therefore, the watetl.ard limit of soil is virturally equivalent to the waterward limit of wetland according to the U.S. Fish and Wildlife classification system (Cowardin ,et al. 1979). The U. S. Soil Conservstion Service, SOU Survey SelLff (1975), recognized two basic types of soils: mineral soil and !)rJ(anic soil. Nine orders of IIlineral soils and one order of organic soils e~alled histosols are recognized within the two major groups. A taxonomic hi.!rarchical system of classification was developed that perlllits soIl descriptIon at several level s of detail. For example, suborders of histosl)ls are identified according to the degree of decomposition of the organic matter content. For soil-classification purposes, mineral soils are differentiated from the so-called organic soils associated with wetland environments. Most types of waterlogged soils are grouped into either hydroaorphic or , balomorphic forms. Hydromorphic soils are fonnd in association wit 11 wetlands. Halomorphic soils are the saline ~ld alkaline soils of imperfectly drained arid regions and the coastal salt fl.ats. Many wetlands are underlain by soil matedal Known as peat or !!lUck. The U.S. Department of Agriculture Soil Survey Manual describes the f ormation and nature of peat and 1Il1ck as follows: In moist situations where organic matter forma IIIOre rapidly than it decOlllposes, peat deposits are formed. These peats become, in turn, parent material for soils. If the organic remains are sufficiently fresh and intact to permit identification of plant forms, the material is rega.rded as peat. If, on the other hand, the peat has oodergone sufficient decomposition to make recognition of the plant part II impossible, the decomposed material is called 1Il1ck. Generally speaking, muck has a higher IIlineral or ash content than peat, because in the process of decomposition the ash that was in the vegetation accumulstes.